Personal Research Database

Full Text: S\Sep Pur Tec16, 83.pdf

Abstract: A microporous hydrophobic membrane allows the permeation of an oil phase at almost zero pressure and retains the water. The separation of dilute oil-in-water mixtures using flat sheet hydrophobic PVDF membranes has been investigated using an unstirred laboratory scale semi-batch experimental system operated at 40°C. The flat sheet membranes were prepared in the laboratory by an immersion precipitation method and were characterised in terms of a mean pore radius, porosity and breakthrough pressure. The oil-in-water mixture contains 1% kerosene in distilled water. The experimental work essentially entails the study of the effects of various system parameters on the oil/water separation characteristics. In particular, the effects of feed flow rate, the operating pressure and pore size and porosity of the membrane were studied. The experimental results can be predicted reasonably well using the Hagen-Poiseuille equation at a high vertical velocity and the percentage of oil removed can be achieved as high as 77% under normal experimental conditions. (C) 1999 Elsevier Science B.V. All rights reserved.

Keywords: Microporous Poly(Vinylidene Fluoride) Membranes, Oil Water Separation, Phase Inversion, Separation

Dutta, M., Dutta, N.N. and Bhattacharya, K.G. (1999), Aqueous phase adsorption of certain beta-lactam antibiotics onto polymeric resins and activated carbon. Separation and Purification Technology, 16 (3), 213-224.

Full Text: S\Sep Pur Tec16, 213.pdf

Abstract: The adsorption of certain beta-lactam antibiotics such as 7-aminocephalosporanic acid, cephalexin, cefadroxyl and 6-aminopenillanic acid in aqueous solution has been studied using polymeric resins of four different types as well as activated carbon. The adsorption intensity was found to be strongly dependent on the aqueous phase pH and this dependence could be interpreted from a model for neutral species adsorption in all cases. Adsorption equilibrium data were correlated with the Langmuir, Freundlich and Redlich-Peterson isotherm, the Langmuir model being found to provide the best fit of the experimental data. The differences in adsorption affinities of the solute obtained for the different adsorbents were interpreted from sorbent surface chemistry and morphological structure. From the correlation obtained between adsorption affinity and estimated enthalpy, it may be predicted that the adsorption is determined by a specific solute-sorbent interaction which is predominantly of enthalpic type. The adsorption rate curves for almost all the solutes appear to be typical of the first order kinetics. However, more precise kinetics will require inclusion of the external mass transfer effect initially and particle diffusion effect at a later stage. (C) 1999 Elsevier Science B.V. All rights reserved.

Keywords: Activated Carbon, Adsorption, Beta-Lactam, Langmuir Isotherm, Polymeric Resin, Cephalosporin-C, Sorbents, Equilibria, Kinetics, Products

Qiao, S. and Hu, X. (1999), Binary adsorption kinetics of ethane and propane in a large heterogeneous microporous particle. Separation and Purification Technology, 16 (3), 261-271.

Full Text: S\Sep Pur Tec16, 261.pdf

Abstract: Sorption kinetics of ethane and propane and their binary mixtures on Norit Row activated carbon (type 0.8 supra) were investigated under various experimental conditions. The experimental kinetics data collected on a differential adsorption bed rig were employed to validate the potential of the heterogeneous macropore and surface diffusion (HMSD) model proposed by Hu and Do [X. Hu, D.D. Do, Langmuir 9 (1993) 2530]. The model takes into account the effects of surface energetic heterogeneity on both sorption kinetics and equilibrium and allows for the diffusion in both bulk and adsorbed phases. The kinetics parameters derived from single component systems were used to predict the sorption kinetics of multicomponent systems. It is found that the model can give a good description of the binary kinetics in general, and in particular, the model is able to accurately predict the overshoot degree of the rapidly diffusing/less strongly adsorbed species. Some discrepancy was also observed between the model prediction and the experimental data of desorption kinetics, and this phenomenon has been discussed. (C) 1999 Elsevier Science B.V. All rights reserved.

Keywords: Activated Carbon, Adsorption, Ethane, Kinetics, Propane, Activated Carbon, Energetic Heterogeneity, Surface-Diffusion, Gases

? Jain, P.M., Smith, J.S. and Valsaraj, K.T. (1999), Reusable adsorbents for dilute solution separation 3. Sorption dynamics of phenanthrene on surfactant-modified alumina. Separation and Purification Technology, 17 (1), 21-30.

Full Text: 1999\Sep Pur Tec17, 21.pdf

Abstract: The formation of surfactant aggregates (hemi-micelles) on alumina substantially increased the adsorption and retarded the breakthrough of a hydrophobic organic compound (phenanthrene) in a laboratory-scale column through adsolubilization. The adsorption waves of both surfactant (sodium dodecylsulfate, SDS) and phenanthrene were predicted adequately by existing models. However, the desorption wave was not predicted satisfactorily. The maximum capacities of the alumina bed for both SDS and phenanthrene were determined and compared with batch adsorption isotherm data, the values were in good agreement. The regeneration of the alumina bed was done by adjusting the feed solution pH to higher values than during the adsolubilization step, three regeneration cycles were studied. The capacities of alumina for phenanthrene and SDS sorption were found to be the same in all three cases, indicating no significant deterioration of the alumina surface. These characteristics make the process of adsolubilization attractive for concentration of dilute aqueous waste streams. (C) 1999 Elsevier Science B.V. All rights reserved.

Keywords: Adsolubilization, Adsorbents, Adsorption, Adsorption Isotherm, Aggregates, Alumina, Cations, Clay, Concentration, Desorption, Dynamics, Hydrophobic, Isotherm, Models, Nonionic Organic-Compounds, Organic, pH, Phenanthrene, Regeneration, Separation, Sodium, Sodium Dodecylsulfate, Soil-Water Systems, Sorption, Streams, Surface, Surfactant, Surfactant-Modified Alumina, Tetrachloromethane Sorption, Waste, Waves

Wang, K., King, B. and Do, D.D. (1999), Rate and equilibrium studies of benzene and toluene removal by activated carbon. Separation and Purification Technology, 17 (1), 53-63.

Full Text: S\Sep Pur Tec17, 53.pdf

Abstract: The adsorption kinetics of benzene, toluene and their binary vapor mixtures were measured on Ajar-activated carbon with a differential adsorber bed (DAB) rig and analyzed using the heterogeneous finite kinetics model [D.D. Do, K. Wang, AIChE J., 44 (1998) 68]. The size distribution of the slit-shaped micropore (MPSD) and the Lennard-Jones potential theory are employed to account for the adsorption energetic heterogeneity of the system. This MPSD is compared with the Fore size distribution (PSD) derived from high-pressure methane adsorption data with the Grand Canonical Monte Carlo (GCMC) technique. It is found that, with three mass transfer mechanisms being used to describe the uptake in activated carbon and the Maxwell-Stefan equation being used to describe the bulk phase diffusion, the finite kinetics model can fit the pure component adsorption kinetics of benzene and toluene and has the capability to simulate the multicomponent adsorption kinetics of their mixtures on Ajar-activated carbon. (C) 1999 Elsevier Science B.V. All rights reserved.

Keywords: Adsorption Kinetics, Aromatics, GCMC, Multicomponent, PSD, Monte-Carlo Simulation, Size Distribution, Adsorption, Diffusion, Model

Korus, I., Bodzek, M. and Loska, K. (1999), Removal of zinc and nickel ions from aqueous solutions by means of the hybrid complexation-ultrafiltration process. Separation and Purification Technology, 17 (2), 111-116.

Full Text: S\Sep Pur Tec17, 111.pdf

Abstract: This paper presents the possibility of removing metal ions by applying the hybrid complexation-ultrafiltration process. The research was conducted on model solutions containing Zn(II) and Ni(II) ions. The complexing agent applied in the research was sodium polyacrylate, To separate the formed polymer-metal complexes, porous membranes made from polysulfone were used. Ultrafiltration of the model wastewater containing metal ions aimed at finding an optimum ratio between the concentrations of the complexing agent and metal, and determining the most favourable pH value. The ratio between polymer and metal concentrations was changed in the range 10: 1-100: 1. In the case of both examined metals, the complexation-ultrafiltration process was most effective at a 10-fold excess of the polymer with respect to the metal. The pH value was adjusted over the range 2-10 using HNO₃ and NaOH solutions. An increase in alkalinity brought about an improvement in the effectiveness of the separation process. To remove metal ions from water solutions, the concentration process was carried out according to the previously determined polymer: metal ratios, and at optimum pH. The permeate obtained comprised 90% of the initial volume of the feed. The process was characterized by good effectiveness and enabled a 97-99% retention of the metal present in the feed solution. The retentate separated during the concentration process was subjected to decomplexation-ultrafiltration. High concentrations of the metals obtained in the permeates after decomplexation indicate the possibility of an effective separation of metal ions from the complexing polymer. (C) 1999 Elsevier Science B.V. All rights reserved.

Keywords: Complexation, Metal Ions Removal, Ultrafiltration, Heavy-Metals, Enhanced Ultrafiltration, Selective Removal, Liquid Membranes, Separation, Microfiltration, Diafiltration, Binding, Water

Hichour, M., Persin, F., Sandeaux, J. and Gavach, C. (2000), Fluoride removal from waters by Donnan dialysis. Separation and Purification Technology, 18 (1), 1-11.

Full Text: S\Sep Pur Tec18, 1.pdf

Abstract: Excess or lack of levels of fluoride in drinking water being harmful to human health, the concentration of F^- ions must be maintained in the range 0.5 to 1.5 mg l^-1. The purpose of this study is to apply Donnan dialysis (DD) for fluoride removal from waters with a concentration exceeding the permitted value. Two synthetic waters, which are models of waters from countries of Africa (Maghreb, Senegal), were prepared and treated with a DD pre-industrial pilot. The anion exchange membrane was the DSV membrane (Asahi Glass), with a total area of 0.176 mt. The initial fluoride concentration was 9.5 and 6.1 mg l^-1 in each model water, respectively. The DD process was studied under two circulating modes of the receiver solution, single pass and batch, while the feed solution flowed continuously as a single pass. To maintain the fluoride concentration below the acceptable values at the outlet of the feed compartment, the extracted fluoride ions are complexed by Al³⁺ ions which were added in the receiver solution. Chemical speciation of aluminum-fluoride compounds was studied in order to define the optimized conditions of pH and concentration. Despite the different anions (Cl^-, HCO₃^-, SO₄^2-) and cations (Na⁺, K+, Ca²⁺, Mg²⁺) generally present in ground waters, a fluoride concentration in agreement with the norm (<1.5 mg l^-1) could be reached whatever the water treated. However, the mineralization of water was increased by about 25% resulting from the electrolyte diffusion which occurs from the receiver to the feed solution. (C) 2000 Elsevier Science B.V. All rights reserved.

Keywords: Anion Exchange Membrane, Defluoridation, Donnan Dialysis, Fluoride Ion, Water, Defluoridation, Enrichment, Ash

Esalah, J.O., Weber, M.E. and Vera, J.H. (2000), Removal of lead from aqueous solutions by precipitation with sodium di-(n-octyl) phosphinate. Separation and Purification Technology, 18 (1), 25-36.

Full Text: S\Sep Pur Tec18, 25.pdf

Abstract: Two organophosphorus compounds, sodium di-(n-octyl) phosphinate and sodium di-(n-dodecyl) phosphinate, were synthesized and purified. Lead was precipitated from aqueous nitrate and chloride solutions with sodium di-(n-octyl) phosphinate (NaL) in the form of PbL2(s). The effects of the feed pH. concentration of chloride, concentration of calcium, and of the chain length of the precipitating agent on the removal of lead were investigated for mole ratios of NaL to lead between 0.1 and 6.5. Adding acid to the feed solution reduced the removal of lead as some of the phosphinate precipitated in the acid form as HL(s). The removal of lead was not affected by the presence of chloride or calcium in the feed solution, up to mole ratios to lead of 250 and 2.75, respectively. The residual lead in solution was reduced by increasing the length of the alkyl group of the phosphinate to dodecyl. Over 99% of the precipitating agent was recovered by adding NaOH to the precipitate, and then contacting the solution with diethyl ether to extract the reagent. The lead was completely recovered from the PbL2(s). Lead-free precipitating agent, and an aqueous solution of lead at a concentration 100 times its concentration in the feed, were obtained. Using measured solubility products of the precipitates and literature values of the stability constants for the expected reactions, the removal of lead, the loss of precipitating agent, and the equilibrium pH were calculated. (C) 2000 Elsevier Science B.V. All rights reserved.

Keywords: Decontamination, Effluent Purification, Heavy Metals, Lead Removal, Waste Water Treatment, Extraction, Systems, Acids, Metals

Nosier, S.A. and Sallam, S.A. (2000), Removal of lead ions from wastewater by cementation on a gas-sparged zinc cylinder. Separation and Purification Technology, 18 (2), 93-101.

Full Text: S\Sep Pur Tec18, 93.pdf

Abstract: Removal of lead from wastewater consisting of lead nitrate by cementation on a gas-sparged zinc rod was investigated experimentally. Detailed observations were made for the deposited lead by scanning electron microscope (SEM) to show the porosity and nodular structure of the lead deposit. The activation energy for the process was found to be 10 kcal/g.mol. The rate controlling step was found to be diffusion of lead ion through a solution boundary layer surrounding the zinc cylinder. Accordingly, rates of cementation were expressed in terms of the mass transfer coefficient. Variables studied were initial lead ion concentration, length of the zinc cylinder, temperature and N₂ flow rate. Increasing the height of the zinc cylinder was found to decrease the mass transfer coefficient. The experimental data were correlated by the equation:

J = 0.195+0.55(Fr.Re)^(-0.109)(L/d)^(-0.5).

Keywords: Cementation, Gas Sparging, Heavy Metals, Mass Transfer Coefficient, Zinc Cylinder

Gupta, V.K. and Ali, I. (2000), Utilisation of bagasse fly ash (a sugar industry waste) for the removal of copper and zinc from wastewater. Separation and Purification Technology, 18 (2), 131-140.

Full Text: S\Sep Pur Tec18, 131.pdf

Abstract: Bagasse fly ash, a waste produced in sugar industries, has been converted into an inexpensive and effective adsorbent. The product was characterised by different chemical and physical methods and has been used for the removal of copper and zinc from wastewater. Various parameters such as pH, adsorbent dose, initial metal ions concentrations, temperature, particle size, etc. were optimised. Copper and zinc are adsorbed by the developed adsorbent up to 90/95% in batch and column experiments. The adsorption was found to be endothermic in nature and follows both the Langmuir and Freundlich models. Isotherms have been used to evaluate thermodynamic parameters for the adsorption process.

Keywords: Blast-Furnace Waste, Low-Cost Adsorbent, Activated Slag, Equilibrium Uptake, Sorption Dynamics, Column Operations, Earth Elements, Water, Adsorption, Cadmium, Adsorbent, Adsorption, Bagasse Fly Ash and Metal Ions, Copper, Wastewater, Zinc

Karabulut, S., Karabakan, A., Denizli, A. and Yurum, Y. (2000), Batch removal of copper(II) and zinc(II) from aqueous solutions with low-rank Turkish coals. Separation and Purification Technology, 18 (3), 177-184.

Full Text: S\Sep Pur Tec18, 177.pdf

Abstract: The removal of heavy-metal ions from aqueous solutions containing low-to-moderate levels of contamination using Turkish Beypazari low-rank coal was investigated. Carboxylic acid and phenolic hydroxyl functional groups present on the coal surface were the adsorption site to remove metal ions from solution via ion exchange. The equilibrium pH of the coal/solution mixture has been shown to be the principal factor controlling the extent of removal of Cu(II) and Zn(II) ions from aqueous solutions. The optimum pH was measured to be 4.0 and it was found that the adsorption reached equilibrium in 20 min. The maximum adsorption capacities of the metal ions from their single solutions were 1.62 mgfor Cu(II) and 1.20 mgfor Zn(II) per g of coal. The order of affinity based on a weight uptake by coal was as follows: Cu(II) > Zn(II). The same behavior was observed during the competitive adsorption, that is in the case of adsorption from their binary solutions. The adsorption phenomena appeared to follow a typical Langmuir isotherm. It was observed that use of low-rank coal was considerably effective in removing Cu(II) and Zn(II) ions from aqueous solutions. Higher amounts of adsorbed metal ions could be desorbed (up to 80%) using 25 mM EDTA. Low-rank Turkish coals are suitable for consecutive use for more than three cycles without significant loss of adsorption capacity.

Keywords: Metal-Ions, Activated Carbons, Amidoxime Groups, Adsorption, Water, Preconcentration, Separation, Recovery, Sorption, Clay, Turkish low-rank coal, metal ions, adsorption

Smičiklas, I.D., Milonjić, S.K., Pfendt, P. and Raičević, S. (2000), The point of zero charge and sorption of cadmium(II) and strontium(II) ions on synthetic hydroxyapatite. Separation and Purification Technology, 18 (3), 185-194.

Full Text: S\Sep Pur Tec18, 185.pdf

Abstract: Surface properties of synthetic well-crystallized hydroxyapatite were investigated. Points of zero charge (pH_PZC) for different solid to solution ratios were determined by the batch equilibration technique, using KNO₃ as a background electrolyte. It has been found that the decrease in solid to solution ratio from 1: 100 to 1: 500 leads to a decrease in pH_PZC from 6.1 to 4.1, respectively. Sorption of Cd²⁺ ions is not influenced by the initial pH value in the investigated range (5-7), while sorption of Sr²⁺-ions, determined in the wider pH range (4.5-11.5), depends only on the initial pH higher than 10, i.e. final pH values higher than 4.5. Negative surface charge established when pH of the solution is higher than pH, leads to a more effective cation sorption. (C) 2000 Elsevier Science B.V. All rights reserved.

Keywords: Hydroxyapatite, Point of Zero Charge, Sorption, Cd²⁺-and Sr²⁺-Ions, Aqueous-Solutions, Lead Immobilization, Chromatography, Apatite, Removal

Khan, A.R., Riazi, M.R. and Al-Roomi, Y.A. (2000), A thermodynamic model for liquid adsorption isotherms. Separation and Purification Technology, 18 (3), 237-250.

Full Text: S\Sep Pur Tec18, 237.pdf

Abstract: Based on the principle of solution thermodynamics for liquid-solid equilibrium, a simple mathematical expression has been developed to express liquid adsorption isotherms. A weight fraction based activity coefficient model has been derived for the solid phase nonideality. The proposed model has been evaluated and compared with four other models commonly used for liquid adsorption isotherms in the literature. Systems used in this study are solute adsorption from dilute aqueous solution on various activated carbon or molecular sieve. For 14 systems at various isotherms for the temperature range 0.1-75°C and the solute concentration range of 5-26540 g/m³ for 382 data points, the proposed model predicts equilibrium concentration with an average deviation of 6%. The proposed model clearly outperforms other available methods such as vacancy solution theory, exponential model and various other modified forms of the Freundlich isotherm. The unique features of the proposed model are its simplicity, generality and accuracy over the entrie experimental concentration and temperature ranges. (C) 2000 Elsevier Science B.V. All rights reserved.

Keywords: Liquid Adsorption Isotherm, Thermodynamic Model, Liquid-Solid Equilibrium, Solid Activity Coefficient, Dilute Aqueous-Solution, Activated Carbon, Equation, Pollutants

Hashim, M.A., Tan, H.N. and Chu, K.H. (2000), Immobilized marine algal biomass for multiple cycles of copper adsorption and desorption. Separation and Purification Technology, 19 (1-2), 39-42.

Full Text: S\Sep Pur Tec19, 39.pdf

Abstract: The biomass of a marine alga, Sargassum baccularia, was immobilized by using polyvinyl alcohol as the polymeric matrix. The reusability of the immobilized biomass was studied by using copper as the model metal ion in five consecutive cycles of adsorption-desorption. Hydrochloric acid at pH 1.0 and ethylenediaminetetraacetic acid (EDTA) solution at 2 mM were used as the desorbing agents. Both desorbents were effective in stripping the adsorbed copper from the immobilized biomass over the five cycles. However, copper uptake in Cycles 2-5 was lower than that in Cycle 1, indicating that the two desorbing agents limited the reuse potential of the immobilized biomass in multiple cycles of adsorption-desorption.

Keywords: Removal, Microorganisms, Accumulation, Biosorption, Alginate, Recovery, Cells, Immobilized, Algal, Copper, Adsorption, Desorption

Cheung, C.W., Porter, J.F. and McKay, G. (2000), Sorption kinetics for the removal of copper and zinc from effluents using bone char. Separation and Purification Technology, 19 (1-2), 55-64.

Full Text: S\Sep Pur Tec19, 55.pdf

Abstract: The removal of copper and zinc ions from aqueous effluents by bone char has been studied in single component sorption systems. The sorption capacity of bone char for copper and zinc is 0.75 and 0.53 mmol per g bone char, respectively. The values indicate that bone char is a suitable sorbent for the two metal ions. The equilibrium isotherms are best described by a Langmuir-Freundlich (L-F) type isotherm equation. The kinetics of sorption of the two metal ions have been analyzed by two kinetic models, namely, the Lagergren pseudo first-order model and the Elovich kinetic model. Kinetic analysis of the two models has been carried out for system variables-initial metal ion concentration and mass of bone char. The rate constants for the two models have been determined and the correlation coefficients have been calculated in order to assess which model provides the best fit predicted data with experimental results. The Elovich equation provides the best fit to experimental data.

Keywords: Bone Char, Elovich, Equilibrium, Kinetics, Pseudo First-Order, Sphagnum Moss Peat, Activated Carbon, Aqueous-Solution, Adsorption, Models, Waters, Ions, Lead

Chen, J.P. and Wang, X.Y. (2000), Removing copper, zinc, and lead ion by granular activated carbon in pretreated fixed-bed columns. Separation and Purification Technology, 19 (3), 157-167.

Full Text: S\Sep Pur Tec19, 157.pdf

Abstract: Adsorption experiments by pretreated fixed-bed columns for single-species (Cu, Zn, and Pb) and multi-species (Cu-Zn, Cu-Pb, and Cu-Pb-Zn) metal ions were carried out in this study. It was demonstrated that the breakthrough occurred more slowly with an increasing influent pH and a decreasing flow rate. An increase in ionic strength slightly increased copper removal, but it did not affect zinc removal. Experiments on competitive adsorption illustrated that the removal of metal ions was decreased when additional metal ions were added. The effect was more signifcant for zinc as the activated carbon was less favourable for its removal. The removal of these three metal ions by the activated carbon columns followed the descending order: Cu > Pb > Zn. Copper and zinc removal was increased significantly when EDTA was added to the influent. At the same time, the removal of copper was almost the same as that of zinc. An increase in ionic strength caused a decrease in the removal of copper and zinc ions complexed with EDTA. (C) 2000 Elsevier Science B.V. All rights reserved.

Keywords: Granular Activated Carbon, Metal Ions, Fixed-Bed Columns, Pretreatment, Breakthrough, Adsorption, Equilibrium, Cadmium

Yao, C.C. (2000), Extended and improved Langmuir equation for correlating adsorption equilibrium data. Separation and Purification Technology,