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  • 1.
    Burks, Terrance
    et al.
    Department of Materials and NanoPhysics, Royal Institute of Technology (KTH).
    Avila, Marta
    Department of Materials and NanoPhysics, Royal Institute of Technology (KTH).
    Akhtar, Farid
    Department of Materials and Environmental Chemistry, Stockholm University.
    Göthelid, Mats
    Department of Materials and NanoPhysics, Royal Institute of Technology (KTH).
    Lansåker, Pia C
    Department of Engineering Sciences, The Ångström Laboratory, Uppsala University.
    Toprak, Muhammet S
    Department of Materials and NanoPhysics, Royal Institute of Technology (KTH).
    Muhammed, Mamoun
    Department of Materials and NanoPhysics, Royal Institute of Technology (KTH).
    Uheida, Abdusalam
    Department of Materials and NanoPhysics, Royal Institute of Technology (KTH).
    Studies on the adsorption of chromium (VI) onto 3-Mercaptopropionic acid coated superparamagnetic iron oxide nanoparticles2014In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 425, p. 36-43Article in journal (Refereed)
  • 2. Carabante, Ivan
    et al.
    Grahn, Mattias
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    In situ ATR-FTIR studies on the competitive adsorption of arsenate and phosphate on ferrihydrite2010In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 351, no 2, p. 523-531Article in journal (Refereed)
    Abstract [en]

    In the present study, in-situ ATR-FTIR spectroscopy was used for the first time to study the competitive adsorption of phosphate and arsenate on ferrihydrite. Deuterium oxide was used as solvent to facilitate the interpretations of recorded infrared spectra.It was found that arsenate and phosphate adsorbed more strongly at lower pD values, showing similarities in the adsorption behavior as a function of pD. However, arsenate complexes were found to be more strongly adsorbed than phosphate complexes in the pD range studied. About five times higher concentration of phosphate in solution was needed to reduce the absorbance due to pre-adsorbed arsenate to the same relative level as for pre-adsorbed phosphate, which was desorbed using a solution containing equal (molar) concentrations in arsenate and phosphate. At pD 4, two phosphate complexes were adsorbed on the iron oxide, one deuterated and one de-deuterated. When phosphate was pre-adsorbed and arsenate subsequently added to the system, the deuterated phosphate complex desorbed rapidly while the de-deuterated phosphate complex was quite stable. At pD 8.5, only the de-deuterated phosphate complex was adsorbed on the iron oxide. Moreover, the arsenate adsorbed was also predominantly de-deuterated as opposite to the arsenate adsorbed at pD 4. During the substitution experiments the configuration of these complexes on the iron oxide surface did not change. To the best of our knowledge, this is the first time this difference in stability of the different phosphate complexes is reported and shows the power of employing in-situ spectroscopy for this kind of studies.

  • 3.
    Di Mauro, Alessandro
    et al.
    Istituto per la Microelettronica e i Microsistemi, IMM-CNR, Via S. Sofia 64, 95123 Catania.
    Landström, Anton
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Concina, Isabella
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Impellizzeri, Giuliana
    Istituto per la Microelettronica e i Microsistemi, IMM-CNR, Via Monteroni, 73100 Lecce.
    Privitera, Vittorio
    Istituto per la Microelettronica e i Microsistemi, IMM-CNR, Via S. Sofia 64, 95123 Catania, Italy.
    Epifani, Mauro
    Istituto per la Microelettronica e i Microsistemi, IMM-CNR, Via Monteroni, 73100 Lecce, Italy.
    Surface Modification by Vanadium Pentoxide Turns Oxide Nanocrystals into Powerful Adsorbents of Methylene Blue2019In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 533, p. 369-374Article in journal (Refereed)
    Abstract [en]

    Hypothesis: If nanocrystals of such semiconductor as SnO2 and TiO2, which are not known as powerful adsorbents, have their surface modified by layer of V2O5, how will the adsorption properties be affected? Answering this question would provide a new set of surface properties to be designed by surface engineering of oxide nanocrystals.

    Experiments: SnO2 and TiO2 colloidal nanocrystals were prepared by coupling sol-gel and solvothermal synthesis. By co-processing with V chloroalkoxide and subsequent heat-treatment at 400-500 °C, surface deposition of V2O5 layers was obtained. The methylene blue adsorption onto the prepared materials was tested and compared with the pure oxide supports. Cycling of the materials and analysis of the adsorption process was also investigated.

    Findings: The V-modified nanocrystals extracted ∼ 80% methylene blue from 1.5 x 10-5 M aqueous solution after 15 min only, contrarily to pure materials, which took up only 30% of the dye even after 120 min. Comparison with pure commercial V2O5 showed that the peculiar adsorption properties were imparted by the surface deposition of the V2O5-like layers. This report demonstrates that new classes of adsorbing materials can be conceived by suitably coupling different metal oxides.

  • 4.
    Du, Qing
    et al.
    Luleå tekniska universitet.
    Sun, Zhongxi
    Luleå tekniska universitet.
    Forsling, Willis
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Hongxiao, Tang
    Research Center for Eco-Environmental Sciences, Academia Sinica.
    Acid-base properties of aqueous illite surfaces1997In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 187, no 1, p. 221-231Article in journal (Refereed)
    Abstract [en]

    In this paper, the acid-base properties of illite/water suspensions are examined using the constant capacitance surface complexation model. On the basis of results of potentiometric titrations and solubility experiments, we conclude that the proton reactions in the supernatants of illite suspensions can be successfully represented by proton reactions of Al(H2O)63+and Si(OH)4in water solutions. For illustrating the acidic characteristics of aqueous illite surfaces, two surface protonation models are proposed: (1) one site-one pKamodel, ≡SOH ≡SO-+ H+, pKaint= 4.12-4.23; (2) two sites-two pKas model, ≡SIOH ≡SIO-+ H+, pKintaI= 4.17-4.44, and ≡SIIOH ≡SIIO-+ H+, [dipKintaII= 6.35-7.74. Evaluation of these two models indicates that both of them can give good descriptions of the experimental data of systems with different illite concentrations and ionic strengths and that the one site-one pKamodel can be considered as a simplification of the two sites-two pKas model. Since both models assume only deprotonation reactions at the illite surfaces, they suggest that the surface behavior of the illite is similar to that of amorphous SiO2. Model assumptions, experimental procedures, and evaluative criteria are detailed in the paper.

  • 5.
    Du, Qing
    et al.
    Luleå tekniska universitet.
    Sun, Zhongxi
    Luleå tekniska universitet.
    Forsling, Willis
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Tang, Hongxiao
    Research Center for Eco-Environmental Sciences, Academia Sinica.
    Adsorption of copper at aqueous illite surfaces1997In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 187, no 1, p. 232-242Article in journal (Refereed)
    Abstract [en]

    In this paper, we conducted potentiometric titrations, batch adsorption experiments and FT-IR analysis to study the uptake of copper in illite/water suspensions and then applied the constant capacitance surface complexation model to interpret the reaction mechanism at the aqueous illite surfaces. Our research shows that the copper adsorption at these surfaces is strongly dependent on pH and that the adsorption causes a deprotonation of surface groups. We propose that the uptake of copper in the carbonate-free illite suspensions can be explained by the formation of mononuclear surface complexes, ≡SOCu+and ≡SOCuOH, and a multinuclear surface complex, ≡SOCu2(OH)2+, followed by the formation of a bulk precipitate, Cu(OH)2(s), or a surface precipitate, ≡SOCu2(OH)3(sp). For the illite suspensions containing carbonates, we propose that the copper-illite interaction can be depicted by the formation of mononuclear surface complexes, ≡SOCu+and ≡SOCuOH, followed by the formation of a copper hydroxylcarbonate precipitate, Cu2(OH)2CO3(s), rather than a copper hydroxide precipitate. The existence of Cu2(OH)2CO3(s) in the carbonate-containing illite suspensions was identified by FT-IR analysis

  • 6. Fredriksson, Andreas
    et al.
    Lidström-Larsson, Margareta
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    n-Heptyl xanthate adsorption on a ZnS layer synthesized on germanium: an in situ attenuated total reflection IR study2005In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 286, no 1, p. 1-6Article in journal (Refereed)
    Abstract [en]

    Adsorption of n-heptyl xanthate on synthesized zinc sulfide was followed in situ by monitoring the methylene absorption band at 2925 cm-1. The zinc sulfide surface used in the adsorption experiments was synthesized on a germanium internal reflection element using the chemical bath deposition method. Characterization of the adsorbent surface was performed by X-ray photoelectron spectroscopy. The time needed to reach adsorption equilibrium varied with the initial concentration of the aqueous potassium heptyl xanthate solution. The amount of adsorbed xanthate ions increased with the concentration of the solution within the range studied (10 μM-50 mM). The experimental data are reasonably well described by the Langmuir adsorption isotherm. Polarized infrared attenuated total reflection (ATR) was used to determine the average orientation of the heptyl chains by measuring the absorbance of the infrared beam polarized perpendicularly and parallely to the plane of incidence. Measured absorbances were corrected for contribution from heptyl xanthate in bulk solution.

  • 7.
    Gai, Fangyuan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. School of Chemistry and biology, Advanced Institute of Materials Science, Changchun University of Technology, Changchun.
    Li, Yin
    School of Chemistry and biology, Advanced Institute of Materials Science, Changchun University of Technology, Changchun.
    Fan, Mengmeng
    School of Chemistry and biology, Advanced Institute of Materials Science, Changchun University of Technology, Changchun.
    Li, Ling
    School of Chemistry and biology, Advanced Institute of Materials Science, Changchun University of Technology, Changchun.
    Grahn, Johnny
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Au, Yuhui
    School of Chemistry and biology, Advanced Institute of Materials Science, Changchun University of Technology, Changchun.
    Yang, Xudong
    School of Chemistry and biology, Advanced Institute of Materials Science, Changchun University of Technology, Changchun.
    Wu, Xuming
    School of Chemistry and biology, Advanced Institute of Materials Science, Changchun University of Technology, Changchun.
    Liu, Yunling
    tate Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun.
    Huo, Qisheng
    tate Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun.
    Novel Schiff base (DBDDP) selective detection of Fe (III): Dispersed in aqueous solution and encapsulated in silica cross-linked micellar nanoparticles in living cell2018In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 514, p. 357-363Article in journal (Refereed)
    Abstract [en]

    This work demonstrated the synthesis of (4E)-4-(4-(diphenylamino)benzylideneamino)-1,2-dihydro-1,5- dimethyl-2-phenylpyrazol-3-one (DBDDP) for Fe (III) detection in aqueous media and in the core of silica cross-linked micellar nanoparticles in living cells. The free DBDDP performed fluorescence enhancement due to Fe (III)-promoted hydrolysis in a mixed aqueous solution, while the DBDDP-doped silica cross-linked micellar nanoparticles (DBDDP-SCMNPs) performed an electron-transfer based fluorescence quenching of Fe (III) in living cells. The quenching fluorescence of DBDDP-SCMNPs and the concentration of Fe (III) exhibited a linear correlation, which was in accordance with the Stern-Volmer equation. Moreover, DBDDP-SCMNPs showed a low limit of detection (LOD) of 0.1 ppm and an excellent selectivity against other metal ions. Due to the good solubility and biocompatibility, DBDDP-SCMNPs could be applied as fluorescence quenching nanosensors in living cells.

  • 8. Gunneriusson, Lars
    Composition and stability of Cd(II)-chloro and -hydroxo complexes at the goethite (α-FeOOH)/water interface1994In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 163, no 2, p. 484-492Article in journal (Refereed)
    Abstract [en]

    The surface complexation of Cd(II) to goethite (α-FeOOH) in the absence and presence of chloride has been investigated. Equilibrium measurements have been performed as potentiometric titrations at 298.2 K, within the range 2.7 < -log[H+] < 9.0, in 0.1 mol dm-3 NaNO3, NaCl, and a mixture (1:1) of both these media. The data were evaluated according to the electrostatic constant capacitance model, including a previously determined model for the acid-base reactions of the goethite surface. The following model is presented (errors ± 3σ): equivalent FeOH + Cd2+ <=> equivalent FeOHCd2+; log β0,1,1,0s(int) = 6.43 ± 0.05; equivalent FeOH + Cd2+ <=> equivalent FeOCd+ + H+; log β-1,1,1,0s(int) = -2.22 ± 0.05; equivalent FeOH + Cd2+ + H2O <=> equivalent FeOCdOH + 2H+; log β-2,1,1,0s(int) = -12.01 ± 0.08; equivalent FeOH + Cd2+ + Cl- <=> equivalent FeOHCdCl+; log β0,1,1,1s(int) = 6.85 ± 0.02; equivalent FeOH + Cd2+ + Cl- <=> equivalent FeOCdCl + H+; log β-1,1,1,1s(int) = -2.38 ± 0.04. In the presence of excess Cd(II) ions to surface hydroxyl groups, it was found that the results could be explained by including bulk precipitation of Cd(OH)2. The calculated formation constant for Cd(OH)2 (s) was within an order of magnitude from the literature value for the stable phase in solution, β-Cd(OH)2. Modeling of natural water conditions showed that relatively high concentrations of goethite have to be present to influence the concentrations of Cd(II). Furthermore, the reactions were found to be nearly fully reversible, which means that adsorbed Cd(II) can be released to the environment by a relatively moderate lowering of pH

  • 9.
    Gunneriusson, Lars
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Baxter, Douglas
    Emteborg, Håkan
    Umeå universitet.
    Complexation at low concentrations of methyl and inorganic mercury(II) to a hydrous goethite (α-FeOOH) surface1995In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 169, no 2, p. 262-266Article in journal (Refereed)
    Abstract [en]

    Surface complexation of inorganic mercury(II) and monomethyl mercury onto a hydrous goethite surface was studied. The pH was varied and low total mercury concentrations were used. The inorganic mercury distribution was evaluated based on the constant capacitance concept. The surface complexation model was derived using about 103 times higher mercury concentrations. A model calculation describing the surface complexation of methyl mercury was also performed

  • 10. Gunneriusson, Lars
    et al.
    Sjöberg, Staffan
    Surface Complexation in the H+-Goethite (α-FeOOH)-Hg (II)-Chloride System1993In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 156, no 1, p. 121-128Article in journal (Refereed)
  • 11.
    Gärd, Rune
    et al.
    Luleå University of Technology.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsling, Willis
    Spectroscopic Studies of Dextrin Adsorption onto Colloidal ZnS1997In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 194, no 2, p. 319-325Article in journal (Refereed)
    Abstract [en]

    The interaction of dextrin with colloidal ZnS has been investigated through adsorption studies and FT-IR spectroscopy in the 4000-400 cm-1range. The adsorption capacity is estimated to be around 1 mg/m2. Maximum adsorption is found to be constant below pH ≈7 and to increase with pH at least up to pH 11. Eighty percent of maximum adsorption is achieved within 3 min after addition of the dextrin. Based upon FT-IR studies and titration data, an adsorption mechanism is proposed.

  • 12.
    Gärd, Rune
    et al.
    Luleå University of Technology.
    Sun, Zhong-Xi
    Luleå University of Technology.
    Forsling, Willis
    FT-IR and FT-Raman studies of colloidal ZnS 1.: Acidic and alkaline sites at the ZnS/water interface1995In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 169, no 2, p. 393-399Article in journal (Refereed)
    Abstract [en]

    The surface complexes of colloidal ZnS have been studied using FT-IR and FT-Raman techniques. The absorption bands at 2500 and 1475-1375 cm-1, which are identified as the S-H bond and the Zn-OHCO2 entity, respectively, can be observed under varied conditions of sample stoichiometry and pH. The correlation between surface spectra and the complexation model is evaluated. The relation between the intensities of FT-IR and FT-Raman spectra and particle size is discussed.

  • 13.
    Jarlbring, Mathias
    et al.
    Luleå tekniska universitet.
    Gunneriusson, Lars
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsling, Willis
    Characterisation of the protolytic properties of synthetic carbonate free fluorapatite2005In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 285, no 1, p. 206-211Article in journal (Refereed)
    Abstract [en]

    The acid/base surface properties of carbonate free fluorapatite (Ca 5(PO4)3F) have been characterised using high precision potentiometric titrations and surface complex modelling. Synthetic carbonate free fluorapatite was prepared and characterised by SEM, XRD, FT-IR and FT-Raman. The specific surface area was determined to be 17.7±1.2 m2g-1 with BET (N2 adsorption). The titrations were performed at 25±0.2°C, within the pH range 5.7-10.8, in 0.10 and 0.50 mol dm -3 NaNO3 ionic media. Experimental data were interpreted using the constant capacitance model and the software FITEQL 4.0. The surface equilibria: S1OH ⇄ S1O- + H+ lgβ-110s (int), S2OH ⇄ S2O- + H+ lgβ-101s (int) well describes the surface characteristics of synthetic fluorapatite. The equilibrium constants obtained were: lgβ-110s(int)=-6.33±0.05 and lgβ-101s(int)=-8.82±0.06 at I=0.10 moldm-3. At the ionic strength 0.50 mol dm-3, the equilibrium constants were slightly shifted to: lgβ-110s(int)=-6.43±0.05 and lgβ-101s(int)=-8.93±0.06. The number of active surface sites, Ns, was calculated from titration data and was found to be 2.95 and 2.34 sites nm-2 for the ionic strengths 0.10 and 0.50 mol dm-3, respectively. pHPZC or the IEP was found to be 5.7 from Z-potential measurements

  • 14.
    Jarlbring, Mathias
    et al.
    Luleå tekniska universitet.
    Gunneriusson, Lars
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Hussmann, Björn
    Technische Universität Hamburg-Harburg.
    Forsling, Willis
    Surface complex characteristics of synthetic maghemite and hematite in aqueous suspensions2005In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 285, no 1, p. 212-217Article in journal (Refereed)
    Abstract [en]

    The acid-base properties of the maghemite (γ-Fe2O3)/water and hematite (α-Fe2O3)/water interfaces have been studied by means of high precision potentiometric titrations and the experimental results are evaluated as surface complexation reactions. Synthetic maghemite and hematite were prepared and characterized using a combination of SEM, FT-IR and XRD. The specific surface area of the minerals was determined by the BET method. The titrations were performed at 25.0± 0.2°C within the range 2.8 < pH < 8.5 NaNO3 ionic medium giving total ionic strengths of 0.10 and 0.50 mol dm-3 in both systems. Experimental data were evaluated using the constant capacitance model. The total proton exchange capacities of the solids were determined by saturation of the surfaces with excess acid. The number of protonated surface sites per nm2 was found to be 0.81 ± 0.05 and 1.03 ± 0.04 for maghemite, at I = 0.10 and 0.50 mol dm-3, respectively. The IEP for maghemite was determined from the ζ-potential using a Zetasizer 4 instrument.

  • 15.
    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.

  • 16.
    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.

  • 17.
    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, Minerals and Metallurgical Engineering.
    Kota, Hanumantha Rao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    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.
    Flotation selectivity of novel alkyl dicarboxylate reagents for apatite-calcite separation2015In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 445, p. 40-47Article in journal (Refereed)
    Abstract [en]

    The investigation aims to demonstrate the conceptual thoughts behind developing mineral specific reagents for use in flotation of calcium containing ores. For this purpose, a series of dicarboxylate-based surfactants with varying distance between the carboxylate groups (one, two or three methylene groups) was synthesized. A surfactant with the same alkyl chain length but with only one carboxylate group was also synthesized and evaluated. The adsorption behavior of these new reagents on pure apatite and pure calcite surfaces was studied using Hallimond tube flotation, FTIR and ζ potential measurements. The relation between the adsorption behavior of a given surfactant at a specific mineral surface and its molecular structure over a range of concentrations and pH values, as well as the region of maximum recovery, was 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. For example, out of the four compounds synthesized, only the one where the carboxylate groups were separated by a single methylene group floated apatite but not calcite, whereas calcite was efficiently floated with the monocarboxylic reagent, but not with the other reagents synthesized. This selective adsorption of a given surfactant to a particular mineral surface relative to other mineral surfaces as evidenced in the flotation studies was substantiated by ζ potential and infra-red spectroscopy data

  • 18. Kundu, Tarun
    et al.
    Rao, K. Hanumantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Parker, S.C.
    School of Chemistry, University of Bath.
    Atomistic simulation studies of magnetite surface structures and adsorption behavior in the presence of molecular and dissociated water and formic acid2006In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 295, no 2, p. 364-373Article in journal (Refereed)
    Abstract [en]

    Static energy minimization techniques have been used to elucidate the surface structures of magnetite crystals in pure and hydroxylated forms. Adsorption energy values in the presence of molecular water, dissociate water and simple carboxylic group molecule (formic acid) are calculated and we found that the carboxylic group do not adsorb strongly in most of the pure and hydroxylated surfaces in comparison to water. Since the associated calcium minerals are floated from magnetite using fatty acid collector, our calculations corroborate the flotation practice of removing these impurity minerals from magnetite.

  • 19.
    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.

  • 20.
    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.

  • 21. 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.

  • 22. 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.

  • 23.
    Liu, Peng
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Surface adsorption and self assembly of Cu(II) ions on TEMPO-oxidised cellulose nanofibers in aqueous media2016In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 464, p. 175-182Article in journal (Refereed)
    Abstract [en]

    TEMPO-mediated oxidized cellulose nanofibers (TOCNFs) have shown potential in the bioremediation of metal ions from contaminated water due to their interaction with positively charged metal ions via electrostatic interactions involving surface carboxyl groups. Copper is one of the most common pollutants in industrial effluents and is thus the target metal in the current study. The specific surface adsorption of Cu(II) was similar for TOCNFs with different degrees of functionalization and directly impacted the zeta potential. SEM imaging of the TOCNF after Cu(II) adsorption revealed interesting nanostructured clusters that were attributable to Cu(II) ions first being adsorbed by carboxylate groups on the TOCNF and subsequently being reduced and self-assembled to Cu(0) nanoparticles (NPs) or copper oxide NPs by microprecipitation. TOCNF turned superhydrophilic and resulted in faster water filtration after copper adsorption due to the stronger polarity of the copper ions or the self-assembled Cu(0) NPs creating voids or highly water-permeable channels at the interface between the interconnected TEMPO-oxidized nanofibers. Thus, the adsorption of Cu(II) ions and self-assembly into the Cu NPs on TOCNF favors a faster water purification process and provides a viable route to reuse/recycle TOCNFs studded with Cu nanoparticles as biocidal materials

  • 24.
    Liu, Wenxin
    et al.
    Luleå tekniska universitet.
    Sun, Zhongxi
    Forsling, Willis
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Du, Qing
    Tang, Hongxiao
    Comparative study of surface acid-base characteristics of natural illites from different origins1999In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 219, no 1, p. 48-61Article in journal (Refereed)
    Abstract [en]

    The acid-base characteristics of naturally occurring illites, collected from different locations, were investigated by potentiometric titrations. The experimental data were interpreted using the constant capacitance surface complexation model. Considerable release of Al and Si from illite samples and subsequent complexation or precipitation of hydroxyl aluminosilicates generated during the acidimetric forward titration and the alkalimetric back titration, respectively, were observed. Therefore, the acidimetric supernatant, rather than the neutral one, was regarded as the system blank for each illite suspension to yield the surface site concentrations. In order to describe the acid-base chemistry of aqueous illite surfaces, two surface proton-reaction models, introducing the corresponding reactions between the dissolved aluminum species and silicic acid, as well as a surface Al-Si complex on homogeneous illite surface sites, were proposed as follows: (i) Model I, qq@SOH<=>qq@SO-+H+, pKinta = 3.76-4.09, qq@SOH+Al3++H4SiO4<=>qq@SOAl(OSi(OH)3 )+ +2H+, pKSC = 3.06-3.53; (ii) Model II, Al3++H4SiO4+2H2O<=>Al(OH)2(OSi( OH)3) +3H+, pKf2 = 9.85-10.71, qq@SOH<=>qq@SO-+H+, pKinta = 3.73-4.08, qq@SOH+Al3++H4SiO4<=>qq@SOAl (OSi(OH)3)++2H+, pKSC = 3.31-3.48. The Kf2 constant in Model II was obtained by simulating the complex formation between the dissolved aluminum species and silicic acid that occurred in acidimetric supernatant when the hydroxide was added. Additionally, the following cation exchange reaction was also considered for a special case, where a large amount of K+ is released during the corresponding acidimetric titration, in which a high concentration of protons are consumed. qq@XH+K+<=>qq@XK+H+, pKi = 8.24-8.52. Optimization results indicated that both models could provide a good description of the titration behavior for all aqueous illite systems in this study. The intrinsic acidity constants for the different illites were similar in Model I, showing some generalities in their acid-base properties. Model I may be considered as a simplification of Model II, evident in the similarities between the corresponding constants. In addition, the formation constant for surface Al-Si species (complexes or precipitates) is relatively stable in this study.

  • 25.
    Lützenkirchen, J.
    et al.
    Institut für Nukleäre Entsorgung, Forschungszentrum Karlsruhe.
    Boily, J.F.
    Pacific Northwest National Laboratory , Richland, WA.
    Gunneriusson, Lars
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Lövgren, L.
    Department of Chemistry, Umeå University.
    Sjöberg, S.
    Department of Chemistry, Umeå University.
    Protonation of different goethite surfaces: unified models for NaNO3 and NaCl media2008In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 317, no 1, p. 155-165Article in journal (Refereed)
    Abstract [en]

    Acid–base titration data for two goethites samples in sodium nitrate and sodium chloride media are discussed. The data are modeled based on various surface complexation models in the framework of the multi site complexation (MUSIC) model. Various assumptions with respect to the goethite morphology are considered in determining the site density of the surface functional groups. The results from the various model applications are not statistically significant in terms of goodness of fit. More importantly, various published assumptions with respect to the goethite morphology (i.e., the contributions of different crystal planes and their repercussions on the “overall” site densities of the various surface functional groups) do not significantly affect the final model parameters within simple 1-pK approximations. The simultaneous fit of the chloride and nitrate data results in electrolyte binding constants, which are applicable over a wide range of electrolyte concentrations including mixtures of chloride and nitrate. Model parameters for the goethite sample with 90 m2/g specific surface area are in excellent agreement with parameters that were independently obtained by another group on different goethite titration data sets.

  • 26.
    Mouzon, Johanne
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Bhuiyan, Iftekhar Uddin
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    The structure of montmorillonite gels revealed by sequential cryo-XHR-SEM imaging2016In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 465, p. 58-66Article in journal (Refereed)
    Abstract [en]

    Imaging by extreme high resolution-scanning electron microscopy (XHR-SEM) with a monochromated and decelerated beam was applied on 5% (wt/wt) Na and Ca-montmorillonite gels frozen by high pressure freezing (HPF). In order to visualize the three-dimensional structure and the contacts between clay platelets, a new approach was developed. It consists in recording a sequence of micrographs on a region of interest during controlled sublimation. This simple method allows to rewind and to relate the instantaneous configuration between several particles to their original position in the hydrated state. Consequently, aggregates of parallel platelets (i.e. curved tactoids) were present in the Ca-sample and the instantaneous position of these aggregates in the course of sedimentation was revealed. The Na-sample consisted of a continuous network of flexible platelets sharing mostly face-to-face (FF) contacts caused by jamming at the relatively high concentration of the suspension (5% (wt/wt)), which was above the gel transition. Yet individual platelets belonging to the smallest size fraction were observed to be fully dispersed within the entangled structure, which confirmed the repulsive character of the gel. Substructures consisting of several platelets connected by FF-associations were also evidenced. The origin and potential impact of such substructures on the occurrence of the sol–gel transition and birefringence are discussed.

  • 27.
    Mu, Liwen
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements. Intelligent Composites Laboratory, Department of Chemical and Biomolecular Engineering, The University of Akron.
    Shi, Yijun
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Guo, Xiaojing
    Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai .
    Zhuang, Wei
    College of Biotechnology and Pharmaceutical Engineering, National Engineering Technique Research Center for Biotechnology, Nanjing Tech University.
    Chen, Long
    Intelligent Composites Laboratory, Department of Chemical and Biomolecular Engineering, The University of Akron.
    Ji, Tuo
    Intelligent Composites Laboratory, Department of Chemical and Biomolecular Engineering, The University of Akron.
    Hua, Jing
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Wang, Huaiyuan
    College of Chemistry and Chemical Engineering, Northeast Petroleum University, Daqing.
    Zhu, Jiahua
    Intelligent Composites Laboratory, Department of Chemical and Biomolecular Engineering, The University of Akron.
    Grafting Heteroelement-Rich Groups on Graphene Oxide: Tuning Polarity and Molecular Interaction with Bio-Ionic Liquid for Enhanced Lubrication2017In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 498, p. 47-54Article in journal (Refereed)
    Abstract [en]

    Two different heteroelement-rich molecules have been successfully grafted on graphene oxide (GO) sheets which were then used as lubricant additives in bio-ionic liquid. The grafting was processed with reactions between GO sheets and synthesized heteroelement-rich molecules (Imidazol-1-yl phosphonic dichloride and 1H-1,2,4-triazol-1-yl phosphonic dichloride, respectively). The modified GO (m-GO) was added into [Choline][Proline] ([CH][P]) bio-ionic liquid, and has been demonstrated effective additive in promoting lubrication. Different characterization techniques have been utilized to study the reaction between GO and the two modifiers. The effect of molecular structure of the modifiers on the rheological and tribological properties of m-GO/[CH][P] lubricants was systematically investigated. Both theoretical calculation and experimental results demonstrated that the introduced heteroelement-rich groups are beneficial to increase the robustness of lubrication film by intensified hydrogen bonding and enhance the lubricant/friction surface adhesion by increased polarity of the m-GO. As a result, the interfacial lubrication could be significantly improved by these newly developed m-GO/[CH][P] lubricants.

  • 28.
    Otterstedt, J-E
    et al.
    Chalmers University of Technology.
    Ghuzel, M.
    Chalmers University of Technology.
    Sterte, Johan
    Colloidal components in solutions of alkali silicates1987In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 115, no 1, p. 95-103Article in journal (Refereed)
    Abstract [en]

    The particle size of colloidal silica in 1 to 5 M SiO2 solutions of lithium, sodium, potassium, and cesium silicates in the ratio range 1.5-20 moles of SiO2 per mole of M2O was determined by reaction with molybdic acid and by Sears titration. The particle size increased from 1.0 to 4.5 nm with increasing ratio but did not depend on the type of alkali-metal cation. The amount of monomeric silicate ions decreased sharply with increasing ratio from 35% for ratio 2 to 2% for ratio 15 in 5 M SiO2 solutions. The polymeric particles were extracted into tetrahydrofuran or tertiary butylalcohol at pH 2, without changing the particle size, in yields which increased to more than 95% for the highest ratios. Previous dilution caused the particle size to grow in high-ratio solutions but to decrease in low-ratio solutions.

  • 29. Potapova, Elisaveta
    et al.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Holmgren, Allan
    Hedlund, Jonas
    The effect of calcium ions and sodium silicate on the adsorption of a model anionic flotation collector on magnetite studied by ATR-FTIR spectroscopy2010In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 345, no 1, p. 96-102Article in journal (Refereed)
    Abstract [en]

    Previous studies have shown that agglomeration of the magnetite concentrate after reverse flotation of apatite is negatively affected by the collector species adsorbed on the surface of magnetite. In this work, the effect of ionic strength, calcium ions and sodium silicate on the unwanted adsorption of a model anionic flotation collector on synthetic magnetite was studied in-situ using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). The amount of collector adsorbed was found to increase with increasing ionic strength at pH 8.5 providing evidence to the contribution of electrostatic forces to the adsorption of the collector. Adding sodium silicate to the system resulted in a three-fold decrease in the amount of collector adsorbed compared to when no sodium silicate was added, confirming the depressing activity of sodium silicate on magnetite. Calcium ions were shown to increase the adsorption of both the collector and sodium silicate on magnetite. The depressing effect of sodium silicate on collector adsorption was completely suppressed in the presence of calcium ions under the conditions studied. Furthermore, the amount of collector adsorbed on magnetite from the silicate-collector solution increased 14 times upon addition of calcium ions suggesting that calcium ions in the process water may increase undesired adsorption of the collector on the iron oxide.

  • 30.
    Potapova, Elisaveta
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Grahn, Mattias
    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.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    The effect of polymer adsorption on the wetting properties of partially hydrophobized magnetite2012In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 367, no 1, p. 478-484Article in journal (Refereed)
    Abstract [en]

    Upon reverse flotation of iron ore, the surface of the iron ore concentrate may become partially hydrophobized due to adsorption of flotation collector, which is facilitated by the calcium ions present in the process water. Hydrophobic areas on the concentrate surface may introduce problems in subsequent pelletization of the concentrate. A possible way to restore the wettability of the surface could be by modifying the surface with a hydrophilic polymer. The effect of hydrophilic polymers of different types, viz. cationic, anionic, and non-ionic, on the wettability of the magnetite surface after adsorption of a surfactant was investigated. Although all the polymers could adsorb on magnetite at pH 8.5, the contact angle measurements revealed that only anionic ammonium polyacrylate could decrease the contact angle of synthetic magnetite after surfactant adsorption to a level close to that of as-synthesized magnetite. Such effect was probably achieved due to shielding of the hydrophobic surfactant chains from the aqueous phase by hydrophilic polyacrylate molecules. The fact that polyacrylate adsorption on magnetite occurred via calcium ions makes polyacrylate suitable for application in calcium-rich process water. The results presented in this work illustrate that ammonium polyacrylate could be successfully used to improve the wettability of magnetite after adsorption of surfactants.

  • 31.
    Raju, G. Bhaskar
    et al.
    Luleå tekniska universitet.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsling, Willis
    Adsorption of dextrin at mineral/water interface1997In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 193, no 2, p. 215-222Article in journal (Refereed)
    Abstract [en]

    The adsorption mechanism of dextrin on aqueous minerals such as fluorite, apatite, galena, magnetite, γ-alumina, and graphite was studied by adsorption experiments, zeta potential measurements, and FT-IR studies. Depending on the nature of the mineral surface, dextrin was found to interact in three different ways viz. by chemisorption, physisorption, or hydrophobic-hydrophobic interaction. The adsorption density of dextrin was found to be pH dependent. Maximum adsorption of dextrin was obtained around the pH at which the mineral surface is highly hydroxylated. The mechanism of dextrin interaction with the surface metal hydroxy sites, (≡MeOH), was found to proceed via chemical complexation. A linear relationship was observed between the adsorption density of dextrin and the pH of maximum surface hydroxylation. Zeta potential measurements have indicated the possibility of dextrin adsorption by electrostatic interaction under the conditions where mineral surface and dextrin are oppositely charged. Furthermore dextrin was found to adsorb on hydrophobic minerals such as graphite by hydrophobic-hydrophobic interaction. However, the magnitude of adsorption by electrostatic and hydrophobic interaction was found to be very marginal compared to that of chemical complexation

  • 32.
    Raju, G. Bhaskar
    et al.
    Luleå tekniska universitet.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsling, Willis
    Complexation mechanism of dextrin with metal hydroxides*11998In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 200, no 1, p. 1-6Article in journal (Refereed)
    Abstract [en]

    The complexation of dextrin with metal hydroxides was studied quantitatively by FT-IR and UV-visible reflectance spectroscopic techniques. Though three hydroxyl groups are present in each dextrin molecule, complexation involving only two hydroxyl groups situated at the C-2 and C-3 positions has been studied by many investigators. Involvement of a third hydroxyl group situated at the C-6 position was examined in the present study. Since metal hydroxy sites were found to play a key role in the complexation, precipitates of Ca(OH)2and Pb(OH)2were separately mixed with dextrin solutions at different ratios. Complexes with a stoichiometry of 2:3 (dextrin:metal ion) were identified, indicating the involvement of a third hydroxyl group. However, the ratio of metal ions to hydroxyl groups of dextrin remained as 1:2. Complexation between dextrin and metal hydroxide via a condensation mechanism is proposed.

  • 33.
    Rao, K. Hanumantha
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Cases, J.M.
    Centre de Recherche sur la Valorisation des Minerais, Vandoeure.
    Forssberg, Eric
    Mechanism of oleate interaction on salt-type minerals. V: Adsorption and precipitation reactions in relation to the solid/liquid ratio in the synthetic fluorite-sodium oleate system1991In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 145, no 2, p. 330-348Article in journal (Refereed)
    Abstract [en]

    The mechanism of adsorption of oleate onto a synthetic fluorite sample at different solid/liquid ratios in alkaline solutions is elucidated through adsorption isotherms in conjunction with ζ-potential and diffuse reflectance Fourier transform-infrared spectroscopic studies. These studies show that the chemisorption of oleate on surface calcium species followed by the physical adsorption of hydrocarbon chains (bilayer formation) precede the precipitation of calcium oleate in bulk solution. With an increase in the solid/liquid ratio, the bulk precipitation of calcium oleate after bilayer formation is found to be reduced, and at a high solid concentration, the isotherm is seen to level off with bilayer formation. As the solid concentration increases, the concentration of calcium in bulk solution decreases because of its adsorption on the head group of the hydrophilic layer of oleate (bilayer), and hence the extent of bulk precipitation decreases. The adsorption density for a monolayer coverage corresponds to the condensed state of an alkyl chain with a cross-sectional area of 33Ao2 (liquid-crystal state). Application of the two-dimensional condensation model is considered and no evidence for the surface precipitation process is observed.

  • 34. Rao, K. Hanumantha
    et al.
    J.M., Cases
    Centre de Recherche sur la Valorisation des Minerais, Vandoeure.
    P, de Donato
    Centre de Recherche sur la Valorisation des Minerais, Vandoeure.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Mechanism of oleate interaction on salt-type minerals: Part IV. Adsorption, electrokinetic and diffuse reflectance FT-IR studies of natural fluorite in the presence of sodium oleate1991In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 145, no 2, p. 314-329Article in journal (Refereed)
    Abstract [en]

    The mechanism of oleate interaction with fluorite is investigated through adsorption, electrokinetic, and diffuse reflectance FT-IR measurements coupled with theoretical thermodynamic chemical equilibrium calculations. The adsorption isotherms exhibit an infinite increase in the slope beyond an oleate density of 10 μmole m-2. This adsorption density corresponds to a bilayer formation of oleate by two-dimensional condensation with a reported molecular coverage area of 33Ao2 (liquid-crystal state). Comparison of the theoretical chemical equilibria with the experimental data shows that the infinite increase in the slope of the isotherms is due to the precipitation of calcium oleate. The solubility product of this three-dimensional phase is found to be in the pK range 14.4-14.5, and agrees with most of the values quoted in the literature. From IR studies, monocoordination of oleate through counter sodium and calcium ions is suggested for the monolayer filling. ζ potentials of fluorite are correlated to the adsorption of oleate up to bilayer formation, and formation on surface of calcium oleate (three-dimensional growth on substrate) at high oleate concentrations. Two-dimensional condensation of oleate on the fluorite surface followed by the association of hydrocarbon chains (tail-tail bond) for the second layer, prior to the precipitation of calcium oleate in the bulk solution, is proposed as the adsorption mechanism.

  • 35. Roonasi, Payman
    et al.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    An ATR-FTIR study of sulphate sorption on magnetite: rate of adsorption, surface speciation, and effect of calcium ions2009In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 333, no 1, p. 27-32Article in journal (Refereed)
    Abstract [en]

    The adsorption of sulphate on magnetite was studied in-situ using ATR-FTIR spectroscopy. Synthetic magnetite particles were deposited on a ZnSe internal reflection element and the spectra of sulphate adsorbed at pH 4-8.5 were recorded. Two different ionic strengths were used viz. 0.01 M and 0.1 M NaCl. The spectra of adsorbed sulphate on magnetite coated ZnSe were compared with the spectra of sulphate solutions at the same pH values and in contact with uncoated ZnSe. The spectrum of adsorbed sulphate at pH 4 showed three maxima at 979, 1044, and 1115 cm-1 indicating a monodentate adsorption in which the Td symmetry of SO42 - is lowered to C3v. At pH 6.5, sulphate adsorbed as an outer-sphere complex with two weak bands appearing at 1102 and 980 cm-1. Moreover, spectra of the adsorbed sulphate at pH 4 were recorded as a function of time and sulphate concentration. The equilibrium absorbance at different concentrations fitted a Langmuir type adsorption isotherm. The Langmuir affinity constant K at pH 4 was determined from the slope and intercept of the Langmuir plot to be K = 1.2344 × 104 M- 1 and the Gibbs free energy of adsorption Δ Gads0 was estimated from this value to be -33.3 kJ/mol. Kinetic analysis indicated that adsorption at pH 4 is fast, whilst the desorption kinetic at the same pH is very slow. In addition, the effect of Ca ions on sulphate adsorption was also studied. It was shown that Ca ions increased the sulphate adsorption on magnetite at pH 8.5.

  • 36. Roonasi, Payman
    et al.
    Yang, Xiaofang
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Competition between sodium oleate and sodium silicate for a silicate/oleate modified magnetite surface studied by in-situ ATR-FTIR Spectroscopy2010In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 343, no 2, p. 546-552Article in journal (Refereed)
    Abstract [en]

    Attenuated Total Reflection (ATR) IR spectroscopy was utilized to monitor adsorption of sodium oleate and sodium silicate onto synthetic magnetite at pH=8.5, both individually and in a competitive manner. Oleate was adsorbed within a concentration range of 0.01 mM-0.5 mM. It was observed that adsorption of oleate increased linearly with increasing concentration of oleate in solution up to a concentration of 0.1 mM. The infrared spectrum of oleate showed a broad single band at 1535 cm-1 assigned to the asymmetric stretching vibration of carboxylate, implying chemisorption of oleate to the magnetite surface. The kinetics of oleate adsorption followed a pseudo first-order reaction with an apparent rate constant of k1= 0.030 ± 0.002 min-1. Competitve adsorption of silicate and oleate was performed either by adding silicate solution to a magnetite film initially equilibrated with 0.1 mM oleate or adding oleate solution to magnetite treated with silicate solutions in the concentration range 0.1 mM - 5mM. It was shown that silicate, within reasonable time, had only minor effect on the amount of oleate already adsorbed on magnetite. On the other hand, oleate did not efficiently compete with silicate if the latter substance was already adsorbed on the iron oxide.

  • 37.
    Ruyter-Hooley, Maika
    et al.
    La Trobe University.
    Larsson, Anna-Carin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Johnson, Bruce B.
    La Trobe University.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Angove, Michael J.
    La Trobe University.
    Surface complexation modeling of inositol hexaphosphate sorption onto gibbsite2015In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 440, p. 282-291Article in journal (Refereed)
    Abstract [en]

    The sorption of Inositol hexaphosphate (IP6) onto gibbsite was investigated using a combination of adsorption experiments, 31P solid-state MAS NMR spectroscopy, and surface complexation modelling. Adsorption experiments conducted at four temperatures showed that IP6 sorption decreased with increasing pH. At pH 6, IP6 sorption increased with increasing temperature, while at pH 10 sorption decreased as the temperature was raised. 31P MAS NMR measurements at pH 3, 6, 9 and 11 produced spectra with broad resonance lines that could be de-convoluted with up to five resonances (+5, 0, -6, -13 and -21 ppm). The chemical shifts suggest the sorption process involves a combination of both outer- and inner-sphere complexation and surface precipitation. Relative intensities of the observed resonances indicate that outer-sphere complexation is important in the sorption process at higher pH, while inner-sphere complexation and surface precipitation are dominant at lower pH. Using the adsorption and 31P MAS NMR data, IP6 sorption to gibbsite was modelled with an Extended Constant Capacitance Model (ECCM). The adsorption reactions that best described the sorption of IP6 to gibbsite included two inner-sphere surface complexes and one outer-sphere complex:

  • 38.
    Ruyter-Hooley, Maika
    et al.
    La Trobe University.
    Larsson, Anna-Carin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Johnson, Bruce B.
    La Trobe University.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Angove, Michael J.
    La Trobe University.
    The effect of inositol hexaphosphate on cadmium sorption to gibbsite2016In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 474, p. 159-170Article in journal (Refereed)
    Abstract [en]

    HypothesisOxides, hydrous oxides and hydroxides of aluminium and iron are important in determining the availability of trace and heavy metals in soil systems. The presence of complexing anions is also known to affect the binding of these metals in soils. Since organophosphates, such as inositol hexaphosphate (IP6), are present in most soil systems they are expected to affect the nature of the interaction between metal ions and metal (hyr)oxides.ExperimentsBoth adsorption edge and isotherm experiments were conducted on Cd(II)–gibbsite and Cd(II)–IP6–gibbsite systems. In addition, solid-state 31P MAS NMR measurements were performed on the ternary system. All results were used to develop Extended Constant Capacitance surface complexation models of both the Cd(II)–gibbsite and IP6–Cd(II)–gibbsite sorption systems.FindingsThe presence of IP6 significantly increased sorption of Cd(II) to gibbsite below pH 8 especially at higher concentrations of Cd(II) and IP6. The 31P MAS NMR spectra, together with surface complexation modeling, indicated the presence of two outer-sphere ternary complexes with the first, [(SOH2)33+–(LHCd)9-]6-, important at relatively low concentrations, while the second, [SLH38-−Cd2+]6-, dominated sorption at higher sorbate concentrations. Thus the presence of organophosphates in soil systems increases sorption and may therefore decrease the availability of trace and heavy metals to plants.

  • 39.
    Rönngren, Lars
    et al.
    Umeå universitet.
    Sjöberg, Staffan
    Umeå universitet.
    Sun, Zhong-Xi
    Luleå tekniska universitet.
    Forsling, Willis
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Surface Reactions in Aqueous Metal Sulfide Systems. 5: The Complexation of Sulfide Ions at the ZnS-H2O and Pbs-H2O Interfaces1994In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 162, no 1, p. 227-235Article in journal (Refereed)
    Abstract [en]

    The reactions between hydrous ZnS or PbS surfaces and sulfide ions have been studied. The measurements were performed as potentiometric titrations in 0.1 M NaNO3 or 0.1 M NaClO4 media at 25°C. Besides determining -log[H+] using a glass electrode, log[S2-] was measured with an Ag/Ag2S selective electrode. Synthetically prepared ZnS (predominantly wurtzite) and PbS, as well as the minerals sphalerite and galena, were studied. When adding sulfide ions to acidic or slightly neutral suspensions, bulk precipitation of metal sulfides occurred. The solubility products for the metal sulfides formed were determined and found to be log K(Me2+ + HS- ↔ MeS(s) + H+) = 10.6 for ZnS and 15.6 for PbS (synthetic preparations). Sulfide additions to neutral and alkaline suspensions resulted in adsorption of H2S, HS-, and S2-. In the PbS-system the best fit was found with a model with the surface complexes ≡SPbSH2, ≡SPbSH-, and ≡SPbS2- without any charge dependent surface complexation constants. In the ZnS-system two models were found to fit experimental data almost equally well. One with the three surface complexes ≡SZnSH2, ≡SZnSH-, and ≡SZnS2- and no charge dependence or one with two surface complexes (≡SZnSH2 and ≡SZnS2-) with charge dependent equilibrium constants. Experimental data were evaluated using the computer program FITEQL. The results explain part of the mechanism behind depression of sulfide minerals in the flotation process.

  • 40.
    Rönngren, Lars
    et al.
    Umeå universitet.
    Sjöberg, Staffan
    Umeå universitet.
    Sun, Zhongxi
    Luleå tekniska universitet.
    Forsling, Willis
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Schindler, Paul W.
    University of Bern.
    Surface reactions in aqueous metal sulfide systems. 2: Ion exchange and acid/base reactions at the ZnSH2O interface1991In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 145, no 2, p. 396-404Article in journal (Refereed)
    Abstract [en]

    The amphoteric properties of hydrous ZnS surfaces as well as an ion exchange reaction between surface coordinated Zn2+ ions and H+ ions of the aqueous phase have been established. The measurements were performed as potentiometric titrations in 0.1 M NaClO4 medium at 25°C. Besides measuring -log[H+] by using a glass electrode, -log[S2-] was recorded (Ag/Ag2S selective electrode). In addition, the total concentrations of H+, Zn2+, and S were analyzed as a function of -log[H+] of the bulk solution. Synthetically prepared ZnS and the mineral sphalerite were studied. Bro¨nsted acidity constants pK1s = 6.91 and pK2s = 10.28 for synthetic ZnS, and pK1s = 7.14 and pK2s = 10.29 for sphalerite, were established, which implies -log[H+] of zero proton condition equal to 8.60 and 8.72, respectively. Furthermore, the ion exchange reaction ≡SZn + 2H+ ↔ ≡SH2 + Zn2+ was characterized within the range 4 ≤ -log[H+] ≤ 7, with log K = 9.59 and 9.65. Experimental data were evaluated on the basis of the constant capacitance model by using the computer program FITEQL. The "best" fit to experimental data was obtained by assuming no charge dependence of K1s and K2s.

  • 41. Sand, Anders
    et al.
    Toivakka, Martti
    Åbo Akademi.
    Hjelt, Tuomo
    KCL.
    Influence of colloidal interactions on pigment coating layer structure formation2009In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 332, p. 394-401Article in journal (Refereed)
  • 42.
    Shoeman, Brian J.
    et al.
    Department of Engineering Chemistry, Chalmers University of Technology.
    Sterte, Johan
    Otterstedt, Jan-Erik
    Department of Engineering Chemistry, Chalmers University of Technology.
    Synthesis of colloidal suspensions of zeolite ZSM-21995In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 170, no 2, p. 449-456Article in journal (Refereed)
    Abstract [en]

    Discrete colloidal particles of zeolite ZSM-2 with crystal sizes less than 100 nm, in the form of aqueous suspensions, have been synthesized in tetramethylammonium (TMA)-aluminosilicate solutions in the presence of either lithium or a combination of lithium and sodium hydroxide. The well-crystallized ZSM-2 has a specific surface area of 781 m2/g after purification and removal of the organic base by calcination. Synthesis times (t) are as short as 3 < t < 12 h and in certain cases, less than 3 h, less than those previously reported in the literature. Prolonged hydrothermal treatment of sols in the presence of sodium cations (>12 h) results in the phase transformation of ZSM-2 to the nitrogeneous edingtonite zeolite (Li,Na)-E. The synthesis of nitrogeneous (Li,Na)-E is also favored by a high TMA content in conjunction with sodium, whereas synthesis of zeolite N-A is favored by a high sodium content. Furthermore, it is shown that colloidal suspensions of TMA sodalite with crystal sizes less than 40 nm are synthesized in the absence of alkali cations.

  • 43.
    Sun, Zhong-Xi
    et al.
    Luleå tekniska universitet.
    Su, Fen-Wei
    Luleå tekniska universitet.
    Forsling, Willis
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Samskog, Per-Olof
    Surface characteristics of magnetite in aqueous suspension1998In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 197, no 1, p. 151-159Article in journal (Refereed)
    Abstract [en]

    Surface characteristics of magnetite at 25°C in aqueous suspensions are systematically studied. The measured specific surface area and concentration of proton binding sites correspond well to the calculated values. Zeta potential of magnetite in the absence of multivalent cations exhibits positive values in acidic solution and becomes negative with increasing pH. pHpzcis about 6. In the presence of excess cations such as Fe2+or Fe3+, specific adsorption takes place at the surface of magnetite, which dramatically influences the value of zeta potential. The concentrations of soluble Fe ions at pH about 4.5 increase with solid concentrations of magnetite indicating some surface-related reaction mechanisms.

  • 44.
    Sun, Zhong-Xi
    et al.
    University of Jinan.
    Ting-Ting, Zheng
    University of Jinan.
    Bo, Qi-Bing
    University of Jinan.
    Miao, Du
    University of Jinan.
    Forsling, Willis
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Effects of calcination temperature on the pore size and wall crystalline structure of mesoporous alumina2008In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 319, no 1, p. 247-251Article in journal (Refereed)
    Abstract [en]

    In this paper, mesoporous alumina with different pore sizes and wall crystalline structures was synthesized at calcination temperatures over 550 °C. The characterization of the samples calcined at 550, 800, 1100, and 1300 °C, respectively, was performed using TEM, XRD, FTIR, TG/DTA, and N2 adsorption/desorption techniques. The correlation between pore size and wall crystalline structure on calcination temperature was systematically investigated.

  • 45.
    Vidyadhar, A.
    et al.
    Luleå University of Technology.
    Rao, K. Hanumantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Adsorption mechanism of mixed cationic/anionic collectors in feldspar-quartz flotation system2007In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 306, no 2, p. 195-204Article in journal (Refereed)
    Abstract [en]

    The adsorption mechanism of mixed cationic alkyl diamine and anionic sulfonate/oleate collectors at acidic pH values was investigated on microcline and quartz minerals through Hallimond flotation, electrokinetic and diffuse reflectance FTIR studies. In the presence of anionic collectors, neither of the minerals responded to flotation but the diamine flotation of the minerals was observed to be pH and concentration dependent. The presence of sulfonate enhanced the diamine flotation of the minerals by its co-adsorption. The difference in surface charge between the minerals at pH 2 was found to be the basis for preferential feldspar flotation from quartz in mixed diamine/sulfonate collectors. The infrared spectra revealed no adsorption of sulfonate collector when used alone but displayed its co-adsorption as diamine–sulfonate complex when used with diamine. The presence of sulfonate increased the diamine adsorption due to a decrease in the electrostatic head–head repulsion between the adjacent surface ammonium ions and thereby increasing the lateral tail–tail hydrophobic bonds. The mole ratio of diamine/sulfonate was found to be an important factor in the orientation of alkyl chains and thus the flotation response of minerals. The increase in sulfonate concentration beyond diamine concentration leads to the formation of soluble 1:2 diamine–sulfonate complex or precipitate and the adsorption of these species decreased the flotation since the alkyl chains are in chaotical orientation with a conceivable number of head groups directing towards the solution phase.

  • 46.
    Vidyadhar, A.
    et al.
    Luleå University of Technology.
    Rao, K. Hanumantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Chernyshova, Irina V.
    St. Petersburg State Technical University.
    Pradip, A.
    Tata Research Development & Design Centre, Pune.
    Forssberg, Eric
    Mechanisms of amine-quartz interaction in the absence and presence of alcohols studied by spectroscopic methods2002In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 256, no 1, p. 59-72Article in journal (Refereed)
    Abstract [en]

    The adsorption mechanism of long-chain alkylamines and their acetate salts on quartz was investigated using Hallimond flotation, zeta-potential, Fourier transform infrared, and X-ray photoelectron spectroscopy (XPS) studies at neutral pH 6-7. The influence of long-chain alcohols on the adsorption of amines in mixed amine-alcohol on quartz was also examined. It is shown by infrared spectroscopy that in differentiation to the electrostatic adsorption model of Gaudin-Fuerstenau-Somasundaran, amine cations form strong hydrogen bonds with the surface silanol groups. The XPS spectra revealed the presence of neutral amine molecules together with protonated ammonium ions at and above the critical hemimicelle concentration. The acetate counterions were found to influence the amine adsorption. Possible mechanisms of adsorption based on these observations were discussed. For the first time it was proved spectroscopically that coadsorption of long-chain alcohols along with amine cations leads to formation of a closely packed surface layer, as compared to the case of adsorption of pure amine alone at the same concentration. The highest order and packing at the surface are observed when the alkyl chain length of mixed amine and alcohol are the same. The condition of same chain length of amines and alcohols adsorbing at the surface corresponds to maximum flotation recovery. The results also confirmed the synergistic enhancement of amine adsorption in the presence of alcohols. The mechanism for mixed long-chain amine and alcohol adsorption onto quartz is consistent with the primary adsorption species of alkylammonium-water-alcohol complex, where deprotonation of ammonium groups in the adsorbed layer leading to two-dimensional precipitation of molecular amine was illustrated.

  • 47.
    Vidyadhar, A.
    et al.
    Luleå University of Technology.
    Rao, K. Hanumantha
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Adsorption of N-tallow 1,3-propanediamine-dioleate collector on albite and quartz minerals, and selective flotation of albite from Greek Stefania feldspar ore2002In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 248, no 1, p. 19-29Article in journal (Refereed)
    Abstract [en]

    The adsorption behavior of tallow 1,3-propanediamine-dioleate (Duomeen TDO) collector on albite and quartz minerals is assessed through Hallimond flotation, zeta potential, and diffuse reflectance FTIR investigations, together with the species distribution of the collector. The collector performance on albite separation from a natural feldspar material is evaluated in bench scale flotation tests. The Hallimond flotation responses of the minerals as a function of pH and collector concentration indicate that albite can be selectively floated from quartz at pH 2 where the doubly positively charged collector species adsorb on albite but not on quartz. However, the zeta potential and infrared spectra reveal that the adsorption behavior of the collector is similar on both minerals. The discrepancy in the flotation and adsorption results is attributed to the coarse and fine particle size fractions, and the shorter and longer equilibration periods employed in these studies respectively. The comparable adsorption on fine particles of albite and quartz at pH 2 is explained by the interaction of ammonium ions on silanol groups by hydrogen bonding as well as electrostatic interactions. The changes in zeta potentials are in good agreement with the formation of ionic species and free molecular forms of the collector. The IR spectra show the coexistence of neutral oleic acid together with charged amine species at low pH values in accordance with the species distribution diagram. Selective flotation of albite is accomplished from a natural feldspar material with tallow diamine-dioleate collector at pH 2 using sulfuric acid, only when the feed is deslimed prior to the bench scale flotation tests. An albite recovery exceeding 85% is achieved from a feed material containing about 50% albite.

  • 48.
    Wang, Xianghuai
    et al.
    Department of Mining Engineering, University of Kentucky, Lexington.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    EDTA-induced flotation of sulfide minerals1990In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 140, no 1, p. 217-226Article in journal (Refereed)
    Abstract [en]

    The native and induced floatabilities of pyrite, galena, arsenopyrite, and glaucodot were investigated by flotation tests in the absence and in the presence of EDTA. The dissolution and electrokinetic behavior of the minerals in EDTA solutions was studied as a function of pH and of EDTA concentration. It was found that the flotation and dissolution of these minerals in EDTA solutions depend strongly on the pH values and on EDTA concentration. At a moderate EDTA concentration, the floatabilities and the released metal concentration are low or absent at pH below 5 and above 10. In the range of pH 6–10, both the flotation recovery and the dissolution of these minerals exhibit a plateau. The amount of released metal species increases with increasing EDTA concentration. The floatabilities of these sulfides first increase with an increase in EDTA concentration. However, a further increase in EDTA concentration to above 10−3M leads to a significant decrease in flotation recovery. ζ-Potential measurements show that in the presence of EDTA the IEP of the sulfide minerals is shifted considerably to lower pH values. The principles underlying the phenomena are discussed in terms of the results obtained from electrochemical studies of these sulfides and the instabilities of iron hydroxides in EDTA solutions.

  • 49.
    Wu, Liuming
    et al.
    Luleå University of Technology.
    Forsling, Willis
    Surface complexation of calcium minerals in aqueous solution III. ion exchange and acid-base properties of hydrous fluorite surfaces1995In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 174, no 1, p. 178-184Article in journal (Refereed)
    Abstract [en]

    The acid-base properties of hydrous fluorite surfaces and ion exchange reactions between surface lattice ions of F- and OH- ions in bulk solution have been investigated. The measurements were performed as potentiometric titrations with varied solid concentrations in 0.1 mol dm-3 KCl medium at 25.0°C using a glass electrode for -log[H+] and a fluoride ion selective electrode for -log[F-]. The experimental data could be explained by a model that assumes the surface equilibria(≡CaOH12≡F ≡CnOH≡F + H+ logβs-1100 (int) = -9.5 ± 0.1≡CaOH+2≡F + H+ ≡CaOH+2≡FH logβs-1100 (int) = 4.4 ± 0.1≡CaOH+2≡F + H+ + H2O+ ≡CaOH≡OH + 2H+ + F- logβs-210-1(int) = -20.3 ± 0.1The equilibrium constants were evaluated using the computer program FITEQL assuming a constant capacitance model for the electric double layer.

  • 50.
    Wu, Liuming
    et al.
    Luleå University of Technology.
    Forsling, Willis
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Surface complexation of calcium minerals in aqueous solution: 4. The complexation of alizarin red S at fluorite-water interfaces2000In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 224, no 2, p. 211-218Article in journal (Refereed)
    Abstract [en]

    The complexation of Alizarin Red S (ARS) at the surface of hydrous fluorite particles has been investigated by means of potentiometric titrations, adsorption experiments, and ζ-potential measurements in 0.1 mol dm-3 KCl ionic medium at 25.0°C, as well as by UV/visible specular reflectance, FT-IR, and FT-Raman spectroscopy. Chemical reaction models describing the equilibria of ARS (HA2-) at the aqueous fluorite surfaces (≡X) have been established as follows:[formula] Experimental data were evaluated using the computer program FITEQL on the basis of a constant capacitance model for the electric double layer. Surface complexation mechanisms involving the R-SO3-, R-β-OH, and R-α-OH active groups of the ARS molecule are proposed to describe coordination to the fluorite surface.

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