Personal Research Database

Full Text: S\Sep Pur Tec36, 23.pdf

Abstract: The removal of chemical oxygen demand (COD), color and suspended solid (SS) from olive oil mill wastewater (OMWW) was experimentally investigated by using electro-coagulation (EC). Aluminum and iron were used in the reactor simultaneously as materials for electrodes. The reactor voltage was 12 V, current density (CD) was changing between 10 and 40 mA cm^-2, pH was taken equal to 4, 6, 7, and 9 units, and duration varied in the limits of 2-30 min. Under the 30-min retention time, 52% COD was removed by the aluminum anode and 42% was removed by the iron anode. CD efficiency versus the percent of COD removal was examined at the 10-min retention time for pH 6.2±10.2. It appeared that with the CD increase, the percent of COD removal was increasing as well. The color removal yield was examined as the result of using different retention times, current densities, and iron and aluminum as materials for anodes. CD values in the range of 10-40 mA cm^-2 were tested at the 10-min retention time each one, color removal was 90-97% by this. In this study the EC process was examined with the aim of determining the highest rate of SS removal from the OMWW as well. (C) 2003 Elsevier B.V. All rights reserved.

Keywords: Analysis, Carbonate, CO₂, Composition, Diffusion, Equilibrium, Exchange-Reaction, Gases, Isotherms, Kinetics, Li₂ZrO₃, Lithium Zirconate, Materials, Mechanism, Membranes, Model, Modified, Oxygen, Permeation, Potassium, Properties, Range, Rate Limiting, Reaction, Solid State Reaction, Sorption, Sorption Mechanism, Sorption Properties, Synthesis, Temperature, Thermodynamics

Sarvinder Singh, T. and Pant, K.K. (2004), Equilibrium, kinetics and thermodynamic studies for adsorption of As(III) on activated alumina. Separation and Purification Technology, 36 (2), 139-147.

Full Text: S\Sep Pur Tec36, 139.pdf

Abstract: Contamination of drinking water due to arsenic is a severe health hazard problem. Most of the techniques developed for pentavalent arsenic [As(V)] species are not very effective for trivalent arsenic ions [As(III)] which are more toxic and mobile than arsenate ions. Present investigation aims to remove arsenite ions [As(III)] by activated alumina. Effect of adsorbent dose, solution pH, and contact time has been investigated. Kinetics reveal that uptake of As(III) ion is very rapid in the first 6 h and equilibrium time is independent of initial As(III) concentration. The arsenite removal was strongly dependent on pH and temperature. Equilibrium studies show that As(III) ions have high affinity towards activated alumina at pH 7.6. Both Freundlich and Langmuir adsorption isotherms were well fit to the experimental data. Thermodynamic parameters depict the exothermic nature of adsorption and the process is spontaneous and favorable. The results suggest that activated alumina can be used effectively for the removal of A(III) ions.

Keywords: Adsorption, Arsenite, Equilibrium, Adsorption Kinetics, Activated Alumina

Zhang, D.H., Kodama, A., Goto, M. and Hirose, T. (2004), Kinetics in hydrogen isotopes cryogenic adsorption. Separation and Purification Technology, 37 (1), 1-8.

Full Text: S\Sep Pur Tec37, 1.pdf

Abstract: The adsorption isotherms of hydrogen and deuterium in a helium carrier gas at 77 K were obtained, using the molecular sieve 5A as adsorbents in a fixed column. The binary adsorption isotherms were extended from the single ones. The kinetic model was built for simulation of the concentration distribution for single and binary in inert helium carrier gas, and compared with the experimental results. Some parameters in the model were considered and examined experimentally.

Keywords: Cryogenic Adsorption, Hydrogen Isotopes, Mass Transfer Coefficient, Molecular Sieve 5A, Adsorption Isotherm

Biškup, B. and Subotić, B. (2004), Kinetic analysis of the exchange processes between sodium ions from zeolite A and cadmium, copper and nickel ions from solutions. Separation and Purification Technology, 37 (1), 17-31.

Full Text: S\Sep Pur Tec37, 17.pdf

Abstract: Kinetics of exchange processes between the sodium ions from zeolite A and cadmium, copper and nickel ions from solutions were determined by measuring the changes in the concentrations of Me²⁺ (Me²⁺ = Cd²⁺, Cu²⁺ and Ni²⁺) and sodium ions in both zeolite and the liquid phase during the exchange processes. The exchange kinetics were analyzed in accordance with the existing models, namely that diffusion and chemical reaction may be the rate-determining steps. Analyses have shown that chemical exchange is possible rate-determining step of the exchange process. Hence, the exchange kinetics were additionally analyzed in accordance with the kinetic model derived on the basis of the second order forward reaction between the Me²⁺ ions from solution and sodium ions from zeolite A, and the second order backward reaction between sodium ions from solution and Me²⁺ ions from zeolite A. Satisfactory agreement between the measured exchange kinetics and the exchange kinetics calculated by numerical solutions of the model equations, show that the exchange process takes place in accordance with the proposed model, i.e. by the second order forward and backward chemical reactions. (C) 2003 Elsevier B.V. All rights reserved.

Keywords: Zeolite A, Ion Exchange Kinetics, Heavy Metals Cations, Available Synthetic Zeolites, Self-Diffusion, Natural Zeolites, Cation-Exchange, Heavy-Metals, Waste-Water, Thin-Layers, Y-Zeolites, Na⁺ Ions, Removal

Çulfaz, M. and Yağız, M. (2004), Ion exchange properties of natural clinoptilolite: Lead-sodium and cadmium-sodium equilibria. Separation and Purification Technology, 37 (2), 93-105.

Full Text: S\Sep Pur Tec37, 93.pdf

Abstract: In the present work. ion exchange of lead and cadmium on the sodium form of Western Anatolia clinoptilolite is examined at 25 degreesC and 0.1 total normality. Its total theoretical cation exchange capacity was 2.3 meq, g. But only the sodium was exchanged during the equilibrium experiments. On this basis, the theoretical exchange capacity is 1.74 meq, g. According to the equilibrium studies, the selectivity sequence can be given as Pb²⁺ > Na⁺ > Cd²⁺. The maximum exchange levels expressed as the percentage of the theoretical exchange capacity were 100% for lead and 54% for cadmium. Using the equilibrium data, the thermodynamic analysis of the system was carried out. The solution non-ideality Correction factor has almost no effect on the Kielland plot and so on the numerical values of the thermodynamic equilibrium constant. The thermodynamic equilibrium constant (K,) and the standard free energy of exchange (DeltaGdegrees) were calculated as 16.6 and -3.48 kJ, eq. for lead-sodium system, and 0.16 and +2.27 kJ, eq. for cadmium-sodium system, respectively. Comparing the results of the present work with the data in literature, it can be concluded that the ion exchange capacities and cation selectivities of clinoptilolites with different cationic compositions are different. So, one should carry out cation exchange experiments on representative samples from the deposit before using it as cation exchanger for any practical application. (C) 2003 Elsevier B.V. All rights reserved.

Keywords: Cadmium, Cd²⁺, Clinoptilolite, Cu²⁺, Ferrierite, Heavy-Metals, Ion Exchange, Lead, Mordenite, Pb²⁺, Removal, Selectivity, Waste-Water, Zeolites

Notes: highly cited

Guibal, E. (2004), Interactions of metal ions with chitosan-based sorbents: A review. Separation and Purification Technology, 38 (1), 43-74.

Full Text: S\Sep Pur Tec38, 43.pdf

Abstract: Metal cations can be adsorbed by chelation on amine groups of chitosan in near neutral solutions. In the case of metal anions, the sorption proceeds by electrostatic attraction on protonated amine groups in acidic solutions. However, the presence of ligands and the pH strongly control sorption performance (sorption isotherm) and the uptake mechanism (changing the speciation of the metal may result in turning the chelation mechanism into the electrostatic attraction mechanism). Several examples are discussed with precious metals (Pd, Pt), oxo-anions (Mo, V) and heavy metals (Cu, Ag). Sorption performance (equilibrium uptake but also kinetics) is also strictly controlled by other structural parameters of the polymer (degree of deacetylation, crystallinity for example) that control swelling and diffusion properties of chitosan. The identification of the limiting steps of the sorption process helps in designing new derivatives of chitosan. Diffusion properties may be improved by physical modification of chitosan (manufacturing gel beads, decreasing crystallinity). Selectivity can be enhanced by chemical modification (grafting, for example, sulfur compounds). Several examples are discussed to demonstrate the versatility of the material. This versatility allows the polymer to be used under different forms (from water soluble form, to solid form, gels, fibers, hollow fibers...) for polymer-enhanced ultrafiltration and sorption processes. These interactions of metal ions with chitosan can be used for the decontamination of effluents, for the recovery of valuable metals but also for the development of new materials or new processes involving metal-loaded chitosan. Several examples are cited in the design of new sorbing materials, the development of chitosan-supported catalysts, the manufacturing of new materials for opto-electronic applications or agriculture (plant disease treatment...). (C) 2003 Elsevier B.V. All rights reserved.

Keywords: Chitosan, Ultrafiltration, Sorption, Kinetics, Isotherms, Diffusion, Cross-Linked Chitosan, Chemically-Modified Chitosan, Partially Deacetylated Chitin, Supported Palladium Catalyst, Highly Phosphorylated Derivatives, Chiral Stationary Phases, N-Carboxymethyl Chitosan, Gel Beads, Heavy-Metals, Aqueous-Solutions

Sèbe, G., Pardon, P., Pichavant, F., Grelier, S. and De Jéso, B. (2004), An investigation into the use of eelgrass (Zostera noltii) for removal of cupric ions from dilute aqueous solutions. Separation and Purification Technology, 38 (2), 121-127.

Full Text: S\Sep Pur Tec38, 121.pdf

Abstract: The ability of eelgrass (Zostera noltii (ZN)) to retain cupric ions from dilute aqueous solutions was studied as a function of pH, contact time and initial metal/sorbent ratio. Copper removal increased with pH, the optimum efficiency being attained between pH 5.5 and 6. When compared with other local lignocellulosic materials such as wood and corncob, Z. noltii appeared to be three times more effective than maritime pine and twice more than corncob. The presence of carboxyl groups in eelgrass was evidenced by infrared spectroscopy and photometric titration. These groups were found to participate in the adsorption process through cation exchange mechanisms, though other active binding sites were shown to be also involved. The metal and eelgrass relative concentrations appeared to influence the sorption capacity: the adsorption capacity of Z. noltii increased from 0.31 to 0.76 mmol Cu per gram as the metal/sorbent ratio increased. This behavior was partly explained by a change in the stoichiometry of a number of complexes as the metal and eelgrass relative concentrations varied. (C) 2003 Elsevier B.V. All rights reserved.

Keywords: Adsorption, Copper, Copper Adsorption, Decontamination, Eelgrass, Ion Exchange, Lignocellulosic, Metal-Ions, Model, Modified Barks, Recovery, Synthetic Solutions, Waste, Wood, Wood Preservatives

Krishna, M.V.B., Rao, S.V., Arunachalam, J., Murali, M.S., Kumar, S. and Manchanda, V.K. (2004), Removal of ¹³⁷Cs and ⁹⁰Sr from actual low level radioactive waste solutions using moss as a phyto-sorbent. Separation and Purification Technology, 38 (2), 149-161.

Full Text: S\Sep Pur Tec38, 149.pdf

Abstract: Moss (Funaria hygrometrica) used as phyto-sorbent, was evaluated for its potential for the removal of ¹³⁷Cs and ⁹⁰Sr from actual low level radioactive waste (LLW) solutions. Laboratory batch experiments with moss were carried out to determine optimal binding pH, exposure time and binding capacity for Cs and Sr binding. These studies indicated that sorbent showed high affinity for both Cs and Sr at pH range 5-9. Time dependence experiments showed a rapid adsorption of Cs and Sr within first 10 min of contact. Maximum sorption capacity for moss was found to be similar to6 mg/g (Cs), similar to 14 mg/g (Sr) and for NaOH treated moss capacity was found to be similar to17 mg/g (Cs) and 38 mg/g (Sr). In addition desorption experiments were carried out to recover the metal ions after sorption. The presence of complementary cations Na⁺, K⁺, Ca²⁺, Mg²⁺ and Al³⁺ at high concentrations suppressed the sorption of Cs and Sr on treated moss. Chemical esterification experiments indicate that carboxyl groups are mainly involved in the binding of Cs and Sr from LLW solutions. These findings show that the use of moss as phyto-sorbent may be a viable alternative, for the removal of Cs and Sr from LLW solutions. (C) 2003 Elsevier B.V. All rights reserved.

Keywords: Moss, Phyto-Sorbent, Radio Cs, Radio Sr, Low-Level Radioactive Waste, Aqueous-Solutions, Radionuclides, Pollution, Cesium, Resins

? Zhai, Y., Wei, X., Zeng, G., Zhang, D. and Chu, K. (2004), Study of adsorbent derived from sewage sludge for the removal of Cd²⁺, Ni²⁺ in aqueous solutions. Separation and Purification Technology, 38 (2), 191-196.

Full Text: 2004\Sep Pur Tec38, 191.pdf

Abstract: The adsorbent derived from sewage sludge through chemical pyrolysis has been used for the adsorption of Cd²⁺ and Ni²⁺ from aqueous solution. Parameters such as the agitation time, metal ion concentration, adsorbent dosage and pH were studied. The adsorption data fit well with the Langmuir and Freundlich isotherm models. The capacity of adsorption calculated from the Langmuir isotherm was 16.9 mg/g for Cd²⁺ and Ni²⁺, respectively at the initial pH of 5.8 at 25 °C. And the agitation time of 60 min was necessary for the adsorption to reach equilibrium, the optimum pH value in the range of 5.5–6.0. Desorption studies were performed with dilute hydrochloric acid. Quantitative recovery of the metal ion is possible. The mechanism of adsorption seems to be ion exchange. As the sewage sludge is discarded as waste from wastewater treatment processing, the adsorbent derived from sewage sludge is expected to be an economical product for metal ion remediation from water and wastewater.

Keywords: Adsorbent, Sewage Sludge, Adsorption, Metal Ions, Adsorption Isotherm

Farajzadeh, M.A. and Monji, A.B. (2004), Adsorption characteristics of wheat bran towards heavy metal cations. Separation and Purification Technology, 38 (3), 197-207.

Full Text: S\Sep Pur Tec38, 197.pdf

Abstract: Different-metal complexing ligands carrying synthetic and natural adsorbents have been reported in the literature for heavy metals removal. We have developed a new approach to obtain relatively high adsorption capacity utilizing wheat bran as a natural metal adsorbent. Adsorption equilibrium was achieved in about 10 min for all studied cations. The adsorption capacities are 93 mg/g for Cr(III), 70 mg/g for Hg(II), 62 mg/g for Pb(II), 21 mg/g for Cd(II), 15 mg/g for Cu(II) and 12 mg/g for Ni(II). The obtained results are an indication of higher specificity of the wheat bran for heavy metal cations compared with sodium and potassium ions. More than 82% of studied cations, except Ni(II), were removed from aqueous solution in single step. Matrix effect was not observed in most real samples in adsorption of cations by the studied sorbent. In this study no attempts were done in order to determine a mechanism for cations removal by the wheat bran, but it seems that complex mechanisms including ion exchange, complexation and size exclusion are possible. (C) 2003 Elsevier B.V. All rights reserved.

Keywords: Modified Wheat Bran, Heavy Metals, Adsorption, Wastewater, Natural Byproduct, Excellent Sorbent, Aqueous-Media, Rice Bran, Carcinogenesis, Sorption, Removal

Dubray, A. and Vanderschuren, J. (2004), Mass transfer phenomena during sorption of hydrophilic volatile organic compounds into aqueous suspensions of activated carbon. Separation and Purification Technology, 38 (3), 215-223.

Full Text: S\Sep Pur Tec38, 215.pdf

Abstract: A new process combining the two conventional control techniques absorption and adsorption, which consists in scrubbing the gases with an aqueous slurry of fine-powdered activated carbon, was studied to reduce the emission of some hydrophilic volatile organic compounds (VOCs).

The collection of airborne isopropyl alcohol (IPA) and acetone vapors, the concentrations of which being in the range 1-5 g/m³, was carried out with aqueous suspensions containing up to 8 % (w/w) activated carbon, in a cables contactor operating at ambient temperature in a semi-continuous way with recycle of the slurry.

To interpret the experiments, a model was developed on the basis of the two-film theory of absorption, a Henry’s law for the solubility of organic compounds in water, and the assumption of a linear relationship between the instantaneous VOC contents of the solid and liquid phases. This model allows determining the overall gas-liquid height of transfer unit of the absorption column.

Experimental results clearly reveal the increase of the global uptake capacity of VOC due to the presence of carbon particles in the absorbent. Nevertheless, it appears that the gas-liquid mass transfer rate is reduced, contrary to the expected enhancement due to the so-called grazing effect or shuttle movement of carbon particles reported in the literature.

Same kinds of runs performed with slurries of non-adsorbing fine particles of silica resulted in a net increase of the overall gas-liquid and particularly of the liquid film mass transfer resistance. These runs show that, in the kind of absorber used, a substantial hindering influence of the solid particles accumulation in the liquid film also occurs when adsorbing particles are added to the liquid.

The lack of enhancement in presence of activated carbon was attributed moreover to an inefficient shuttle effect caused by a too small adsorption capacity of the soluble VOCs on the activated carbon. This was confirmed by some tests carried out with an hydrophobic compound which being strongly adsorbed led to an appreciable enhancement. (C) 2003 Elsevier B.V. All rights reserved.

Keywords: Volatile Organic Compounds, Absorption, Activated Carbon, Adsorption, Slurries, Mass Transfer, Gas-Absorption, Slurry Reactors, Solid Particles, Stirred Cell, Phase, Water

Adhoum, N. and Monser, L. (2004), Removal of phthalate on modified activated carbon: application to the treatment of industrial wastewater. Separation and Purification Technology, 38 (3), 233-239.

Full Text: S\Sep Pur Tec38, 233.pdf

Abstract: This work investigates the efficiency of activated carbon that has undergone surface modification by impregnation with tetrabutylammonium (TBA) and copper in the removal of phthalate. Initially, the adsorption isotherms of phthalate on plain-carbon were measured at different pH values. It was concluded, using Langmuir model, that the adsorption capacity increased upon decreasing pH. To enhance the removal capacity at moderate pH, activated carbons were modified by immobilizing copper or TBA at their surface. The phthalate removal efficiencies of two separate fixed bed columns of Cu- and TBA-impregnated carbons were compared with that of plain activated carbon at pH 4. The results indicated that Cu-impregnated carbon has a removal capacity of nearly two times that of plain carbon. TBA impregnation was also shown to enhance the phthalate adsorption capacity with a factor of 1.7 times that of plain carbon. The observed results were explained in terms of chemisorption by forming Cu(Pht)₂ or electrostatic interaction between positively charged TBA and phthalate anions. The overall phthalate removal is a combination adsorption capacity of plain activated carbon, and the extent of copper metal ions and TBA agent molecules immobilized on the carbon.

Keywords: Activated Carbon, TBA- and Cu-Modified Carbon, Fixed Bed Column

Deosarkar, S.P. and Pangarkar, V.G. (2004), Adsorptive separation and recovery of organics from PHBA and SA plant effluents. Separation and Purification Technology, 38 (3), 241-254.

Full Text: S\Sep Pur Tec38, 241.pdf

Abstract: Adsorption as a process for the removal and recovery of organics from actual industrial effluents has been studied. The wastewater was obtained from Salicylic acid (SA) and p-hydroxy benzoic acid (PHBA) manufacturing units. The major constituents of the wastewater were Phenol, PHBA, SA and sodium sulphate. Equilibrium adsorption studies were carried out for four different polymeric resins, Amberlite XAD-2, -4, -7 and INDION 1014 MN-2 (IMN-2) having different surface areas, to find out the resin with maximum equilibrium loading capacity. Since IMN-2 gave the highest capacity it was used for further studies. Effect of presence of salt was also studied since the effluent contained a substantial amount of it. An attempt was made to correlate multi-solute equilibrium data using extended Langmuir model with a modification to account for salting out effect. The discrepancies in experimental and predicted values were attributed to the possible hydrogen bonding ability among the solutes. Column studies were also carried out to investigate the breakthrough behavior at two different flow rates to investigate the column capacity. LUB values were calculated to find out column efficiency. Regeneration was accomplished by four to five bed volumes of acetone. Quantitative recoveries of organics were obtained from the column operations for SA and PHBA plant effluents. (C) 2003 Elsevier B.V. All rights reserved.

Keywords: Polymeric Adsorbents, Industrial Effluents, Organics, Recovery, Multi-Solute Adsorption, Aqueous-Solution, Polymeric Adsorbents, Polystyrene Resins, Dissolved Organics, Activated Carbon, Mass-Transfer, Salting-Out, Sorption, Equilibria

? Çay, S., Uyanık, A. and Özaşık, A. (2004), Single and binary component adsorption of copper(II) and cadmium(II) from aqueous solutions using tea-industry waste. Separation and Purification Technology, 38 (3), 273-280.

Full Text: 2004\Sep Pur Tec38, 273.pdf

Abstract: The adsorption ability of Turkish tea waste (fibrous) obtained from various tea-processing factories was investigated for the removal of Cu(II) and Cd(II) from single (non-competitive) and binary (competitive) aqueous systems. Adsorption of the investigated heavy metal ions by tea waste strongly depends on pH, contact time, initial concentration of the heavy metal ions and adsorbent dosage. The maximum adsorption capacities of Cu(II) and Cd(II) per gram tea waste were calculated as 8.64±0.51 and 11.29±0.48 mg for single and 6.65±0.31 and 2.59±0.28 mg for binary systems, respectively. The experimental data for single and binary Cu(II) and Cd(II) systems fitted the Freundlich isotherm model excellently (r² = 0.977–0.992). The results show that tea-processing factory waste, which has a very low economical value, may be used effectively in removal of Cu(II) and Cd(II) ions from aqueous systems for environmental cleaning purposes.

Keywords: Adsorption, Tea Waste, Copper, Cadmium, Isotherms

Wibulswas, R. (2004), Batch and fixed bed sorption of Methylene blue on precursor and QACs modified montmorillonite. Separation and Purification Technology,