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Adsorption Studies (adsorption + studies)
Selected AbstractsBridging the Gap between CO Adsorption Studies on Gold Model Surfaces and Supported Nanoparticles,ANGEWANDTE CHEMIE, Issue 11 2010Miguel López-Haro Theorie und Praxis in Einklang: Die volumetrische Adsorption von CO bei 308,K sowie Daten aus UHR-HAADF-STEM, HREM und computergestützten Modellierungen wurden verglichen. Experimentelle CO/Au-Verhältnisse bei Sättigungsbedeckung für zwei Goldträgerkatalysatoren stimmten gut mit den Vorhersagen eines Nanostrukturmodells überein, das eine CO-Adsorption an Goldpositionen mit Koordinationszahlen kleiner acht berücksichtigt. [source] Improved methods for carbon adsorption studies for water and wastewater treatmentENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 2 2006Wei-chi Ying Abstract An improved method was developed to rank activated carbon in removing organic water pollutants. The simple and standardized evaluation method uses a set of four adsorptive capacity indicators: phenol, iodine, methylene blue, and tannic acid numbers; those four indicator compounds were selected because they cover the molecular size range of most organic water pollutants. An improved microcolumn rapid breakthrough (MCRB) test method was developed from the existing HPMC (high-pressure minicolumn) and RSSCT (rapid small-scale column test) methods by simplifying the experimental procedure and using readily available low-cost pump, sampler, piping, and fittings. This method can be practiced in an ordinary environmental laboratory to select the best carbon, to verify the treatment effectiveness, and to estimate the adsorption treatment cost based on the observed capacity utilization rate for carbon in the adsorber without the problems often encountered with using small and mini traditional columns. The benefits of the four-parameter carbon selection method and the MCRB method were demonstrated by adsorption isotherm and breakthrough data for several indicator compounds and organic water pollutants. These improved methods will enable efficient carbon adsorption studies necessary for more applications of carbon adsorption technology in water and wastewater treatment. © 2006 American Institute of Chemical Engineers Environ Prog, 2006 [source] Efficient Removal of Anionic Surfactants Using Mesoporous Functionalised Hybrid MaterialsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 25 2009Carmen Coll Abstract A new hybrid system for surfactant removal from water has been developed using mesoporous material (MCM-41) functionalised with suitable binding groups. Solid S1, S2 and S3 were prepared by reaction of the mesoporous material with N -methyl- N, -(propyltrimethoxysilyl)imidazolium chloride, (3-aminopropyl)trimethoxysilane or 4-[(triethoxysilylpropylthio)methyl]pyridine, respectively. The functionalised materials were characterised following standard solid-state techniques. The final prepared solids consist of a siliceous MCM-41-type mesoporous support with the surface decorated by imidazolium, amine and pyridine binding groups suitable for anion coordination. Equilibrium adsorption studies of linear alkylbenzenesulfonate (LAS) using S1, S2 and S3 in water have been carried out. The obtained adsorption data were correlated with a Langmuir isotherm model that gives an acceptable description of the experimental data. The maximum surfactant uptake/binding site (mol,mol,1) and the surfactant adsorption capacity (mmol,g,1) for materials S1, S2 and S3 were calculated. S1 shows a positive-charged functionalised surface that is independent of the pH of the solution, whereas S2 and S3 are functionalised with neutral groups that need to be protonated in order to display electrostatic binding interactions with the anionic surfactants. Therefore, whereas the adsorption capacity of S1 is pH-independent, S2 and S3 display larger LAS adsorption at acidic pH. The adsorption ability at a certain pH follows the order S1 >> S3 > S2. A remarkable maximum surfactant adsorption of 1.5 mmol per gram of material was observed for S1 at neutral pH. S2 and S3 behave as poorer adsorbents and show maximum surfactant adsorption of 0.197 and 0.335 mmol per gram of material, respectively, at pH 2.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] A modified cellulose adsorbent for the removal of nickel(II) from aqueous solutionsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 11 2006David W O'Connell Abstract A series of adsorption studies was carried out on a glycidyl methacrylate- modified cellulose material functionalised with imidazole (Cellulose- g -GMA-Imidazole) to assess its capacity in the removal of Ni(II) ions from aqueous solution. The study sought to establish the effect of a number of parameters on the removal of Ni(II) from solution by the Cellulose- g -GMA-Imidazole. In particular, the influence of initial metal concentration, contact time, solution temperature and pH were assessed. The studies indicated a Ni(II) uptake on the Cellulose- g -GMA-Imidazole sorbent of approximately 48 mg g,1 of nickel from aqueous solution. The adsorption process fitted the Langmuir model of adsorption and the binding process was mildly endothermic. The kinetics of the adsorption process indicated that nickel uptake occurred within 400 min and that pseudo-second order kinetics best describe the overall adsorption process. Nickel(II) adsorption, recovery and re-adsorption studies indicated that at highly acidic pH values the adsorbent material becomes unstable, but in the range pH 3,6, the adsorbent is stable and shows limited but significant Ni(II) recovery and re-adsorption capability. Copyright © 2006 Society of Chemical Industry [source] Synthesis, stereochemistry and adsorption studies of new spiranes and polyspiranes containing 1,2-dithiolane unitsJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 3 2007Radu A. Gropeanu The synthesis and stereochemistry of a series of new cyclic disulfides containing (poly)spirane 1,2-dithiolane units are reported. Also included is a study of the self-assembled monolayers (SAMs) of these compounds on a gold surface. The characteristics of the resultant SAMs were determined by IR spectroscopy using molecular mechanics calculations. [source] Factors influencing the adsorption of stabilizers onto carbon black: Flow microcalorimetry studiesJOURNAL OF VINYL & ADDITIVE TECHNOLOGY, Issue 2 2000J. M. Peñta The surface activity of various kinds of carbon black toward phenolic antioxidants and hindered amine light stabilizers (HALS) was examined by using flow microcalorimetry (FMC). Phenolic hydroxyl and ester groups were found to be the moieties responsible for the adsorption activity of primary phenolic antioxidants onto the carbon black surfaces. Furthermore, a difference in the degree of phenolic hydroxyl hindrance by alkyl groups was found to be the main factor affecting the adsorption activity of the phenol group. A difference in the degree of substitution of the piperidine amine, as well as the number and type of functionality per molecule, are important factors that were found to influence the adsorption activity of HALS. Data from adsorption studies using model compounds, some of which represented functional portions of the stabilizer molecules, reflected behavior sin ilar to that observed with the stabilizers. In addition, these latter results showed that FMC analysis can yield potentially useful information beyond that given by the usual parameters such as BET surface area, I2, DBP, and CTAB adsorption values. Differences in the behavior between types of carbon black were evident and showed that the specific surface area is not the most important factor in the adsorption/desorption activity, but also the chemical nature of the surface. From the activity observed for model compounds, it was deduced that the presence of secondary and tertiary amine in the backbone and branch structures also has an important role in the adsorption activity of polymeric HALS. In general, the observed quantities can be related to the values of adsorption/desorption energy and to the molar mass of the probe. [source] Degradation and adsorption of terbuthylazine and chlorpyrifos in biobed biomixtures from composted cotton crop residuesPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 10 2010Konstantina Kravvariti Abstract BACKGROUND: Biobeds have been well studied in northern Europe, whereas little is known regarding their use in southern Europe. The degradation and adsorption of terbuthylazine (TA) and chlorpyrifos (CP) were studied in three different biomixtures composed of composted cotton crop residues, soil and straw in various proportions, and also in sterilised and non-sterilised soil. RESULTS: Compost biomixtures degraded the less hydrophobic TA at a faster rate than soil, while the opposite was evident for the more hydrophobic CP. These results were attributed to the rapid abiotic hydrolysis of CP in the alkaline soil (pH 8.5) compared with the lower pH of the compost (6.6), but also to the increasing adsorption (Kd = 746 mL g,1) and reduced bioavailability of CP in the biomixtures compared with soil (Kd = 17 mL g,1), as verified by the adsorption studies. CONCLUSIONS: Compost had a dual but contrasting effect on degradation that depended on the chemical nature of the pesticide studied: a positive effect towards TA owing to increasing biodegradation and a negative effect towards CP owing to increasing adsorption. Overall, composted cotton crop residues could be potentially used in local biobed systems in Greece, as they promoted the degradation of hydrophilic pesticides and the adsorption of hydrophobic pesticides. Copyright © 2010 Society of Chemical Industry [source] Surface characterization of flax, hemp and cellulose fibers; Surface properties and the water uptake behaviorPOLYMER COMPOSITES, Issue 5 2002Alexander Bismarck The surface characteristics of several natural fibers,flax, hemp and cellulose,were investigated using scanning electron microscopy, BET-surface area and zeta (,-) potential measurements. ,-Potential measurements using the streaming potential method were performed in order to study the water uptake behavior as well as the surface properties of several natural fibers. The influence of different flax-fiber separation methods and several modifications, like industrial purification, and such a treatment followed by alkaline purification as well as polypropylene grafting on the fiber surface morphology, surface area and time- and pH-depending ,-potentials were studied. The time-dependence of the ,-potential, measured in 1 mM KCl solution, offeres and alternative possibility to estimate the water uptake behavior for nearly all investigated natural fibers. The water uptake data derived from the ,-potential measurements (, = f(t)) were compared with data from conventional water adsorption studies for some chosen examples. [source] Spectroscopic and thermal studies of poly[(N -vinylimidazole)- co -(maleic acid)] hydrogel and its quaternized formPOLYMER INTERNATIONAL, Issue 4 2008Nursel Pekel Abstract BACKGROUND: In this study, poly[(N -vinylimidazole)- co -(maleic acid)] (poly(VIm/MA)) hydrogels were prepared by ,-irradiation of ternary mixtures of N -vinylimidazole,maleic acid,water using a 60Co ,-source. Spectroscopic and thermal analyses of these hydrogels as a function of protonation showed that the results are consistent with the existence of an H-bridged complex when the imidazole rings are partially protonated. Finally, the efficiency and binding trends of Cu2+, Co2+, Cd2+ and Pb2+ ions with both protonated and unprotonated poly(VIm/MA) hydrogels were determined. RESULTS: Gelation of 90% was reached at around 180 kGy dose at the end of irradiation. The poly(VIm/MA) hydrogels synthesized were further protonated in HCl solutions with different concentrations. Hydrogels originally showed 450% volumetric swelling; this ratio reached 1900% after protonation at pH = 5.0. Fourier transform infrared spectral changes in the +NH stretching region (3200,3600 and 1173 cm,1) and the ring mode deformation at 915 cm,1 are consistent with the formation of an H-bridged complex between the protonated and unprotonated imidazole rings upon partial protonation. Similar changes were obtained from NMR spectra of both the protonated and unprotonated forms of the hydrogels. CONCLUSION: Protonated and unprotonated hydrogels have been used in heavy metal ion adsorption studies for environmental purposes. Adsorption decreased with decreasing pH value due to the protonation of the VIm ring. The adsorption of Me2+ ions decreased in the order Cu2+ > Co2+ > Cd2+ > Pb2+, which is related to the complexation stability as well as the ionic radius of the metal ions. These results show that P(VIm/MA) hydrogels can be used efficiently to remove heavy metal ions from aqueous solutions. However, the protonated form is a bad choice for heavy metal ion adsorption due to electrostatic repulsion forces; it can nevertheless be assumed to be a good choice for anion adsorption from environmental waste water systems. Copyright © 2007 Society of Chemical Industry [source] | |||||||||||||