| 11. |
- Kaplun, Marina, et al.
(författare)
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Crystal structures and spectroscopic properties of palladium complexes isolated from Pd–EDTA solutions
- 2005
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Ingår i: Inorganica Chimica Acta. - : Elsevier. - 0020-1693 .- 1873-3255. ; 358:3, s. 527-534
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Tidskriftsartikel (refereegranskat)abstract
- Two complexes were isolated from aqueous Pd(NO3)2–Na2H2EDTA solutions and studied by single crystal X-ray diffraction, IR/Raman spectroscopy, and photoelectron spectroscopy. The first complex, Pd(Hkpda)2 (kpda = ketopiperazinediacetate dianion, C8H10N2O5), forms yellow parallelepipeds during slow evaporation of Pd(NO3)2–Na2H2EDTA solution at 25 °C, and is a result of EDTA oxidation. The second one, [Pd(μ-H2EDTA)]2 · 2NaNO3 · 7.5H2O, with two EDTA molecules acting as bridges between two palladium atoms, forms yellow bipyramides during fast evaporation at 60 °C. In both complexes, the palladium atoms adopt a planar trans-geometry by bonding to two nitrogen and two oxygen atoms of two ligand molecules.
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| 12. |
- Kiselev, A, et al.
(författare)
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Solar light decomposition of DFP on the surface of anatase and rutile TiO2 prepared by hydrothermal treatment of microemulsions
- 2005
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 584:1, s. 98-105
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Tidskriftsartikel (refereegranskat)abstract
- The photocatalytic decomposition of diisopropylfluorophosphate (DFP) over nanostructured anatase and rutile TiO2 powder was investigated by FTIR and XPS. Upon irradiation with artificial solar light DFP decomposed on both polymorphs as evidenced by FTIR. For both crystalline structures acetone and subsequently coordinated formate and carbonate were observed on the surface during the photocatalytic reaction is the isopropyl groups dissociated from DFP. XPS revealed that small amounts of phosphates and inorganic fluoride (Ti-F) gradually built up on both TiO2 surfaces, while organic F was present only on the rutile phase. From repeated cycles of intermittent DFP adsorption and irradiation measurements, the decomposition rates and formation of residuals on the surface were deduced. It was found that the overall oxidation yield is higher on anatase than rutile. The oxidation rate decreases with increasing irradiation time. an effect that is more pronounced on rutile. We find that both the difference between the polymorphs and the initial decrease of the oxidation yield can largely be explained by variations in surface area rather than poisoning by POx or F species. In particular, we observe a dramatic decrease of the specific area or rutile as a function of photocatalytic oxidation cycle. (c) 2005 Elsevier B.V. All rights reserved.
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| 13. |
- Leone, Laura, et al.
(författare)
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Modeling the Acid-Base Properties of Bacterial Surfaces : A Combined Spectroscopic and Potentiometric Study of the Gram-Positive Bacterium Bacillus subtilis
- 2007
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 41:18, s. 6465-6471
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Tidskriftsartikel (refereegranskat)abstract
- In this study, macroscopic and spectroscopic data were combined to develop a surface complexation model that describes the acid-base properties of Bacillus subtilis. The bacteria were freeze-dried and then resuspended in 0.1 M NaCl ionic medium. Macroscopic measurements included potentiometric acid-base titrations and electrophoretic mobility measurements. In addition, ATR-FTIR spectra of wet pastes from suspensions of Bacillus subtilis at different pH values were collected. The least-squares program MAGPIE was used to generate a surface complexation model that takes into account the presence of three acid-base sites on the surface: COOH, NH+, and PO-, which were identified previously by XPS measurements. Both potentiometric titration data and ATR-FTIR spectra were used quantitatively, and electrostatic effects at the charged bacterial surface were accounted for using the constant capacitance model. The model was calculated using two different approaches: in the first one XPS data were used to constrain the ratio of the total concentrations of all three surface sites. The capacitance of the double layer, the total buffer capacity, and the deprotonation constants of the NH+, POH, and COOH species were determined in the fit. A second approach is presented in which the ratio determined by XPS of the total concentrations of NH+ to PO- sites is relaxed. The total concentration of PO- sites was determined in the fit, while the deprotonation constant for POH was manually varied until the minimization led to a model which predicted an isoelectric point that resulted in consistency with electrophoretic mobility data. The model explains well the buffering capacity of Bacillus subtilis suspensions in a wide pH range (between pH = 3 and pH = 9) which is of considerable environmental interest. In particular, a similar quantitative use of the IR data opens up possibilities to model other bacterial surfaces at the laboratory scale and help estimate the buffering capacity of carboxylate-containing compounds in natural samples.
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| 14. |
- Leone, Laura, et al.
(författare)
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Surface characterization of the Gram-positive bacteria Bacillus subtilis-an XPS study
- 2006
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Ingår i: Surface and Interface Analytsis. - : Wiley. - 0142-2421 .- 1096-9918. ; 38, s. 202-5
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Tidskriftsartikel (refereegranskat)abstract
- Interactions at the bacteria-solid interface in aquatic environments are of crucial importance in biofilm formation processes. The characterization of microbial surfaces properties is therefore a very important step for the understanding of these interactions. In this study, XPS spectra of Bacillus subtilis wet pastes centrifuged from suspensions over a span of pH values were recorded using a fast-freezing procedure. The chemical composition of the bacterial surface was elucidated and the presence of surface sites containing carboxylate, phosphate and amine functional groups was established. It was possible to distinguish between charged and uncharged amine sites on the surface and follow their deprotonation reactions as a function of pH. It is suggested that increased metabolic activity around the physiological pH results in the excretion of proteins and/or peptides which are possibly related to the production of extracellular polymeric substances (EPS). Copyright © 2006 John Wiley & Sons, Ltd.
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| 15. |
- Nguyen, Anh Mai, et al.
(författare)
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Thermally induced dissolution/precipitation : A simple approach for the preparation of Macroporous Monoliths from Linear Aliphatic Polyamides
- 2009
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Ingår i: Journal of Separation Science. - : Wiley InterScience. - 1615-9306 .- 1615-9314. ; 32:15-16, s. 2619-2628
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Tidskriftsartikel (refereegranskat)abstract
- A versatile way of preparing macroporous monolithic materials from linear aliphatic polyamides is presented. Simply, polyamide pellets were treated in benzyl alcohol (BA) at elevated temperature, causing dissolution by interchain hydrogen bond disruption. Subsequent cooling below the upper critical solution temperature (UCST) resulted in precipitation and partial restoration of the semicrystalline polymer, which is organized into network structures. The final steps were a solvent exchange of BA for methanol, followed by drying to form monolithic entities. A number of polyamides ranging from hydrophilic to hydrophobic were tested and under the experimental conditions, poly(1-aza-2-cycloheptanone (PA6) and (poly-[imino-1,6-hexanediylimino{1,10-dioxo-1,10-decanediyl}] (PA610) yielded entities with macroporous properties that were deemed useful for liquid chromatography. The morphological features and porous properties of the monoliths produced by this dissolution-precipitation procedure were studied by scanning electron microscopy, adsorption/desorption of N2(g) according to the Brunauer-Emmett-Teller (BET) principle, and mercury intrusion porosimetry. Degradation of the polymer backbone was noticeable when the dissolution time was extended and shortening of the polymer chains was confirmed by MALDI-MS, viscosity measurements, X-ray photoelectron spectroscopy (XPS), and potentiometric titration. When the heating was limited to the time it took to dissolve the polymers, mechanically stable monoliths could be obtained. The dissolution/heat treatment time further seemed to be useful for controlling the macroporous morphology.
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| 16. |
- Nordborg, Anna, et al.
(författare)
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A cation-exchange material for protein separations based on grafting of thiol-terminated sulfopropyl methacrylate telomers onto hydrophilized monodisperse divinylbenzene particles
- 2008
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Ingår i: Journal of Separation Science. - : Wiley-VCH Verlagsgesellschaft. - 1615-9306 .- 1615-9314. ; 31:12, s. 2143-2150
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Tidskriftsartikel (refereegranskat)abstract
- A strong cation-exchange separation material has been prepared from monodisperse divinylbenzene particles modified by a grafting to approach, utilizing as anchoring points epoxy groups introduced onto the surface of the particles via oxidation of residual vinyl groups. The grafted chains consisted of thiol-terminated telomers of sulfopropyl methacrylate prepared by iniferter mediated polymerization, and grafting was performed by reaction of the corresponding thiolate anion with the surface epoxy groups. Attachment through epoxy moieties that were subsequently converted into 2,3-propanediol groups increased the hydrophilicity of the polymeric particles and incubation experiments showed no signs of the proteins denaturing on the column during an extended contact time of 1 h at room temperature. The performance of the grafted material was demonstrated by the chromatographic separation of cytochrome C, lysozyme, myoglobin, and ribonuclease A, in a cation-exchange mode.
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| 17. |
- Persson, Ylva, et al.
(författare)
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Dioxins, chlorophenols and other chlorinated organic pollutants in colloidal and water fractions of groundwater from a contaminated sawmill site
- 2008
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Ingår i: Environmental Science and Pollution Research. - : Springer. - 0944-1344 .- 1614-7499. ; 15:6, s. 463-471
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Tidskriftsartikel (refereegranskat)abstract
- Background, aim, and scope: The distribution of chlorinated organic contaminants in groundwater and the importance of colloids were studied in groundwater from a sawmill site contaminated by chlorophenol preservatives.Materials and methods: The groundwater was fractionated into three different size ranges: (1) >0.7 μm, (2) 0.4–0.7 μm and (3) 0.2–0.4 μm and the filtered water phase. The concentrations of chlorophenols (CP), chlorinated phenoxy phenols (PCPP), chlorinated diphenyl ethers (PCDE), chlorinated dibenzofurans (PCDF) and chlorinated dibenzo-p-dioxins (PCDD) were determined in each fraction. The colloids were characterised regarding the chemical composition using X-ray photoelectron spectroscopy (XPS).Results: Chlorophenols were mostly found in the water fraction and PCDD/Fs were found almost exclusively in the particulate fractions. For example, the filtered water phase contained 2,100 μg l−1 and 0.72 ng l−1 for CPs and PCDD/Fs, respectively, and the particulate fractions contained 27 μg l−1 and 32 ng l−1 for CPs and PCDD/Fs, respectively. XPS evaluation of the particulate phases showed no correlation between the surface chemistry of the particle properties and the distribution of chlorinated compounds.Discussion: The results suggest that groundwater transport of CPs, PCPPs, PCDEs and PCDD/Fs may occur from contaminated sawmill sites and that the colloid-facilitated transport, especially of PCDD/Fs, is substantial. The results correlated well with previous studies of compounds sorbed to dissolved organic carbon, which indicate that dissolved and colloidal organic carbon facilitated the transport of PCDEs, PCDFs and PCDDs particularly.Conclusions: Several classes of chlorinated compounds were readily detected in the groundwater samples. Due to the differences in their physicochemical properties, CPs, PCPPs, PCDEs and PCDD/Fs vary in their partitioning between colloidal fractions and the filtered groundwater. The proportion of the bound fraction increased with an increasing hydrophobicity of the chlorinated compounds. The groundwater transport of colloid-associated pollutants from the site may be significant.Recommendations and perspectives: The results imply that colloidal particles <0.7 μm are freely mobile in groundwater from this site. The groundwater transport of colloid-associated pollutants may be significant. However, the extent of the problem is not yet known and, thus, further research is needed to evaluate the impact of colloidal transport of hydrophobic organic contaminants. In Sweden alone, 400 to 500 sawmill sites are estimated to be contaminated with PCDD/Fs as a result of the former use of CP-based wood preservatives. The widespread use of CP mixtures for a variety of applications, including wood preservation, indicates that potential colloidal transport will be an issue of concern in many countries.
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| 18. |
- Ramstedt, Madeleine, et al.
(författare)
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Bacterial and mammalian cell response to poly(3-sulfopropyl methacrylate) brushes loaded with silver halide salts
- 2009
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Ingår i: Biomaterials. - : Elsevier BV. - 0142-9612 .- 1878-5905. ; 30:8, s. 1524-31
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Tidskriftsartikel (refereegranskat)abstract
- This study investigates the antibacterial and cytotoxic effect of surfaces with sulphonate brushes containing silver salts. By using the same type of samples for both cytotoxicity and antibacterial studies, these two parameters could be compared in a controlled way. The silver was incorporated into the brush in four different forms to enable release of silver ions at different concentrations and different rates. It was found that although the surfaces displayed very good antibacterial properties in buffer solutions, this effect disappeared in systems with high protein content. Similarly, the silver-containing surfaces displayed cytotoxic effects in the absence of serum proteins but this effect was reduced in the presence of serum. The speciation of silver in the different solutions is discussed. Cytotoxic and antibacterial effects are compared at the different silver concentrations released. The implications of a concentration range where silver could be used to kill bacterial without harmful effects on mammalian cells are also discussed and questioned.
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| 19. |
- S A, Simanova, et al.
(författare)
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Adsorption of palladium, platinum, and gold chloride complexes by carbon fibers with various structures
- 2008
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Ingår i: Fibre Chemistry. - : Springer?Business Media, Inc. - 0015-0541 .- 1573-8493. ; 40:4, s. 365-75
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Tidskriftsartikel (refereegranskat)abstract
- Data are given characterizing the effects of the porous structures in activated carbon fibers (ACF) and the amounts of oxidized carbon forms on the extent and rate of adsorption for various chloride complexes of the platinum metals and gold. The adsorption mechanisms on ACF are considered for these metal chloride complexes. The practical significance of the research is considered.
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| 20. |
- Sandström, Åke, et al.
(författare)
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XPS characterisation of chalcopyrite chemically and bio-leached at high and low potential
- 2005
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Ingår i: Minerals Engineering. - : Elsevier BV. - 0892-6875 .- 1872-9444. ; 18:5, s. 505-515
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Tidskriftsartikel (refereegranskat)abstract
- Leaching of chalcopyrite in sulphuric acid media has been investigated under constant redox potential conditions in solution. The leaching residues were analysed by X-ray diffraction and X-ray photoelectron spectroscopy. The leaching was performed at two different levels of redox potential, 420 mV and 600 mV (Pt vs. Ag, AgCl), at 65 °C. Both bioleaching and chemical leaching were investigated. The bioleaching was continuous, with a culture of the extremely thermophilic microorganism Sulfolobus metallicus. The high redox potential experiment was a "normal" bioleaching experiment; i.e., normal air flow, etc., the redox potential obtained at steady state was 600 mV and the low redox condition was achieved by a reduced airflow and additions of a sodium sulphite solution. The chemical leaching was done as a redox titration with potassium permanganate as oxidising agent to maintain the redox potential at 600 mV and 420 mV, respectively. Chalcopyrite leaching was greatly enhanced at the lower redox potential for both types of leaching, but especially during chemical leaching, which also resulted in large amounts of elemental sulphur. Passivation of the leaching at high redox potential was followed by a concomitant precipitation of large amounts of jarosite. Bioleaching resulted in a more complete sulphur oxidation to sulphate, even at low redox potential. It is thus concluded that passivation during chalcopyrite leaching is caused by jarosite and not elemental sulphur.
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