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Adsorption Process (adsorption + process)
Selected AbstractsProbability Density Function (PDF) Simulation of Turbulent Reactive Gas-Solid Flow in a RiserCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 3 2009S. N. P. Vegendla Abstract A hybrid Lagrangian-Eulerian methodology is developed for the numerical simulation of turbulent reactive gas-solid flow. The SO2 -NOx Adsorption Process (SNAP) in a riser reactor with dilute gas-solid flow is taken as a test case. A three-dimensional time-dependent simulation is performed. By using the transported composition PDF method [1], modeling of the mean chemical source term and mass transfer terms in the gas-solid flow model equations is no longer needed. A notional particle-based Monte-Carlo algorithm is used to solve the transported composition PDF equations. A Finite-Volume technique is used to calculate the hydrodynamic fields from the Reynolds Averaged Navier Stokes (RANS) equations combined with the k -, turbulence model for the gas phase and the Kinetic Theory of Granular Flow (KTGF) for the solid phase [2]. The newly developed hybrid solution technique is tested with the SNAP chemistry that has a total of 13 scalars (i.e., 5 gas phase components and 8 solid phase species) for which the composition fields of the reactive species are calculated. A good agreement between simulated and experimental gas-outlet composition of a demonstration unit is obtained. [source] Effects of Adsorbent Characteristics on Adiabatic Vacuum Swing Adsorption Processes for Solvent Vapor RecoveryCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 11 2006S. A. Al-Muhtaseb Abstract The effects of the adsorbent characteristics on the performance parameters and periodic state behavior of the vacuum swing adsorption (VSA) solvent vapor recovery (SVR) processes are examined and optimized. The adsorbent characteristics studied were the adsorbent particle's porosity, density, radius and heat capacity, the packed bed void fraction, the isosteric heat of adsorption, the monolayer saturation limit of the solvent molecules on the adsorbent, the adsorbent's affinity to adsorb the solvent molecules and the mass transfer coefficient for the adsorption of the solvent molecules. It was found that the best VSA-SVR process performances can be obtained using adsorbents characterized by the minimum possible packed bed void fraction and particle porosity, with the maximum possible adsorbent heat capacity and density, adsorption monolayer saturation capacity and mass transfer coefficient, and at intermediate adsorption affinity and isosteric heat of adsorption of the solvent molecules. [source] Effect of internal cooling/heating coil on adsorption/regeneration of solid desiccant tray for controlling air humidityINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 11 2008B. N. Hung Abstract Thermal performances of solid desiccant tray having internal cooling/heating coil for air humidity adsorption and desiccant regeneration are investigated. Three units of desiccant tray each of 48,cm,×,48,cm cross-sectional area and 2.5,cm thickness filled with silica gel are tested in a wind tunnel. For adsorption process, an air stream is flowing through the desiccant trays and the air humidity is captured by the silica gel. Approximately 10,40% of air humidity could be adsorbed more in case of the internal cooling. Besides, the outlet air temperature increases only slightly. In regeneration process, a hot air stream is used to repel the moisture in the silica gel. With the internal heating, the regeneration time is shorter compared with that without internal water heating. In addition, a correlation for calculating the adsorption/regeneration performance of the silica gel trays is developed and the results from the model agree well with the experimental data. Copyright © 2008 John Wiley & Sons, Ltd. [source] In-situ small-angle neutron scattering study of pore filling and pore emptying in ordered mesoporous silicaJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 1 2010M. Erko The capillary condensation and capillary emptying of water and perfluoropentane in ordered mesoporous SBA-15 silica is studied by in-situ small-angle neutron scattering (SANS). The SANS data can be perfectly described by a simple analytical model for spatially random pore filling (Laue scattering) for the entire range of pore-filling fractions. From this it is concluded that recently proposed pore correlations due to elastic interactions between neighbouring pores upon capillary condensation do not play a role in this system. The pores fill randomly according to their size distribution, in perfect agreement with the classical Kelvin equation. The relation between the overall pore-filling fraction as determined from the volumetric sorption isotherm, and the fraction of completely filled pores as obtained from the fit of the SANS data, allows conclusions to be drawn about the thermodynamic metastability of the adsorption process. [source] Polyethylene glycol and polyvinyl alcohol as corrosion inhibitors for aluminium in acidic mediumJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007S. A. Umoren Abstract The corrosion inhibition of aluminum in H2SO4 in the presence of polyethylene glycol (PEG) and polyvinyl alcohol (PVA) as inhibitors at 30,60 °C was studied using gravimetric, gasometric, and thermometric techniques. The inhibition efficiency (%I) increased with increase in concentration of the inhibitors. Increase in temperature increased the corrosion rate in the absence and presence of inhibitors but decreased the inhibition efficiency. Both PEG and PVA were found to obey Temkin adsorption isotherm at all concentrations and temperatures studied. Phenomenon of physical adsorption is proposed from the activation parameters obtained. Thermodynamic parameters reveal that the adsorption process is spontaneous. PEG was found to be a better inhibitor than PVA. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source] Behaviour and mechanism of Zn(II) adsorption on Chinese loess at dilute slurry concentrationsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2008Xiaowu Tang Abstract BACKGROUND: Zn(II) is commonly present in mining drainage in developing countries. Since loess is abundant and always located near mining sites in China, it would be useful to investigate the possibility and efficiency of using loess to remove Zn(II) from aqueous solution. RESULTS: The Zn(II) adsorption capacity of Chinese loess was determined as 215.9 mg g,1. The adsorption followed pseudo-second-order kinetics and took place mainly by surface diffusion. Generally, higher initial pH and solute concentration resulted in higher % Zn(II) removal, while higher temperature and slurry concentration led to lower % Zn(II) removal. A thermodynamic study revealed that the adsorption process was exothermic, with the predicted enthalpy change ranging from ,20.87 to ,4.06 kJ mol,1. With the assistance of X-ray photoelectron spectroscopy and X-ray diffraction, the high adsorption capacity was ascribed to the growth of micro-organisms and mineral constituents such as kaolinite and goethite. CONCLUSION: Chinese loess proved effective for Zn(II) adsorption in this study. The optimal adsorption conditions included pH > 3.0, temperature ,15 °C and contact time , 400 min. As an abundant natural soil in arid areas with very low population density, it would be appropriate to develop this material into a wastewater-purifying agent. Copyright © 2008 Society of Chemical Industry [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] Reliable production of highly concentrated bioethanol by a conjunction of pervaporation using a silicone rubber sheet-covered silicalite membrane with adsorption processJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 8 2004Toru Ikegami Abstract For the production of highly concentrated bioethanol by pervaporation using an ethanol-permselective silicalite membrane, pervaporation performance was investigated using a silicalite membrane entirely covered with a silicone rubber sheet to prevent direct contact with acidic compounds. By using a resistance model for membrane permeation, the separation factor of the covered silicalite membrane towards ethanol can be estimated from the individual pervaporation performances of the silicalite membrane and the silicone rubber sheet. No decrease in the ethanol concentration through the silicone rubber sheet-covered membrane was caused when ethanol solutions containing succinic acid were supplied. By directly passing the permeate-enriched ethanol vapor mixed with water vapor through a dehydration column packed with a molecular sieve of pore size 0.3 nm, highly concentrated bioethanol up to 97% (w/w), greater than the azeotropic point in the ethanol/water binary systems, can be obtained from 9% (w/w) fermentation broth. Copyright © 2004 Society of Chemical Industry [source] Recovery of lipase by adsorption at the n -hexadecane,water interfaceJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 11 2003Hui-Min Wang Abstract A novel separation process based on the hydrophobic adsorption at the n -hexadecane,water interface was developed for the recovery of Acinetobacter radioresistens lipase from a pre-treated fermentation broth. In a mixture containing water, lipase and n -hexadecane, a water-in-oil emulsion was formed when the n -hexadecane-to-water ratio (o/w ratio) was larger than 3, and a large amount of lipase was found to be adsorbed at the interface. Compared with the oil-in-water emulsion (occurring when o/w ratio < 3), the water-in-oil emulsion generated smaller droplets and larger interfacial area, and was more stable. The harvested emulsion phase could be centrifuged to give an aqueous, concentrated lipase solution. Adsorption of lipase at the interface could be described by the Langmuir isotherm. For lipase concentrations ranging from 8.4 to 87.2 U cm,3, a single-stage adsorption resulted in a six- to four-fold concentration and 16,45% activity recovery, where lipase concentration was the dominant factor. A method using data from a single-stage adsorption to predict multiple-stage operation was described, and the agreement between the experimental and the predicted results was good. To improve the enzyme recovery, a multiple-run adsorption process was proposed. The use of salts enhanced the hydrophobic interaction between lipase and n -hexadecane. Advantages of the proposed process include simple operation, low operational cost, environmentally friendly, no requirement for pre-concentration of the enzyme solution, and negligible enzyme denaturation. Copyright © 2003 Society of Chemical Industry [source] Adsorption and desorption behaviour of taurine on macroporous adsorption resinsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2001Tang Zhigang Abstract Adsorption of taurine on S-8, NKA2 and Amberlite XAD-1 resins was measured with respect to time and the results indicated that equilibrium was reached in 50,min. The adsorption isotherms of taurine on D4006, AB-8, S-8, NKA2 were recorded and compared with those using Amberlite XAD-1, XAD-3, XAD-6 and XAD-7 at 28,°C. For an aqueous concentration range of 0,100,mg,g,1, each isotherm could be represented as a straight line. S-8 and XAD-1 resins had the highest solid/liquid distribution coefficients of 0.92 and 0.9. Since the locally produced S-8 resin is less expensive than XAD-1 resin, it was selected for further studies with adsorption isotherms being measured over the aqueous concentration range of 0,160,mg,g,1. These experimental results could be fitted by the Langmuir equation. The effects of pH, salting-out and temperature on the adsorption were studied with the results showing that the influence of temperature was the most important. A temperature-swing adsorption process was then tested to separate taurine from aqueous solutions and gave a overall yield >90% when taurine was adsorbed at 28,°C and eluted by deionized water at 70,°C. © 2001 Society of Chemical Industry [source] ADSORPTION CHARACTERISTICS OF CROCIN IN THE EXTRACT OF GARDENIA FRUITS (GARDENIA JASMINOIDES ELLIS) ON MACROPOROUS RESINSJOURNAL OF FOOD PROCESS ENGINEERING, Issue 1 2009BIN YANG ABSTRACT To study resin adsorptions and investigate the differences between processes in crude extracts and microfiltrates, the adsorption characteristics of crocin in the extract of Gardenia jasminoides Ellis on 10 macroporous styrene-divinylbenzene (SDVB) resins were investigated. Ground gardenia fruit was extracted with water and the crude extract was partially purified by microfiltration. The crude extract and microfiltrate were mixed with the 10 resins until the adsorption of crocin reached equilibrium on resins. The adsorption followed the pseudo-second-order kinetics closely, but the data also fitted the first-order and intraparticle diffusion models. Furthermore, the Freundlich isotherm was found suitable for describing the equilibrate adsorption data. XAD-1180, HP20, HPD-100A and AB-8 stood out as the best performing resins in terms of their adsorptive capacities and selectivities for crocin. The thermodynamics of the adsorption process was shown to be spontaneous and exothermal in nature, and controlled by physical rather than chemical mechanisms. Adsorption with SDVB resins in conjunction with microfiltration was found to be an efficient process for the purification of crocin in gardenia extract. PRACTICAL APPLICATIONS Macroporous resins have been industrially applied in the recovery and purification of some products from plant extracts. However, there is a lack of understanding of the adsorption process and many of the applications are based on empirical data rather than on predicable models. Therefore, the development of reliable mathematical models that can accurately describe and predicate experimental data of adsorption would be extremely helpful in understanding the adsorption process as well as optimizing the design of adsorption systems. [source] Application of heterogeneous adsorbents in removal of dimethyl phthalate: Equilibrium and heatAICHE JOURNAL, Issue 10 2010Jun Wu Abstract Aminated resin (NDA-101) and oxidized resin (NDA-702) were synthesized to remove Dimethyl phthalate (DMP) from the contaminated water. The equilibrium and heat properties in the course of adsorption process were examined and compared with two commercial heterogeneous adsorbents, namely an acrylic ester resin (Amberlite XAD-7) and a coal-based granular activated carbon (AC-750). The associated equilibrium isotherms can be well fitted by Freundlich equation and the adsorption capacities for DMP followed the order: NDA-702 > NDA-101 > AC-750 > XAD-7. The surface of XAD-7 was demonstrated to be relatively homogeneous through surface energy heterogeneity analysis, offering the sole hydrogen bonding interaction. Contrarily, heterogeneous surface of oxidized resins NDA-702 and the aminated resins NDA-101 exhibited a promising adsorption capacity and affinity toward DMP probably derived by multiple hydrogen bonding, ,,, stacking, and micropore filling interactions. © 2010 American Institute of Chemical Engineers AIChE J, 2010 [source] Removal of arsenic from simulated groundwater by GAC-Fe: A modeling approachAICHE JOURNAL, Issue 7 2009P. Mondal Abstract A study on kinetics and equilibrium is presented on the adsorption of arsenic species from simulated groundwater containing arsenic (As(III):As(V)::1:1), Fe and Mn in concentrations of 0.188 mg/L, 2.8 mg/L and 0.6 mg/L, respectively, by iron impregnated granular activated charcoal (GAC-Fe). Also presented is the interaction effect of As, Fe and Mn on the removal of arsenic species from water, which simulates contaminated groundwater. Among conventional models, pseudo second-order kinetic model and Freundlich isotherm were adequate to explain the kinetics and equilibrium of adsorption process, respectively. However, in comparison to conventional isotherm empirical polynomial isotherm provided a more accurate prediction on equilibrium specific uptakes of arsenic species. Effects of initial concentrations of As, Fe and Mn on the removal of total arsenic (As(T)), As(V) & As(III) have been correlated within the error limit of ,0.2 to +5.64%. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Do G protein-coupled receptors expressed in human lingual epithelium interact with HPV11?JOURNAL OF MEDICAL VIROLOGY, Issue 10 2007Lukasz Durzy Abstract Human papillomaviruses infect epithelia but little is known about the nature of cell surface receptors interacting with the viral particles. It has been proposed that glycosaminoglycans and integrins may be involved in the attachment process. In the present study, the putative interactions of virus-like particles of human papillomavirus type 11 (HPV11), which present a tropism for nasopharyngeal epithelia, with olfactory and taste receptors expressed in the human lingual epithelium were studied. The L1 protein of HPV11 was produced in insect cells. The presence of L1 virus-like particles was analyzed by ELISA using monoclonal antibodies specific for full-size particles and by electron microscopy. Using immunofluorescence, it was observed that virus-like particles interacted with taste buds from murine tongue, with the tagged human olfactory receptor hJCG5 expressed in HEK-293 but not with the tagged taste receptor hT2R4. This therefore suggests that hJCG5 may be involved in the adsorption process of HPV11 to lingual epithelium serving as a so-called "adsorption-adhesive molecule." J. Med. Virol. 79:1545,1554, 2007. © Wiley-Liss, Inc. [source] Heat-exchange pressure swing adsorption process for hydrogen separationAICHE JOURNAL, Issue 8 2008Jang-Jae Lee Abstract A current focus in the energy field is on the use of hydrogen in fuel cells. Development of a hydrogen station system is important to the commercialization of fuel cells and fuel cell powered vehicles. In this study, the heat-exchange pressure swing adsorption (HE-PSA) was developed to design a compact H2 PSA process for small spatial occupancy in the hydrogen station. The adsorption dynamics and performance of the newly designed bed were compared with those of a conventional bed by using a quaternary mixture (H2/CO2/CH4/CO 69:26:3:2 vol %) which is generally obtained from the steam-reforming reaction of natural gas. Because the detrimental exothermic/endothermic heat effects accompanied by the adsorption/desorption steps were reduced by heat exchange between the adsorption beds, the separation performance of the HE-PSA was higher than that of a conventional PSA. In addition, the spatial occupancy of the beds could be significantly reduced, compared with a conventional PSA, because the single annular-type bed performed the function of two beds in the HE-PSA. © 2008 American Institute of Chemical Engineers AIChE J, 2008 [source] Three-bed PVSA process for high-purity O2 generation from ambient airAICHE JOURNAL, Issue 11 2005Jeong-Geun Jee Abstract A three-bed PVSA (pressure vacuum swing adsorption) process, combining equilibrium separation with kinetic separation, was developed to overcome the 94% O2 purity restriction inherent to air separation in the adsorption process. To produce 97+% and/or 99+% purity O2 directly from air, the PVSA process with two zeolite 10X beds and one CMS bed was executed at 33.44,45.60 to 253.31 kPa. In addition, the effluent gas from the CMS bed to be used for O2 purification was backfilled to the zeolite 10X bed to improve its purity, recovery, and productivity in bulk separation of the air. PVSA I, which made use of a single blowdown/backfill step, produced an O2 product with a purity of 95.4,97.4% and a recovery of 43.4,84.8%, whereas PVSA II, which used two consecutive blowdown/backfill steps, produced O2 with a purity of 98.2,99.2% and a recovery of 47.2,63.6%. Because the primary impurity in the O2 product was Ar, the amounts of N2 contained in the product were in the range of 4000,5000 ppm at PVSA I and several tens of ppm at PVSA II. A nonisothermal dynamic model incorporating mass, energy, and momentum balances was applied to predict the process dynamics. Using the linear driving force (LDF) model with constant diffusivity for the equilibrium separation bed and a modified LDF model with concentration dependency of the diffusion rate for the kinetic separation bed, the dynamic model was able to accurately predict the results of the experiment. © 2005 American Institute of Chemical Engineers AIChE J, 2005 [source] Vacancy solution theory for binary adsorption equilibria in heterogeneous carbonAICHE JOURNAL, Issue 9 2002L. P. Ding A heterogeneous modified vacancy solution model of adsorption developed is evaluated. The new model considers the adsorption process through a mass-action law and is thermodynamically consistent, while maintaining the simplicity in calculation of multicomponent adsorption equilibria, as in the original vacancy solution theory. It incorporates the adsorbent heterogeneity through a pore-width-related potential energy, represented by Steele's 10,4,3 potential expression. The experimental data of various hydrocarbons, CO2 and SO2 on four different activated carbons,Ajax, Norit, Nuxit, and BPL,at multiple temperatures over a wide range of pressures were studied by the heterogeneous modified VST model to obtain the isotherm parameters and micropore-size distribution of carbons. The model successfully correlates the single-component adsorption equilibrium data for all compounds studied on various carbons. The fitting results for the vacancy occupancy parameter are consistent with the pressure change on different carbons, and the effect of pore heterogeneity is important in adsorption at elevated pressure. It predicts binary adsorption equilibria better than the IAST scheme, reflecting the significance of molecular size nonideality. [source] Propylene/propane separation by vacuum swing adsorption using 13X zeoliteAICHE JOURNAL, Issue 2 2001Francisco A. Da Silva A vacuum swing adsorption process using 13X zeolite pellets with five steps was designed to split an equimolar mixture of propylene/propane: pressurization with feed; high-pressure feed; high-pressure purge with product; cocurrent blowdown; and counter-current vacuum blowdown, where the enriched propylene product is withdrawn. In the process, the partial pressure of the C3 -mixture is controlled with nitrogen, which is used as inert gas. With an equimolar feed of C3 diluted to 50% with nitrogen, the column is fed at 5 bar and 423 K, and the product is obtained when the total pressure is lowered to 0.1 bar. After 15,20 cycles, the cyclic steady-state condition is achieved, a propylene-enriched stream of 98% mol relative to propylene/propane mixture, with 3.2% of nitrogen, a recovery of 19% (molar basis), and a productivity of 0.785 mol/kg·h is obtained. The experimental work was complemented with numerical simulations, and the effect of different operating parameters on the performance of the VSA was considered. [source] Drug adsorption in human skin: A streaming potential studyJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 12 2003Johanna Raiman Abstract The objective of this study was to investigate the drug adsorption process in human skin using in vitro streaming potential measurements. Streaming potential is an electrokinetic phenomenon, which reflects both the charge density and the pore size of a membrane. Thus, the adsorption of charged solutes on the pore walls can be detected as a change of streaming potential, viz., as a change in the slope ,E/,P. In these streaming potential measurements, hydrophilic nadolol and luteinizing hormone-releasing hormone, and lipophilic propranolol and Nafarelin were used as model drugs. As could be expected, the hydrophilic drugs did not change the slope. The more lipophilic propranolol and Nafarelin, instead, changed the slope. Propranolol changed the slope gradually from negative to positive when the concentration was increased from 1 to 10 mM. With Nafarelin, a straight line with a slope of about 0 was obtained at pH 7.3 and an ascending curve at pH 4.2. These results indicate that the negative charges on the pore walls of human skin are blocked by adsorption of the lipophilic cations. The adsorption of lipophilic cations in the skin alters the permselectivity of the skin, which, in turn, may lead to the inhibition of electroosmotic flow across the skin during iontophoresis and to the shut down of transdermal drug permeation of higher molecular weight drugs. © 2003 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 92:2366,2372, 2003 [source] Effect of an aliphatic spacer group on the adsorption mechanism on the colloidal silver surface of L -proline phosphonodipeptidesJOURNAL OF RAMAN SPECTROSCOPY, Issue 12 2008Edyta Podstawka Abstract A comparative study of molecular structures of five L -proline (L -Pro) phosphonodipeptides: L -Pro-NH-C(Me,Me)-PO3H2 (P1), L -Pro-NH-C(Me,iPr)-PO3H2 (P2), L -Pro- L -NH-CH(iBu)-PO3H2 (P3), L -Pro- L -NH-CH(PA)-PO3H2 (P4) and L -Pro- L -NH-CH(BA)-PO3H2 (P5) has been carried out using Raman and absorption infrared techniques of molecular spectroscopy. The interpretation of the obtained spectra has been supported by density functional theory calculations (DFT) at the B3LYP; 6,31 + + G** level using Gaussian 2003 software. The surface-enhanced Raman scattering (SERS) on Ag-sol in aqueous solutions of these phosphonopeptides has also been investigated. The surface geometry of these molecules on a silver colloidal surface has been determined by observing the position and relative intensity changes of the Pro ring, amide, phosphonate and so-called spacer (,R) groups vibrations of the enhanced bands in their SERS spectra. Results show that P4 and P5 adsorb onto the silver as anionic molecules mainly via the amide bond (,1630, ,1533, ,1248, ,800 and ,565 cm,1), Pro ring (,956, ,907 and ,876 cm,1) and carboxylate group (,1395 and ,909 cm,1). Coadsorption of the imine nitrogen atom and PO group with the silver surface, possibly by formation of a weaker interaction with the metal, is also suggested by the enhancement of the bands at 1158 and 1248 cm,1. P1, P2 and P3 show two orientations of their main chain on the silver surface resulting from different interactions of the CCH3, NH and CONH fragments with this surface. Bonding to the Ag surface occurs mainly through the imino atom (1166 cm,1) for P2, while for P1 and P3 it occurs via the methyl group(s) (1194,1208 cm,1). The amide group functionality (CONH) is practically not involved in the adsorption process for P1 and P2, whereas the CsP bonds do assist in the adsorption. Copyright © 2008 John Wiley & Sons, Ltd. [source] Adsorption of benzene over the rutile TiO2 (110) surfaces: A theoretical studyPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2010A. R. R. Neto Abstract In this work, we present our theoretical results for the relaxation of the rutile TiO2 (110), as well as for the adsorption of benzene over this surface. Our results are in good agreement with both the available theoretical and experimental data, whenever these comparisons were possible. Based on our obtained results, we show that the interaction between the adsorbate and the TiO2 (110) surface shows a van der Waalslike character, with the calculated adsorption energies at the order of 43 to 173 meV. In this adsorption process, the H atoms of the benzene prefer to bind with the surface Ti atoms. As a result, two occupied electronic levels appear at the surface bandgap, which are responsible for the optical absorption peaks at the blue-violet region of the electromagnetic spectra. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] The adsorption of L-cysteine on Au(110) in ultra-high vacuum and electrochemical environmentsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2005G. E. Isted Abstract We have investigated the adsorption of L-cysteine (L-Cys) onto Au(110) in an electrochemical cell and under ultra-high vacuum (UHV) conditions using reflection anisotropy spectroscopy (RAS). The L-Cys saturated surfaces created by both deposition methods exhibit similar RA profiles which indicates a similar adsorption process. Our results are consistent with L-Cys binding to the Au(110) surface through a goldthiolate (Au-S) linkage. Heating the L-Cys saturated surface in UHV to 580 K results in the decomposition of the adsorbate and leaves behind a sulphur/Au surface composed of different structural domains. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Equilibrium and heat of adsorption of phosphine on CaCl2 -modified molecular sieveASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2009Qiongfen Yu Abstract Adsorption characteristics of the virgin and CaCl2 -immersed molecular sieves at 298 K were investigated to select the adsorbent with high adsorption capacity to phosphine. Adsorption isobars and adsorption isotherms over the phosphine partial pressure and temperature ranged 0 , 1000 Pa and 298 , 343 K were measured. The adsorption equilibrium data for phosphine at various temperatures were fitted to Langmuir and Freundlich isotherm models and their isosteric heats of adsorption were determined by the Clausius-Clapeyron equation. It was found the Freundlich was more suitable for description of phosphine adsorption process through calculating average absolute relative error, and the fitted result about Langmuir model showed the heterogeneous characteristics of modified adsorbent. The isosteric heat of adsorption was about 15 kJ/mol, which indicated adsorptive phosphine removal performance may be a dominant of physical adsorption being easy for desorption. The isosteric heat of adsorption decreased with an increase of the surface loading on CaCl2/5A, which means that CaCl2/5A molecular sieve had an energetically heterogeneous surface. The present study confirmed that the CaCl2/5A molecular sieves would be one of the candidates for separation and recycle of phosphine. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Separation of oil and carotenes from palm oil mill effluent by adsorption chromatography with silica based adsorbentASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2009A. L. Ahmad Abstract Malaysia is an agricultural country and the major polluting industrial effluents have been from palm oil industry. Palm oil mill effluent (POME) is a liquid waste which causes a significant impact on the environment if it is not dealt properly. POME contains oil and carotenes that need to be treated before discharge. Owing to the readily available source of POME and growing demand of carotenes, the objective of this paper is to recover the carotenes from POME whilst tackling the environmental problem. In this study, solvent extraction is used to retrieve oil from POME and adsorption chromatography is further adopted to recover the carotenes contained in the oil. Residual oil extracted from POME in this study was about 5000 mg/L in a single stage solvent extraction. The carotenes content in recovered oil was about 450 ppm. Synthetic adsorbent with silica based material was used in the adsorption chromatography. Carotenes was concentrated to about 25 times of the concentration in the recovered oil by adsorption chromatography. Carotenes recovery was found to be depended on the process conditions. Different types of solvent, column temperatures and initial loading volumes were evaluated to determine the effects on the percentage of carotenes extracted and carotenes concentration. The suitable temperature for adsorption process was 40 °C. Carotenes was successfully concentrated from the recovered oil by adsorption chromatography process. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Nociceptin and its natural and specifically-modified fragments: Structural studiesBIOPOLYMERS, Issue 12 2010E. Podstawka-Proniewicz Abstract The vibrational structures of Nociceptin (FQ), its short bioactive fragments, and specifically-modified [Tyr1]FQ (1-6), [His1]FQ (1-6), and [His1,4]FQ (1-6) fragments were characterized. We showed that in the solid state, all of the aforementioned peptides except FQ adopt mainly turn and disordered secondary structures with a small contribution from an antiparallel ,-sheet conformation. FQ (1-11), FQ (7-17) [His1]FQ (1-6), and [His1,4]FQ (1-6) have an ,-helical backbone arrangement that could also slightly influence their secondary structure. The adsorption behavior of these peptides on a colloidal silver surface in an aqueous solution (pH = ,8.3) was investigated by means of surface-enhanced Raman scattering (SERS). All of the peptides, excluding FQ (7-17), chemisorbed on the colloidal silver surfaces through a Phe4 residue, which for FQ, FQ (1-11), FQ (1-6), [Tyr1]FQ (1-6), and [His1]FQ (1-6) lies almost flat on this surface, while for FQ (1-13) and FQ (1-13)NH2 adopts a slightly tilted orientation with respect to the surface. The Tyr1 residue in [Tyr1]FQ (1-6) does not interact with the colloidal silver surface, suggesting that the Tyr1 and Phe4 side chains are located on the opposite sides of the peptide backbone, which can be also true for His1 and Phe4 in [His1]FQ (1-6). The lone pair of electrons on the oxygen atom of the ionized carbonyl group of FQ (1-13) and FQ (7-17) appears to be coordinated to the colloidal silver nanoparticles, whereas in the case of the remaining peptides, it only assists in the adsorption process, similar to the NH2 group. We also showed that upon adsorption, the secondary structure of these peptides is altered. © 2010 Wiley Periodicals, Inc. Biopolymers 93: 1039,1054, 2010. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] Protein adsorption at air,water interfaces: A combination of detailsBIOPOLYMERS, Issue 1-2 2004Harmen H. J. de Jongh Abstract Using a variety of spectroscopic techniques, a number of molecular functionalities have been studied in relation to the adsorption process of proteins to air,water interfaces. While ellipsometry and drop tensiometry are used to derive information on adsorbed amount and exerted surface pressure, external reflection circular dichroism, infrared, and fluorescence spectroscopy provide, next to insight in layer thickness and surface layer concentration, molecular details like structural (un)folding, local mobility, and degree of protonation of carboxylates. It is shown that the exposed hydrophobicity of the protein or chemical reactivity of solvent-exposed groups may accelerate adsorption, while increased electrostatic repulsion slows down the process. Also aggregate formation enhances the fast development of a surface pressure. A more bulky appearance of proteins lowers the collision intensity in the surface layer, and thereby the surface pressure, while it is shown to be difficult to affect protein interactions within the surface layer on basis of electrostatic interactions. This work illustrates that the adsorption properties of a protein are a combination of molecular details, rather than determined by a single one. © 2004 Wiley Periodicals, Inc. Biopolymers, 2004 [source] Conformational changes of enzymes adsorbed at liquid, solid interface: Relevance to enzymatic activityBIOPOLYMERS, Issue 4-5 2002S. Noinville Abstract FTIR with attenuated total reflectance spectroscopy was used to study in situ adsorption of enzymes at water,solid interfaces to better understand how conformational changes may monitor enzymatic activity. Because the adsorption process depends on hydrophobic and electrostatic interactions, conformational changes were studied as a function of the nature of the adsorbing substrates, which are hydrophobic or hydrophilic in character. The adsorption kinetics of two examples of serine enzymes, ,-chymotrypsin (,-chym) and Humicola lanuginosa lipase (HLL), were studied. The secondary structure and solvation of the adsorbed enzymes were both compared to the dissolved enzymes. The positively charged ,- chym was adsorbed on a negatively charged hydrophilic support with minor structural changes, but the negatively charged lipase had no affinity for a similar support. Both enzymes were strongly retained on the hydrophobic support. The secondary and tertiary structures of the ,-chym adsorbed on the hydrophobic support were strongly altered, which correlates to the inhibition of enzymatic hydrolysis. The specific solvation obtained for the adsorbed HLL is consistent with the existence of the open conformer in relation to the enhanced enzymatic activity at the water,hydrophobic interface. © 2002 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 67: 323,326, 2002 [source] Purification of the two major proteins from whey concentrate using a cation-exchange selective adsorption processBIOTECHNOLOGY PROGRESS, Issue 1 2010Mayyada M. H. El-Sayed Abstract The packed-bed adsorption and elution of aqueous solutions of whey concentrate powders were investigated at pH 3.7 using a 5-mL SP Sepharose FF column to separate and isolate two major proteins namely, ,-lactalbumin (ALA) and ,-lactoglobulin (BLG) from these solutions. ALA displaced and eluted BLG from the column in a pure form. Pure ALA could then be eluted with good recovery. A novel consecutive two-stage separation process was developed to separate ALA and BLG from whey concentrate mixtures. Almost all of the BLG in the feed was recovered, with 78% being recovered at 95% purity and a further 20% at 86% purity. In addition, 67% of ALA was recovered, 48% at 54% purity and 19% at 60% purity. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010 [source] Influence of Cationic Starch Adsorption on Fiber FlocculationCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 8 2009N. Zakraj Abstract The adsorption of cationic starch on hardwood fibers and its influence on flocculation were studied in relation to the dosage of cationic starch, the effect of shear forces and the presence of different concentrations of inorganic salts in the paper stock. Flocculation was monitored by means of a focused beam reflectance measurement (FBRM) probe. It was established that floc size at low shear rates depends on adsorption efficiency. At high shear forces, flocs were irreversibly decomposed despite the presence of a higher amount of adsorbed cationic starch on the fibers. Therefore, flocculation was produced by a bridging mechanism. The results show a significant effect of inorganic salts on the adsorption of cationic starch on fibers. Low concentrations of inorganic salts usually improved the adsorption process while higher concentrations (> 0.01 mol/L) reduced the adsorption and limited the flocculation process. [source] Kinetic and Statistical Studies of Adsorptive Desulfurization of Diesel Fuel on Commercial Activated CarbonsCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 3 2008M. Muzic Abstract Diesel fuel desulfurization by different commercial activated carbons was studied in a batch adsorber. Experiments, carried out to determine the sulfur adsorption dependency on time, were used to perform kinetic characterization and to screen the best performing activated carbon. The equilibrium characterization of the adsorption process was also performed. The statistical study of the process was undertaken by way of a two-level one-half fractional factorial experimental design with five process parameters. Individual parameters and their interaction effects on sulfur adsorption were determined and a statistical model of the process was developed. Chemviron Carbon SOLCARBTM C3 was found to be the most efficient adsorbent. The kinetic pseudo-second order model and Freundlich isotherm are shown to exhibit the best fits of experimental data. The lowest achieved sulfur concentration in treated diesel fuel was 9.1,mg kg,1. [source] | |||||||||||||||||||||||||||||||||||||