Personal Research Database

Full Text: S\Sep Pur Tec42, 91.pdf

Abstract: This work addresses the adsorption of methyl ethyl ketone (MEK) and trichloroethene (TCE) from aqueous solutions on agglomerated silicalite. Results from both equilibrium and fixed-bed adsorption studies in aqueous solutions are given. The breakthrough curves of MEK could be described adequately with a bidisperse model. It was observed that the mass transfer of MEK is controlled by both the external and the macropore transport. The breakthrough curves of TCE are also adequately described with the same model, for which the micropore resistance was the most important one. The thermal regeneration of the agglomerated silicalite loaded with MEK by passing a purging gas through the bed (nitrogen and air) was also studied. No decrease of the adsorption capacity with the number of regeneration cycles was observed.

Keywords: Methyl Ethyl Ketone, Trichloroethene, Silicalite, Adsorption, Modeling

? Košutić, K., Furač, L., Sipos, L. and Kunst, B. (2005), Removal of arsenic and pesticides from drinking water by nanofiltration membranes. Separation and Purification Technology, 42 (2), 137-144.

Full Text: S\Sep Pur Tec42, 137.pdf

Abstract: The removal of arsenic and pesticides from natural ground water from the Slavonia region, Croatia, by two commercial nanofiltration membranes (NF270 and NFc) was investigated. The nanofiltration membranes and a comparing reverse osmosis membrane were first examined using sodium dibasic arsenate solution and judged against their performances using sodium chloride and sodium sulfate solutions. The rejections of the sodium dibasic arsenate as well as the arsenate anion from the natural groundwater by the nanofiltration membranes are satisfactory high, and one of the nanofiltration membranes exhibit the superior permeation rate values. The outstanding permeation rate values of these membranes in relation to the reverse osmosis membrane promise a noteworthy decrease of energy consumption and energy costs for the process when using these membranes.

The prevailing mechanism of ion retention by the negatively charged nanofiltration membranes is the charge exclusion. The size exclusion mechanism is also important but not sufficient for the uncharged organic molecules rejection. The membrane material and the membrane pore size distribution (PSD) also influence the uncharged organic molecules rejections. The rejections of pesticides are reasonably high, and besides the size effect, the specific physicochemical phenomena should be considered in order to understand their rejection by the nanofiltration membranes.

Keywords: Nanofiltration, Membranes, Arsenic Removal, Pesticides Removal, Groundwater, Pore Size Distribution

? Boonamnuayvitaya, V., Sae-ung, S. and Tanthapanichakoon, W. (2005), Preparation of activated carbons from coffee residue for the adsorption of formaldehyde. Separation and Purification Technology, 42 (3), 159-168.

Full Text: S\Sep Pur Tec42, 159.pdf

Abstract: Six types of activated carbons were prepared from coffee residues by varying activating agents of zinc chloride, nitrogen, carbon dioxide and steam. Characterization of these samples was performed by using nitrogen adsorption isotherms, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) in order to understand the coffee residue activated carbon and its adsorptive capacity. All of activated carbons and one commercial activated carbon (CH-I1000) were subjected to the adsorption of formaldehyde vapor. The coffee activated carbon prepared with ZnCl₂ impregnation and nitrogen activation (CZn-N₂) demonstrates its highest capacity of formaldehyde adsorption owing to the hydrophilic functional groups of O-H, C=O, C-O on the surface. The coffee activated carbon prepared with ZnCl₂ impregnation coupled with carbon dioxide activation (CZn-N₂-CO₂) yields the highest total surface area (914±21 m²/g) and total pore volume (1.010±0.003 cc/g) with the hydrophobic groups on the surface adsorbed formaldehyde less than CZn-N₂. Therefore, we conclude that the formaldehyde adsorption by activated carbons in this work is affected by surface chemistry more than texture characteristics of surface area and pore volume.

Keywords: Activated Carbon, Coffee residues, ZnCl₂, Formaldehyde, Adsorption

? Dhakal, R.P., Ghimire, K.N., Inoue, K., Yano, M. and Makino, K. (2005), Acidic polysaccharide gels for selective adsorption of lead(II) ion. Separation and Purification Technology, 42 (3), 219-225.

Full Text: S\Sep Pur Tec42, 219.pdf

Abstract: The adsorption behavior of lead(II), zinc(II) and copper(II) on crosslinked pectic and alginic acids, and their amide derivatives form has been investigated. The selectivity order for metal ion uptake is lead(II) > copper(II) > zinc(II). The nature of such acidic polysaccharides for the removal of lead(II) ion was examined through batch wise tests and column tests and compared with that for the commercially available weakly acidic cation exchange DIAION WK resins. The experimental results revealed that chemically modified acidic polysaccharides exhibit much better separation performance compared to the latter, which suggests a high possibility of their applications in the practical separation and purification of lead(II) ion.

Keywords: Pectic Acid, Alginic Acid, Polysaccharide Gels, Lead(II) Ion, Adsorptive Removal

? Li, N. and Bai, R.B. (2005), Copper adsorption on chitosan–cellulose hydrogel beads: Behaviors and mechanisms. Separation and Purification Technology, 42 (3), 237-247.

Full Text: S\Sep Pur Tec42, 237.pdf

Abstract: The application of chitosan–cellulose hydrogel beads as an adsorbent for Cu adsorption from aqueous solutions was examined. Chitosan was blended with cellulose to make chitosan–cellulose hydrogel beads and the hydrogel beads were crosslinked with ethylene glycol diglycidyl ether (EGDE). It was found that the addition of cellulose to chitosan made the hydrogel beads materially denser and the crosslinking reaction improved the chemical stability of the chitosan–cellulose beads in solutions with pH values down to 1. Batch adsorption experiments indicated that both the chitosan–cellulose and the crosslinked chitosan–cellulose hydrogel beads had high adsorption capacities for Cu removal, with the optimum pH in the range around neutral, although the crosslinked chitosan–cellulose beads always exhibited slightly lower adsorption capacities than the non-crosslinked beads. The adsorption isotherm of the chitosan–cellulose beads can be well-fitted to the Langmuir model, but that of the crosslinked chitosan–cellulose can only be well described by the Freundlich model. Copper adsorption kinetics on both types of the beads clearly followed an initial transport-controlled adsorption phenomenon. Fourier Transform Infrared (FTIR) Spectroscopy and X-ray photoelectron spectroscopy (XPS) revealed that Cu adsorption on the beads mainly involved the nitrogen atoms in chitosan to form surface complexes.

Keywords: Chitosan–cellulose Beads, EDGE Crosslinking, Cu Adsorption, Surface Interaction, Mechanisms

? Erdem, M. and Özverdi, A. (2005), Lead adsorption from aqueous solution onto siderite. Separation and Purification Technology, 42 (3), 259-264.

Full Text: S\Sep Pur Tec42, 259.pdf

Abstract: In this paper, the ability of siderite to remove Pb²⁺ from aqueous solution by adsorption has been investigated through batch experiments. The Pb²⁺ adsorption property of the siderite was evaluated as a function of pH, siderite dosage, initial Pb²⁺ concentration, and temperature. Maximum Pb²⁺ adsorption yield was obtained to be 99.6% for initial Pb²⁺ concentration of 50 mg/l at 25 °C and pH 2.97 for 180 min in the presence of 10 g/l siderite. Adsorption data obtained at 25, 30 and 35 °C showed that the adsorption process fitted first-order adsorption rate expression and Langmuir and Freundlich adsorption models. Adsorption capacities of siderite at 25, 30 and 35 °C were found to be 10.32, 12.45 and 14.06 mg Pb²⁺/g siderite, respectively. Adsorption enthalpy and activation energy values were calculated to be 49.73 and 32.49 kJ/g mol from the isotherm and kinetic data, respectively.

Keywords: Lead Removal, Adsorption, Siderite, Heavy Metal, Wastewater Treatment

? Ghorai, S. and Pant, K.K. (2005), Equilibrium, kinetics and breakthrough studies for adsorption of fluoride on activated alumina. Separation and Purification Technology, 42 (3), 265-271.

Full Text: S\Sep Pur Tec42, 265.pdf

Abstract: Contamination of drinking water due to fluoride is a severe health hazard problem. Excess of fluoride (>1.5 mg/l) in drinking water is harmful to the human health. Various treatment technologies for removing fluoride from groundwater have been investigated in the past. Present investigation aims to remove fluoride by activated alumina. Adsorption isotherm has been modeled by Langmuir equation and isotherm constants. The dependence of the adsorption of fluoride on the pH of the solution has been studied to achieve the optimum pH value and a better understanding of the adsorption mechanism. It was found that maximum adsorption takes place at pH value of 7. Breakthrough analysis revealed that early saturation and lower fluoride removal takes place at higher flow rate and at higher concentrations. Predicted simulation results of one-dimensional model for isothermal, axially dispersed fixed bed on the assumption of pore-diffusion rate-control conditions matches with the experimental data in the initial zone of the breakthrough curve, but deviated marginally in the final tailing zone. Bed depth service time (BDST) model was also applied successfully.

Keywords: Fluoride, Activated Alumina, Adsorption, Regeneration, Breakthrough, Modeling

? Shukla, S.R. and Pai, R.S. (2005), Adsorption of Cu(II), Ni(II) and Zn(II) on dye loaded groundnut shells and sawdust. Separation and Purification Technology, 43 (1), 1-8.

Full Text: S\Sep Pur Tec43, 1.pdf

Abstract: The potential of cheap cellulose-containing natural materials like groundnut shells and sawdust was assessed for Cu(II), Ni(II) and Zn(II) adsorption from their aqueous solutions. These materials showed good adsorption capacities, although the levels differed depending on the combination of adsorbing material and metal ion. Application of a specific dye, C.I. Reactive Orange 13 onto the material further enhanced the adsorption capacity. The maximum metal ion uptake values for Cu(II), Ni(II) and Zn(II) were 7.60, 7.49 and 9.57 mg/g, respectively, for the dye loaded groundnut shells as against the respective values 4.46, 3.83 and 7.62 mg/g achieved when the unloaded groundnut shells was used as adsorbent. Similarly, the dye loaded sawdust gave the adsorption values 8.07 mg/g for Cu(II), 9.87 mg/g for NI(11) and 17.09 mg/g for Zn(11), which were higher than the corresponding values 4.94, 8.05 and 10.96 mg/g achieved with unloaded sawdust as adsorbent. With lowering of the pH of a metal ion solution, all the adsorbing materials showed a decrease in the adsorption capacities. When the pH of a metal cation solution was decreased to the lowest level at 1.5, the adsorption reached to very low values in all the cases. Even under low pH, the adsorption of metal ions on dye-loaded adsorbents was comparatively higher. This was made use of in desorption studies. Adsorption isotherm models were developed wherein the best fit was obtained in the Langmuir model. The regeneration and reusability of the adsorbents were also assessed for three successive adsorption-desorption cycles and were found to retain the adsorptive capacity. (C) 2004 Elsevier B.V. All rights reserved.

Keywords: Adsorption-Desorption, Groundnut Shells, Heavy Metals, Reactive Dye, Sawdust, Cellulosic Materials, Aqueous-Solutions, Ion Removal, Metal-Ions, Sorption, Cadmium, Lead, Biosorption, Effluents, Zinc

? Mittal, A., Krishnan, L. and Gupta, V.K. (2005), Removal and recovery of malachite green from wastewater using an agricultural waste material, de-oiled soya. Separation and Purification Technology, 43 (2), 125-133.

Full Text: S\Sep Pur Tec43, 125.pdf

Abstract: De-oiled soya is a waste product obtained during the processing of soyabean in soya oil extraction mills. Attempts have been made to exploit this wonder crop for different purposes to mitigate many of our problems. This laboratory utilized de-oiled soya as waste material and low cost adsorbent for the removal of toxic textile dye ‘malachite green’. The characterization of the adsorbent was done through IR and DTA curves and preliminary investigations were carried out by batch adsorption technique, which includes effect of pH, adsorbate concentration, sieve size, adsorbent dosage, contact time, temperature, etc. Tenable mechanism of the ongoing adsorption process and thermodynamic parameters were also obtained from Langmuir and Freundlich adsorption isotherm models. The kinetic measurements helped in determining the specific rate constant confirming the applicability of the first-order rate expression. To identify whether the on-going process is particle diffusion or film diffusion, the treatment given by Boyd and Reichenberg was employed. To assess the practical utility of the adsorbent a fixed bed column was designed and necessary parameters were calculated by applying mass transfer kinetic approach. Experiments were also performed for recovery of loaded dye through chemical regeneration of spent column and an estimate of the operational cost was also calculated.

Keywords: Waste Material, Malachite Green, De-Oiled Soya, Adsorption, Kinetics

? Sivaiah, M.V., Venkatesan, K.A., Krishna, R.M., Sasidhar, P. and Murthy, G.S. (2005), Ion exchange properties of strontium on in situ precipitated polyantimonic acid in amberlite XAD-7. Separation and Purification Technology, 44 (1), 1-9.

Full Text: S\Sep Pur Tec44, 1.pdf

Abstract: Polyantimonic acid was precipitated in the pores of Amberlite XAD-7 (PAA–XAD) and studied for the ion exchange of strontium as a function of various parameters, such as time, strontium ion concentration and temperature. Nearly 30% of the Sb₂O₅ was impregnated into XAD-7 exhibiting an experimental capacity of 23 mg/g of strontium. Distribution coefficient of strontium on PAA–XAD was found to be 6069 mL/g at 0.1 mol/L nitric acid and it decreased with increase in the concentration of nitric acid. Rapid uptake in the initial stages of equilibration was observed followed by sluggish rate of exchange and the ion exchange reaction was found to follow the second order rate equation. The rate constant and energy of activation for such reaction were found to be 8.4×10⁻³ L mg^-1 min^-1 at 300 K and 79 kJ/mol, respectively. The data obtained in this study were fitted into Langmuir adsorption model and Langmuir constants obtained at various temperatures were utilized for estimating the enthalpy change (ΔH^o) accompanied by the ion exchange. The performance of the sorbent under dynamic conditions was evaluated by following a breakthrough curve using simulated waste solutions.

Keywords: Polyantimonic Acid, Ion Exchange, Breakthrough Curve, Langmuir Model

? Adak, A., Bandyopadhyay, M. and Pal, A. (2005), Removal of crystal violet dye from wastewater by surfactant-modified alumina. Separation and Purification Technology, 44 (2), 139-144.

Full Text: S\Sep Pur Tec44, 139.pdf

Abstract: Sodium dodecyl sulfate (SDS), an anionic surfactant (AS) was used for the surface modification of neutral alumina. Micelle-like structures are formed on the surface of alumina, which are capable of removing organic pollutants from water environment. The surfactant-modified alumina (SMA) was used for the removal of crystal violet (CV), a well-known cationic dye from aquatic environment. The kinetic studies showed that 1 h shaking time was sufficient to achieve the equilibrium. The removal of CV followed the second order kinetics. Studies were conducted to see the effects of adsorbent dose and initial CV concentration on the removal of CV using SMA. The pH was maintained at 6.7±0.1. SMA was found to be very efficient adsorbent, and ~99% efficiency could be achieved under optimised conditions for the removal of CV when present even at a high concentration (200 ppm). The effects of various other parameters such as pH, temperature, the presence of different ions (Cl⁻, NO₃⁻, SO₄⁻², HPO₄⁻² and Fe³⁺), and humic acid on the CV removal were also studied. The pH in the range of 7.0–8.5 favours the removal. It was observed that the removal efficiency was increased due to the presence of anions and humic acid and was decreased due to the presence of cations. Temperature had no effect in this process. To test whether the removal of CV was possible from real water using SMA, the adsorption study was conducted using CV spiked samples using distilled water, tap water and synthetically prepared wastewater. It was interesting to note that the removal efficiency was even better for tap water and much better for wastewater when compared to that using distilled water. Desorption of CV from the SMA surface was possible using 1 M sodium hydroxide solution, rectified spirit and acetone.

Keywords: Alumina, Sodium Dodecyl Sulfate, Surfactant-Modified Alumina, Crystal Violet, Removal

? Du, Q., Liu, S., Cao, Z. and Wang, Y. (2005), Ammonia removal from aqueous solution using natural Chinese clinoptilolite. Separation and Purification Technology, 44 (3), 229-234.

Full Text: S\Sep Pur Tec44, 229.pdf

Abstract: This paper assesses the potential of natural Chinese clinoptilolite for ammonia removal from aqueous solution. In batch study, the effects of relevant parameters, such as contact time, pH and initial ammonia concentration were examined, respectively. The results show that although contact time needs at least 4 h in order to attain exchange equilibrium, ammonia removal by clinoptilolite occurs rapidly within the first 15 min of contact time, the pH has an effect on ammonia removal efficiency as it can influence both the character of the exchanging ions and the clinoptilolite itself, the ammonia removal capacity of clinoptilolite increases with the increase of initial ammonia concentration. In column study, clinoptilolite bed was exhausted at different flow velocities and ammonia breakthrough capacity of clinoptilolite bed was calculated. Furthermore, the optimum regeneration conditions were considered. The results show that flow velocity can affect breakthrough capacity of clinoptilolite by changing hydraulic retention time and the volume of 15–20 BV of 0.5 mol/L sodium chloride solution at pH 11–12 is sufficient for complete regeneration of clinoptilolite in column.

Keywords: Ammonia removal, Capacity, Clinoptilolite, Ion exchange, Zeolite

? Zhang, T., Walawender, W.P. and Fan, L.T. (2005), Increasing the microporosities of activated carbons. Separation and Purification Technology, 44 (3), 247-249.

Full Text: S\Sep Pur Tec44, 247.pdf

Abstract: The microporosities of activated carbons were increased by two treatments. One involved depositing fine carbon particles on the activated carbons from pyrolyzing methanol accompanied by heating, and the other involved solely the heating of activated carbons in an inert atmosphere. The surface areas and pore volumes of the activated carbons increased by 43.43% and 75.75%, respectively, upon the former treatment, and as much as 61.96% and 100.82%, respectively, upon the latter treatment. Moreover, the number of pores with diameters ranging from 0.4 to 2.0 nm was appreciably magnified by both treatments, thereby giving rise to an increase in their microporosities.

Keywords: Activated carbons, Adsorption, Carbon deposition, Heat treatment, Methanol

? Lin, H.R. and Lin, C.I. (2005), Kinetics of adsorption of free fatty acids from water-degummed and alkali-refined soy oil using regenerated clay. Separation and Purification Technology, 44 (3), 258-265.

Full Text: S\Sep Pur Tec44, 258.pdf

Abstract: The adsorption kinetics of residual free fatty acids (FFA) from water-degummed and alkali-refined soy oil with regenerated clay was investigated by determining the concentration change of FFA in the oils before and after adsorption. Experimental results indicated that FFA concentration was reduced as adsorption proceeded, reached a minimum at fifteen min and then increased as time increased further. The initial adsorption rate was found to increase upon increasing the initial FFA concentration, the ratio of clay/oil or agitation speed. The rate could also be increased upon decreasing the particle size or adsorption pressure. The effects of water content of clay and temperature on the initial adsorption rate, however, were found to be mild. Furthermore, the empirical rate expression for the adsorption of FFA has been determined.

Keywords: Adsorption, Adsorption Kinetics, Free Fatty Acids, Regenerated Clay, Soy Oil

? Saeed, A., Akhter, M.W. and Iqbal, M. (2005), Removal and recovery of heavy metals from aqueous solution using papaya wood as a new biosorbent. Separation and Purification Technology, 45 (1), 25-31.

Full Text: S\Sep Pur Tec45, 25.pdf

Abstract: Papaya wood was evaluated as a new biosorbent of heavy metals. On contacting 10 mg l^−l copper(II), cadmium(II) and zinc(II) solutions with 5 g l⁻¹ papaya wood, during shake flask contact time of 60 min, the respective metal removal was noted to be 97.8, 94.9 and 66.8%. Sorption was most efficient at pH 5. Metal ion biosorption increased as the ratio of metal solution to the biomass quantity decreased. Conversely, biosorption/g biosorbent decreased as the quantity of biomass increased. The increase in initial metal ion concentration was associated with steep increase in biosorption at lower concentrations, progressively reaching towards plateau at higher metal concentrations. At equilibrium, the affinity of papaya wood to biosorb metals was in the order of copper(II) > cadmium(II) > zinc(II), which remained the same during the testing of variables of different factors. The biosorption data perfectly fit the Langmuir adsorption isotherms model with 0.99 regression coefficient (r²) for all the metals. The fit on Freundlich adsorption isotherms model was acceptable but not as good. The biosorption kinetics studies indicated that the data followed the second-order reaction with r² of 0.99. The first-order reaction was not applicable to the data. The metal-loaded papaya wood was completely desorbed with 0.1N HCl. During repeated biosorption–desorption for five cycles, no loss in the efficiency of copper(II) and cadmium(II) removal from their respective solutions and the metal-loaded biomass was noted. The study points to the potential of a novel use of papaya wood, itself a cause of environmental degradation and otherwise of no utility, for the treatment of wastewaters contaminated with heavy metals.

Keywords: Carica Papaya, Biosorption, Heavy Metal Removal, Sorption Isotherm, Biosorption Kinetics, Desorption

? Leyva-Ramos, R., Bernal-Jacome, L.A., and Acosta-Rodriguez, I. (2005), Adsorption of cadmium(II) from aqueous solution on natural and oxidized corncob. Separation and Purification Technology, 45 (1), 41-49.

Full Text: 2005\Sep Pur Tec45, 41.pdf

Abstract: Adsorption isotherms were determined experimentally for Cd(II) adsorption from aqueous solution onto natural and oxidized corncob in a batch adsorber. The adsorption capacity of natural corncob was increased 10.8 and 3.8 times when the corncob was oxidized with citric acid (CA) and nitric acid (NA), respectively. The Cd(II) ions were adsorbed mainly to the carboxylic sites since the adsorption capacity increased directly proportionally to the concentration of carboxylic sites in the corncob. The effect of the solution pH in the adsorption isotherm on natural and corncob modified with CA was assessed and it was observed that the adsorption capacity of Cd(II) on corncob depends considerably on the solution pH, Cd(II) was not adsorbed at pH less than 2 and the adsorption capacity was increased five times while the solution pH increased from 3 to 6. The adsorption of Cd(II) on corncob was reversible and the Cd(II) desorbed almost completely while reducing solution pH from 6 to 2. The adsorption capacity of natural and modified corncob was increased slightly by augmenting the temperature. By performing mass balances of ions, it was corroborated that the adsorption is mainly due to ion exchange.

Keywords: Adsorption, Cadmium(II), Carboxylic Sites, Citric Acid Oxidation, Natural Corncob, Oxidized Corncob, Activated Carbons, Waste-Water, Metal-Ions, Surface-Chemistry, Heavy-Metals, Removal, Sorption, Equilibrium, Biosorption, Isotherms

? Lao, C., Zeledón, Z., Gamisans, X. and Solé, M. (2005), Sorption of Cd(II) and Pb(II) from aqueous solutions by a low-rank coal (leonardite). Separation and Purification Technology,