Personal Research Database

Full Text: S\Sep Pur Tec39, 3.pdf

Abstract: The use of montmorillonite and its modified forms as an adsorbent in aqua system have been widely considered but the scope of much of the works has been restricted to batch tests, which may be a mean of selecting the best adsorbent for a given application but not necessary how it would be used in practice. This paper, therefore, deals with the comparison of batch and fixed bed adsorption of Methylene blue (C₁₆H₁₈ClN₃S) by montmorillonite and its derivatives. The modified clays were prepared by altering the surface properties of the raw montmorillonite clay, from organophobic to organophilic, with four types of quaternary ammonium compounds (QACs). They are tetramethylammonium chloride (C₄H₁₂ClN), tetradecyltrimethylammonium bromide (C₁₇H₃₈BrN), hexadecyltrimethyl ammonium bromide (C₁₉H₄₂BrN), and benzyldimethylhexadecylammonium chloride (C₂₅H₄₆ClN), which are different in their molecular size and number of carbon atoms. The clay products, namely organo-clays, were characterized for their physical properties by BET surface analysis, particle sizing, and X-ray diffraction (XRD). Adsorption experiments of Methylene blue were performed by batch and fixed bed column techniques. The objective of the batch test is to determine the effect of the number of carbon atoms in QACs used for the preparation of organo-clays on their physical properties and also on the adsorption affinity of each clay towards the Methylene blue. For the column experiments, mixed sand-clays bed was used due to the fine particle size of clays. The effect of adsorbate flow rate, contact time, and the initial concentration of the solute were explored. The permeability of the mixed sand-clay bed was also studied. The results showed that the permeability of the mixed bed was decreased considerably in the presence of even small amount of clays. Batch results were well characterized by a Langmuir isotherm. Column results were correlated by Fornwalt and Hutchins method. (C) 2004 Elsevier B.V. All rights reserved.

Keywords: Adsorbent, Adsorbents, Adsorption, Adsorption, Ammonium, Analysis, Carbon, Chloride, Clay, Concentration, Dye, Fine Particle, Fixed Bed, Flow, Isotherm, Langmuir, Langmuir Isotherm, Methylene Blue, Modified, Montmorillonite, Organic Phenols, Organo-Clays, Organoclays, Paper, Particle, Particle Size, Permeability, Physical Properties, Pillared Clays, Practice, Products, Properties, Quaternary, Quaternary Ammonium, Removal, Smectite, Sorption, Surface, Surface Analysis, Surface Properties, Techniques, Water, X-Ray Diffraction, XRD

? Dwivedi, P., Gaur, V., Sharma, A. and Verma, N. (2004), Comparative study of removal of volatile organic compounds by cryogenic condensation and adsorption by activated carbon fiber. Separation and Purification Technology, 39 (1-2), 23-37.

Full Text: S\Sep Pur Tec39, 23.pdf

Abstract: This paper describes studies on two abatement techniques, namely: adsorption by activated carbon fiber (ACF) and condensation at cryogenic temperatures for controlling emissions of volatile organic compounds (VOCs). The breakthrough analysis was carried out on commercially ACF packed in a tubular reactor under dynamic adsorption conditions. The breakthrough time was found to significantly decrease with increase in VOC concentration from 5000 to 50,000 ppm. The regeneration of ACF was carried out by electrical (dc 50 V) heating. A temperature range of 120–150 °C and regeneration time of 45–60 min were typically required for the complete regeneration of ACF pre-equilibrated with 8000 ppm of VOC. The VOC removal by condensation was carried out in a vertical tubular condenser using liquid nitrogen (LN) as a coolant medium. The studies showed that adsorption was effective if VOCs concentrations in the pollutants laden gas were in parts per million (ppm) levels, whereas the removal by cryogenic condensation was found to be effective at the relatively higher VOCs concentrations levels (>1%). The simulation results from the mathematical models developed to understand the separation process in each of two methods studied were found to be in good agreement with the experimental data.

Keywords: Volatile Organic Compounds (VOC), Adsorption, Cryogenic Condensation, Activated Carbon Fiber (ACF), Breakthrough Analysis

Bektaş, N. and Kara, S. (2004), Removal of lead from aqueous solutions by natural clinoptilolite: Equilibrium and kinetic studies. Separation and Purification Technology, 39 (3), 189-200.

Full Text: S\Sep Pur Tec39, 189.pdf

Abstract: In this study, the removal of lead ions from aqueous solution using natural clinoptilolite under different experimental conditions was investigated. The effects of the initial metal concentration, agitation speed, temperature and pH on the removal efficiency of lead were studied. Langmuir and Freundlich isotherm constants and correlation coefficients for the present system at different conditions were calculated and compared. The equilibrium process was described well by the Langmuir isotherm model with the maximum sorption capacity of 166 mg/g of lead on clinoptilolite.

The sorption kinetics were tested for the first order reaction, intra-particle diffusion, pseudo-first order, and pseudo-second order reaction at different experimental conditions. The rate constants of sorption for all these kinetic models were calculated. Good correlation coefficients were obtained for the pseudo-second order kinetic model showing that lead uptake process followed the pseudo-second order rate expression.

Keywords: Lead Removal, Clinoptilolite, Equilibrium Isotherm, Kinetics

Draa, M.T., Belaid, T. and Benamor, M. (2004), Extraction of Pb(II) by XAD7 impregnated resins with organophosphorus extractants (DEHPA, IONQUEST 801, CYANEX 272). Separation and Purification Technology, 40 (1), 77-86.

Full Text: S\Sep Pur Tec40, 77.pdf

Abstract: The aim of this work is to study the extraction of Pb(II) from nitrate solutions (0.1 m) by solvent impregnated resins (SIR). The resins have been prepared by impregnating the amberlite XAD7 using three different organophosphorus extractants namely DEHPA, IONQUEST 801 and CYANEX 272. The impregnation of XAD7 is characterised by a higher affinity for DEHPA than for IONQUEST 801 and CYANEX 272. The adsorption of the extractant has been studied by FTIR which shows that the immobilisation of the extractant results from hydrophobic interaction between the alkyl group of the extractant and the aliphatic chain of the support, and also from other mechanisms like polar or electrostatic forces. Batch sorption studies shows that the sorption of the metal increases with aqueous pH solution and the best sorption efficiency obtained is higher than 95% for DEHPA and IONQUEST 801 in the pH range of 2.75–3 and 3.5–3.75, respectively, and it is about 70% for CYANEX 272 in the pH range 4.5–4.75. An equilibrium model is proposed for the analysis of the distribution data. The extraction of Pb(II) can be explained by the formation of PbL₂ and PbNo₃L complex in the resin phase in the case of XAD7–DEHPA resin, by the formation of PbL₂HL₂ and PbNo₃L complex in the case of XAD7–IONQUEST 801, and by the formation of the single complex PbLNo₃HL in the case of XAD7CY–ANEX 272. The equilibrium constants of these species are also reported.

Keywords: Pb(II), Solvent Impregnated Resin, DEHPA, IONQUEST 801, CYANEX

Gupta, V.K., Mittal, A., Krishnan, L. and Gajbe, V. (2004), Adsorption kinetics and column operations for the removal and recovery of malachite green from wastewater using bottom ash. Separation and Purification Technology, 40 (1), 87-96.

Full Text: S\Sep Pur Tec40, 87.pdf

Abstract: The thermal power plant waste material, ‘bottom ash’ was utilized as a potential adsorbent for the toxic textile dye ‘malachite green’. Preliminary information was gathered by batch adsorption studies, which include effect of pH, adsorbent dose, contact time, adsorbate concentration and temperature. Plausible mechanism of the on-going adsorption process and thermodynamic parameters involved were obtained by carrying out kinetic measurements. The data obtained was successfully used to equate Langmuir and Freundlich adsorption isotherm models. A fixed-bed column was designed and necessary parameters were calculated by applying mass transfer kinetic approach. Attempts were also made to recover dye and regenerate the column.

Keywords: Malachite Green, Bottom Ash, Adsorption, Waste Material, Kinetics

Silva, J.P., Sousa, S., Gonçalves, I., Porter, J.J. and Ferreira-Dias, S. (2004), Modelling adsorption of acid orange 7 dye in aqueous solutions to spent brewery grains. Separation and Purification Technology, 40 (2), 163-170.

Full Text: S\Sep Pur Tec40, 163.pdf

Abstract: Acid orange 7 (AO7) is a monoazo acid dye currently used in paper and textile industries. The modelling and optimisation of AO7 adsorption to spent brewery grains (SBG), a by-product of the brewing process, was performed using response surface methodology (RSM). SBG was used dried or previously acid hydrolysed. Five central composite rotatable designs (CCRD), as a function of two variables, each, were followed, namely: (1) amount of SBG and hydrolysis time of SBG, (2) hydrolysis and adsorption times, (3) amount of SBG and adsorption time (T), (4) T and pH medium and (5) T and AO7 concentration.

Hydrolysis of SBG showed not significantly increase its adsorption capacity for AO7 dye. Tri-dimensional response surfaces were fitted to the experimental data concerning the removal of dye obtained in CCRD-3 to CCRD-5. From CCRD-3, the best adsorption conditions (96% removal) were estimated for 5.1% (m/v) of SBG after 36 min contact. From CCRD-4, removals above 90% were observed for lower pH values and adsorption times higher than 30 min. An increase in AO7 adsorbed per unit weight of SBG was observed with increasing initial AO7 concentration.

Also, SBG was reused in 12 consecutive batches, under previously optimised conditions. SBG residual adsorption activity can be well described by a first-order decay model. A maximum amount of adsorbed AO7 of 29 mg/g SBG is predicted from the cumulative curve.

Keywords: Acid Orange 7, Adsorption, Monoazo Acid Dye, Response Surface Methodology, Reutilisation, Spent Brewery Grains

Ghiaci, M., Abbaspur, A., Kia, R. and Seyedeyn-Azad, F. (2004), Equilibrium isotherm studies for the sorption of benzene, toluene, and phenol onto organo-zeolites and as-synthesized MCM-41. Separation and Purification Technology, 40 (3), 217-229.

Full Text: S\Sep Pur Tec40, 217.pdf

Abstract: Nonionic organic contaminants (NOCs) such as benzene, toluene, and phenol from contaminated wastewater can be effectively adsorbed by organo-zeolites. Organo-zeolites were prepared from synthetic ZSM-5 and natural zeolites, by exchanging the quaternary amines, i.e. hexadecyltrimethylammonium (HDTMA) bromide and n-cetylpyridinium bromide (CPB). The maximum adsorption of CPB onto these zeolites is in the order of clinoptilolite>ZSM-5-88 (SiO₂/Al₂O₃=88)>ZSM-5-31 (SiO₂/Al₂O₃=31) which is mainly dependent on the external cation exchange capacity (ECEC) of each zeolite. Batch adsorption experiment was carried out to remove benzene, toluene, and phenol from aqueous solution using the above-mentioned organo-zeolites. In addition, as-synthesized MCM-41 molecular sieve was employed for removal of organic contaminants from aqueous solution. The experimental results were fitted to the Langmuir, Freundlich, Redlich–Peterson and linear equation isotherms to obtain the characteristic parameters of each model. Our resultant data showed that nonlinear form of Langmuir, the Freundlich and Redlich–Peterson could be fitted well with sorption data in most cases. According to the evaluation using the Langmuir equation, the maximum organics adsorption by synthesized MCM-41 was much greater than that of the natural clinoptilolite and ZSM-5 zeolites.

Keywords: Adsorption, Benzene, Toluene, Phenol, ZSM-5, MCM-41, Natural Clinoptilolite, HDTMA bromide, CPB

Shawabkeh, R., Al-Harahsheh, A. and Al-Otoom, A. (2004), Copper and zinc sorption by treated oil shale ash. Separation and Purification Technology, 40 (3), 251-257.

Full Text: S\Sep Pur Tec40, 251.pdf

Abstract: Jordanian oil shale ash was used as an adsorbent for the removal of copper and zinc from aqueous solution. This ash was treated with either hydrochloric, nitric, sulfuric or phosphoric acids followed by washing and/or neutralization with sodium hydroxide in order to enhance its adsorption capacity. The sample that was treated with nitric acid showed the highest cation exchange capacity (CEC) of 146 meq/100 g, while the one that was treated with sulfuric acid showed a value of 32 meq/100 g. Different adsorption isotherm data for both copper and zinc were obtained using the nitric acid-treated sample at different pH values. Freundlich and BET models were used to fit the experimental data, which showed that BET best-fitted these data. The separation factor for these isotherms shows unfavorable adsorption type at lower pH value.

Keywords: Oil Shale, Ash, Adsorption, Copper and Zinc Removal

? Ghiaci, M., Kia, R., Abbaspur, A. and Seyedeyn-Azad, F. (2004), Adsorption of chromate by surfactant-modified zeolites and MCM-41 molecular sieve. Separation and Purification Technology, 40 (3), 285-295.

Full Text: 2004\Sep Pur Tec40, 285.pdf

Abstract: Synthetic and natural zeolites, modified by the quaternary amines, i.e. hexadecyltrimethylammonium (HDTMA) bromide and n-cetylpyridinium bromide (CPB) as well as MCM-41 molecular sieve were employed for removal of chromate from aqueous solution. Obtained data from chromate adsorption experiments over the mentioned materials were compared. It was shown that adsorption data for modified zeolite using the amine was consistent with Langmuir isotherm equation. The maximum chromate adsorption over as synthesized MCM-41 was much greater than that of the natural clinoptilolite and ZSM-5 zeolites. (C) 2004 Elsevier B.V All rights reserved.

Keywords: Adsorption, Amine, Amines, Cationic Surfactant, Chromate, Chromate Adsorption, Clinoptilolite, CPB, Hdtma, Hexadecyltrimethylammonium, Isotherm, Langmuir, Langmuir Isotherm, Materials, MCM-41, Modified, Natural, Natural Clinoptilolite, Quaternary, Reduction, Removal, Sorption, Zeolite, ZSM-5

Silva, J.P., Sousa, S., Rodrigues, J., Antunes, H., Porter, J.J., Gonçalves, I. and Ferreira-Dias, S. (2004), Adsorption of acid orange 7 dye in aqueous solutions by spent brewery grains. Separation and Purification Technology, 40 (3), 309-315.

Full Text: S\Sep Pur Tec40, 309.pdf

Abstract: Spent brewery grains (SBG), a by-product of the brewing process, were tested as an adsorbent of acid orange 7 dye (AO7), a monoazo acid dye currently used in paper and textile industries. The presence of AO7 in these effluents causes obvious environmental problems.

Kinetics studies of adsorption of AO₇ to SBG (3.75%, m/v) were carried out at 20 °C, using aqueous solutions with different AO7 concentrations (30–834 mg/L). For every situations tested, no significant variation in residual AO7 concentration in solution was detected after 1 h contact between the dye and the adsorbent. The adsorption process followed a pseudo-first order model.

The equilibrium process showed to be well described by both Freundlich and Langmuir isotherm models, at 20 and 30 °C. The maximum adsorption capacity was estimated to be 30.5 mg AO7/g SBG, at 30 °C.

Free energy of adsorption (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) changes were calculated to predict the nature of adsorption. The estimated values for ΔG° were −22.78 and −24.53 kJ/mol, respectively, at 293.3 K (20 °C) and 303.3 K (30 °C), which are rather low indicating that a spontaneous process occurred. The enthalpy changes and entropy of adsorption were 28.66 and 175.36 J/mol K, respectively. The positive value for ΔH° indicates that the adsorption of AO7 dye to SBG is an endothermic process. The positive value of entropy reflects the affinity of the adsorbent for AO7 dye.

The obtained results are very promising since: (i) high levels of colour removal (>90%) were achieved with low contact times adsorbent/dye (less than 1 h contact), and (II) the whole SBG can be successfully used as adsorbent of AO7 dye in aqueous solution without needing any previous treatments such as milling and/or sieving. Spent grains, being a cheap, and easily available material, can be an alternative for more costly adsorbents used for dye removal in wastewater treatment processes.

Keywords: Acid Orange 7 (AO7), Adsorption Isotherms, Monoazo Acid Dye, Spent Brewery Grains (SBG)

Sarioglu, M. (2005), Removal of ammonium from municipal wastewater using natural Turkish (Dogantepe) zeolite. Separation and Purification Technology, 41 (1), 1-11.

Full Text: S\Sep Pur Tec41, 1.pdf

Abstract: This paper concerns the removal of ammonium ions from wastewater using a naturally occurring zeolite from Dogantepe region in Turkey. Both batch and continuous (column) experiments were carried out. In batch studies, effects of stirring time (5–120 min) and initial ammonium concentration (8.8–885 mg NH₄⁺-N l⁻¹) on removal efficiency and adsorption isotherms were investigated. In column studies, effects of flowrate, pH, initial ammonium concentration, washing with acid and regeneration on the ammonium adsorption capacity of the zeolite were determined. Increasing initial ammonium nitrogen concentration from 5.0 to 12.0 mg l⁻¹, increased the exchange capacity from 0.70 to 1.08 mg NH₄⁺-N g⁻¹. The flowrate and pH values, at which the highest adsorption capacities were obtained, were found to be 0.5 ml min⁻¹ (0.87 mg NH₄⁺-N g⁻¹ zeolite) and 4 (mg NH₄-N l⁻¹), respectively. The corresponding values after washing with acid and regeneration were determined to be 1.32 and 0.73 mg NH₄⁺-N g⁻¹, respectively. The cation exchange capacity of Dogantepe zeolite was found to be 164.62 meq. per 100 g. These findings show that Dogantepe zeolite can be used for the removal of ammonium from wastewater.

Keywords: Zeolite, Clinoptilolite, Mordenite, Ammonium Removal, Exchange Capacity, Wastewater

Dubey, S.S. and Gupta, R.K. (2005), Removal behavior of Babool bark (Acacia nilotica) for submicro concentrations of Hg²⁺ from aqueous solutions: A radiotracer study. Separation and Purification Technology, 41 (1), 21-28.

Full Text: S\Sep Pur Tec41, 21.pdf

Abstract: The uptake behavior of Babool bark (Acacia nilotica) for the micro to trace levels of Hg²⁺ from aqueous solutions has been carried out in batch equilibrium experiments, employing a ‘radiotracer technique’. A high level of uptake of metal ions on the solid surface occurs within ca. 2 h of contact time. The increase of sorptive concentration (10⁻⁷ to 10⁻² M), temperature (303–333 K), and pH (3–10) favored the removal process of ions. The percentage adsorption increases from 54.3 to 91.3% with an increase in dilution of sorptive solution from 10⁻² to 10⁻⁷ M. First order uptake of Hg²⁺ followed the Freundlich and Dubinin–Radushkevich (D–R) isotherms for the entire range of adsorptive concentration studied. Temperature dependence data show that this process is endothermic in nature. Desorption experiments further confirm the irreversibility of the sorption process as no significant desorption took place in the bulk concentration of the adsorptive.

Keywords: Sorption, Hg(II), Radiotracer, Freundlich, Babool Bark, Desorption

Gawade, A.S., Vanjara, A.K. and Sawant, M.R. (2005), Removal of herbicide from water with sodium chloride using surfactant treated alumina for wastewater treatment. Separation and Purification Technology, 41 (1), 65-71.

Full Text: S\Sep Pur Tec41, 65.pdf

Abstract: Alumina surface was modified by adsorption of an anionic surfactant, sodium dodecyl sulfate (SDS). Typical S-shaped isotherm of surfactant on alumina was observed. The adsorption of herbicide on alumina and surfactant treated alumina has been investigated. The enhancement in adsorption of herbicide on surfactant treated alumina is observed, which may be attributed to the solubilization of herbicide on surfactant aggregates formed at solid/liquid interface. The effect of pH on adsorption has been studied. The adsorption is greatly influenced by pH of the medium. The applicability of Freundlich equation was tested for equilibrium data.

The influence of various factors such as initial concentration, agitation speed, mass of adsorbent and temperature on adsorption was also studied. The batch kinetics has been tested to pseudo second order reaction and rate constants were calculated.

Keywords: Alumina, Surfactant-Treated Alumina, Herbicide, Solubilization

? Ning, P., Bart, H.J., Jiang, Y.J., de Haan, A. and Tien, C. (2005), Treatment of organic pollutants in coke plant wastewater by the method of ultrasonic irradiation, catalytic oxidation and activated sludge. Separation and Purification Technology, 41 (2), 133-139.

Full Text: 2005\Sep Pur Tec41, 133.pdf

Abstract: The paper deals with the degradation of the organic pollutants in coke plant wastewater by the combination process of ultrasonic irradiation, catalytic oxidation and activated sludge. The effect factors of ultrasonic irradiation on the degradation of the organic pollutants such as saturating Vs, initial pollutant concentration, ultrasonic power density, the category and consumption of catalyst were investigated. The results indicate that putting the saturating gas into the reaction solution in the process of the ultrasonic irradiation, low COD initial concentration and high ultrasonic power density are the favorable conditions for their degradation. Compared with single activated-sludge process, co-approach of ultrasonic irradiation and activated-sludge can greatly increase the COD degradation efficiency. When the wastewater was firstly treated by ultrasonic irradiation process and then followed by activated-sludge process for 240 min, respectively, the COD degradation efficiency increased by 48.29-80.54%. Additionally, when 3.0 mmol/l of ferrous sulfate was added into the ultrasonic irradiation process, the COD degradation efficiency was as high as 95.74%, 63.49% higher than that of the activated-sludge approach alone. (C) 2004 Elsevier B.V. All rights reserved.

Keywords: Aqueous-Solution, COD Degradation, Coke Plant Wastewater, Coking Wastewater, Combination Process, Water Quality Model

Alam, J.B., Dikshit, A.K. and Bandyopadhayay, M. (2005), Evaluation of thermodynamic properties of sorption of 2,4-D and atrazine by tire rubber granules. Separation and Purification Technology, 42 (1), 85-90.

Full Text: S\Sep Pur Tec42, 90.pdf

Abstract: An attempt has been made in this paper to develop simple and easily understandable thermodynamic parameters related with the formation of activated complex and sorption process at equilibrium. The overall scenario represented by thermodynamic parameters was found to be a better indicator of understanding the process. Because it gives a general idea whether the process is exothermic or endothermic and also whether the process is stable or unstable. Sorption of 2,4-dichloro-phenoxy-acetic acid (2,4-D) and 2-chloro-4-ethyalamino-6-isopropylamino-s-traiazine (atrazine) on rubber granules followed second order reversible kinetic equation. 2,4-d–rubber granules system showed endothermic nature while atrazine–rubber granules showed exothermic nature. The values of E_a (associated with formation of activated species) were in the range of 3.49 kcal/mol and −2.40 kcal/mol for 2,4-d and atrazine, respectively. During equilibrium condition, both the systems showed negative Gibb’s energy, which indicates stability of system.

Keywords: 2,4-D, Atrazine, Enthalpy Change, Entropy Change, Gibb’s Energy, Arrhenius Activated Energy, Aqueous-Solution, Adsorption, Carbofuran, Removal, Soils, Field

Uguina, M.A., Sotelo, J.L., Delgado, J.A., Gómez, J.M. and Celemín, L.I. (2005), Adsorption of methyl ethyl ketone and trichloroethene from aqueous solutions onto silicalite fixed-bed adsorbers. Separation and Purification Technology,