Change search
Refine search result
45678910 301 - 350 of 595
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 301.
    Jolsterå, Rickard
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Surface reactions of magnetite and maghemite with dissolved and added ions in process water2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Reactions between mineral surfaces and dissolved species in process water, both inorganic and organic play an important role in mineral processing. Reverse flotation of finely comminuted iron ore is sometimes employed in order to remove the phosphorous mineral apatite. An anionic collector, designed to specifically adsorb at the calcium specific surface sites of apatite is added, rendering the apatite particles hydrophobic properties. However, some of the collector adsorbs also at the magnetite surfaces, thereby introducing undesired characteristics to the upgraded iron ore concentrate.Of this reason, magnetite and maghemite surfaces and their interactions with the most abundant and important ions in the process water during flotation, and their potential influence on collector adsorption at magnetite was studied. Maghemite was included in the experiments, since previous work had shown that oxidation of the magnetite surface into maghemite may occur during the processing of the iron ore concentrate. The complex system that the dissolved ions in the process water and the iron oxide particles constitute at flotation and agglomeration was divided into smaller subsystems.The protolytic characteristics for the magnetite-H+ and maghemite-H+ systems proved to be similar when their modelled intrinsic surface complexation constants were compared. However, the surface site density of magnetite was found to be 50 % greater than for maghemite. Both potentiometric titrations and ATR-FTIR spectroscopy were used to study and characterize the adsorption of silicate. The results from the surface complexation modelling suggested that the silicate adsorbed as monodentate surface complexes at the maghemite surfaces. The results showed a silicate adsorption maximum at pH 8.5 to 9.5 for both iron oxides. Within this range pH, the surface complex ΞFeOSiO(OH)2 - was proposed as the dominating surface specie in the maghemite-silicate system.The iron ore pellet additive olivine proved to release substantial amounts of Mg2+ when immersed in water, indicating that olivine probably is the main source of Mg2+ to the process water. Thus, the surface characteristic of olivine particles in water suspensions was studied. Since olivine proved to be a significant source of magnesium ions, adsorption of Mg2+ at maghemite and magnetite was studied and modelled. The results suggested that magnesium ions adsorbed as a mix of mono- and bidentate surface complexes when the number of surface sites was in excess. Increased amounts of Mg2+ i.e., ≥1 Mg2+ site-1, resulted in a model including only monodentate surface complexes.Experiments involving competitive adsorption of carbonate and silicate showed that added silicate replaced adsorbed carbonate. Other competitive experiments, with Mg2+ and Ca2+, showed that Mg2+ had a stronger affinity for the magnetite surface than Ca2+. The preferential adsorption of Mg2+ at the iron oxide surface may then have protective properties, by preventing adsorption of the calcium specific collector. Results from both in-situ ATR-FTIR spectroscopy and contact angle measurements indicated also that added Mg2+ reduced the adsorption of collector and thereby increased the wettability of the magnetite surfaces.

  • 302.
    Jolsterå, Rickard
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Gunneriusson, Lars
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsling, Willis
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Adsorption and surface complex modeling of silicates on maghemite in aqueous suspensions2010In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 342, no 2, p. 493-498Article in journal (Refereed)
    Abstract [en]

    Adsorption of soluble silicate species, (Si(OH)4) on maghemite, (γ-Fe2O3) has been studied by high precision potentiometric titrations, spectroscopic analyses and zeta potential determinations. Titrations were performed at 25.0 °C within the range 2.8 < pH < 11.1 and at a constant ionic strength of 0.100 mol dm-3. The experimental data were evaluated using the constant capacitance model. For the maghemite - H+ system, the following values for the surface complexation constants and capacitance were found: ≡FeOH + H+ ↔ ≡FeOH2+; log βs11(int) = 5.39 ± 0.01 ≡FeOH ↔ ≡FeO- + H+; log βs-11(int) = -7.51 ± 0.01; C = 2.40 Fm-2.Three different concentration ratios of the determined concentration of active surface sites and added total silicate concentration, [≡FeOH]:[Si(OH)4], were examined (1:1, 2:1 and 3:1). A model comprising of three surface complexes, ≡FeOSi(OH)3, log βs011(int) = 3.61 ± 0.02; ≡FeOSiO(OH)2-, log βs-111(int) = -3.00 ± 0.01; and ≡FeOSiO2(OH)2-, log βs-211(int) = -11.35 ± 0.02; was found to best describe the experimental observations. Attempts to model the adsorption of silicates on maghemite as bidentate or polynuclear silicate complexes were not successful. The maximum silicate adsorption for the 1:1 ratio, approximately 80%, was obtained at pH 9 - 9.5. The IEP of maghemite in the presence of silicates (1:1 ratio) was determined from ζ-potential measurements, giving pHIEP ≈ 6.6.

  • 303.
    Jolsterå, Rickard
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Gunneriusson, Lars
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsling, Willis
    Surface characterisation and modelling of olivine at alkaline conditions2010In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 74, no 12/Suppl 1, p. A477-Article in journal (Other academic)
  • 304.
    Jolsterå, Rickard
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Gunneriusson, Lars
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Surface complexation modeling of Fe3O4-H+ and Mg(II) sorption onto maghemite and magnetite2012In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 386, no 1, p. 260-267Article in journal (Refereed)
    Abstract [en]

    The surface acid/base properties of magnetite (Fe3O4) particles and the sorption of Mg2+ onto magnetite and maghemite (γ-Fe2O3), have been studied using high precision potentiometric titrations, batch experiments and zeta potential measurements. The acid/base properties of magnetite were found to be very similar to maghemite except for the difference in surface site density, Ns (sites nm-2), 1.50±0.08 for magnetite and 0.99±0.05 for maghemite. The experimental proton exchange of the magnetite surface increased from pH 10 and above, indicating dissolution/transformation reactions of magnetite at alkaline conditions. Thus, magnetite with its Fe(II) content proved to be less stable towards dissolution in comparison with pure Fe(III) oxides also at high pH values.Three different ratios between surface sites and added Mg2+ were used in the sorption experiments viz. 0.5, 1 and 2 Mg2+ site-1. Surface complexation modeling of the Mg2+ sorption onto maghemite and magnetite, was restricted to pH conditions where the interference from Mg(OH)2(s) precipitation could be ruled out. The model calculations showed that Mg2+ sorb onto the magnetite and maghemite surfaces as a mixture of mono- or bidentate surface complexes at 0.5 Mg2+ site-1 and as monodentate complexes at 1 and 2 Mg2+ site-1 conditions. Mg2+ was also found to adsorb more readily at the maghemite surfaces in comparison with magnetite surfaces. For experiments with excess Mg2+ relative to the number of surface sites, the calculations suggested the formation of polynuclear surface complexes on maghemite.

  • 305.
    Jonsson, Julia
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Förslag på riktvärden för sulfathalter i ytvatten2019Independent thesis Basic level (university diploma), 80 credits / 120 HE creditsStudent thesis
    Abstract [sv]

    Detta examensarbete kommer att vara den avslutande delen i mina studier inom samhällsbyggnads-programmet vid Luleå tekniska universitet. Under min verksamhetsförlagda utbildning, på WSP Sverige AB har jag fått arbeta i uppdrag där kunskaper om vattenkemi och biologi har behövts. Syftet med examenarbetet är att undersöka möjliga förslag på riktvärden för sulfathalter i ytvatten. Examensarbetet tog sin början med att formulera frågeställningar att forma arbetet kring. Utifrån frågeställningarna har jag sedan börjat undersöka vilka länder som har riktvärden för sulfathalter implementerat i miljölagstiftningen. Valet var självklart, att hitta ett land med liknande klimat som norra Sverige för att riktvärdena skulle vara relevanta och trovärdiga. Valet blev att undersöka riktvärden i Kanada. Under examensarbetets gång har jag fått lära mig mycket. Till exempel att kunna läsa och ta till mig information om toxikologiska undersökningar och förstå dess relevans. Detta har i sin tur lett till att jag lärt mig nya begrepp som används inom området miljö och vatten. Jag har även fått en inblick över hur komplext och stort arbetet området miljö och vatten är och fått en bra grund att stå på inför kommande utmaningar i mitt framtida yrkesliv.

  • 306.
    Jonsson, Lotta
    Luleå tekniska universitet.
    Amino acid adsorption on aqueous hydroxyapatite: a spectroscopic study1999Licentiate thesis, comprehensive summary (Other academic)
  • 307.
    Jullian, Carolina
    et al.
    Departamento de Química Orgánica y Fisicoquímica, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile.
    Morales, Javier O.
    Departamento de Química Orgánica y Fisicoquímica, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile.
    Zapata-Torres, Gerald
    Departamento de Química Inorgánica y Analítica, Facultad de de Ciencias Químicas y Farmacéuticas, Universidad de Chile.
    Aguilera, Benjamín
    Departamento de Química Inorgánica y Analítica, Facultad de de Ciencias Químicas y Farmacéuticas, Universidad de Chile.
    Rodriguez, Jorge
    Departamento de Química Inorgánica y Analítica, Facultad de de Ciencias Químicas y Farmacéuticas, Universidad de Chile.
    Arán, Vicente
    Instituto de Química Médica, CSIC.
    Olea-Azar, Claudio
    Departamento de Química Inorgánica y Analítica, Facultad de de Ciencias Químicas y Farmacéuticas, Universidad de Chile.
    Characterization, phase-solubility, and molecular modeling of inclusion complex of 5-nitroindazole derivative with cyclodextrins.2008In: Bioorganic & Medicinal Chemistry, ISSN 0968-0896, E-ISSN 1464-3391, Vol. 16, no 9, p. 5078-5084Article in journal (Refereed)
    Abstract [en]

    The slightly water-soluble 5-nitroindazole derivative (5-NI) and its inclusion with either beta-cyclodextrin (betaCD) or Heptakis (2,6-di-O-methyl)-beta-cyclodextrin (DMbetaCD) were investigated. The stoichiometric ratios and stability constants describing the extent of formation of the complexes were determined by phase-solubility measurements obtaining type-A(L) diagrams in both cases. According to the continuous variation method (Job's plot) a 1:1 stoichiometry has been proposed for the complexes. Also electrochemical studies were carried out on both CDs complexes, where the observed change in the E(PC) value for DMbetaCD indicated a lower feasibility of the nitro group reduction. The detailed spatial configuration is proposed based on two-dimensional NMR methods. These results are further interpreted using molecular modeling studies. The latter results are in good agreement with the experimental data.

  • 308. Kalinkin, Alexander M.
    et al.
    Forsling, Willis
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Makarov, Dmitriy V
    Kola Science Centre, Russian Academy of Sciences, Apatity.
    Makarov, Victor N.
    Kola Science Centre, Russian Academy of Sciences, Apatity.
    Surface oxidation of synthetic pyrrhotite during wetting-drying treatment2000In: Environmental Engineering Science, ISSN 1092-8758, E-ISSN 1557-9018, Vol. 17, no 6, p. 329-335Article in journal (Refereed)
    Abstract [en]

    The surface changes of synthetic hexagonal pyrrhotite Fe[10]S[11] during laboratory wetting-drying treatment at 45°C were investigated using FTIR (DRIFT) spectroscopy, FTIR Raman microscopy, and scanning electron microscopy. α-FeO(OH) (goethite) and elemental sulphur were the main products of the surface pyrrhotite oxidation. The formation of goethite and elemental sulphur was studied on the basis of the corrosion theory and using a potential-pH (Pourbaix) diagram. The appearance of oxidation products on the surface of pyrrhotite grains was detected between 10 and 20 h of treatment. The obtained results can be used for comparison of oxidation processes of synthetic pyrrhotite with that of natural sulphide minerals in dumps.

  • 309.
    Kalinkina, Elena
    Luleå tekniska universitet.
    Changes of Ca and Mg silicate minerals induced by grinding and interaction with water1999Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    FT-IR spectroscopy, powder XRD, 29Si MAS-NMR, 13C CP/1H-decoupling MAS-NMR, BET surface area and CO2-content measurements have been used to study the processes which occur during dry grinding of Ca and Mg silicate minerals: diopside, enstatite, åkermanite, and wollastonite. In the course of grinding alongside to hydration and amorphisation considerable sorption of atmospheric CO2 by ground minerals occur. According to FT-IR spectra carbon dioxide is present in the ground minerals, in the same form as in silicate glasses after dissolution of CO2 at high temperatures and pressures relevant to the magma state. The degree of carbonisation increases with the fraction of Ca in octahedral positions in the silicate structure. The structure of silicate is less important in the carbonisation process during grinding. Water treatment of diopside leads to a significant increase of BET surface area of the mineral (8-10 times). This may be caused by an increase of surface roughness, which is a result of dissolution at dislocations or other imperfect sites on the mineral surface.

  • 310.
    Kalinkina, Elena V.
    et al.
    Kola Science Centre, Russian Academy of Sciences, Apatity.
    Kalinkin, Alexander M.
    Kola Science Centre, Russian Academy of Sciences, Apatity.
    Forsling, Willis
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Makarov, Victor N.
    Kola Science Centre, Russian Academy of Sciences, Apatity.
    Sorption of atmospheric carbon dioxide and structural changes of Ca and Mg silicate minerals during grinding: I. Diopside2001In: International Journal of Mineral Processing, ISSN 0301-7516, E-ISSN 1879-3525, Vol. 61, no 4, p. 273-288Article in journal (Refereed)
    Abstract [en]

    Processes which occur during dry grinding of the magnesium and calcium silicate minerals enstatite MgSiO3, åkermanite Ca2MgSi2O7 and wollastonite CaSiO3, have been studied with the use of diffuse reflectance Fourier transform infrared spectroscopy (DRIFT), powder X-ray diffraction, 29Si MAS-NMR spectroscopy, CO2-content analysis, and BET surface area measurements. It has been found that the extensive sorption of atmospheric CO2 (carbonization) by the ground mineral that was reported earlier for diopside CaMgSi2O6 also occurs for the minerals included in this study. The shape and position of the double peak of the CO32--group in the 1430-1515 cm-1 region in the FT-IR spectra of ground minerals are similar to that of ground diopside. CO2-content analysis and BET surface area measurements show that carbonate groups are present not only at the surface but also in the bulk of the ground minerals. The degree of carbonization of silicate depends on its calcium content. The higher the fraction of Ca in octahedral positions in the silicate structures, the higher the degree of carbonization. For synthetic wollastonite CaSiO3, which is a pure calcium silicate, the degree of carbonization is 102.6 mg CaCO3 per gram of sample after 36 h of grinding. The structure of silicate appears to be less important for the degree of carbonization during grinding.

  • 311. Kalinkina, Elena V
    et al.
    Kalinkin, Alexander M
    Forsling, Willis
    Makarov, Viktor N
    Sorption of atmospheric carbon dioxide and structural changes of Ca and Mg silicate minerals during grinding: II, Enstatite, akermanite and wollastonite2001In: International Journal of Mineral Processing, ISSN 0301-7516, E-ISSN 1879-3525, Vol. 61, no 4, p. 289-299Article in journal (Refereed)
    Abstract [en]

    Processes which occur during dry grinding of the magnesium and calcium silicate minerals enstatite MgSiO3, åkermanite Ca2MgSi2O7 and wollastonite CaSiO3, have been studied with the use of diffuse reflectance Fourier transform infrared spectroscopy (DRIFT), powder X-ray diffraction, 29Si MAS-NMR spectroscopy, CO2-content analysis, and BET surface area measurements. It has been found that the extensive sorption of atmospheric CO2 (carbonization) by the ground mineral that was reported earlier for diopside CaMgSi2O6 also occurs for the minerals included in this study. The shape and position of the double peak of the CO32--group in the 1430-1515 cm-1 region in the FT-IR spectra of ground minerals are similar to that of ground diopside. CO2-content analysis and BET surface area measurements show that carbonate groups are present not only at the surface but also in the bulk of the ground minerals. The degree of carbonization of silicate depends on its calcium content. The higher the fraction of Ca in octahedral positions in the silicate structures, the higher the degree of carbonization. For synthetic wollastonite CaSiO3, which is a pure calcium silicate, the degree of carbonization is 102.6 mg CaCO3 per gram of sample after 36 h of grinding. The structure of silicate appears to be less important for the degree of carbonization during grinding.

  • 312. Kanwal, Sehrish
    et al.
    Ali, Naveed Zafar
    Hussain, Rizwan
    Shah, Faiz Ullah
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Akhter, Zareen
    Poly-thiourea formaldehyde based anticorrosionmarine coatings on type 304 stainless steel2020In: Journal of Materials Research and TechnologyArticle in journal (Refereed)
    Abstract [en]

    In the present study, hexamethylene diisocyanate (HMDI) encapsulated poly-thiourea formaldehyde (PTF) (10 wt%) coating was developed in an epoxy-polyamine matrix and their anticorrosion studies on Type SS304 stainless steel substrate have been conducted using electrochemistry techniques. The compact and hydrophobic shell wall of PTF proved to be a potent shell wall material for HMDI encapsulation. The effect of temperature and pH values was found to be decisive factor in the synthesis of microcapsules. The PTF microcapsules were synthesized in acidic condition with a pH value of 3. Over 90% of the core fraction is retained in water after 21 days immersion. However, core content decreased with increasing temperature. The capsules were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy(SEM), thermogravimetric analysis (TGA) and Electrochemical Impedance spectroscopy (EIS). Scanning electron microscopic analysis depicts the uniform morphology of coating with a particle size in the range of 1.08 μm–22.06 μm. The vibrational band at 2271 cm−1 attributed to NCO signal further endorses the successful encapsulation of HMDI into the PTF capsules. Electrochemical testing on steel specifies the appreciable anticorrosion performance of the synthesized poly thiourea formaldehyde (PTF) coating against artificial sea water.

  • 313.
    Karimi, Somayeh
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Korelskiy, Danil
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Mortazavi, Yadollah
    Catalysis and Nanostructured Materials Research Laboratory, College of Engineering, School of Chemical Engineering, University of Tehran.
    Khodadadi, Abbas Ali
    Catalysis and Nanostructured Materials Research Laboratory, College of Engineering, School of Chemical Engineering, University of Tehran.
    Sardari, Kaymar
    Catalysis and Nanostructured Materials Research Laboratory, College of Engineering, School of Chemical Engineering, University of Tehran.
    Esmaeili, Mohammad
    Catalysis and Nanostructured Materials Research Laboratory, College of Engineering, School of Chemical Engineering, University of Tehran.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Shah, Faiz Ullah
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    High flux acetate functionalized silica membranes based on in-situ co-condensation for CO2/N2 separation2016In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 520, p. 574-582Article in journal (Refereed)
    Abstract [en]

    Acetate-functionalized silica membranes were prepared via co-condensation. The molar ratio of functional groups in the silica matrix was varied in the range of 0–0.6, denoted by x. The presence of functional groups bonded to the silica network was revealed by FTIR and 29Si and 13C solid-state NMR analysis. The stability of the groups was studied by TG analysis. The membranes were evaluated for CO2/N2 mixture separation in a temperature range of 253–373 K using a feed pressure of 9 bar and a sweep gas kept at atmospheric pressure on the permeate side. The membranes were found to be CO2-selective at all the conditions studied. The highest observed selectivity was 16 for x=0.4, with a CO2 permeance of 5.12×10−7 mol s−1 m−2 Pa−1. For x=0.2, a permeance of as high as 20.74×10−7 mol s−1 m−2 Pa−1 with a CO2/N2 selectivity of 7.5 was obtained. This permeance is the highest reported for CO2/N2 separation using functionalized silica membranes. It is proposed that the separation mechanism between CO2 and N2 was the preferential adsorption of CO2, which inhibited adsorption and permeation of N2 through the silica pore network. Permporometry results revealed that as the loading of functional groups increased, the He permeance decreased. It was also indicated that the quantity of micropores in the functionalized membrane was higher than that in the parent silica membrane.

  • 314.
    Karlkvist, Tommy
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Patra, Anuttam
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rao, Hanumantha
    Bordes, Romain
    Chalmers University of Technology, Chalmers University of Technology, Department of Chemical and Biological Engineering.
    Holmberg, Krister
    Chalmers University of Technology, Chalmers University of Technology, Department of Chemical and Biological Engineering.
    Fredriksson, Andreas
    LKAB.
    Molecular recognition in mineral flotation: Selectivity in apatite-calcite system2014Conference paper (Refereed)
    Abstract [en]

    The present investigation aims to develop and distinguish mineral specific reagents with two functional groups for use in flotation of calcium containing minerals. For this purpose, a series of dicarboxylate-based surfactants with varying length between the carboxylate groups (one, two or three methylene groups) were synthesized. As reference, a surfactant with the same alkyl chain length but with only one carboxylate group in the polar part was synthesized. The adsorption behavior of these new reagents on pure apatite and calcite mineral surfaces was studied using Hallimond tube flotation, FTIR and ζ potential measurements. The relation between the adsorption behavior of a given surfactant on a specific mineral surface and its molecular structure over a range of concentration and pH values, as well as the region of maximum recovery were established. It was found that one of the reagents, with a specific distance between the carboxylate groups, was much more selective for a particular mineral surface than the other homologues synthesized. This selective adsorption of a given surfactant to a particular mineral surface relative to other mineral surfaces as evidenced in flotation studies is substantiated by ζ potential and infra-red spectroscopy data.

  • 315.
    Khan, Amir Sada
    et al.
    Center of Research in Ionic Liquids, Department of Chemical Engineering, Universiti Teknologi PETRONAS .
    Man, Zakaria
    Center of Research in Ionic Liquids, Department of Chemical Engineering, Universiti Teknologi PETRONAS .
    Bustam, Mohamad Azmi
    Center of Research in Ionic Liquids, Department of Chemical Engineering, Universiti Teknologi PETRONAS .
    Nasrullah, Asma
    Fundamental and Applied Science Department, Universiti Teknologi PETRONAS .
    Ullah, Zahoor
    Department of Chemistry, Balochistan University of IT, Engineering and Management Sciences (BUITEMS).
    Sarwono, Ariyanti
    Center of Research in Ionic Liquids, Department of Chemical Engineering, Universiti Teknologi PETRONAS .
    Shah, Faiz Ullah
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Muhammad, Nawshad
    Interdisciplinary Research Center in Biomedical Materials, COMSATS Institute of Information Technology, Lahore, Pakistan.
    Efficient Conversion of Lignocellulosic Biomass to Levulinic Acid Using Acidic Ionic Liquids2018In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 181, p. 208-214Article in journal (Refereed)
    Abstract [en]

    In the present research work, dicationic ionic liquids, containing 1,1-Bis(3-methylimidazolium-1-yl) butylene ([C4(Mim)2]) cation with counter anions [(2HSO4)(H2SO4)0], [(2HSO4)(H2SO4)2] and [(2HSO4)(H2SO4)4] were synthesised. ILs structures were confirmed using 1H NMR spectroscopy. Thermal stability, Hammett acidity, density and viscosity of ILs were determined. Various types of lignocellulosic biomass such as rubber wood, palm oil frond, bamboo and rice husk were converted into LA. Among the synthesized ionic liquids, [C4(Mim)2][(2HSO4)(H2SO4)4] showed higher % yield of LA up to 47.52 from bamboo biomass at 100 °C for 60 min, which is the better yield at low temperature and short time compared to previous reports. Surface morphology, surface functional groups and thermal stability of bamboo before and after conversion into LA were studied using SEM, FTIR and TGA analysis, respectively. This one-pot production of levulinic acid from agro-waste will open new opportunity for the conversion of sustainable biomass resources into valuable chemicals.

  • 316.
    Khan, Zakir Zaman
    et al.
    Catalysis and Nanomaterials Lab 27, Department of Chemistry, Quaid-i-Azam University, Islamabad, Pakistan.
    Khan, Inayat Ali
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Catalysis and Nanomaterials Lab 27, Department of Chemistry, Quaid-i-Azam University, Islamabad, Pakistan.
    Khan, Ishtiaq
    Catalysis and Nanomaterials Lab 27, Department of Chemistry, Quaid-i-Azam University, Islamabad, Pakistan.
    Wattoo, Muhammad Hamid Sarwar
    Ishfaq Ahmad Research Laboratories Complex, R-Block, Pakistan Institute of Engineering and Applied Sciences (PIEAS), Islamabad, Pakistan.
    Badshah, Amin
    Catalysis and Nanomaterials Lab 27, Department of Chemistry, Quaid-i-Azam University, Islamabad, Pakistan.
    Pt and Co3O4 supported on ceria and zirconia for the catalytic reduction of N2O in the presence of CO2019In: Solid State Sciences, ISSN 1293-2558, E-ISSN 1873-3085, Vol. 98, article id 106035Article in journal (Refereed)
    Abstract [en]

    Ceria (CeO2) and zirconia (ZrO2) supported Pt and Co3O4-based nanocatalysts were synthesized and characterized by different instrumental techniques. The catalysts redox properties and active surface areas were evaluated using temperature-programmed reduction (TPR), temperature-programmed oxidation (TPO) and H2-pulse chemisorption, respectively. The catalysts were tested for the thermal oxidation of carbon monoxide (CO), reduction of nitrous oxide (N2O) and conversion of N2O/CO mixture (1:1 vol%) . In catalytic tests, Pt–Co3O4/CeO2 (10:10%) oxidized CO up to 100% at 25 °C and Co3O4/CeO2 (20%) reduced N2O up to 90% at 320 °C. Moreover, Pt–Co3O4/CeO2 (10:10%) converted N2O/CO mixture to N2/CO2 up to 90% at about 210 °C. The low-temperature catalytic activity of Pt–Co3O4/CeO2 (10:10%) for CO oxidation and N2O/CO mixture redox conversion were attributed to uniform particle size, metals and support proper combination and electron interaction.

  • 317.
    Klug, Otto
    et al.
    Luleå tekniska universitet.
    Forsling, Willis
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    A Spectroscopic Study of Phthalate Adsorption on γ-Aluminum Oxide1999In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 15, no 20, p. 6961-6968Article in journal (Refereed)
    Abstract [en]

    Surface complexation of phthalic acid/phthalate has been investigated on synthetically produced, nonaged γ-aluminum oxide by infrared and Raman spectroscopy. Effects of time, pH, and ionic strength have been studied both on the total adsorbed amount of phthalate and on the surface complexes. The spectroscopic results indicated the formation of two different types of complexes: outer sphere and inner sphere. The relative concentrations of these complexes were shown to vary considerably with pH but very little with increasing ionic strength, which equally reduced the amount of both types of complexes. Considering the electrostatic interaction between the surface and adsorbate, a complexation model was proposed that is in accordance with the spectroscopic results. Adsorption on the synthetic γ-alumina was compared to the adsorption on γ-aluminum oxide films produced by anodic oxidation, where the adsorbed amount was greatly reduced; however, both inner- and outer-sphere types of complexation have been observed.

  • 318.
    Klug, Otto
    et al.
    Luleå tekniska universitet.
    Parlagh, G.
    Technical University of Budapest.
    Forsling, Willis
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Raman spectroscopy of aromatic acids adsorbed on oxidised aluminium foil1997In: Journal of Molecular Structure, ISSN 0022-2860, E-ISSN 1872-8014, Vol. 410, p. 183-188Article in journal (Refereed)
    Abstract [en]

    Adsorption of ortho- and para-phthalic acids on oxidised aluminium foil was investigated by Raman and surface-enhanced Raman spectroscopy (SERS). Without any treatment of the foil only a modified method of SERS provided spectroscopic evidence of the adsorption. However, by dissolving the metal aluminium from the Al2O3-Al-Al2O3 structure of the foil, the adsorption could be investigated by Raman spectroscopy without surface-enhanced conditions. The vibrational bands of the adsorbed species, obtained by both types of Raman spectroscopy, are compared to the solid-state spectra of the pure acids and their dipotassium salts. The band shifts suggest that the adsorbed species are essentially in the carboxylate form; however, the Raman and the SER spectra of the same species are not identical indicating a separate chemical reaction occurring at the surface upon depositing the sol. (C) 1997 Elsevier Science B.V.

  • 319.
    Klug, Otto
    et al.
    RIFA ELECTROLYT AB.
    Szaraz, L.
    Forsling, Willis
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    A novel method for investigation of dibasic aromatic acids on oxidized aluminium surfaces by NIR-FT-SERS1997In: Microchimica Acta, ISSN 0026-3672, E-ISSN 1436-5073, Vol. Suppl. 14, p. 649-651Article in journal (Refereed)
    Abstract [en]

    A new technique is presented for detecting dibasic aromatic acids on an SERS-inactive oxidized aluminium foil by utilizing near-infrared Fourier-transform surface-enhanced Raman spectroscopy (NIR-FT-SERS). Identification of adsorbed ortho-, meta- and para-phthalic acids on a typical anodic foil of electrolytic capacitors From electrolytes containing 1 ppm substrate was successfully accomplished

  • 320.
    Klug, Ottó
    Luleå tekniska universitet.
    Optical spectroscopy of anodically oxidized aluminium foil1997Licentiate thesis, comprehensive summary (Other academic)
  • 321.
    Klug, Ottó
    Luleå tekniska universitet.
    Phthalate adsorption on gamma-alumina: a spectroscopic study1998Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Adsorption of phthalic acid/phthalate has been investigated on anodically oxidized aluminium foils - used in wet electrolytic capacitors -, by different spectroscopic methods like UV, infrared, Raman and surface- enhanced Raman spectroscopy. In addition to the capacitor foils the adsorption was studied utilizing a high surface area, synthetic Y-aluminium oxide powder as a model material. The capacitor foils were first characterized comprising BET, SIMS, XRF and electron microscopic (SEM) measurements in order to determine the composition and structure of the oxide surface. Adsorption on the two different substrates has been compared and concluded to lead to the same type of surface complexes approving the applicability of the model material for further adsorption studies. In the adsorption experiments, the influence of time, pH and ionic media on the adsorbed amount, as well as on the structure of the surface complex has been studied. Based on the analyses of the different spectra the following conclusions can be drawn: The adsorption is a fast process driven by electrostatic forces. Complexation of the aromatic compound starts with either inner- or outer sphere co-ordination of the hydrogen phthalate ion. The ratio of the two types of complexes shows pH dependence which can be correlated to the different type of surface sites preferred at different pHs. Surface-enhanced Raman spectroscopy (SERS) was applied directly on the capacitor foils for detecting the adsorbed species. Besides of the analytical aspects of the method, a detailed investigation has been performed to explore of the mechanism of the SER effect in this particular experimental approach. It was concluded that SER spectra originate from a silver-phthalate complex rather than from the phthalate adsorbed on the oxide. The structure and orientation of the final SER species is discussed. Although the aluminium oxide surface of the capacitor foil is not involved in the SER complex, the roughness of the surface, and other properties of the substrate can have positive contribution to the enhancement.

  • 322.
    Kong, Na
    et al.
    Royal Institute of Technology, Department of Chemistry.
    Shimpi, Manishkumar
    Royal Institute of Technology, Department of Chemistry.
    Park, Jae Hyeung
    Department of Chemistry, University of Massachusetts, Lowell.
    Ramström, Olof
    Organic Chemistry, School of Chemical Science and Engineering, KTH – Royal Institute of Technology, Stockholm, Royal Institute of Technology, Department of Chemistry.
    Yan, Mingdi
    Royal Institute of Technology, Department of Chemistry.
    Carbohydrate conjugation through microwave-assisted functionalization of single-walled carbon nanotubes using perfluorophenyl azides2015In: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 405, p. 33-38Article in journal (Refereed)
    Abstract [en]

    Carbohydrate-functionalized single-walled carbon nanotubes (SWNTs) were synthesized using microwave-assisted reaction of perfluorophenyl azide with the nanotubes. The results showed that microwave radiation provides a rapid and effective means to covalently attach carbohydrates to SWNTs, producing carbohydrate-SWNT conjugates for biorecognition. The carbohydrate-functionalized SWNTs were furthermore shown to interact specifically with cognate carbohydrate-specific proteins (lectins), resulting in predicted recognition patterns. The carbohydrate-presenting SWNTs constitute a new platform for sensitive protein-or cell recognition, which pave the way for glycoconjugated carbon nanomaterials in biorecognition applications.

  • 323.
    Korneeva, E V
    et al.
    Institute of Geology and Nature Management, Far East Branch, Russian Academy of Sciences, Blagoveshchensk.
    Rodina, T A
    Amur State University, Blagoveshchensk, Russian Federation.
    Ivanov, A V
    Institute of Geology and Nature Management, Far East Branch, Russian Academy of Sciences, Blagoveshchensk.
    Gerasimenko, A V
    Institute of Chemistry, Far Eastern Branch of the Russian Academy of Sciences, 690022, Vladivostok.
    Larsson, Anna-Carin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Polymeric Gold(I) Diisobutyl Dithiophosphate, [Au2{S2P(O-iso-C4H9)2}2]n: Synthesis, Supramolecular Self-Organisation (a Role of Aurophilic Interaction), 13C and 31P MAS NMR Spectroscopy, and Thermal Behavior2014In: Russian journal of coordination chemistry, ISSN 1070-3284, E-ISSN 1608-3318, Vol. 40, no 10, p. 748-756Article in journal (Refereed)
    Abstract [en]

    A new polymeric gold(I) diisobutyl dithiophosphate (Dtph), [Au2{S2P(O-iso-C4H9)2}2] n (I), was preparatively obtained and characterized by 13C and 31P MAS NMR spectroscopy and X-ray diffraction (CIF file CCDC no. 977818). Diagrams of the χ2 statistic were constructed from the complete 31P MAS NMR spectra and used to calculate the 31P chemical shift anisotropy (δ aniso = δ zz − δ iso ) and the asymmetry parameter η = (δ yy − δ xx )/(δ zz − δ iso ). The main structural unit of complex I is the noncentrosymmetric dinuclear molecule [Au2{S2P(O-iso-C4H9)2}2], in which the gold atoms are linked by two bridging ligands Dtph. The central cyclic structural fragment of the dimer [Au2S4P2] is additionally stabilized by the intramolecular aurophilic interaction Au⋯Au. Further supramolecular self-organization of the complex involves intermolecular aurophilic bonds Au⋯Au that serve to unite adjacent dinuclear molecules [Au2{S2P(O-iso-C4H9)2}2] with different spatial orientations into the polymer chains ([Au2{S2P(O-iso-C4H9)2}2]) n . The thermal behavior of complex I was examined by synchronous thermal analysis under argon. The character of the thermolysis of the complex to reduced metallic gold as a final product was determined.

  • 324.
    Korneeva, E.V.
    et al.
    Institute of Geology and Nature Management, Far East Branch, Russian Academy of Sciences, Blagoveshchensk.
    Larsson, Anna-Carin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Ivanov, Alexander V.
    Institute of Geology and Nature Management, Far Eastern Branch of the Russian Academy of Sciences .
    Novikova, E.V.
    Institute of Geology and Nature Management, Far East Branch, Russian Academy of Sciences, Blagoveshchensk.
    Smolentsev, A.I.
    Nikolaev Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences, Novosibirsk.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Crystalline nickel(II) di-i-amyl dithiophosphate, [Ni{S2P(O-i-C5H11)2}2]: Preparation, structure, heteronuclear (13C, 31P) CP/MAS NMR spectra, and thermal behavior2017In: Russian journal of coordination chemistry, ISSN 1070-3284, E-ISSN 1608-3318, Vol. 43, no 4, p. 223-231Article in journal (Refereed)
    Abstract [en]

    The crystalline nickel(II) di-i-amyl) dithiophosphate (Dtph), [Ni{S2P(O-i-C5H11)2}2] (I) was isolated on a preparative scale and characterized by 13C, 31P MAS NMR, and X-ray diffraction (CIF file CCDC no. 1469369). The χ2-statistic diagrams were constructed from full 31P CP/MAS NMR spectra for calculating the 31P chemical shift anisotropy: δaniso = δzz–δiso and the asymmetry parameter η = (δyy–δxx)/(δzz–δiso). The key structural unit of I is the centrosymmetric [Ni{S2P(O-i-C5H11)2}2] molecule in which the nickel atom coordinates two Dtph ligands in the isobidentate fashion. In molecule I, each carbon, oxygen, and sulfur atom is statistically disordered over two sites with equal occupancies. However, the disorder does not affect nickel and phosphorus. These results were interpreted as the presence in I of two [Ni{S2P(O-i-C5H11)2}2] molecules rotated through 21.0(1)° (the angle between the [NiS4] chromophore planes) relative to each other around the bisecting P–Ni–P axis passing through both four-membered [NiS2P] rings. The two molecules occupy crystal lattice sites with equal probabilities. The thermal behavior of I was studied by simultaneous thermal analysis under argon. The course of the thermal destruction of the complex was established, nickel pyrophosphate (Ni2P2O7) was identified as the final product of thermal transformations.

  • 325.
    Korneeva, E.V.
    et al.
    Institute of Geology and Nature Management, Far-Eastern Branch of the Russian Academy of Sciences, Blagoveschensk, Russian Federation.
    Smolentsev, A. I.
    Nikolaev Institute of Inorganic Chemistry, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russian Federation. Novosibirsk State University, Novosibirsk, Russian Federation.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. University of Warwick, Coventry, United Kingdom.
    Ivanov, A. V.
    Institute of Geology and Nature Management, Far-Eastern Branch of the Russian Academy of Sciences, Blagoveschensk, Russian Federation.
    Binding of gold(iii) with silver(i) dipropyldithiocarbamate: supramolecular self-assembly (role of secondary Au…S and Ag…S bonds) and thermal behavior of the ionic-polymer complex ([Au(S2CNPr2)2][AgCl2])n2019In: Russian chemical bulletin, ISSN 1066-5285, E-ISSN 1573-9171, Vol. 68, no 1, p. 40-47Article in journal (Refereed)
    Abstract [en]

    The double ionic-polymer complex ([Au(S2CNPr2)2][AgCl2])n (1) was prepared as an individual fixation form of gold(III) from NaCl solutions with silver(I) dipropyldithiocarbamate and was characterized by single-crystal X-ray diffraction and 13C magic-angle spinning (MAS) NMR spectroscopy. The structure of 1 comprises two nonequivalent centrosymmetric complex cations [Au(S2CNPr2)2]+ (A and B) and the discrete linear anion [AgCl2]. Gold(III) cations are linked by pairs of unsymmetrical secondary Au…S bonds to form linear supramolecular chains (…A…B…)n. Neighboring cations are additionally linked by [AgCl2] anions via secondary Ag…S and Cl…S bonds, the anions being involved in the overall stabilization of the supramolecular structure. The cation–anion interactions lead to a distortion of the linear configuration of the [AgCl2] anion. The character of thermolysis of 1 accompanied by quantitative regeneration of bound Au and Ag was established by simultaneous thermal analysis.

  • 326.
    Kotenkov, Sergey A.
    et al.
    Institute of Physics, Kazan Federal University, Kazan, Russia.
    Gnezdilov, Oleg I.
    Institute of Physics, Kazan Federal University, Kazan, Russia.
    Khaliullina, Aliya V.
    Institute of Physics, Kazan Federal University, Kazan, Russia;Kazan State Medical University, Kazan, Russia.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Gimatdinov, Roustam S.
    Kazan State Medical University, Kazan, Russia.
    Filippov, Andrei
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Institute of Physics, Kazan Federal University, Kazan, Russia.
    Effect of Cholesterol and Curcumin on Ordering of DMPC Bilayers2019In: Applied Magnetic Resonance, ISSN 0937-9347, E-ISSN 1613-7507, Vol. 50, no 1-3, p. 511-520Article in journal (Refereed)
    Abstract [en]

    In this work, we compared the effects of curcumin and cholesterol directly competing to insert into the DMPC lipid bilayer during bilayer formation from an initially non-ordered state. 2H and 14N nuclear magnetic resonance spectroscopy showed that curcumin is not embedded deep in the lipid bilayer and interacts mainly with the head group of the lipid. In a more complex system of DMPC/CHOL/CUR, curcumin amplifies the effect of cholesterol on the ordering of lipid acyl chains.

  • 327.
    Kovács, Krisztina
    et al.
    Eötvös Loránd University.
    Kuzmann, E.
    Hungarian Academy of Sciences.
    Homonnay, Z.
    Hungarian Academy of Sciences.
    Vértes, Attila
    Hungarian Academy of Sciences.
    Gunneriusson, Lars
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Sandström, Åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Mössbauer study of synthetic jarosites2008In: Hyperfine Interactions, ISSN 0304-3843, E-ISSN 1572-9540, Vol. 186, no 1-3, p. 69-73Article in journal (Refereed)
    Abstract [en]

    57Fe Mössbauer spectroscopy and PXRD were used to study artificially prepared jarosites with the compositions of KFe3(SO4)2(OH)6 - x F x x = 0 - 1.6 PXRD measurements revealed single phase jarosite samples. All Mössbauer spectra taken at room temperature exhibit a quadrupole doublet corresponding to mineral jarosite. However, at low temperature where the mineral jarosite has a well resolved sextet, the synthetic jarosite even with x = 0 F -  content shows a relaxation transition. The spectra indicate that with increasing F -  concentration, the paramagnetic-antiferromagnetic transition temperature is decreasing. The results can be used in the analysis of artificial jarosites or those formed during biomineralization processes.

  • 328.
    Kumar, Raj
    et al.
    National Centre of Excellence in Analytical Chemistry, University of Sindh, Jamshoro, 76080, Pakistan.
    Sirajuddin,
    National Centre of Excellence in Analytical Chemistry, University of Sindh, Jamshoro, 76080, Pakistan.
    Solangi, Amber Rehana
    National Centre of Excellence in Analytical Chemistry, University of Sindh, Jamshoro, 76080, Pakistan.
    Amin, Sidra
    National Centre of Excellence in Analytical Chemistry, University of Sindh, Jamshoro, 76080, Pakistan.
    Mahar, Ali Muhammad
    National Centre of Excellence in Analytical Chemistry, University of Sindh, Jamshoro, 76080, Pakistan.
    Abro, Muhammad Ishaque
    Department of Metallurgy and Materials Engineering, Mehran University of Engineering and Technology, Jamshoro, Pakistan.
    Shaikh, Tayyaba
    National Centre of Excellence in Analytical Chemistry, University of Sindh, Jamshoro, 76080, Pakistan.
    Shah, Syed Muhammad Usman Ali
    Department of Electronics, NED University of Engineering and Technology, Karachi, Pakistan.
    Tahira, Aneela
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Ibupoto, Zafar Hussain
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Dr. M. A. Kazi Institute of Chemistry, University of Sindh, Jamshoro, 76080, Pakistan.
    Synthesis of Sheet Like Morphology of NiO for Sensitive and Selective Determination of Urea2017In: Sensor Letters, ISSN 1546-198X, E-ISSN 1546-1971, Vol. 15, no 10, p. 803-810Article in journal (Refereed)
    Abstract [en]

    An efficient and simple method has been demonstrated for the synthesis of nickel oxide nanostructures using urea as a capping agent. The nanosheet-like morphology was confirmed by scanning electron microscopy, crystalline nature was studied by using the X-ray diffraction (XRD) and surface area of nanomaterial was investigated by automated sorption analyzer. Then synthesized NiO nanostructures were used to fabricate the surface of glassy carbon electrode (GCE). The electrocatalytic parameters of modified NiO/GCE electrode were investigated by using various techniques such as electrochemical impedance spectroscopy (EIS), square wave voltammetry (SWV), differential pulse voltammetry (DPV), normal pulse voltammetry (NPV) and cyclic voltammetry (CV) and chronoamperometry. Various working experimental conditions were optimized in order to attain the highest sensitivity for the determination of urea and the highest peak current 1032 μA of response were obtained at 100 μM concentration of urea. A linear calibration plot was obtained for peak current versus concentration of urea in the range of 10 μM urea to 80 μM urea with a good detection limit of 2 μM. The proposed working strategy was successfully employed for the estimation of urea in human urine samples and the obtained results are found satisfactory. The newly functional urea sensor can be exploited at large scale as an alternative analytical device beside to the other reported urea sensors

  • 329.
    Kumari, Sangita
    et al.
    Chemical Science Division, CSIR-Indian Institute of Petroleum, Dehradun .
    Mungse, Harshal P.
    Department of Materials Science and Engineering, Kyoto University.
    Gusain, Rashi
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Kumar, Niranjan
    Materials Science Group, Indira Gandhi Centre for Atomic Research, HBNI, Kalpakkam .
    Sugimura, Hiroyuki
    Department of Materials Science and Engineering, Kyoto University.
    Khatri, Om P.
    Chemical Science Division, CSIR-Indian Institute of Petroleum, Dehradun .
    Octadecanethiol-grafted molybdenum disulfide nanosheets as oil-dispersible additive for reduction of friction and wear2017In: FlatChem, ISSN 2452-2627, Vol. 3, p. 16-25Article in journal (Refereed)
    Abstract [en]

    Molybdenum disulfide (MoS2) easily shears at the contact interfaces because of weak interplaner interaction and exhibits high mechanical strength, which promises its potential for tribological applications. However, poor dispersibility of MoS2 in the lube oils has been a great challenge. Herein, a facile and scalable hydrothermal approach is presented to synthesize the MoS2 nanosheets and then chemically functionalized with octadecanethiol (ODT). The structural defects and vacant sulfur sites on the Mo-atoms of MoS2 nanosheets are targeted for grafting of ODT via Mo-S dative linkage. The chemical and structural features of MoS2-ODT are characterized by FTIR, XPS, XRD and HRTEM analyses. The dispersion stability of MoS2-ODT nanosheets in the polyol ester lube oil is examined by UV–Visible spectroscopy. The van der Waals interaction between the octadecyl chain of MoS2-ODT and oleate chains of polyol ester lube oil facilitates the dispersion of MoS2-ODT nanosheets. Tribological results revealed that minute dosing (0.05 mg.mL−1) of thoroughly dispersed MoS2-ODT nanosheets, as an additive to polyol lube oil, significantly reduced the friction and the wear of steel tribo-pair. The uninterrupted supply of MoS2-ODT nanosheets on the tribo-contacts, formation of MoS2 thin film on tribo-interfaces, ease of shearing driven by weak van der Waals interaction between MoS2 lamellae and high mechanical strength of MoS2, collectively enhanced the tribo-performance, when thoroughly dispersed MoS2-ODT was used as an additive to the polyol lube base oil.

  • 330.
    Larsson, Anna-Carin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    A nuclear magnetic resonance study of dialkyldithiophosphate complexes: polycrystalline and surface adsorbed2004Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    31P, 13C and 207Pb NMR were used to characterize different metal (Ni, Zn, Pb) dialkyldithiophosphate complexes. Eight different sodium or potassium dialkyldithiophosphate salts (alkyl groups R=ethyl-, n-propyl, iso-propyl, n- butyl, iso-butyl, sec-butyl, iso-amyl and cyclo-hexyl) were used as starting materials. The metal complexes studied are mononuclear, binuclear, tetranuclear or polynuclear and the structural diversity is reflected in different 31P chemical shifts and chemical shift aniostropies of the complexes. A correlation between the 31P chemical shift tensor principal value d22 and the S-P-S angle of the complexes was revealed. The ligands were also adsorbed on the surface of synthetic ZnS and PbS and studied by 31P CP/MAS NMR: spectra of the dry samples showed that in both cases chemisorption of the ligands on the mineral surfaces occured. The ligands chemisorbed on ZnS have a bridging coordination, while the coordination of the ligand to PbS is terminal. Products of oxidation and hydrolysis were also found on the mineral surfaces; disulfides were detected on the surface of ZnS and monothiophosphates and orthophosphates on the surface of PbS. After three months of storing of the PbS samples, more hydrolysis products were formed as well as precipitated lead(II) dithiophosphate complexes.

  • 331.
    Larsson, Anna-Carin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    A nuclear magnetic resonance study of polycrystalline and surface O, O´-dialkyldithiophosphate complexes2001Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    O, O'-dialkyldithiophosphate (dtp) complexes are known to be useful collectors of e. g. ZnS, PbS and CuS minerals in froth flotation. However, the precise surface chemistry is yet not understood. In this work model systems have been thoroughly studied by both liquid and solid state 31P NMR. Nickel and zinc dtp complexes have been precipitated from aqueous solutions of dtps and metal chlorides. Ionic sodium and potassium salts of eight different dtps have been used. The nickel complexes are known to be mononuclear with only terminal ligands while the zinc complexes are known to be binuclear or polymeric with both terminal and bridging types of ligands. In organic solvents the binuclear complexes dissolve into the mononuclear type which has only terminal ligands. There is also a tetranuclear type of zinc dtp complex where all ligands are bridging. By using solid state CP/MAS and liquid state 31P NMR together with analysis of the chemical shift anisotropy (CSA) it is possible to assign 31P resonance lines to different types of ligands. The least shielded 31P sites in zinc dtp complexes are assigned to the bridging ligands and the most shielded 31P sites to the terminal ligands. By comparing the spectra of precipitated complexes with the spectra of surface complexes it has been possible to assign a bridging coordination between two surface sites and the ligand. Traces of oxidized dtp, bis-(O, O'-dialkyldithio-phosphoryl) disulfide, as well as hydrolyzed dtp have also been detected on the sphalerite surface. The CSA parameters daniso and h are simulated with a Mathematica program and the principal values of the chemical shift tensor, dxx, dyy and dzz, have been calculated for the different compounds. Ligands of the same type have the same type of chemical shift tensor.

  • 332.
    Larsson, Anna-Carin
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Ivanov, Alexander V.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsling, Willis
    Nuclear magnetic resonance spectroscopy studies of mineral surfaces: application in the froth flotation2005In: Centenary of Flotation Symposium Proceedings, The Australian Institute of Mining and Metallurgy , 2005, p. 497-505Conference paper (Refereed)
    Abstract [en]

    Polycrystalline and surface complexes (at synthetic sphalerite, ZnS, and galena, PbS) of zinc(II) and lead(II) ions with eight different O,O'-dialkyldithiophosphate (Dtph) substances have been prepared and comparatively studied by means of 31P CP/MAS NMR spectroscopy. The 31P resonances have been assigned to dithiophosphate groups with terminal S,S'-chelating or bridging coordinations in the mono-, bi-. tetra- and polynuclear complexes respectively. The bridging coordination of two neighbouring zinc(II) ions by O,O '-dialkyldithio-phosphate ligands was established at the surface of synthetic sphalerite. The adsorption mechanism of dialkyldithiophosphate on synthetic galena includes formation of a surface complex as well as surface precipitation. Principally different coordination modes of the reagent were discovered at the surfaces of galena and sphalerite (ie terminal S,S'-chelating coordination to the lead atom). Derivatives of monothiophosphoric and phosphoric acids were displayed as hydrolysis products of dialkyldithiophosphates at synthetic PbS

  • 333.
    Larsson, Anna-Carin
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Hellström, Pär
    Fredriksson, Andreas
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Study of potassium O,O′-dibutyldithiophosphate combining DFT, 31P CP/MAS NMR and infrared spectroscopy2008In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 112, no 46, p. 11777-11783Article in journal (Refereed)
    Abstract [en]

    Dithiophosphates are used in many different industrial applications. To explain their functions and properties in these applications, a fundamental understanding on a molecular level is needed. Potassium O,O′-Dibutyldithiophosphate and its anion have been investigated by means of a combination of DFT and 31P CP/MAS NMR and infrared spectroscopy. Several low-energy conformations were studied by DFT. Three different conformations with significantly different torsion angles of the O-C bond relative to the O-P-O plane were selected for further studies of infrared frequencies and 31P NMR chemical-shift tensors. A good agreement between theoretical and experimental results was obtained, especially when the IR spectra or 31P chemical shift tensor parameters of all three conformations were added, indicating that, because of the low energy difference between the conformations, the molecules are rapidly fluctuating between them.

  • 334.
    Larsson, Anna-Carin
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Ivanov, Alexander V.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsling, Willis
    A 31P CP/MAS NMR study of PbS surface O,O′-dialkyldithiophosphate lead(II) complexes2008In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 327, no 2, p. 370-376Article in journal (Refereed)
    Abstract [en]

    31P CP/MAS NMR spectroscopy was used to study the adsorption of six different O,O′-dialkyldithiophosphate ions on the surface of synthetic galena (PbS). The 31P CP/MAS NMR spectra of the surface lead(II) dithiophosphates were compared with the 31P CP/MAS NMR spectra of polycrystalline lead(II) dithiophosphate complexes of the same ligands. Surface complexation of the dialkyldithiophosphate ions was established on the surface of PbS. A terminal S,S′-chelating coordination is suggested for the surface complexes. The bulkier alkyl groups lead to surface precipitation in addition to the surface adsorption. Derivatives of monothiophosphoric and phosphoric acids were displayed as hydrolysis products of dialkyldithiophosphates on the synthetic PbS, the amount of which depends on the type of alkyl group.

  • 335.
    Larsson, Anna-Carin
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Ivanov, Alexander V.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Gerasimenko, Andrey V.
    Far Eastern Branch of the Russian Academy of Sciences, Vladivostok.
    Forsling, Willis
    Complexation of lead(II) with O,O′-dialkyldithiophosphate ligands: 31P and 13C CP/MAS NMR and single-crystal X-ray diffraction studies2004In: Inorganica Chimica Acta, ISSN 0020-1693, E-ISSN 1873-3255, Vol. 357, no 9, p. 2510-2518Article in journal (Refereed)
    Abstract [en]

    Polycrystalline lead(II) complexes with O,O′-dipropyl- and O,O′-di-cyclo-hexyldithiophosphate ions were prepared and studied by means of 31P, 31C CP/MAS NMR spectroscopy and single-crystal X-ray diffraction. Prepared complexes are characterised by polynuclear structures, in which pairs of dithiophosphate groups asymmetrically link neighbouring lead atoms, forming infinite linear zigzag chains. In spite of the same combined structural function, dithiophosphate ligands in both complexes display structural inequivalence. To characterise the combined structural state of the dialkyldithiophosphate ligands, 31P chemical shift anisotropy parameters, δaniso and η, were estimated from spinning sideband patterns in experimental CP/MAS NMR spectra for each of the two prepared complexes as well as the initial potassium O,O′-dipropyl- and O,O′-di-cyclo-hexyldithiophosphate salts.

  • 336.
    Larsson, Anna-Carin
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Ivanov, Alexander V.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsling, Willis
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Abraham, Anu
    Georgetown University.
    Dios, Angel de
    Georgetown University.
    Correlations between 31P Chemical Shift Anisotropy and Molecular Structure in Polycrystalline O,O'-Dialkyldithiophosphate Zinc(II) and Nickel(II) Complexes: 31P CP/MAS NMR and Ab Initio Quantum Mechanical Calculation Studies2005In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 127, no 7, p. 2218-2230Article in journal (Refereed)
    Abstract [en]

    Different potassium salts and zinc(II) and nickel(II) O,O'-dialkyldithiophosphate complexes were studied by solid-state 31P CP/MAS and static NMR and ab initio quantum mechanical calculations. Spectra were obtained at different spinning frequencies, and the intensities of the spinning sidebands were used to estimate the chemical shift anisotropy parameters. Useful correlations between the shapes of the 31P chemical shift tensor and the type of ligand were found: terminal ligands have negative values of the skew , while bridging and ionic ligands have positive values for this parameter. The experimental results were compared with known X-ray diffraction structures for some of these complexes as well as with ab initio quantum mechanical calculations, and a useful correlation between the δ22 component of the 31P chemical shift tensor and the S-P-S bond angle in the O,O'-dialkyldithiophoshate zinc(II) and nickel(II) complexes was found: δ22 increases more than 50 ppm with the increase of S-P-S bond angle from ca. 100 to 120, while the other two principal values of the tensor, δ11 and δ33, are almost conserved. This eventually leads to the change in sign for in the bridging type of ligand, which generally has a larger S-P-S bond angle than the terminally bound O,O'-dialkyldithiophoshate group forming chelating four-membered P<>Me heterocycles

  • 337.
    Larsson, Anna-Carin
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Ivanov, Alexander V.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Pike, Kevin J.
    Materials and Engineering Science, ANSTO.
    Forsling, Willis
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Solid state 31P and 207Pb MAS NMR studies on polycrystalline O,O′-dialkyldithiophosphate lead(II) complexes2005In: Journal of magnetic resonance, ISSN 1090-7807, E-ISSN 1096-0856, Vol. 177, no 1, p. 56-66Article in journal (Refereed)
    Abstract [en]

    A number of lead(II) O,O′-dialkyldithiophosphate complexes were studied by 13C, 31P, and 207Pb MAS NMR. Simulations of 31P chemical shift anisotropy using spinning sideband analysis reveal a linear relationship between the SPS bond angle and the principal values δ22 and δ33 of the 31P chemical shift tensor. The 31P CSA data were used to assign ligands with different structural functions. In the cases of Adiethyldithiophosphate and di-iso-butyldithiophosphate lead(II) complexes, 2J (31P, 207Pb)-couplings were resolved and used to confirm the suggested assignment of the ligands. The SIMPSON computer program was used to calculate 31P and 207Pb spectral sideband patterns.

  • 338.
    Larsson, Anna-Carin
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Ivanov, Maxim A.
    Institute of Geology and Nature Management, Far East Branch, Russian Academy of Sciences, Blagoveshchensk.
    Gerasimenko, Andrey V.
    Institute of Chemistry, Far Eastern Branch of the Russian Academy of Sciences, 690022, Vladivostok.
    Ivanov, Alexander V.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Synthesis of four different antimony(III) O,O’-dialkyldithiophosphates: characterization by 31P CP/MAS NMR, single crystal X-ray diffraction, and adsorption at a stibnite surface (Sb2S3)2012In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 368, no 1, p. 488-495Article in journal (Refereed)
    Abstract [en]

    Four different dialkyldithiophosphate (DTP) ions, (RO)2PSS– (R = C3H7, iso-C3H7, iso-C4H9, cyclo-C6H11) have been adsorbed on the surface of synthetically prepared stibnite, Sb2S3, and studied by means of 31P CP/MAS NMR. Corresponding individual [Sb{(S2P(OR)2}3] complexes have also been synthesized and used for comparison with the surface adsorbed DTP species. The results show that a low concentration of collector at the surface leads to a chemisorbed monolayer of DTP on the mineral surface. At high concentration of DTP, a surface precipitate of Sb(DTP)3 is formed. 31P CP/MAS NMR and chemical shift anisotropy data indicate that the S–P–S bite angle of the chemisorbed DTP groups on the surface is larger than in the corresponding precipitated complexes and the coordination of the ligands differ. Using single-crystal X-ray diffraction technique, the molecular structure of a solvated form of crystalline O,O’-di-cyclo-hexyldithiophosphate antimony(III) complex has been resolved. In this novel molecular structure, the central antimony atom S,S’-anisobidentately coordinates three structurally non-equivalent DTP groups and, therefore, the geometry of the [SbS6] chromophore can be approximated by a distorted octahedron. Besides that, useful correlations between 31P CSA parameters and structural data on this complex were also established.

  • 339.
    Larsson, Anna-Carin
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Study on potassium iso-propylxanthate and its decomposition products: experimental 13C CP/MAS NMR combined with DFT calculations2011In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 115, no 8, p. 1396-1407Article in journal (Refereed)
  • 340.
    Lendel, Christofer
    et al.
    Department of Chemistry and Biotechnology, Swedish University of Agricultural Sciences (SLU).
    Bjerring, Morten
    Department of Chemistry and Biotechnology, Swedish University of Agricultural Sciences (SLU).
    Dubnovitsky, Anatoly
    Department of Chemistry and Biotechnology, Swedish University of Agricultural Sciences (SLU).
    Kelly, Robert T.
    Department of Physics, Warwick University, Coventry.
    Filippov, Andrei
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Nielsen, Niels Chr.
    Center for Insoluble Protein Structures (inSPIN), Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, Aarhus University.
    Härd, Torleif
    Department of Chemistry and Biotechnology, Swedish University of Agricultural Sciences (SLU).
    A Hexameric Peptide Barrel as Building Block of Amyloid-β Protofibrils2014In: Angewandte Chemie, ISSN 0044-8249, E-ISSN 1521-3757, Vol. 126, no 47, p. 12970-12974Article in journal (Refereed)
    Abstract [en]

    Oligomeric and protofibrillar aggregates formed by the amyloid-β peptide (Aβ) are believed to be involved in the pathology of Alzheimer’s disease. Central to Alzheimer pathology is also the fact that the longer Aβ42 peptide is more prone to aggregation than the more prevalent Aβ40. Detailed structural studies of Aβ oligomers and protofibrils have been impeded by aggregate heterogeneity and instability. We previously engineered a variant of Aβ that forms stable protofibrils and here we use solid-state NMR spectroscopy and molecular modeling to derive a structural model of these. NMR data are consistent with packing of residues 16 to 42 of Aβ protomers into hexameric barrel-like oligomers within the protofibril. The core of the oligomers consists of all residues of the central and C-terminal hydrophobic regions of Aβ, and hairpin loops extend from the core. The model accounts for why Aβ42 forms oligomers and protofibrils more easily than Aβ40.

  • 341.
    Lendel, Christofer
    et al.
    Department of Chemistry and Biotechnology, Swedish University of Agricultural Sciences (SLU).
    Bjerring, Morten
    Department of Chemistry and Biotechnology, Swedish University of Agricultural Sciences (SLU).
    Dubnovitsky, Anatoly
    Department of Chemistry and Biotechnology, Swedish University of Agricultural Sciences (SLU).
    Kelly, Robert T.
    Department of Physics, Warwick University, Coventry.
    Filippov, Andrei
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Nielsen, Niels Chr.
    Center for Insoluble Protein Structures (inSPIN), Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, Aarhus University.
    Härd, Torleif
    Department of Chemistry and Biotechnology, Swedish University of Agricultural Sciences (SLU).
    A Hexameric Peptide Barrel as Building Block of Amyloid-β Protofibrils2014In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 53, no 47, p. 12756-12760Article in journal (Refereed)
    Abstract [en]

    Oligomeric and protofibrillar aggregates formed by the amyloid-β peptide (Aβ) are believed to be involved in the pathology of Alzheimer’s disease. Central to Alzheimer pathology is also the fact that the longer Aβ42 peptide is more prone to aggregation than the more prevalent Aβ40. Detailed structural studies of Aβ oligomers and protofibrils have been impeded by aggregate heterogeneity and instability. We previously engineered a variant of Aβ that forms stable protofibrils and here we use solid-state NMR spectroscopy and molecular modeling to derive a structural model of these. NMR data are consistent with packing of residues 16 to 42 of Aβ protomers into hexameric barrel-like oligomers within the protofibril. The core of the oligomers consists of all residues of the central and C-terminal hydrophobic regions of Aβ, and hairpin loops extend from the core. The model accounts for why Aβ42 forms oligomers and protofibrils more easily than Aβ40.

  • 342. Lidström-Larsson, Margareta
    Orientation of collectors adsorbed at the ZnS/solution interface2003Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The separation and concentration of minerals by flotation is a well-known industrial process. In this process collectors are used to increase the hydrophobicity of the surfaces of the minerals. Still there is a lot to find out about adsorption mechanism, organisation, and orientation of the adsorbed collectors, to be able to improve the characteristics of the collectors or to design new ones. In this work the organisation and orientation of sulphide mineral collectors adsorbed on a ZnS surface have been studied by the FTIR-ATR (attenuated total reflection) technique. The collectors used in this study are heptyl xanthate, O,O-dibutyldithiophosphate, and 2-mercaptobenzothiazole. The adsorbed collectors were studied both in contact with air and exposed to water. The orientation could be determined by using polarized light and the dichroic ratio. The adsorption and orientation of heptyl xanthate on germanium has also been studied, mainly because Ge is a suitable ATR-crystal on which ZnS or other sulphide minerals may be precipitated and used for future studies of mineral surfaces. In flotation copper activation is used to increase the flotability of minerals. How this affect the orientation, as well as how minimizing the oxygen content of the solutions affect the adsorption have been investigated. The alkyl chains of adsorbed heptyl xanthate tilted approximately 44 degrees from the normal of the surface when the adsorbed layer was in contact with air. When the adsorbed layer was in contact with water the tilt angle increased to about 50 degrees, and the order of the adsorbed layer decreased according to the shift of the asymmetric methylene stretch to higher frequency. Dixanthogen formed during the adsorption process on ZnS but not on Ge. The Germanium surface resulted in an adsorbed heptyl xanthate monolayer with the highest order and a tilt angle of about 47 degrees from the surface normal when the adsorbed layer was in contact with water. Besides the information on orientation of collectors this study has given knowledge about the coordination of xanthate to ZnS surfaces and reactions that may occur in the interface between minerals and water.

  • 343.
    Lidström-Larsson, Margareta
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Sulphide mineral collectors adsorbed on a ZnS internal reflection element: an infrared linear dichroism study2000Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Separation and concentration of minerals by flotation is a well-known industrial process. In this process collector chemicals are used to modify the mineral surface to increase the hydrophobicity of the mineral particles. Still there is a lot to find out about adsorption mechanisms, orientation and organization of the adsorbed collectors on the surfaces to be able to improve the characteristics of the collectors or todesign new ones. In this work, the structure and orientation of sulphide mineral collectors adsorbed on a ZnS surface have been studied by the FTIR-ATR technique. The collectors that have been studied are heptylxanthate (R-CS2-, R = O-C7H15), O,O-dibutyldithiophosphate, 2-mercaptobenzothiazole and a mixture of 2-mercaptobenzothiazole and O,O-dibutyldithiophosphate. The adsorbed layer was prepared by self-assembly from solution or by spraying the solution onto the surfaces of the ATR-crystal for a short time. By using polarized light and the dichroic ratio a quantitative determination of the orientation of heptylxanthate could be performed. The tilt angle from the normal of the surface was found to be approximately 44 degrees. From the spectra it was concluded that the adsorbed species on the ZnS surface is a mixture between heptylxanthate and diheptyldixanthogen. A bridging coordination of the adsorbed heptylxanthate is proposed. The difference between the absorbance of the s-polarized light and p-polarized light was used to draw conclusions about the orientation of O,O-dibutyldithiophosphate and 2-mercaptobenzothiazole adsorbed on ZnS. The collectors are mixed in the flotation process and the influence on the orientation of O,O-dibutyldithiophosphate and 2-mercaptobenzothiazole when adsorbing from a mixture of the two collectors is also reported. In ATR-experiments very small amounts of substances are detected and problem due to contamination of the surfaces and the adsorbed thin film can be severe. Such problems encountered in the present work are described and discussed.

  • 344. Lidström-Larsson, Margareta
    et al.
    Fredriksson, Andreas
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Direct observation of a self-assembled monolayer of heptyl xanthate at the germanium/water interface: a polarized FTIR study2004In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 273, no 2, p. 345-349Article in journal (Refereed)
    Abstract [en]

    The adsorption of heptyl xanthate on germanium has been studied by the attenuated total reflection (ATR) technique. Polarized infrared light was used in situ to determine the average orientation of the alkyl chain in heptyl xanthate adsorbed at the germanium/solution interface. Spectra reveal the formation of closely packed xanthate ions with the alkyl chains in the all-trans conformation. The average tilt angle of the alkyl chains of heptyl xanthate was approximately 47° from the surface normal.

  • 345. Lidström-Larsson, Margareta
    et al.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Reversible phase transition in Zn₂(O,O-di(cyclohexyl)dithiophosphate)₄, studied by Raman spectroscopy and compared with NMR results2004In: Vibrational Spectroscopy, ISSN 0924-2031, E-ISSN 1873-3697, Vol. 34, no 2, p. 243-246Article in journal (Refereed)
    Abstract [en]

    It was recently shown by solid state ³¹P NMR spectroscopy that the number of phosphorous signals from the complex Zn₂(O,O-di(cyclohexyl)DTP)₄ varied reversibly with the temperature. According to the present study, Raman spectra of the same metal complex were also temperature dependent. Spectral features affected by the temperature changed reversibly upon raising and lowering the temperature. It was shown that conformational change of the hexyl rings and the P---O---C entities occurred in the temperature range between 40 and 55°C.

  • 346. Lidström-Larsson, Margareta
    et al.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsling, Willis
    Structure and orientation of collectors adsorbed at the ZnS/water interface2001In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 242, no 1, p. 25-30Article in journal (Refereed)
    Abstract [en]

    The adsorption of O,O-dibutyldithiophosphate and 2-mercaptobenzothiazole on the surface of ZnS has been studied by using the attenuated total reflection (ATR) technique. By utilizing polarized infrared radiation, we got qualitative information about the orientation of the adsorbed collectors. The difference between the absorbance of the s-polarized light and the absorbance of p-polarized light was used to draw conclusions about the orientation. The influence on the orientation of O,O-dibutyldithiophosphate and 2-mercaptobenzothiazole when adsorbing from a mixture of the two collectors is also reported, as well as the influence of these collectors on the hydrophobicity of the ZnS surface obtained by contact angle measurements.

  • 347. Lidström-Larsson, Margareta
    et al.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsling, Willis
    Xanthate adsorbed on ZnS studied by polarized FTIR-ATR spectroscopy2000In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 16, no 21, p. 8129-8133Article in journal (Refereed)
    Abstract [en]

    The structure and orientation of heptylxanthate adsorbed on a ZnS surface have been studied by the FTIR-ATR technique. By using polarized light and the dichroic ratio, we found the average tilt angle to be approximately 44 degrees. The adsorbed layer studied was prepared by self-assembly from solution or by spraying the solution onto the surfaces of the ATR crystal for a short time and then rinsing with water. From the spectra we can conclude that there is a mixture of adsorbed heptylxanthate and formed diheptyldixanthogen on the ZnS surface. A bridging coordination of the adsorbed heptylxanthate is proposed.

  • 348.
    Lindgren, M.
    et al.
    Linköping University.
    Eriksson, R.
    Benetis, N. P.
    Antzutkin, Oleg
    The [H-2(8)]THF radical-cation in CF3CCL3 AND CFCL3: an EPR and ENDOR study1993In: Journal of the Chemical Society. Perkin Transactions 2 (2001), ISSN 1472-779X, E-ISSN 1364-5471, no 11, p. 2009-2014Article in journal (Refereed)
    Abstract [en]

    The structure and dynamics of the radical cation of deuteriated tetrahydrofuran ([H-2(8)]THF) stabilized in the freon matrices CFCl3 and CF3CCl3 have been investigated by means of EPR and ENDOR spectroscopy. The EPR and ENDOR results of the rigid structure give two pairs of strongly interacting beta-deuterium hf splittings [a(D) = 1.36 (2 D) and a(D)) = 0.60 mT (2 D)] consistent with the protonated analogue [Kubodera et al., J. Phys. Chem., 1 981, 85, 2583 (ref. 1)]. An additional hf splitting (0.9-1.1 mT) assigned to the matrix fluorine was resolved above ca. 110 K in CFCl3. The temperature dependent EPR lineshapes (77-145 K) involving the exchange between four coupled (l = 1) nuclei have been analysed. A two-site model explained qualitatively the alterating line-widths at intermediate temperatures and resulted in an activation energy of ca. 1.7 kcal mol-1 A non-perturbative approach adopting a four-site model to account for puckering motion was tested. The dynamics were also manifested as a reversible temperature effect for the ENDOR. The relative abundance of resonances due to an averaged (hf) structure become predominant as the temperature is increased.

  • 349. Lindström, E. Börje
    et al.
    Gunneriusson, Lars
    Thermophilic bioleaching of arsenopyrite using Sulfolobus and a semi-continuous laboratory procedure1990In: Journal of Industrial Microbiology & Biotechnology, ISSN 1367-5435, E-ISSN 1476-5535, Vol. 5, no 6, p. 75-82Article in journal (Refereed)
    Abstract [en]

    A laboratory equipment for pumping slurries is described. The pumping is performed semi-continuously by using a plastic syringe, a set of different valves, and a programmable electronic unit. The reproducibility of the pumping is demonstrated. Bioleaching of a gold-containing arsenopyrite slurry was done withSulfolobus at 70°C using the semi-continuous procedure and with a retention time of 100 h for the mineral. Arsenic was completely released at a rate of 109 mg l-1 h-1. The gold recovery is related to the amount of iron and arsenic dissolved and is shown to have a correlation factor of approximately one relative to the release of arsenic.

  • 350.
    Liu, Wenxin
    Luleå tekniska universitet.
    A comparative study of natural illites from different origins1998Licentiate thesis, comprehensive summary (Other academic)
45678910 301 - 350 of 595
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf