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Adsorption Kinetics (adsorption + kinetics)
Selected AbstractsAdsorption Kinetics and Thermodynamics of Acid Dyes on a Carboxymethylated Chitosan-Conjugated Magnetic Nano-AdsorbentMACROMOLECULAR BIOSCIENCE, Issue 3 2005Yang-Chuang Chang Abstract Summary: The monodisperse chitosan-conjugated Fe3O4 nanoparticles with a mean diameter of 13.5 nm were fabricated by the carboxymethylation of chitosan and its covalent binding onto Fe3O4 nanoparticles via carbodiimide activation. The carboxymethylated chitosan (CMCH)-conjugated Fe3O4 nanoparticles with about 4.92 wt.-% of CMCH had an isoelectric point of 5.95 and were shown to be quite efficient as anionic magnetic nano-adsorbent for the removal of acid dyes. Both the adsorption capacities of crocein orange G (AO12) and acid green 25 (AG25), as the model compounds, decreased with increasing pH, and the decreasing effect was more significant for AO12. On the contrary, the increase in the ionic strength decreased the adsorption capacity of AG25 but did not affect, obviously, the adsorption capacity of AO12. By the addition of NaCl and NaOH, both AO12 and AG25 could desorb and their different desorption behavior could be attributed to the combined effect of pH and ionic strength. From the adsorption kinetics and thermodynamics studies, it was found that both the adsorption processes of AO12 and AG25 obeyed the pseudo-second-order kinetic model, Langmuir isotherm, and might be surface reaction-controlled. Furthermore, the time required to reach the equilibrium for each one was significantly shorter than those using the micro-sized adsorbents due to the large available surface area. Also, based on the weight of chitosan, the maximum adsorption capacities were 1,883 and 1,471 mg,·,g,1 for AO12 and AG25, respectively, much higher than the reported data. Thus, the anionic magnetic nano-adsorbent could not only be magnetically manipulated but also possessed the advantages of fast adsorption rate and high adsorption capacity. This could be useful in the fields of separation and magnetic carriers. Acid dyes adsorption onto the CMCH-conjugated Fe3O4 nanoparticles. [source] Ni2+ removal from aqueous solutions using conditioned clinoptilolites: Kinetic and isotherm studiesENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 1 2009Semra Çoruh Abstract The aim of this study is to investigate the effects of conditioning with NaCl and HCl solutions on removal of Ni2+ ions from aqueous solutions using natural clinoptilolite. Batch studies were performed to evaluate the effects of various parameters such as chemically conditioning, adsorbent amount, contact time, initial pH of the solution, mixing temperature, and initial metal ions. The results clearly showed that the conditioning improved both the exchange capacity and the removal efficiency. Langmuir, Freundlich, Temkin, and Dubinin-Kaganer-Radushkevich (DKR) isotherm models were adopted to describe the adsorption isotherms. Adsorption isotherms of Ni2+ ions could be best modeled by Langmuir equation. Three simplified models including pseudo-second-order, intraparticle diffusion and Elovich were used to test the adsorption kinetics. These results indicate a significant potential for the natural and conditioned clinoptilolites as an adsorbent/ion-exchange material for heavy metal removal. © 2008 American Institute of Chemical Engineers Environ Prog, 2009 [source] Association of europium(III), americium(III), and curium(III) with cellulose, chitin, and chitosanENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2006Takuo Ozaki Abstract The association of trivalent f-elements,Eu(III), Am(III), and Cm(III),with cellulose, chitin, and chitosan was determined by batch experiments and time-resolved, laser-induced fluorescence spectroscopy (TRLFS). The properties of these biopolymers as an adsorbent were characterized based on speciation calculation of Eu(III). The adsorption study showed that an increase of the ionic strength by NaCl did not affect the adsorption kinetics of Eu(III), Am(III), and Cm(III) for all the biopolymers, but the addition of Na2CO3 significantly delayed the kinetics because of their trivalent f-element complexation with carbonate ions. It also was suggested from the speciation calculation study that all the biopolymers were degraded under alkaline conditions, leading to their masking of the adsorption of Eu(III), Am(III), and Cm(III) on the nondegraded biopolymers. The masking effect was higher for cellulose than for chitin and chitosan, indicating that of the three, cellulose was degraded most significantly in alkaline solutions. Desorption experiments suggested that some portion of the adsorbed Eu(III) penetrated deep into the matrix, being isolated in a cavity-like site. The TRLFS study showed that the coordination environment of Eu(III) is stabilized mainly by the inner spherical coordination in chitin and by the outer spherical coordination in chitosan, with less association in cellulose in comparison to chitin and chitosan. These results suggest that the association of these biopolymers with Eu(III), Am(III), and Cm(III) is governed not only by the affinity of the functional groups alone but also by other factors, such as the macromolecular steric effect. The association of degraded materials of the biopolymers also should be taken into consideration for an accurate prediction of the influence of biopolymers on the migration behavior of trivalent f-elements. [source] Synthesis,Structure,Property Relationships for Hyperbranched Aminosilica CO2 AdsorbentsADVANCED FUNCTIONAL MATERIALS, Issue 23 2009Jeffrey H. Drese Abstract Hyperbranched aminosilica (HAS) adsorbents are prepared via the ring-opening polymerization of aziridine in the presence of mesoporous silica SBA-15 support. The aminopolymers are covalently bound to the silica support and capture CO2 reversibly in a temperature swing process. Here, a range of HAS materials are prepared with different organic loadings. The effects of organic loading on the structural properties and CO2 adsorption properties of the resultant hybrid materials are examined. The residual porosity in the HAS adsorbents after organic loading, as well as the molecular weights and degrees of branching for the separated aminopolymers, are determined to draw a relationship between adsorbent structure and performance. Humid adsorption working capacities and apparent adsorption kinetics are determined from experiments in a packed-bed flow system monitored by mass spectrometry. Dry adsorption isotherms are presented for one HAS adsorbent with a high amine loading at 35 and 75,°C. These combined results establish the relationships between adsorbent synthesis, structure, and CO2 adsorption properties of the family of HAS materials. [source] Preparation and characterization of polyalginate,glutaraldehyde membranes,Swelling analysis by microcalorimetry and adsorption kinetics of cationic dyeJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2010Eunice F. S. Vieira Abstract Thin crosslinked polyalginate,glutaraldehyde membranes were prepared and characterized by Fourier-transformed infrared spectroscopy, thermal analysis (TG/DTG), and X-ray diffractometry. Microcalorimetric analyses have pointed out that water swellings of the membranes are slightly exothermic, and the swelling energies decrease with increasing temperature. The membranes were tested for the adsorption of methylene blue (MB) dye from aqueous solutions. The adsorption capacity of the membranes increased with increasing initial MB concentration and decreased with increasing temperature. It was observed that the MB adsorption kinetic data were best fitted by the Avrami model. Intraparticle diffusion of MB into the interior of the membranes was detected after 60 min of contact time. The MB adsorption on the membranes was also evaluated by three new 22 full factorial designs (36 experiments). It was found that binary interactions between initial dye concentration and temperature are statistically important for MB adsorption on the membranes. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Preparation and adsorption properties of chitosan,poly(acrylic acid) nanoparticles for the removal of nickel ionsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2008Jian-Wen Wang Abstract Chitosan (CS) nanoparticles with different mean sizes ranging from 100 to 195 nm were prepared by ionic gelation of CS and poly(acrylic acid) (PAA). Variations in the final solution pH value and CS : PAA volume ratio were examined systematically for their effects on nanoparticle size, intensity of surface charge, and tendency toward particle aggregation. The sorption capacity and sorption isotherms of the CS,PAA nanoparticles for nickel ions were evaluated. The parameters for the adsorption of nickel ions by the CS,PAA nanoparticles were also investigated. The CS,PAA nanoparticles could sorb nickel ions effectively. The sorption rate for nickel ions was affected significantly by the initial concentration of the solution, sorbent amount, particle size, and pH value of the solution. The samples of nanoparticles were well correlated with Langmuir's isotherm model, and the adsorption kinetics of nickel correlated well with the pseudo-second-order model. The maximum capacity for nickel sorption deduced from the use of the Langmuir isotherm equation was 435 mg/g, which was significantly higher than that of the micrometer-sized CS. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008 [source] Novel hydrogel composite for the removal of water-soluble cationic dyeJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2006Li-Ming Zhang Abstract A novel hydrogel composite was prepared by incorporating Laponite RDS clay into poly(acrylic acid- co - N -vinyl-2-pyrrolodone) hydrogel during in - situ polymerization, and investigated with respect to its adsorption kinetics and isotherm toward Crystal Violet, a widely used cationic dye. It was found that the adsorption kinetics of Crystal Violet onto the hydrogel composite was consistent with the pseudo-second-order model. Compared with pure hydrogel, the hydrogel composite is characterized by greater amounts being adsorbed at equilibrium, and a higher rate constant and initial adsorption rate. By analyzing the experimental data using the Langmuir isotherm equation, an enhanced adsorption capacity was found for the hydrogel composite. Such material is expected to be a good adsorbent for water pollutants such as cationic dyes and treatment of these organic contaminants from wastewater. Copyright © 2006 Society of Chemical Industry [source] Protein adsorption kinetics in charged agarose gels: Effect of agarose content and modelingAICHE JOURNAL, Issue 2 2009Emily B. Schirmer Abstract The adsorption kinetics of myoglobin in charged gels of varying agarose content have been measured macroscopically, through batch uptake experiments, and microscopically, using light microscopy with gels supported in microfluidics chips. The apparent effective pore diffusivities, determined by fitting either set of rate data to the shrinking core model, were greater than the free solution diffusivity and concentration-dependent. Moreover, the microscopically derived concentration profiles were qualitatively different from the predicted ones. Therefore, a new model taking into account an assumed favorable partitioning of the protein in the pore liquid is proposed to describe the adsorption kinetics. The new model yields effective pore diffusivities that are in approximate agreement with the values determined chromatographically under nonbinding conditions and with hindered diffusion theory. In addition, it predicts concentration profiles in the gel that are consistent with those observed microscopically. The overall increase in mass transfer is attributed to the favorable partitioning of the protein in the pores at low ionic strength, which results in a greater diffusional driving force. © 2008 American Institute of Chemical Engineers AIChE J, 2009 [source] Optimization of inlet temperature for deactivating LTWGS reactor performanceAICHE JOURNAL, Issue 7 2005J. L. Ayastuy Abstract An industrial Cu-based low-temperature water-gas shift (LTWGS) reactor, subject to deactivation by irreversible chlorine adsorption, has been modeled and optimized. Both the chlorine adsorption kinetics and deactivation kinetics were assumed first order to chlorine partial pressure, and the rate constants were considered independent of temperature. The Efficient Production (EP) method has been used to compute the reactor production until the outlet CO conversion decays below a permissible minimum level. Two alternative strategies for the inlet temperature have been used to maximize the EP: constant and time-variable. Compared to the EP obtained for the optimum constant inlet temperatures, EP resulting from the use of the optimum time-variable inlet temperature sequence were higher, affording important energy savings. Furthermore, a sensitivity study with respect to most influential operational variables, such as inlet total flow rate, steam-to-gas ratio, pressure, and concentrations of chlorine, hydrogen, carbon monoxide, and inert content, was carried out. © 2005 American Institute of Chemical Engineers AIChE J, 2005 [source] Analysis of multicomponent adsorption kinetics on activated carbonAICHE JOURNAL, Issue 4 2003L. P. Ding An integrated mathematical model for the kinetics of multicomponent adsorption on microporous carbon was developed. Transport in this bidisperse solid is represented by balance equations in the macropore and micropore phases, in which gas-phase diffusion dominates the mass transfer in the macropores, with the phenomenological diffusivities represented by the generalized Maxwell,Stefan (GMS) formulation. Viscous flow also contributes to the macropore fluxes and is included in the MS expressions. Diffusion of the adsorbed phase controls the mass transfer in the micropore phase, which is also described in a similar way by the MS method. The adsorption isotherms are represented by a new heterogeneous modified vacancy solution theory formulation of adsorption, which has proved to be a robust method for adsorption on activated carbons. The model is applied to the coadsorption and codesorption of C2H6 and C3H8 on Ajax and Norit carbon, as well as the displacement on Ajax carbon. The effect of the viscous flow in the macropore phase is not significant for the cases studied. The model accurately predicts the overshoot behavior and rollup of C2H6 during coadsorption. The prediction for the heavier compound C3H8 is always satisfactory, though at higher C3H8 mole fraction, the overshoot extent of C2H6 is overpredicted, possibly due to neglect of heat effects. [source] Protein ion-exchange adsorption kineticsAICHE JOURNAL, Issue 7 2001J. A. Wesselingh The kinetics of the adsorption of the protein BSA on the ion exchanger Q-Sepharose FF were measured for several values of the pH and ionic strength, using several techniques. The measurements were best described with a model incorporating both surface and pore diffusion and with the chemical potential gradient as the driving force for diffusion. The surface-diffusion coefficients from this model show an inverse exponential dependency on the binding strength. This dependency can be explained by an activated jump mechanism. The pore-diffusion coefficient is much lower than that in free solution, which is probably caused by a combination of steric and electric exclusion. [source] Adsorption Kinetics and Thermodynamics of Acid Dyes on a Carboxymethylated Chitosan-Conjugated Magnetic Nano-AdsorbentMACROMOLECULAR BIOSCIENCE, Issue 3 2005Yang-Chuang Chang Abstract Summary: The monodisperse chitosan-conjugated Fe3O4 nanoparticles with a mean diameter of 13.5 nm were fabricated by the carboxymethylation of chitosan and its covalent binding onto Fe3O4 nanoparticles via carbodiimide activation. The carboxymethylated chitosan (CMCH)-conjugated Fe3O4 nanoparticles with about 4.92 wt.-% of CMCH had an isoelectric point of 5.95 and were shown to be quite efficient as anionic magnetic nano-adsorbent for the removal of acid dyes. Both the adsorption capacities of crocein orange G (AO12) and acid green 25 (AG25), as the model compounds, decreased with increasing pH, and the decreasing effect was more significant for AO12. On the contrary, the increase in the ionic strength decreased the adsorption capacity of AG25 but did not affect, obviously, the adsorption capacity of AO12. By the addition of NaCl and NaOH, both AO12 and AG25 could desorb and their different desorption behavior could be attributed to the combined effect of pH and ionic strength. From the adsorption kinetics and thermodynamics studies, it was found that both the adsorption processes of AO12 and AG25 obeyed the pseudo-second-order kinetic model, Langmuir isotherm, and might be surface reaction-controlled. Furthermore, the time required to reach the equilibrium for each one was significantly shorter than those using the micro-sized adsorbents due to the large available surface area. Also, based on the weight of chitosan, the maximum adsorption capacities were 1,883 and 1,471 mg,·,g,1 for AO12 and AG25, respectively, much higher than the reported data. Thus, the anionic magnetic nano-adsorbent could not only be magnetically manipulated but also possessed the advantages of fast adsorption rate and high adsorption capacity. This could be useful in the fields of separation and magnetic carriers. Acid dyes adsorption onto the CMCH-conjugated Fe3O4 nanoparticles. [source] Process modeling of in situ-adsorption of a bacterial lipaseBIOTECHNOLOGY & BIOENGINEERING, Issue 6 2005Marcus Millitzer Abstract In situ adsorption, known as an in situ-roduct removal (ISPR) technique for low molecular mass bioproducts, was in this study applied to a bacterial exoenzyme proving that this method is also suitable for the separation of macromolecules like proteins. For this, adsorbent particles were added to growing cultures of Staphylococcus carnosusrec., therefore both production and adsorption occurred simultaneously in shaking flasks, stirred tank, or airlift bioreactor as the chosen types of fermenters. The exoenzyme lipase adsorbed rapidly and, after separating cells and adsorbents, desorbed in a packed bed column. Up to 85% of the produced lipase were recovered, fractions of these had been concentrated up to the factor 20 and purified up to a factor of 40 by the procedure. By using the airlift bioreactor an enhancement of biomass production was observed, but the necessity of the addition of an anti-foam reagent resulted in higher product losses in adsorption as well as in desorption. Production and adsorption kinetics have been modeled and applied to in situ-adsorption. The model was used to perform a parameter study in which the influence of biological and physical parameters as well as process parameters on discontinuous and continuous in situ-adsorption was investigated. © 2005 Wiley Periodicals, Inc. [source] Stochastic Modeling of Affinity AdsorptionBIOTECHNOLOGY PROGRESS, Issue 3 2001John Hubble A stochastic model is described that allows surface proximity and packing effects to be incorporated into predictions of adsorption kinetics and equilibrium of affinity adsorption. Equilibrium predictions show that, depending on conditions chosen, the results obtained for equilibrium conditions can exhibit either a Freundlich- or a Langmuir-type relationship. Under conditions of surface density imposed adsorption constraints, the time taken for equilibrium to be reached increases as the "off" constant is decreased. This suggests that for resins having a high immobilized ligand density binding kinetics may be more highly limited by the "off" constant than by mass transfer limitations. [source] Equilibrium and kinetic studies of the cationic dye removal capability of a novel biosorbent Tamarindus indica from textile wastewaterCOLORATION TECHNOLOGY, Issue 5 2010Shooka Khorramfar In this paper, the use of tamarind hull biosorbent (Tamarindus indica) has been investigated to remove cationic dyes from textile eflluent. Basic Violet 6 and Basic Red 18 were used as cationic dye models. The surface characteristics of tamarind hull were investigated using Fourier Transform,infrared and scanning electron microscopy. The influence of process variables such as adsorbent dosage, initial dye concentration and pH were studied. The presence of fuctional groups such as hydroxy and amine groups onto the tamarind hull surface were proved by Fourier Transform,infrared analysis. Data were evaluated for compliance with the Langmuir and Freundlich isotherm models. The results indicated that the data for adsorption of Basic Violet 6 and Basic Red 18 onto tamarind hull fitted well with the Freundlich isotherm model. Also, the adsorption kinetics of Basic Violet 6 and Basic Red 18 on biosorbent was studied. The rates of sorption were found to conform to pseudo-second-order kinetics with good correlation. Results indicated that tamarind hull could be used as a biosorbent to remove cationic organics from contaminated watercourses. [source] | ||||||||||||||||