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  • 1.
    Barai, Manas
    et al.
    Department of Chemistry and Chemical Technology, Vidyasagar University, Midnapore, West Bengal, India.
    Mandal, Manas Kumar
    Department of Chemistry and Chemical Technology, Vidyasagar University, Midnapore, West Bengal, India.
    Karak, Atanu
    Department of Chemistry and Chemical Technology, Vidyasagar University, Midnapore, West Bengal, India.
    Bordes, Romain
    Chemistry and Chemical Engineering, Applied Surface Chemistry, Chalmers University of Technology, Gothenburg, Sweden.
    Patra, Anuttam
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Dalai, Sudipta
    Department of Chemistry and Chemical Technology, Vidyasagar University, Midnapore, West Bengal, India.
    Panda, Amiya Kumar
    Department of Chemistry and Chemical Technology, Vidyasagar University, Midnapore, West Bengal, India.
    Interfacial and Aggregation Behavior of Dicarboxylic Amino Acid-Based Surfactants in Combination with a Cationic Surfactant2019In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 35, no 47, p. 15306-15314Article in journal (Refereed)
    Abstract [en]

    The interfacial and micellization behavior of three dicarboxylic amino acid-based anionic surfactants, abbreviated as AAS (N-dodecyl derivative of -aminomalonate, -aspartate, and -glutamate) in combination with hexadecyltrimethylammonium bromide (HTAB) were investigated by surface tension, conductance, UV–vis absorption/emission spectroscopy, dynamic light scattering (DLS), and viscosity studies. Critical micelle concentration (CMC) values of the surfactant mixtures are significantly lower than the predicted values, indicating associative interaction between the components. Surface excess, limiting molecular area, surface pressure at the CMC, and Gibbs free energy indicate spontaneity of the micellization processes compared to the pure components. CMC values were also determined from the sigmoidal variation in the plot of micellar polarity and pyrene UV–vis absorption/emission intensities with surfactant concentration. The aggregation number, determined by static fluorescence quenching method, increases with decreasing mole fraction of the AAS (αAAS), where the micelles are mainly dominated by the HTAB molecules. The size of the micelle increases with decreasing αAAS, leading to the formation of larger and complex aggregates, as also supported by the viscosity studies. Micelles comprising 20–40 mol % AAS are highly viscous, in consonance with their sizes. Some of the mixed surfactant systems show unusual viscosity (shear thickening and increased viscosity with increasing temperature). Such mixed surfactant systems are considered to have potential in gel-based drug delivery and nanoparticle synthesis.

  • 2.
    Björklund, Robert B.
    et al.
    Linköping University.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Carlsson, Bill
    Vadstena Varmförzinkning AB.
    Ellipsometric study of oxide removal from steel surfaces in hydrochloric acid solutions1999In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 15, no 2, p. 494-499Article in journal (Refereed)
    Abstract [en]

    Iron oxide films formed on three different steel surfaces by thermal oxidation were removed in hydrochloric acid solutions at 20 C. The oxide removal process in flowing solutions was followed in situ by ellipsometry. Two different removal mechanisms were observed in 0.5-2 M HCl, one where undermining of the film resulted in large intact pieces of the oxide leaving the substrate surface at the end of the removal period, and one where the film scaled off the surface in small pieces during the entire removal process. Oxide films which exhibited the undermining mechanism were found to contain about 10% hematite (Fe2O3) and 90% magnetite (Fe3O4). The scaling off mechanism was observed for films which were nearly pure magnetite. Optical models were constructed using data from scanning electron microscopy (SEM) and X-ray diffraction (XRD) measurements for the thicknesses and compositions of films after different immersion times in HCl solutions. Spectra calculated from the models agreed well with the experimental spectra.

  • 3.
    Chernyschova, Irina V.
    et al.
    St. Petersburg State Technical University.
    Rao, K. Hanumantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Vidyadhar, A.
    St. Petersburg State Technical University.
    Shchukarev, A.V.
    Avdelningen för oorganisk kemi, Umeå universitet.
    Mechanism of adsorption of long-chain alkylamines on silicates: a spectroscopic study. 2. Albite2001In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 17, no 3, p. 775-785Article in journal (Refereed)
    Abstract [en]

    Using FTIR (DRIFTS and IRRAS) and XPS spectroscopy, ζ potential measurements, and Hallimond flotation tests, we confirmed that long-chain primary amines are adsorbed on silicates at pH 6-7 through the 2D-3D precipitation mechanism. The orientation and packing of dodecyl- and hexadecylammonium acetate and chloride adsorbed on albite in the different regions of the adsorption isotherm were determined. It was shown that these characteristics depend strongly on the substrate. Coadsorption of the counterion was not revealed, but the counterion was found to affect indirectly the adsorption at concentrations above the concentration of the bulk amine precipitation

  • 4.
    Chernyshova, Irina V.
    et al.
    Luleå University of Technology.
    Rao, K. Hanumantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Mechanism of coadsorption of long-chain alkylamines and alcohols on silicates. Fourier transform spectroscopy and X-ray photoelectron spectroscopy studies2001In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 17, no 9, p. 2711-2719Article in journal (Refereed)
    Abstract [en]

    Coadsorption of long-chain primary amines and alcohols on silicates (quartz and albite) at pH 6-7 was studied using Fourier transform (DRIFTS and IRRAS) and X-ray photoelectron spectroscopy. The ionization state of the amino headgroups, the molecular orientation, and packing in the adsorbed mixed monolayers were determined. The results were interpreted in terms of the modified model of 2D-3D precipitation, where the elementary adsorbing species from the solution is the amine-alcohol-water association.

  • 5.
    Chernysova, Irina V.
    et al.
    Luleå University of Technology.
    Rao, K. Hanumantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Vidyadhar, A.
    Luleå University of Technology.
    Shchukarev, A. V.
    Avdelningen för oorganisk kemi, Umeå universitet.
    Mechanism of adsorption of long-chain alkylamines on silicates: a spectroscopic study. 1. Quartz2000In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 16, no 21, p. 8071-8084Article in journal (Refereed)
    Abstract [en]

    The mechanism of adsorption of long-chain alkylamines at pH 6-7 onto quartz was studied using FTIR and XPS spectroscopy. The spectroscopic data were correlated with ζ potential and Hallimond flotation results. For the first time it was shown that (1) amine cation in the first monolayer is H-bonded with surface silanol group and this H-bond becomes stronger after the break in the adsorption characteristics (isotherm, ζ potential, floatability); (2) at the break the origin of the adsorbed amine species changes qualitatively, and along with alkylammonium ion attached to deprotonated silanol group, molecular amine appears at the surface and, as a result, monolayer thick patches of well-oriented and densely packed adsorbed amine species form rendering the surface highly hydrophobic; and (3) at higher amine concentration, bulk precipitation of molecular amine takes place. The counterion was found to influence both these steps. A model of successive two-dimensional and three-dimensional precipitation was suggested to explain amine adsorption on a silicate surface.

  • 6.
    Emmerik, Tristan J. Van
    et al.
    La Trobe University.
    Sandström, Dan
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Angove, Michael J.
    La Trobe University.
    Johnson, Bruce B.
    La Trobe University.
    31P solid-state nuclear magnetic resonance study of the sorption of phosphate onto gibbsite and kaolinite2007In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 23, no 6, p. 3205-3213Article in journal (Refereed)
    Abstract [en]

    Sorption of phosphate onto gibbsite (Υ-Al(OH)3) and kaolinite has been studied by both macroscopic and 31P solid-state NMR measurements. Together these measurements indicate that phosphate is sorbed by a combination of surface complexation and surface precipitation with the relative amounts of these phases depending on pH and phosphate concentration. At low pH and high phosphate concentrations sorption is dominated by the presence of both amorphous and crystalline precipitate phases. The similarity between the single-pulse and CP/MAS NMR spectra suggests that the precipitate phases form a thin layer on the surface of the particles in close contact with protons from surface hydroxyl groups or coordinated water molecules. While the crystalline phase is only evident on samples below pH 7, amorphous AlPO4 was found at all pH and phosphate concentrations studied. As pH was increased the fraction of phosphate sorbed as an inner-sphere complex increased, becoming the dominant surface species by pH 8. Comparison of sorption and NMR results suggests that the inner-sphere complexes form by monodentate coordinat

  • 7.
    Farzaneh, Amirfarrokh
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    DeJaco, Robert F.
    Department of Chemical Engineering and Materials Science and Department of Chemistry and Chemical Theory Center, University of Minnesota , Minneapolis.
    Ohlin, Lindsay
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Siepmann, J. Ilja
    Department of Chemical Engineering and Materials Science and Department of Chemistry and Chemical Theory Center, University of Minnesota , Minneapolis.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Comparative Study of the Effect of Defects on Selective Adsorption of Butanol from Butanol/Water Binary Vapor Mixtures in Silicalite-1 Films2017In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 33, no 34, p. 8420-8427Article in journal (Refereed)
    Abstract [en]

    A promising route for sustainable 1-butanol (butanol) production is ABE (acetone, butanol, ethanol) fermentation. However, recovery of the products is challenging because of the low concentrations obtained in the aqueous solution, thus hampering large-scale production of biobutanol. Membrane and adsorbent-based technologies using hydrophobic zeolites are interesting alternatives to traditional separation techniques (e.g., distillation) for energy-efficient separation of butanol from aqueous mixtures. To maximize the butanol over water selectivity of the material, it is important to reduce the number of hydrophilic adsorption sites. This can, for instance, be achieved by reducing the density of lattice defect sites where polar silanol groups are found. The density of silanol defects can be reduced by preparing the zeolite at neutral pH instead of using traditional synthesis solutions with high pH. In this work, binary adsorption of butanol and water in two silicalite-1 films was studied using in situ attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy under equal experimental conditions. One of the films was prepared in fluoride medium, whereas the other one was prepared at high pH using traditional synthesis conditions. The amounts of water and butanol adsorbed from binary vapor mixtures of varying composition were determined at 35 and 50 °C, and the corresponding adsorption selectivities were also obtained. Both samples showed very high selectivities (100-23 000) toward butanol under the conditions studied. The sample having low density of defects, in general, showed ca. a factor 10 times higher butanol selectivity than the sample having a higher density of defects at the same experimental conditions. This difference was due to a much lower adsorption of water in the sample with low density of internal defects. Analysis of molecular simulation trajectories provides insights on the local selectivities in the zeolite channel network and at the film surface.

  • 8.
    Farzaneh, Amirfarrokh
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Zhou, Ming
    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.
    Bacsik, Zoltan
    Department of Materials and Environmental Chemistry, Stockholm University.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Adsorption of Butanol and Water Vapors in Silicalite‑1 Films with a Low Defect Density2016In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 32, p. 11789-11798Article in journal (Refereed)
    Abstract [en]

    Pure silica zeolites are potentially hydrophobic and have therefore been considered to be interesting candidates for separating alcohols, e.g., 1-butanol, from water. Zeolites are traditionally synthesized at high pH, leading to the formation of intracrystalline defects in the form of silanol defects in the framework. These silanol groups introduce polar adsorption sites into the framework, potentially reducing the adsorption selectivity toward alcohols in alcohol/water mixtures. In contrast, zeolites prepared at neutral pH using the fluoride route contain significantly fewer defects. Such crystals should show a much higher butanol/water selectivity than crystals prepared in traditional hydroxide (OH−) media. Moreover, silanol groups are present at the external surface of the zeolite crystals; therefore, minimizing the external surface of the studied adsorbent is important. In this work, we determine adsorption isotherms of 1-butanol and water in silicalite-1 films prepared in a fluoride (F−) medium using in situ attenuated total reflectance−Fourier transform infrared (ATR−FTIR) spectroscopy. This film was composed of well intergrown, plate-shaped b-oriented crystals, resulting in a low external area. Single-component adsorption isotherms of 1-butanol and water were determined in the temperature range of 35− 80 °C. The 1-butanol isotherms were typical for an adsorbate showing a high affinity for a microporous material and a large increase in the amount adsorbed at low partial pressures of 1-butanol. The Langmuir−Freundlich model was successfully fitted to the 1-butanol isotherms, and the heat of adsorption was determined. Water showed a very low affinity for the adsorbent, and the amounts adsorbed were very similar to previous reports for large silicalite-1 crystals prepared in a fluoride medium. The sample also adsorbed much less water than did a reference silicalite-1(OH−) film containing a high density of internal defects.The results show that silicalite-1 films prepared in a F− medium with a low density of defects and external area are very promising for the selective recovery of 1-butanol from aqueous solutions.

  • 9.
    Farzaneh, Amirfarrokh
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Zhou, Ming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Potapova, Elisaveta
    Bacsik, Zoltan
    Department of Materials and Environmental Chemistry, Stockholm University.
    Ohlin, Lindsay
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Holmgren, Allan
    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.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Adsorption of Water and Butanol in Silicalite-1 Film Studied with in-situ ATR-FTIR Spectroscopy2015In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 31, no 17, p. 4887-4894Article in journal (Refereed)
    Abstract [en]

    Biobutanol produced by, e.g., acetone–butanol–ethanol (ABE) fermentation is a promising alternative to petroleum-based chemicals as, e.g., solvent and fuel. Recovery of butanol from dilute fermentation broths by hydrophobic membranes and adsorbents has been identified as a promising route. In this work, the adsorption of water and butanol vapor in a silicalite-1 film was studied using in situ attenuated total reflectance–Fourier transform infrared (ATR–FTIR) spectroscopy to better understand the adsorption properties of silicalite-1 membranes and adsorbents. Single-component adsorption isotherms were determined in the temperature range of 35–120 °C, and the Langmuir model was successfully fitted to the experimental data. The adsorption of butanol is very favorable compared to that of water. When the silicalite-1 film was exposed to a butanol/water vapor mixture with 15 mol % butanol (which is the vapor composition of an aqueous solution containing 2 wt % butanol, a typical concentration in an ABE fermentation broth, i.e., the composition of the gas obtained from gas stripping of an ABE broth) at 35 °C, the adsorption selectivity toward butanol was as high as 107. These results confirm that silicalite-1 quite selectively adsorbs hydrocarbons from vapor mixtures. To the best of our knowledge, this is the first comprehensive study on the adsorption of water and butanol in silicalite-1 from vapor phase.

  • 10.
    Filippov, Andrei
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Kotenkov, Sergey A.
    Kazan (Volga Region) Federal University, Kazan.
    Munavirov, Bulat
    Kazan (Volga Region) Federal University, Kazan.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Effect of Curcumin on Lateral Diffusion of Phosphatidylcholines in Saturated and Unsaturated Bilayers2014In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, no 35, p. 10686-10690Article in journal (Refereed)
    Abstract [en]

    Curcumin, a dietary polyphenol, is a natural spice with preventive and therapeutic potential for neurodegenerative diseases such as Alzheimer's and Parkinson's diseases. Curcumin possesses a spectrum of antioxidant, anti-inflammatory, anticarcinogenic, and antimutagenic properties. Because of this broad spectrum of pharmacological activity, it has been suggested that, like cholesterol, curcumin exerts its effect on a rather basic biological level, such as on lipid bilayers of biomembranes. The effect of curcumin on translational mobility of lipids in biomembranes has not yet been studied. In this work, we used 1H NMR diffusometry to explore lateral diffusion in planar-oriented bilayers of dimyristoylphosphatidylcholine (DMPC) and dioleoylphosphatidylcholine (DOPC) at curcumin concentrations of up to 40 mol % and in the temperature range of 298-333 K. The presence of curcumin at much lower concentrations (∼7 mol %) leads to a decrease in the lateral diffusion coefficient of DOPC by a factor of 1.3 at lower temperatures and by a factor of 1.14 at higher temperatures. For DMPC, the diffusion coefficient decreases by a factor of 1.5 at lower temperatures and by a factor of 1.2 at higher temperatures. Further increasing the curcumin concentration has no effect. Comparison with cholesterol showed that curcumin and cholesterol influence lateral diffusion of lipids differently. The effect of curcumin is determined by its solubility in lipid bilayers, which is as low as 10 mol % that is much less than that of cholesteroĺs 66 mol %.

  • 11.
    Filippov, Andrei
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Munavirov, Bulat
    Kazan (Volga Region) Federal University, Kazan.
    Sparrman, Tobias
    Umeå university.
    Ishmuhametova, Valentina
    Kazan (Volga Region) Federal University, Kazan.
    Rudakova, Maya
    Kazan (Volga Region) Federal University, Kazan.
    Shriram, Prashant
    Umeå university.
    Tavelin, Staffan
    Umeå university.
    Interaction of a Poly(acrylic acid) Oligomer with Dimyristoylphosphatidylcholine Bilayers2011In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 27, no 7, p. 3754-3761Article in journal (Refereed)
    Abstract [en]

    We studied the influence of 5 kDa poly(acrylic acid) (PAA) on the phase state, thermal properties, and lateral diffusion in bilayered systems of dimyristoylphosphatidylcholine (DMPC) using 31P NMR spectroscopy, differential scanning calorimetry (DSC), 1H NMR with a pulsed field gradient, and 1H nuclear Overhauser enhancement spectroscopy (NOESY). The presence of PAA does not change the lamellar structure of the system. 1H MAS NOESY cross-peaks observed for the interaction between lipid headgroups and polyion protons demonstrated only surface PAA−biomembrane interaction. Small concentrations of PAA (up to 4 mol %) lead to the appearance of a new lateral phase with a higher main transition temperature, a lower cooperativity, and a lower enthalpy of transition. Higher concentrations lead to the disappearance of measurable thermal effects. The lateral diffusion coefficient of DMPC and the apparent activation energy of diffusion gradually decreased at PAA concentrations up to around 4 mol %. The observed effects were explained by the formation of at least two types of PAA−DMPC lateral complexes as has been described earlier (Fujiwara, M.; Grubbs, R. H.; Baldeschwieler, J. D. J. Colloid Interface Sci., 1997, 185, 210). The first one is characterized by a stoichiometry of around 28 lipids per polymer, which corresponds to the adsorption of the entire PAA molecule onto the membrane. Lipid molecules of the complex are exchanged with the “pure” lipid bilayer, with the lifetime of the complex being less than 0.1 s. The second type of DMPC−PAA complex is characterized by a stoichiometry of 6 to 7 lipids per polymer and contains PAA molecules that are only partially adsorbed onto the membrane. A decrease in the DMPC diffusion coefficient and activation energy for diffusion in the presence of PAA was explained by the formation of a new cooperative unit for diffusion, which contains the PAA molecule and several molecules of lipids.

  • 12.
    Gannon, Greg
    et al.
    Tyndall National Institute, Lee Makings, Prospect Row, Cork.
    Larsson, Andreas
    Greer, James C.
    Tyndall National Institute, Lee Makings, Prospect Row, Cork.
    Thompson, Damien J.
    Tyndall National Institute, Lee Makings, Prospect Row, Cork.
    Quantification of ink diffusion in microcontact printing with self-assembled monolayers2009In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, no 1, p. 242-247Article in journal (Refereed)
    Abstract [en]

    Spreading of ink outside the desired printed area is one of the major limitations of microcontact printing (μ-CP) with alkanethiol self-assembled monolayers (SAMs) on gold. We use molecular dynamics (MD) computer simulations to quantify the temperature and concentration dependence of hexadecanethiol (HDT) ink spreading on HDT SAMs, modeling 18 distinct printing conditions using periodic simulation cells of ∼7 nm edge length and printing conditions ranging from 7 ink molecules per cell at 270 K to 42 ink molecules per cell at 371K. The computed alkanethiol ink diffusion rates on the SAM are of the same order of magnitude as bulk liquid alkanethiol diffusion rates at all but the lowest ink concentrations and highest temperatures, with up to 20-30 times increases in diffusion rates at the lowest concentration-highest temperature conditions. We show that although alkanethiol surfaces are autophobic, autophobicity is not enough to pin the ink solutions on the SAM, and so any overinking of the SAM will lead to spreading of the printed pattern. Comparison of experimental and calculated diffusion data supports an interpretation of pattern broadening as a mixture of spreading on fully and partially formed SAMs, and the calculated spreading rates establish some of the fundamental limitations of μ-CP in terms of stamp contact time and desired pattern width

  • 13.
    Huangfu, Changan
    et al.
    State Key Laboratory of Materials-Oriented and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Dong, Yihui
    State Key Laboratory of Materials-Oriented and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Ji, Xiaoyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Wu, Na
    State Key Laboratory of Materials-Oriented and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Lu, Xiaohua
    State Key Laboratory of Materials-Oriented and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Mechanistic Study of Protein Adsorption on Mesoporous TiOin Aqueous Buffer Solutions2019In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 35, no 34, p. 11037-11047Article in journal (Refereed)
    Abstract [en]

    Protein adsorption is of fundamental importance for bioseparation engineering applications. In this work, a series of mesoporous TiO2 with various geometric structures and different aqueous buffer solutions were prepared as platforms to investigate the effects of the surface geometry and ionic strength on the protein adsorptive behavior. The surface geometry of the TiO2 was found to play a dominant role in the protein adsorption capacity when the ionic strength of buffer solutions is very low. With the increase in ionic strength, the effect of the geometric structure on the protein adsorption capacity reduced greatly. The change of ionic strength has the highest significant effect on the mesoporous TiO2 with large pore size compared with that with small pore size. The interaction between the protein and TiO2 measured with atomic force microscopy further demonstrated that the adhesion force induced by the surface geometry reduced with the increase in the ionic strength. These findings were used to guide the detection of the retention behavior of protein by high-performance liquid chromatography, providing a step forward toward understanding the protein adsorption for predicting and controlling the chromatographic separation of proteins.

  • 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.
    Forsling, Willis
    Protolytic surface reactions of a fluorapatite-maghemite mixture in aqueous suspension2005In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 21, no 17, p. 7717-7721Article in journal (Refereed)
    Abstract [en]

    Synthetically prepared maghemite and fluorapatite, characterized with BET, SEM, XRD, FT-IR, and FT-Raman, are used to investigate the protolytic properties and surface characteristics in a mixed system of maghemite and fluorapatite by means of potentiometric titrations and surface complex modeling. Titrations were performed in the pH range of 7.3-10.5 at 25 ± 0.2 C in ionic media of 0.10 mol dm-3 NaNO3 with 0.0100 mol dm-3 HNO3 and 0.0100 mol dm-3 NaOH used as titrants. The constant capacitance model (CCM) was applied to interpret the titration data. Two models with different surface equilibria were tested. In the first model, the mixed system was treated as a one-component system with a total surface area of 40.04 ± 5.2 m2 g-1 without any consideration to the subsystems. The surface equilibria, XOH + H + XOH2+, lg (int) = 6.74 ± 0.07; XOH XO- + H +, lg (int) = -7.75 ± 0.07, were found to represent an accurate model for the system, and the specific capacitance was optimized to 2.0 F m-2. The number of active surface sites Ns was found to be 1.2 sites nm-2. This model has, however, no relation to the subsystems of maghemite and fluorapatite. The second model is related to the subsystems and displays the surface equilibria, S2OH S2O- + H +, lg (int) = -9.12 ± 0.01; FeOH + H + FeOH2+, lg (int) = 6.80 ± 0.01; FeOH FeO- + H +, lg (int) = -7.77 ± 0.01, where S2OH is related to fluorapatite and FeOH is representing maghemite. Fluorapatite corresponds to the dominating active surface in the system. The specific capacitance was optimized to 18 F m-2. The Ns values were found to be 2.27 sites nm-2 for fluorapatite and 0.80 sites nm-2 for maghemite. The Ns values together with evidence from the FT-Raman and SEM investigations reveal that interactions between maghemite and fluorapatite surfaces occur during the titration. The acid-base properties and surface characteristics of the subsystems maghemite-H+ and fluorapatite-OH- using the CCM have been published earlier.

  • 15.
    Jarlbring, Mathias
    et al.
    Luleå tekniska universitet.
    Sandström, Dan
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsling, Willis
    Characterization of active phosphorus surface sites at synthetic carbonate-free fluorapatite using single-pulse 1H, 31P, and 31P CP MAS NMR2006In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 22, no 10, p. 4787-4792Article in journal (Refereed)
    Abstract [en]

    The chemically active phosphorus surface sites defined as POx, POxH, and POxH2, where x = 1, 2, or 3, and the bulk phosphorus groups of PO43- at synthetic carbonate-free fluorapatite (Ca5(PO4)3F) have been studied by means of single-pulse 1H,31P, and 31P CP MAS NMR. The changes in composition and relative amounts of each surface species are evaluated as a function of pH. By combining spectra from single-pulse 1H and 31P MAS NMR and data from 31P CP MAS NMR experiments at varying contact times in the range 0.2-3.0 ms, it has been possible to distinguish between resonance lines in the NMR spectra originating from active surface sites and bulk phosphorus groups and also to assign the peaks in the NMR spectra to the specific phosphorus species. In the 31P CP MAS NMR experiments, the spinning frequency was set to 4.2 kHz; in the single-pulse 1H MAS NMR experiments, the spinning frequency was 10 kHz. The 31P CP MAS NMR spectrum of fluorapatite at pH 5.9 showed one dominating resonance line at 2.9 ppm assigned to originate from PO43- groups and two weaker shoulder peaks at 5.4 and 0.8 ppm which were assigned to the unprotonated POx (PO, PO2-, and PO32-) and protonated POxH (PO2H and PO3H-) surface sites. At pH 12.7, the intensity of the peak representing unprotonated POx surface sites has increased 1.7% relative to the bulk peak, while the intensity of the peaks of the protonated species POxH have decreased 1.4% relative to the bulk peak. At pH 3.5, a resonance peak at -4.5 ppm has appeared in the 31P CP MAS NMR spectrum assigned to the surface species POxH2 (PO3H2). The results from the 1H MAS and 31P CP MAS NMR measurements indicated that H+, OH-, and physisorbed H2O at the surface were released during the drying process at 200 °C.

  • 16.
    Johnson, Bruce B.
    et al.
    La Trobe University.
    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
    31P nuclear magnetic resonance study of the adsorption of phosphate and phenyl phosphates on γ-Al2O32002In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 18, no 4, p. 1104-1111Article in journal (Refereed)
    Abstract [en]

    Adsorption of diphenyl-, phenyl- and orthophosphate on γ-Al2O3 was studied with a combination of macroscopic and 31P solid-state NMR measurements. Results for adsorption suggest that diphenyl phosphate was bound largely as an outer-sphere complex, while phenyl phosphate was held largely as inner-sphere surface complexes with an outer-sphere complex present only at higher pH values. Both the adsorption edge and the cross polarization magic angle spinning NMR spectra were consistent with the interaction between the surface and phenyl phosphate being driven by electrostatic forces. Adsorption of orthophosphate was more complex, with evidence of outer- and inner-sphere complexes and surface precipitation. Increasing the orthophosphate concentration and equilibration time tended to increase the fraction bound as a surface precipitate.

  • 17.
    Ju, Minhua
    et al.
    State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing Tech University , P. R. China.
    Li, Yupeng
    State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing Tech University , P. R. China.
    Yu, Liang
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Wang, Chongqing
    State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing Tech University , P. R. China.
    Zhang, Lixiong
    State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing Tech University , P. R. China.
    Two-Phase Diffusion Technique for the Preparation of Ultramacroporous/Mesoporous Silica Microspheres via Interface Hydrolysis, Diffusion, and Gelation of TEOS2018In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 34, no 5, p. 2046-2056Article in journal (Refereed)
    Abstract [en]

    Honeycombed hierarchical ultramacroporous/mesoporous silica microspheres were prepared via the hydrolysis of TEOS in the oil-water interface, with subsequent diffusion and gelation in the acidic water-phase microdroplets with the assistance of a simple homemade microdevice. The diffusion of furfuryl alcohol (FA) also happened at a relatively high rate during the hydrolysis and diffusion of TEOS. Therefore, plenty of FA will be inside of the water microdroplets and form a decent number of polyfurfuryl alcohol (PFA) microparticles, thereby obtaining honeycombed hierarchical porosity silica microspheres with abundant ultramacroporous cavities and mesopores after calcination. It was found that the concentration of FA, residence time, and reaction temperature have significant effects on the porosity and pore size due to the influence on the diffusion rate and amount of FA in water-phase microdroplets. The honeycombed silica microspheres have obvious microscopic visible ultramacroporous cavities with the submicrometer cavity diameter as high as 85% porosity based on the rough overall volume of microsphere. N2 adsorption-desorption isotherms show that the honeycombed hierarchical porosity silica microspheres have a high surface area of 602 m2 g-1, a mesopore volume of 0.77 cm3/g, and a mesopore porosity of 99.6% based on the total pore volume of N2 adsorption-desorption. On the basis of the experiment results, a rational formation process of the honeycombed hierarchical porosity silica microspheres was deduced.

  • 18.
    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.

  • 19.
    Leeuw, N.H. de
    et al.
    School of Chemistry, University of Bath.
    Parker, S.C.
    School of Chemistry, University of Bath.
    Rao, K. Hanumantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Modeling the competitive adsorption of water and methanoic acid on calcite and fluorite surfaces1998In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 14, no 20, p. 5900-5906Article in journal (Refereed)
    Abstract [en]

    Atomistic simulation techniques were used to investigate the interaction between the minerals calcite and fluorite with water and methanoic acid. The relative adsorption energies suggest that methanoic acid preferentially adsorbs onto fluorite surfaces, while adsorption of water is energetically preferred over methanoic acid on the calcite cleavage plane in agreement with experiment. The coverage and configuration of adsorbed methanoic acid on the surfaces depends largely on lattice spacing between the cations, and bridging between surface calcium atoms is highly favored. These findings have given an insight into interactions at the atomic level which indicate that modeling techniques should be capable of predicting adsorption behavior and designing collector molecules, which is of central importance to the mineral processing technique of flotation

  • 20.
    Li, Jie
    et al.
    State Key Laboratory of Materials-Oriented Chemical Engineering and College of Chemical Engineering, Nanjing Tech University, Nanjing, PR China.
    Jiang, Leilei
    State Key Laboratory of Materials-Oriented Chemical Engineering and College of Chemical Engineering, Nanjing Tech University, Nanjing, PR China.
    Yu, Liang
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Zhang, Lixiong
    State Key Laboratory of Materials-Oriented Chemical Engineering and College of Chemical Engineering, Nanjing Tech University, Nanjing, PR China.
    Preparation of Silica@Silica Core–Shell Microspheres Using an Aqueous Two-Phase System in a Novel Microchannel Device2020In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 36, no 2, p. 576-584Article in journal (Refereed)
    Abstract [en]

    In the present work, a novel microchannel device was developed and used for the preparation of core–shell microspheres combining with a dextran/poly(ethylene glycol) diacrylate (DEX/PEGDA) aqueous two-phase system. Silica@silica core–shell microspheres were prepared as a model material. Silica@silica core–shell microspheres with different sizes of cores and thicknesses of shells were prepared by using different flowrate ratios of DEX/silica and PEGDA/silica aqueous solutions. The content of colloidal silica and the calcination temperature have a significant effect on the texture properties of the prepared core–shell microspheres. The surface area decreased from 199 to 177 m2/g with an increase in the colloidal silica content from 30 to 60 wt %. For a specific colloidal silica content (50 wt %), with the increase in calcination temperature from room temperature to 650 °C, the total pore volume went through a maximum of 0.7 cm3 g–1 with a surface area of 178 m2 g–1 and pore size of 7.32 nm at 450 °C. Due to the accumulation of metal nanoparticles in DEX, different metal nanoparticles (Ni and Pd) were successfully introduced into the core of the core–shell microspheres for the preparation of silica/metal nanoparticles@silica core–shell microsphere catalysts. The catalysts showed similar catalytic performance as the metal nanoparticles for hydrogenation of 4-nitrophenol with a conversion higher than 95%. However, the core–shell microsphere catalyst is much easier to recover. The reuse experiments indicated that the core–shell catalyst has high stability.

  • 21. 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.

  • 22. Patra, Anuttam
    et al.
    Ralston, John
    Ian Wark Research Institute, University of South Australia.
    Sedev, Rossen
    Ian Wark Research Institute, University of South Australia.
    Zhou, Jingfang
    Ian Wark Research Institute, University of South Australia.
    Design of Pyrimidine-Based Photoresponsive Surfaces and Light-Regulated Wettability2009In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, no 19, p. 11486-11494Article in journal (Refereed)
    Abstract [en]

    Photoresponsive surfaces were prepared by attaching pyrimidine-terminated molecules to flat gold substrates (as thiol self-assembled monolayers) or by dip-coating quartz surfaces. Both types of films underwent photodimerization (two pyrimidine rings react with one another and form a cyclobutane type dimer through the C5═C6 double bond) when irradiated with light of 280 nm wavelength. The reverse reaction was carried out by irradiating the dimerized surface with light of 240 nm wavelength. The photoinduced chemical changes are accompanied by a change in the physical properties of the surface (e.g., wettability and acidity), and are highly dependent on the structure of the photoactive molecules. The surface dimerization reaction follows a pseudo-first order reaction. The rate constant is determined by the structure of the pyrimidine headgroup. In self-assembled monolayers, uracil derivatives dimerize faster than thymine derivatives due to a reduced steric repulsion near the reaction center. In dip-coated films, however, uracil derivatives appear to be less ordered and, correspondingly, the efficiency of the reaction is lower. The reaction rate is also very sensitive to the ordering within the layer, which can be manipulated through the structure of the tail. In SAMs, faster dimerization occurs with molecules containing flexible chains. In dip-coated films, the presence of a polar group at the chain terminus favors dimerization.

  • 23. Rusanova, Daniela
    et al.
    Forsling, Willis
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Pike, Kevin J.
    University of Warwick.
    Dupree, Ray
    University of Warwick.
    Formation of {Cu6[S2P(OC2H5)2]6} on Cu2S Surfaces from Aqueous Solutions of the KS2P(OC2H5)2 Collector: Scanning Electron Microscopy and Solid-State 31P Cross-Polarization/Magic Angle Spinning and Static 65Cu NMR Studies2005In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 21, no 10, p. 4420-4424Article in journal (Refereed)
    Abstract [en]

    The interactions of synthetic chalcocite surfaces with diethyldithiophosphate, potassium salt, K[S2P(OC2H5)2], were studied by means of 31P cross-polarization/magic angle spinning (CP/MAS) NMR spectroscopy and scanning electron microscopy (SEM). To identify the species formed on the Cu2S surfaces, a polycrystalline {CuI6[S2P(OC2H5)2]6} cluster was synthesized and analyzed by SEM, powder X-ray diffraction techniques and solid-state 31P CP/MAS NMR and static 65Cu NMR spectroscopy. 31P chemical shift anisotropy (CSA) parameters, CS and CS, were estimated and used for assigning the bridging type of diethyldithiophosphate ligands in the {CuI6[S2P(OC2H5)2]6} cluster. The latter data were compared to 31P CSA parameters estimated from the spinning sideband patterns in 31P NMR spectra of the collector-treated mineral surfaces: formation of polycrystalline {CuI6[S2P(OC2H5)2]6} on the Cu2S surfaces is suggested. The second-order quadrupolar line shape of 65Cu was simulated, and the NMR interaction parameters, CQ and Q, for the copper(I) diethyldithiophosphate cluster were obtained.

  • 24.
    Samyn, Pieter
    et al.
    Freiburg University, Institute for Forest Utilization and Works Science.
    Airoudj, Aissam
    Université de Haute-Alsace, Institut de Science des Matériaux de Mulhouse.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Roucoules, Vincent
    Université de Haute-Alsace, Institut de Science des Matériaux de Mulhouse.
    Haidara,, Hamidou
    Université de Haute-Alsace, Institut de Science des Matériaux de Mulhouse.
    Laborie, Marie-Pierre
    Freiburg University, Institute for Forest Utilization and Works Science.
    Metastable patterning of plasma nanocomposite films by incorporating cellulose nanowhiskers2012In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 28, no 2, p. 1427-1438Article in journal (Refereed)
    Abstract [en]

    A new method is presented for developing patterned thin nanocomposite films, by introducing cellulose nanowhiskers during pulsed plasma polymerisation of maleic anhydride. Metastable film structures develop as a combination of dewetting and buckling phenomena. By variation of the maleic anhydride monomer to nanocellulose weight ratio, the whiskers incorporate into a homogeneously covering patterned polymer film. An excess of nanowhiskers is required to prevent complete dewetting and deposit dimensionally stable films. The formation of anchoring points is assumed to stabilize the film through a ‘pinning’ effect to the substrate. The latter control the in-plane film stresses, similar to the effects of surface inhomogeneities such as artificial scratches. The different morphologies are evaluated by optical microscopy, AFM, contact angle measurements and ellipsometry. Further analysis by infrared spectroscopy and XPS suggests esterification between the maleic anhydride and cellulose moieties. The incorporation of renewable materials into a polymer film under solvent-free conditions demonstrates a further contribution to sustainable surface engineering, replacing traditional solvent-based processes.

  • 25. Sandström, Dan
    et al.
    Jarlbring, Mathias
    Luleå University of Technology.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsling, Willis
    A spectroscopic study of calcium surface sites and adsorbed iron species at aqueous fluorapatite by means of 1H and 31P MAS NMR2006In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 22, no 26, p. 11060-11064Article in journal (Refereed)
    Abstract [en]

    Assignments of the protolytic speciation at the calcium hydroxyl surface sites of synthetic fluorapatite and the chemical interactions between fluorapatite-maghemite and fluorapatite-Fe2+ ions have been studied by means of 1H and 31P single-pulse and 31P CP MAS NMR. Three possible forms of calcium hydroxyl surface sites have been suggested and assigned to CaOH, Ca(OH)2-, and CaOH2+, and their mutual ratios were found to vary as a function of pH. Due to their paramagnetic properties, iron species and Fe2+ ions adsorbed at the fluorapatite surface display a broad spinning sideband manifold in the single-pulse 31P MAS NMR spectra. The resonance lines in the 31P CP MAS NMR spectra originating from the bulk phosphate groups PO43- and phosphorus surface sites POx and POxH decrease with increasing Fe2+ ion adsorption. When iron species originating from maghemite are adsorbed at the fluorapatite surface, no 31P NMR signal is detected, which supports the hypothesis that surface reactions occur between the phosphorus surface sites of fluorapatite and iron

  • 26. Shao, Y.
    et al.
    Chen, W.
    Wold, E.
    Paul, Jan
    Dispersion and electronic structure of titania-supported cobalt and cobalt oxide1994In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 10, no 1, p. 178-187Article in journal (Refereed)
  • 27.
    Sivamohan, Rajaratnam
    et al.
    Luleå tekniska universitet.
    Donato, P. de
    Centre de Recherche sur la Valorisation des Minerais, Vandoeure.
    Cases, J.M.
    Centre de Recherche sur la Valorisation des Minerais, Vandoeure.
    Adsorption of oleate species at the fluorite-aqueous solution interface1990In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 6, no 3, p. 637-644Article in journal (Refereed)
    Abstract [en]

    Adsorption of oleate onto fluorite was measured as a function of the pH and residual concentration. Diffuse reflectance associated with the FTIR spectroscopy, ζ potential measured by electrophoresis, and turbidity have been used for the identification of adsorbed oleate at the fluorite surface. The adsorption isochrones are characterized by four distinct regions

  • 28.
    Szaraz, Ildiko
    et al.
    Luleå tekniska universitet.
    Forsling, Willis
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Spectroscopic study of the simultaneous adsorption of PVP and azelaic acid on γ-aluminia2001In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 17, no 13, p. 3987-3996Article in journal (Refereed)
    Abstract [en]

    The adsorption mechanism of 1-vinyl-2-pyrrolidone (VP), poly(1-vinyl-2-pyrrolidone) (PVP), and azelaic acid was investigated on synthetic -aluminum oxide surfaces using FT-IR, FT-Raman, UV, and 13C NMR spectroscopy (solid state). It was found that VP adsorption from ethylene glycol (EG) solution, as well as PVP adsorption from both aqueous and EG solutions, was negligible. In the case of EG solutions, the solvent adsorbed at the -alumina surface. The presence of dicarboxylic acid enhances the adsorption of the PVP, due to a hydrophobic interaction between the carbon chains of the polymer and the dicarboxylic acid. The simultaneous adsorption of PVP and azelaic acid was studied as a function of time, pH, and solvent in order to establish a more detailed surface complexation model. Surface complexation of azelaic acid in aqueous solution starts with mainly outer sphere coordination, driven by electrostatic forces, which is transformed to an inner sphere complex in time, forming a covalent bond between the carboxylate entity and the alumina surface, especially at low pH. At high pH the outer sphere complex is dominating.

  • 29.
    Wang, Liwei
    et al.
    State Key Laboratory of Materials-Oriented Chemical Engineering and College of Chemical Engineering , Nanjing Tech University , Nanjing, P. R. China.
    Yu, Liang
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Zeng, Changfeng
    College of Mechanical and Power Engineering , Nanjing Tech University , Nanjing , P. R. China. .
    Wang, Chongqing
    State Key Laboratory of Materials-Oriented Chemical Engineering and College of Chemical Engineering , Nanjing Tech University , Nanjing, P. R. China.
    Zhang, Lixiong
    State Key Laboratory of Materials-Oriented Chemical Engineering and College of Chemical Engineering , Nanjing Tech University , Nanjing, P. R. China.
    Fabrication of PAA-PETPTA Janus Microspheres with Respiratory Function for Controlled Release of Guests with Different Sizes2018In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 34, no 24, p. 7106-7116Article in journal (Refereed)
    Abstract [en]

    Poly(acrylic acid)–poly(ethoxylated trimethylolpropane triacrylate) (PAA–PETPTA) Janus microspheres with “respiratory” function for controlled release were prepared by polymerization of acrylic acid–ethoxylated trimethylolpropane triacrylate (AA–ETPTA) Janus microdroplets in a continuous oil phase in a simple capillary-based microfluidic device with the assistance of UV radiation. The flow rate ratios of AA and ETPTA phases and surfactant content in the continuous oil phase have a significant effect on the structure of the Janus microspheres. PAA part in the Janus microspheres has respiratory function for loading and release due to the different stimuli responses to different pHs. The hollow structure of PETPTA part with different sizes of opening serves as the host materials for PAA and could control release rate further due to the different opening sizes. The obtained PAA–PETPTA Janus microspheres showed high rhodamine B (RhB) loading of 860 mg g–1 and different controlled-release behavior in water with different pHs. The release rate increases with the increase of pH and the contact area of PAA part with water. The maximum controlled-release time for RhB was about 3 h in water with pH of 5. In addition, the Janus microspheres also showed controlled-release behavior for larger size guests, e.g., 150 nm polystyrene beads, which indicated a wide range of application. The loading and release behaviors for guests, for instance, for RhB, have almost no change even after six times of reuse, which indicated a high stability.

  • 30.
    Wu, Nanhua
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Ji, Xiaoyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Xie, Wenlong
    China Petroleum Chemicals Kunshan Company.
    Liu, Chang
    State Key Laboratory of Materials-Oriented and Chemical Engineering, Nanjing Tech University.
    Feng, Xin
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, Nanjing .
    Lu, Xiaohua
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing .
    Confinement Phenomenon Effect on the CO2 Absorption Working Capacity in Ionic Liquids Immobilized into Porous Solid Supports2017In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 33, no 42, p. 11719-11726Article in journal (Refereed)
    Abstract [en]

    In this work, the CO2 absorption working capacity and solubility in the ionic liquids immobilized into porous solid materials (substrates) was studied both experimentally and theoretically. The CO2 absorption working capacity in the immobilized ionic liquids was measured experimentally. It was found that the CO2 absorption working capacity and solubility increased up to 10 times compared to that in the bulk ionic liquids when the film thickness is nearly 2.5 nm in the [HMIm][NTf2] immobilized into the P25. Meanwhile, a new model was proposed to describe the Gibbs free energy of CO2 in the immobilized ionic liquids, and both macro- and micro-analyses of the CO2 solubility in the confined ionic liquids were conducted. The theoretical investigations reveal that the substrate has a crucial effect on the gas solubility in the ionic liquid immobilized into the substrates, and the model performance was approved with the consideration of substrate effect.

  • 31.
    Zhou, Han
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Farzaneh, Amirfarrokh
    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.
    Grahn, Mattias
    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.
    Colloidal Defect-Free Silicalite-1 Single Crystals: Preparation, Structure Characterization, Adsorption, and Separation Properties for Alcohol/Water Mixtures2015In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 31, no 30, p. 8488-8494Article in journal (Refereed)
    Abstract [en]

    In this work, colloidal silicalite-1 single crystals are for the first time synthesized using fluoride as mineralizing agent at near neutral pH. SEM, TEM, DLS, XRD, solid-state 29Si MAS NMR, and adsorption/desorption experiments using nitrogen, water, n-butanol, and ethanol as adsorbates were used to characterize the crystals. The single crystals have a platelike habit with a length of less than 170 nm and an aspect ratio (length/width) of about 1.2, and the thickness of the crystals is less than 40 nm. Compared with silicalite-1 crystals grown using hydroxide as mineralizing agent, the amount of structural defects in the lattice is significantly reduced and the hydrophobicity is increased. Membrane separation and adsorption results show that the synthesized defect-free crystals present high selectivity to alcohols from alcohol/water mixtures. The n-butanol/water adsorption selectivities were ca. 165 and 14 for the defect-free crystals and a reference sample containing defects, respectively, illustrating the improvement in n-butanol/water selectivity by eliminating the polar silanol defects.

  • 32.
    Zhu, Chuantao
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Dobryden, Illia
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Ryden, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Adsorption Behavior of Cellulose and Its Derivatives toward Ag(I) in Aqueous Medium: An AFM, Spectroscopic, and DFT Study2015In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 31, no 45, p. 12390-12400Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to develop a fundamental understanding of the adsorption behavior of metal ions on cellulose surfaces using experimental techniques supported by computational modeling, taking Ag(I) as an example. Force interactions among three types of cellulose microspheres (native cellulose and its derivatives with sulfate and phosphate groups) and the silica surface in AgNO3 solution were studied with atomic force microscopy (AFM) using the colloidal probe technique. The adhesion force between phosphate cellulose microspheres (PCM) and the silica surface in the aqueous AgNO3 medium increased significantly with increasing pH while the adhesion force slightly decreased for sulfate cellulose microspheres (SCM), and no clear adhesion force was observed for native cellulose microspheres (CM). The stronger adhesion enhancement for the PCM system is mainly attributed to the electrostatic attraction between Ag(I) and the negative silica surface. The observed force trends were in good agreement with the measured zeta potentials. The scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) analyses confirmed the presence of silver on the surface of cellulose microspheres after adsorption. This study showed that PCM with a high content of phosphate groups exhibited a larger amount of adsorbed Ag(I) than CM and SCM and possible clustering of Ag(I) to nanoparticles. The presence of the phosphate group and a wavenumber shift of the P−OH vibration caused by the adsorption of silver ions on the phosphate groups were further confirmed with computational studies using density functional theory (DFT), which gives support to the above findings regarding the adsorption and clustering of Ag(I) on the cellulose surface decorated with phosphate groups as well as IR spectra.

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