Personal Research Database

Full Text: S\Sep Pur Tec19, 237.pdf

Abstract: The Langmuir adsorption isotherm equation is extended to include a third parameter. The extended Langmuir model is then compared with the Langmuir, the Langmuir-Freundlich and the Tóth models in their ability to fit experimental data. (C) 2000 Elsevier Science B.V. All rights reserved.

Keywords: Adsorption Equilibrium Model, Langmuir Equation, Data Correlation, Carbon

Figueiredo, S.A., Boaventura, R.A. and Loureiro, J.M. (2000), Color removal with natural adsorbents: Modeling, simulation and experimental. Separation and Purification Technology, 20 (1), 129-141.

Full Text: S\Sep Pur Tec20, 129.pdf

Abstract: The adsorption in some natural materials containing chitin namely, Squid (Loligo vulgaris) and Sepia (Sepia officinalis) pens, and Anodonta (Anodonta cygnea) shells for color removal from textile wastewaters was studied. A reactive and a direct green dyestuff, the Cibacron green T3G-E (CI reactive green 12) and the Solophenyl green BLE 155% (CI direct green 26) from CIBA, respectively, were selected for this study. Continuous experiments in a packed column at 20°C with the natural materials showed a large internal resistance to mass transfer. In order to improve the adsorbents performances, the materials were submitted to chemical treatment (demineralization and/or deproteinization). Isotherms at 20°C were determined for all systems and compared with the ones using the materials after chemical treatment. These results were fitted by both Langmuir and Freundlich models. The determined parameters showed that equilibrium adsorption capacities increased at least five times. These results and the mathematical simulation of the column runs showed that there are improvements both in equilibrium and kinetic data. The adsorbents physical and chemical properties before and after chemical treatment were briefly characterized in order to investigate the changes responsible for those improvements. Biodegradation of the direct dyestuff was observed during the column operation using both the Anodonta shell and Sepia pen. For these two systems the chemical treatment of the materials did not improve the color removal. Biodegradation was included in the developed model and the influence of the model parameters on the system behavior was analyzed. (C) 2000 Elsevier Science B.V. All rights reserved.

Keywords: Natural Adsorbents, Color Removal, Textile Dyestuffs, Modeling and Simulation, Biodegradation, Chitosan Fibers, Adsorption, Chitin, Dyes, Diffusion

Wang, K., Qiao, S. and Hu, X. (2000), On the performance of HIAST and IAST in the prediction of multicomponent adsorption equilibrium. Separation and Purification Technology, 20, 243-249.

Full Text: S\Sep Pur Tec20, 243.pdf

Abstract: The performance of the heterogenous ideal absorbed solution theory (HIAST) using a uniform energy distribution and the global ideal adsorbed solution theory (IAST) is studied on their predictability f multicomponent adsorption equilibria along with experimental data of gases on two activated carbons. Results show that HIAST may not always provide better predictability than IAST if the energy distribution parameters are not properly chosen, although it is reported in the literature that in most cases HIAST is superior to IAST. © 2000 Elsevier Science B.V. All rights reserved.

Keywords: Adsorption equilibrium, Multicomponent, IAST, HIAST

? Yuan, Q.Z., Jain, P.M. and Valsaraj, K.T. (2000), Reusable adsorbents for dilute solution separation. 4: Adsorption of 1,2 dichlorobenzene and phenanthrene on a surfactant-modified semiconductor (titania) surface. Separation and Purification Technology, 21 (1-2), 9-16.

Full Text: 2000\Sep Pur Tec21, 9.pdf

Abstract: The surface of a semi-conducting surface, viz., titania was modified by adsorbing an anionic surfactant, viz., sodium dodecyl sulfate (SDS) at aqueous pH values less than the point of zero charge of 6.8. The hydrophobic titania surface was capable of adsorbing hydrophobic organic compounds, such as 1,2-dichlorobenzene and phenanthrene at dilute concentrations from the aqueous phase. The adsorption partition coefficients for both compounds on SDS hemi-micelles on TiO₂ are of magnitudes similar to their octanol-water partition constants, which are indicators of similar hydrophobic environments. The potential uses of SDS-coated TiO₂ for simultaneously adsorbing and photo-chemically degrading hydrophobic organic compounds as a means of treating dilute wastewater streams are suggested. (C) 2000 Elsevier Science B.V. All rights reserved.

Keywords: Adsorbents, Adsorption, Anionic Surfactant, Aqueous Phase, Dioxide, Heterogeneous Photocatalysis, Hydrophobic, Hydrophobic Organic Compounds, Indicators, Modified, Modified Alumina, Organic, Organic Compounds, Partition, Partition Coefficients, Partition Constant, pH, pH Values, Photo-Catalysis, Semi-Conductor, Separation, Sodium, Sodium Dodecyl Sulfate, Streams, Sulfate, Surface, Surfactant, Surfactant-Modified Surface, TiO₂, Titania, Wastewater, Water, Zero Charge

Aksu, Z. and Akpinar, D. (2000), Modelling of simultaneous biosorption of phenol and nickel(II) onto dried aerobic activated sludge. Separation and Purification Technology, 21 (1-2), 87-99.

Full Text: S\Sep Pur Tec21, 87.pdf

Abstract: The equilibrium uptake of phenol and nickel(II) ions, both singly and in combination, by dried aerobic activated sludge was studied in a batch system. From the previous studies, the optimum biosorption pH values were determined as 4.5 for nickel(II) and as 1.0 for phenol. Adsorption isotherms were developed for both the single-and dual-component systems at these two pH values and expressed by the mono-and multi-component Langmuir, Freundlich and Redlich-Peterson adsorption models and model parameters were estimated by the non-linear regression method. It was seen that the mono-component adsorption equilibrium data fitted very well to the Redlich-Peterson model for both the components and for both the pH values while all the multi-component adsorption models adequately predicted the multi-component adsorption equilibrium data at moderate ranges of concentration. (C) 2000 Elsevier Science B.V. All rights reserved.

Keywords: Simultaneous Biosorption, Phenol, Nickel(II), Dried Aerobic Activated Sludge, Mono-and Multi-Component Adsorption Models, Multicomponent Adsorption-Isotherms, Chlorella-Vulgaris, Organic Pollutants, Chromium(VI), Mixtures, Biomass, Metals, Ions

Banat, F., Al-Asheh, S. and Mohai, F. (2000), Batch zinc removal from aqueous solution using dried animal bones. Separation and Purification Technology, 21 (1-2), 155-164.

Full Text: S\Sep Pur Tec21, 155.pdf

Abstract: The effectiveness of animal bones (AB) to adsorb zinc from aqueous solution was studied. Batch kinetics and isotherm studies were carried out to investigate the effect of contact time, initial concentration of the adsorbate, particle size, temperature, pH, and the addition of salt (NaCl) on this adsorption process. It was noted that an increase in the zinc concentration, temperature, and initial pH of the metal solution resulted in an increase in the metal uptake per unit weight of the sorbent. The decrease in the particle size of the sorbent resulted in an increase in the metal uptake per unit weight of the sorbent. The concentration of salt in the metal solution showed significant influence on the zinc ion sorption by the sorbent. Freundlich and Langmuir isotherm models were found to be applicable for the experimental data of Zn²⁺ sorption by AB. Desorption of metals from pre-loaded AB with zinc ions was carried out with different acid eluants and it was found that H₂SO₄ is the most effective desorbent. (C) 2000 Elsevier Science B.V. All rights reserved.

Keywords: Sorption, Zinc, Animal Bones, Desorption, Ion-Exchange, Adsorption, Vulgaris, Cadmium, Copper, Moss, Lead

Denizli, A., Say, R. and Arica, Y. (2000), Removal of heavy metal ions from aquatic solutions by membrane chromatography. Separation and Purification Technology, 21 (1-2), 181-190.

Full Text: S\Sep Pur Tec21, 181.pdf

Abstract: Polyvinylalcohol membranes were prepared by a solvent casting technique. Metal-complexation ligand, i.e. monochlorotriazinyl-dye Cibacron Blue F3GA was then attached. These membranes with a high water content of 119%, and containing 8.7 mmol Cibacron Blue F3GA/m² were used in the adsorption/stripping of some selected heavy metal ions [Cu(II), Hg(II), Pb(II) and Cd(II)] from aquatic solutions containing varying initial concentration of metal ions. Adsorption rates were very high, and equilibrium was achieved in about 10 min. The non-specific adsorption of heavy metal ions on the plain membranes was low [0.63 mmol/m² for Cu(II), 0.75 mmol/m² for Hg(II), 0.94 mmol/m² for Pb(II) and 1.22 mmol/m² for Cd(II)]. The maximum adsorptions of heavy metal ions onto the Cibacron Blue F3GA-attached affinity membranes for non-competitive conditions were 16.9 mmol/m² for Hg(II), 19.2 mmol/m² for Cu(II), 25.8 mmol/m² for Pb(II), 32.4 mmol/m² for Cd(II). The observed order in adsorption was found to be Cd(II) > Pb(II) > Cu(II) > Hg(II). Different behavior was observed for competitive adsorption. The order of affinity was Cu(II) > Cd(II) > Hg(II) > Pb(II). Regeneration of polyvinylalcohol membranes was done by using 0.1 M HNO₃ in 30 min. Heavy metal ions could be repeatedly adsorbed and stripped without significant decrease in adsorption capacity. The experimental data of adsorption from solutions containing metal ions were found to correlate well with Langmuir isotherm equation. (C) 2000 Elsevier Science B.V. All rights reserved.

Keywords: Affinity Membranes, Microporous, Porous Membranes, Water Treatment, Povinyl Alcohol, Cibacron Blue F3GA, Chromatography, Liquid Membranes, Separation, Transport, Recovery, Adsorption, Extraction, Sorption, Zinc

Dutta, S., Basu, J.K. and Ghar, R.N. (2001), Studies on adsorption of p-nitrophenol on charred saw-dust. Separation and Purification Technology, 21 (3), 227-235.

Full Text: S\Sep Pur Tec21, 227.pdf

Abstract: An effective adsorbent developed from common sawdust has been used for the removal of p-nitrophenol from aqueous solution. It is observed that the degree of agitation has a significant effect on the rate of removal of p-nitrophenol. Higher initial concentration and lower temperature are more favorable for the adsorption of p-nitrophenol. The experimental results confirmed that the intraparticle diffusion has a hindering effect on the adsorption rate. An external mass-transfer model has been applied to interpret the rate data. The values of fluid- particle mass-transfer coefficient obtained from the experimental data have been compared with the predicted value. The mass-transfer coefficient is found to decrease with increasing concentration of p-nitrophenol. Adsorption equilibrium data fit most satisfactorily with the Langmuir adsorption isotherm. (C) 2001 Elsevier Science B.V. All rights reserved

Keywords: Activated Carbon, Adsorbent, Adsorbents, Adsorption, Adsorption Isotherm, Dyes, Equilibrium, Intraparticle Diffusion, Mass Transfer, Mass Transfer Coefficient, Mass-Transfer Coefficient, P-Nitrophenol, Phenol, Rates, Removal, Sawdust, Stirrer Speed, Waste

Pereira, P.R., Pires, J. and de Carvalho, M.B. (2001), Adsorption of methane and ethane in zirconium oxide pillared clays. Separation and Purification Technology, 21 (3), 237-246.

Full Text: S\Sep Pur Tec21, 237.pdf

Abstract: In zirconium oxide pillared clays (A(BET) similar to 266 m² g^-1), prepared with clays from different sources, the adsorption of pure methane and ethane, the more abundant hydrocarbon components of natural gas, were determined in the temperature range between 215 and 293 K up to the atmospheric pressure. The Langmuir model and the vacancy solution theory (VST) of Suwanayuen and Danner were used to fit the experimental data. As expected, the VST model leads to a better adjustment. The parameters obtained with this model were used to predict the binary adsorption isotherms. The data Predicted for mixtures were consistent with the experimental results obtained in the same volumetric apparatus used for the adsorption of pure components, analysing by gas chromatography the evolution of the fluid phase until the attainment of equilibrium. The results reveal a higher affinity towards ethane. The equilibrium selectivity towards ethane decreases when temperature and pressure increase, ranging from more than 100, at the lowest temperatures and pressures studied, to 3-4 near ambient temperature and atmospheric pressure. Even in the latter, less favourable situation, which in fact corresponds to the more usual working conditions, the phase diagram, predicted by the VST model indicates that the studied zirconium pillared clays are promising materials for ethane/methane separation. (C) 2001 Elsevier Science B.V. All rights reserved.

Keywords: Methane, Ethane, Zirconium Oxide, Pillared Clays, Vacancy Solution Theory, Carbon-Dioxide, Gas-Adsorption, Zeolites, Mixtures, Propane, Equilibrium, Separation, Isotherms, Catalysts

Notes: highly cited

Aksu, Z. (2001), Equilibrium and kinetic modelling of cadmium(II) biosorption by C. Vulgaris in a batch system: Effect of temperature. Separation and Purification Technology, 21 (3), 285-294.

Full Text: S\Sep Pur Tec21, 285.pdf

Abstract: The biosorption of cadmium(II) ions to C. Vulgaris studied in a batch system with respect to the temperature, initial pH and initial metal ion concentration. The algal biomass exhibited the highest cadmium(II) uptake capacity at 20°C, at the initial pH value of 4.0 and at the initial cadmium(II) ion concentration of 200 mg l^-1. Biosorption capacity decreased from 85.3 to 51.2 mg g^-1 with an increase in temperature from 20 to 50°C at this initial cadmium(II) concentration. Freundlich and Langmuir isotherm models were tried to represent the equilibrium data of cadmium(II) biosorption depending on temperature. Equilibrium data fitted very well to both the models in the studied concentration range of cadmium(II) ions at all the temperatures studied. The pseudo first-and pseudo second-order kinetic models were also applied to experimental data assuming that the external mass transfer limitations in the system can be neglected and biosorption is sorption controlled. The results showed that cadmium(II) uptake process followed the second-order rate expression and adsorption rate constants decreased with increasing temperature. Using the second-order kinetic constants, the activation energy of biosorption was also evaluated. (C) 2001 Elsevier Science B.V. All rights reserved.

Keywords: Activation, Activation Energy, Adsorption, Adsorption Rate, Batch System, Binding, Biomass, Biosorption, C.Vulgaris, Cadmium(II), Cadmium(II) Ions, Capacity, Cell-Walls, Chlorella-Vulgaris, Copper, Equilibrium, Experimental, Expression, First, First Order, Freundlich, Isotherm, Isotherms, Kinetic, Kinetic Modelling, Kinetic Models, Kinetics, Langmuir, Langmuir Isotherm, Lead(II) Ions, Marine-Algae, Mass Transfer, Metal, Metal-Ions, Modelling, Models, pH, Pseudo Second Order, Pseudo Second-Order, Pseudo-Second-Order, Rate Constants, Rights, Second Order, Second-Order, Sorption, Temperature

? Gomes, C.P., Almeida, M.F. and Loureiro, J.M. (2001), Gold recovery with ion exchange used resins. Separation and Purification Technology, 24 (1-2), 35-57.

Full Text: 2001\Sep Pur Tec24, 35.pdf

Abstract: In this paper one strong acidic, one strong basic and one weak basic ion-exchange resins, considered as exhausted in an industrial demineralizing plant, are screened for gold recovery from cyanide solutions. Based on the observed ability for the recovery and on the ease of regeneration, the weak base anion exchanger Purolite A-100 is selected. This spent resin is stable until 60°C and, after regeneration, conserves its physical properties as compared with a new one. Equilibrium data for the resin are determined, proving the very high capacity of the resin for gold (500 mg Au/g dry resin) and modeled by the Freundlich and mass action isotherm models. A kinetic experiment is conducted in a batch adsorber and modeled with an equivalent Fick’s diffusivity using the linear driving force approximation, showing that the film resistance to mass transfer controls the operation. Finally, a fixed bed adsorber is saturated with gold aurocyanide and regenerated with a potassium hydroxide solution. The model used for the simulation of both steps incorporates axial dispersion and the same equivalence for the ionic diffusivity. During the elution process, precipitation of dihydrated potassium aurocyanide occurs inside the resin, increasing the intraparticle resistance to mass transfer. The model is able to reasonably represent the experimental elution results when a large internal resistance to mass transfer is used. A 25-fold concentration of the initial gold solution is obtained in this saturation/elution process, albeit the precipitation, showing the feasibility of the method for the recovery of gold, increasing the useful life of the resins and decreasing pollution. The anionic Purolite A-100 resin showed also a significant capacity for removing silver, although less than for gold, probably because silver cyanide complexes occupy, on the average, more than one ion exchange site in the resin.

Keywords: Gold Recovery, Spent Resins, Ion Exchange, Ion Diffusivity, Mass Transfer

Snukiškis, J. and Kaušpėdienė, D. (2001), Kinetics of the combined sorption of copper(II) and nonionic surfactant by carboxylic acrylcationic exchanger. Separation and Purification Technology, 24 (1-2), 59-65.

Full Text: S\Sep Pur Tec24, 59.pdf

Abstract: Kinetics of the simultaneous sorption of nonionic surfactant alkylmonoethers (ALM-10) and copper(II) cations by the hydrogen-containing form of Purolite C106 carboxylic acrylcationic exchanger has been investigated considering the possibility to control the concentration of both copper(II) and the surfactant in sewage effluents: kinetic curves were measured. coefficients of intraparticle diffusion (D) and external mass transfer diffusion (beta) calculated. On increasing the acidity from pH 5 to 3 both the rate of intraparticle diffusion and the equilibrium sorption of copper(II) decrease but the corresponding parameters for ALM-10 increase. The action of copper(II) leads to an increase in the rate of ALM-10 intraparticle diffusion but results to a decrease in ALM-10 equilibrium sorption. Combined sorption of nonionic surfactant and copper(II) by hydrogen-containing form of Purolite C106 can be applicable for the purification of sewage including copper plating rinsewater from both contaminants simultaneously: accordingly to the coefficients of intraparticle diffusion for both copper(IT) and the surfactant, the sorber filled with Purolite C106 would not limit the productivity if integrated into the system of sewage purification by ion exchangers. (C) 2001 Elsevier Science B.V. All rights reserved.

Keywords: Cation Exchanger, Copper(II), Nonionic Surfactants, Sorption, Ion-Exchange, Adsorption

Raichur, A.M. and Basu, M.J. (2001), Adsorption of fluoride onto mixed rare earth oxides. Separation and Purification Technology, 24 (1-2), 121-127.

Full Text: S\Sep Pur Tec24, 121.pdf

Abstract: Fluoride pollution of water is widespread in several parts of India. Fluoride although beneficial to humans in small quantities, causes dental fluorosis when consumed in larger quantities over a period of time. In the present study a novel adsorbent was used to remove fluoride from synthetic solutions. The adsorbent, which is a mixture of rare earth oxides, was found to adsorb fluoride rapidly and effectively. The effect of various parameters such as contact time. initial concentration, pH. and adsorbent dose on adsorption efficiency was investigated. More than 90% of the adsorption occurred within the first 5 - 10 min. Adsorption efficiency was found to be dependent on the initial fluoride concentration and adsorption behavior followed Langmuir adsorption model. The optimum pH was found to be about 6.5. The presence of other ions such as nitrate and sulphate did not affect the adsorption of fluoride significantly (adsorption efficiency reduced from 85 to 79%) indicating the selective nature of the adsorbent. The adsorbed fluoride could be easily desorbed by washing the adsorbent with a pH 12 solution. This study clearly shows the applicability of naturally occurring rare earth oxides as selective adsorbent for fluoride from solutions. (C) 2001 Elsevier Science BN. All rights reserved.

Keywords: Fluoride, Adsorption, Rare Earth Oxide, Anion, Desorption, Aqueous-Solution, Removal, Water

McGrellis, S., Serafini, J.N., JeanJean, J., Pastol, J.L. and Fedoroff, M. (2001), Influence of the sorption protocol on the uptake of cadmium ions in calcium hydroxyapatite. Separation and Purification Technology, 24 (1-2), 129-138.

Full Text: S\Sep Pur Tec24, 129.pdf

Abstract: The maximum uptake of cadmium ions from aqueous solution by sorption on calcium hydroxyapatite was measured in different experimental conditions. A ‘slow introduction process’ leads to a larger uptake than for standard batch experiments. The main differences are: a larger incorporation of Cd in the crystal framework of apatite through a substitution -diffusion process, a different distribution among Ca(1) and Ca(2) sites and a lower concentration gradient. For the larger Cd concentration, a dissolution -precipitation also appears. leading to the formation of cadmium hydrogenophosphate, but the formation of this solid phase remains a minor process, The results also confirmed that sorption of cadmium ions on calcium hydroxyapatites does not achieve equilibrium in standard experimental laboratory time intervals. The higher achieved uptake is particularly attractive for the practical use of apatites in the decontamination of solutions polluted by cadmium. (C) 2001 Elsevier Science B.V. All rights reserved.

Keywords: Hydroxyapatites, Cadmium, Sorption, Decontamination, Inorganic Cation-Exchangers, Synthetic Hydroxyapatites, Solid-Solutions, Cd²⁺

Pal, O.R. and Vanjara, A.K. (2001), Removal of malathion and butachlor from aqueous solution by clays and organoclays. Separation and Purification Technology, 24 (1-2), 167-172.

Full Text: S\Sep Pur Tec24, 167.pdf

Abstract: Adsorption of malathion and butachlor onto kaolin. montmorillonite. bentonite clays and respective organoclays were studied, Organoclays were prepared by the exchange of quaternary ammonium type surfactants such as tetradecyltrimethyl ammonium bromide (TTAB), dodecyltrimethylammonium bromide (DTAB), and cetylpyridinium chloride (CPC) for inorganic cations like Na⁺ and Ca²⁺ on internal and external surface of the clays. This modification produces a change of surface property of clay from hydrophilic to hydrophobic. The adsorption equilibrium data points were fitted to Freundlich isotherm equations. The adsorption of malathion and butachlor were significantly enhanced by surfactant treatment of the clays. The amount of both pesticides adsorbed per unit mass of organoclay followed the order of TTA-kaolin < TTA-montmorillonite < TTA-bentonite, which is inconsistent with the organic carbon content of the clays. The removal efficiency of organomontmorillonite to treat malathion is in the order of CP(C-16)-montmorillonite > TTA(C-14)-montmorillonite > DTA(C-12)-montmorillonite. Butachlor is adsorbed to greater extent than malathion by each adsorbent. which may be due to the higher hydrophobicity of butachlor, indicating considerable hydrophobic interaction between adsorbent/radsorbate system. These findings may find applications in the removal of sparingly water soluble pesticides from aquifers. (C) 2001 Elsevier Science B.V. All rights reserved.

Keywords: Adsorption, Clays, Organoclays, Pesticides, Water Treatment, Activated Bentonite, Water

Ricordel, S., Taha, S., Cisse, I. and Dorange, G. (2001), Heavy metals removal by adsorption onto peanut husks carbon: Characterization, kinetic study and modeling. Separation and Purification Technology,