Personal Research Database

Keywords: Adsorption, Endothermic, Langmuir Isotherm, Monolayer Coverage, Activation Energy, Chemisorption

? Yavuz, H., Denizli, A., Güngüneş, H., Safarikova, M. and Safarik, I. (2007), Biosorption of mercury on magnetically modified yeast cells. Separation and Purification Technology, 52 (2), 253-260.

Full Text: 2006\Sep Pur Tec52, 253.pdf

Abstract: Brewer’s yeast (bottom yeast, Saccharomyces cerevisiae subsp. uvarum) cells were magnetically modified using water based magnetic fluid stabilized perchloric acid. The magnetically modified yeast cells were characterized by scanning electron microscopy (SEM) and electron spin resonance (ESR). Hg²⁺ biosorption-desorption properties of magnetically modified yeast cells from synthetic solutions were utilized in batch system. The biosorption process was fast, 80% of biosorption occured within 60 min and equilibrium was achieved at around 90 min. The maximum Hg²⁺ biosorption capacity was obtained to be 114.6 mg/g at 35 °C. The suitability of the Langmuir, Freundlich and Redlich-Peterson adsorption models to the equilibrium data was investigated for mercury-biosorbent system. The results were well fitted to the Langmuir isotherm. The applicability of two kinetic models including pseudo-first order and pseudo-second order model was estimated on the basis of comparative analysis of the corresponding rate parameters, equilibrium capacity and correlation coefficients. Results suggest that chemisorption processes could be the rate-limiting step in the biosorption process. The yeast biomass can be easily regenerated by 0.1 M HNO₃ with higher effectiveness. Biosorption of heavy metal ions from artificial wastewater was also studied. The biosorption capacities are 29.9 mg/g for Cu²⁺, 76.2 mg/g for Hg²⁺, 14.1 mg/g for Ni²⁺ and 11.8 mg/g for Zn²⁺.

Keywords: Mercury Removal, Magnetic Biosorbents, Yeast, Heavy Metal Removal

? Bastani, D., Safekordi, A.A., Alihosseini, A. and Taghikhani, V. (2006), Study of oil sorption by expanded perlite at 298.15 K. Separation and Purification Technology, 52 (2), 295-300.

Full Text: 2006\Sep Pur Tec52, 295.pdf

Abstract: Sorption capacity as well as sorption kinetics of oil onto four different expanded perlites with different physical and surface properties were studied. In order to meticulously measure the amount of oil to be sorbed onto the adsorbents used in this study both static and dynamic methods were employed. It would be worth noting that the adsorbent, i.e., perlite can spread on the oil and float on the surface thanks to its low density. The variation of the amount of oil sorbed onto the adsorbents with time was recorded and the weight of adsorbent was monitored at each specified time. The experimental results showed that grain sizes with high surface area can sorb oil to be spread on water surface. It should be also stressed that the experiments conducted were replicated three times and the results reported are the average of replicas. The results obtained were correlated with the first order, second order sorption kinetics as well as the intra-particle diffusion models. The results showed that the second order kinetic model studied can more accurately correlate the experimental data generated than the first order sorption kinetic and the intra-particle diffusion models.

Keywords: Perlite, Oil Spill, Sorption Capacity, Sorption Kinetics

? Aloulou, F., Boufi, S. and Labidi, J. (2006), Modified cellulose fibres for adsorption of organic compound in aqueous solution. Separation and Purification Technology, 52 (2), 332-342.

Full Text: 2006\Sep Pur Tec52, 332.pdf

Abstract: This paper presents the results of an experimental study of removal of organic contaminant from wastewater using chemically modified cellulose fibres. The adsorption capacities of the modified fibres towards various organic molecules were investigated. The ensuing modified fibres appeared to be efficient absorbent for different dissolved organic molecules in water. The recycling tests revealed that the exhausted substrates could be regenerated without loosing their capacity. The adsorption isotherm related to different solutes follows the Langmuir model in entire range of concentration. To confirm the possibility of using the modified cellulose fibres as a sorbent for the removal of dissolved organic pollutant, adsorption breakthrough curves were established under different operating condition such as concentration, flow rate and the column length. The main advantage of this substrate lies in its relative facile regeneration without a significant loss of its adsorption capacity.

Keywords: Activated Carbon, Adsorption, Adsorption Isotherm, Capacity, Cellulose, Cellulose Fibres, Concentration, Condition, Dissolved, Flow, Isotherm, Langmuir, Metals, Model, Modified, Organic, Organic Molecules, Organic Pollutant, Organic Solute, Paper, Pollutant, Range, Recycling, Regeneration, Removal, Sorption, Substrate, Wastewater, Water

? Yin, C.Y., Aroua, M.K. and Daud, W.M.A.W. (2007), Review of modifications of activated carbon for enhancing contaminant uptakes from aqueous solutions. Separation and Purification Technology, 52 (3), 403-415.

Full Text: 2007\Sep Pur Tec52, 403.pdf

Abstract: Due to its versatility and wide range of applications, activated carbon is widely used as contaminant removal media. Recent research have focused on enhancing the effectiveness of activated carbon by modifying their specific properties in order to enable the carbon to develop affinity for certain contaminants. In view of this, a comprehensive list of literatures on chemical, physical and biological modification techniques of activated carbon pertaining to enhancement of contaminant removal from aqueous solutions was compiled and reviewed. Acidic treatment to introduce acidic functional groups onto surface of activated carbon was by far, the most studied technique. It was apparent from the literature survey that the beneficial effects of specific modification techniques on activated carbon adsorption of targeted contaminant species from aqueous solutions were profound, with some studies reported increase of contaminant uptake factors of more than 2. Concurrently, considerable decreases associated with certain contaminant uptakes can also occur depending on the technique used.

Keywords: Activated Carbon Modification, Surface Functional Groups, Impregnation, Contaminant, Aqueous Solution

? Shukla, A. and Kumar, A. (2007), Separation of Cr(VI) by zeolite–clay composite membranes modified by reaction with NO_x. Separation and Purification Technology, 52 (3), 423-429.

Full Text: 2007\Sep Pur Tec52, 423.pdf

Abstract: In this work, we report the use of modified zeolite–clay composite ultrafiltration membranes (preparation of the unmodified (Z₁), the nitrated (Z₂, modified using NO_x) and the aminated (Z₃) membrane have been described in our earlier publication [1]) for the separation of chromic acid solution. Experiments show that the observed rejection coefficients of the membranes increase on modification from 20% for Z₁ to 40% for Z₂ and 50% for Z₃ membrane. Experimental data is analyzed using the irreversible thermodynamic approach (Spiegler–Kedem equations) [2]. The study shows that the chemical modification of membranes leads to a rise in the intrinsic rejection (highest R 50% for Z₁ to 60% for Z₂ and 66% for Z₃ membrane) coefficients. It is also found that while the observed rejection show anomalous trend with variation in pressure while the intrinsic rejection increases with increase in pressure, a trend typical of the separation of electrolyte through charged membranes.

Keywords: Chromic Acid, Charged Ultrafiltration, Zeolite Membranes

? Ayoob, S., Gupta, A.K. and Bhakat, P.B. (2007), Analysis of breakthrough developments and modeling of fixed bed adsorption system for As(V) removal from water by modified calcined bauxite (MCB). Separation and Purification Technology, 52 (3), 430-438.

Full Text: 2007\Sep Pur Tec52, 430.pdf

Abstract: The feasibility of As(V) removal from aqueous environment by a fixed bed of the adsorbent, modified calcined bauxite (MCB), in a continuous flow system has been investigated. The response of the adsorbent bed under various operating conditions of bed depth, flow rate and influent concentration were examined. The various column parameters including adsorption rate, adsorption capacity and depth of exchange zone were evaluated using the Bohart and Adams adsorption model. MCB exhibited an adsorption capacity of 627.3 mg/l with an adsorption rate constant 0.9925 l/mg h at an influent As(V) concentration of 2 mg/l. A minimum adsorbent depth of 1.3 cm is enough to produce effluent with As(V) concentration less than 0.01 mg/l from an influent of 2 mg/l, in a 20 mm diameter MCB column. The service time of adsorbent beds under different flow rate and influent concentration were predicted using the bed depth service time (BDST) model and are compared with experimental observations. The observed data on service time and breakthrough curve correlated well with the theoretical values. The breakthrough curves of MCB obtained by experimental observations under different flow rates were compared with those developed by mass transfer model using Langmuir isotherm data. In the continuous flow system, MCB is found to have As(V) scavenging potential of 0.470 mg of As(V)/g.

Keywords: As(V), Adsorption, Bdst, Breakthrough Curve, Modified Calcined Bauxite

? Ünlü, N. and Ersoz, M. (2007), Removal of heavy metal ions by using dithiocarbamated-sporopollenin. Separation and Purification Technology, 52 (3), 461-469.

Full Text: 2007\Sep Pur Tec52, 461.pdf

Abstract: In this study, the sorption conditions of Cu(II), Pb(II) and Cd(II) metal ions onto dithiocarbamated-spororpollenin (DTC-S) have been investigated. The different variables affecting the sorption capacity such as pH of the solution, sorption time, initial metal ion concentration and temperature have been investigated. Experimental data were exploited for kinetic and thermodynamic evaluations related to the sorption processes. Sorption isotherms correlated well with the Langmuir type sorption isotherm and sorption capacities were found to be 0.2734, 0.4572 and 0.0631 mmol g⁻¹ for Cu(II), Pb(II) and Cd(II) metal ions, respectively. Sorption processes for three target heavy metal ions were found to follow pseudo-second order type sorption kinetics. Intraparticle diffusion was found to take part in sorption processes but it could not be accepted as the primary rate determining step. On the evaluation of the results obtained for the mean free energies of sorption (E) and enthalpy of sorption (ΔH°) it was observed that the resin mainly shows the characteristics of a chelating exchanger. Thermodynamic parameters, ΔH°, ΔS° and ΔG° were also calculated from graphical interpretation of the experimental data. Standard heats of sorption (ΔH°) were found to be endothermic and ΔS° values were calculated to be positive for the sorption of Cu(II), Pb(II) and Cd(II) ions onto the adsorbent. Negative ΔG° values indicated that sorption process for these three metal ions onto DTC-Sp is spontaneous.

Keywords: Heavy Metals, Dithiocarbamate, Sporopollenin, Langmuir Isotherm, Freundlich Isotherm, D–R Isotherm, Kinetics, Thermodynamics

? Deliyanni, E.A., Peleka, E.N. and Lazaridis, N.K. (2007), Comparative study of phosphates removal from aqueous solutions by nanocrystalline akaganéite and hybrid surfactant-akaganéite. Separation and Purification Technology, 52 (3), 478-486.

Full Text: 2007\Sep Pur Tec52, 478.pdf

Abstract: In this study, phosphates removal from aqueous solutions was investigated using synthetic prepared nanocrystalline oxyhydroxide material in unmodified and surfactant modified form. Equilibrium and kinetic studies were carried out to determine the sorption capacity of akaganéite and the rate of phosphate ions uptake. Equilibrium data were analyzed by Langmuir and Freundlich isotherms. The sorption capacity was found to be 59.62 mg P g⁻¹ for pure nanocrystalline akaganéite and 451.20 mg P g⁻¹ for hybrid surfactant-akaganéite. Kinetic data followed a pseudo-second-order kinetic model. FT-IR spectra indicate the presence of inner-sphere complexes. Desorption studies showed entirely different behaviour between the two materials.

Keywords: Adsorption, Phosphate, Akaganéite, Hybrid Surfactant-Akaganéite, Isotherms

? Anirudhan, T.S., Senan, P. and Unnithan, M.R. (2007), Sorptive potential of a cationic exchange resin of carboxyl banana stem for mercury(II) from aqueous solutions. Separation and Purification Technology, 52 (3), 512-519.

Full Text: 2007\Sep Pur Tec52, 512.pdf

Abstract: A cationic exchange resin of carboxyl banana stem (CBS) was fabricated through the hydrolysis of graft copolymer of banana stem (BS) with acrylonitrile that was made using ceric ammonium nitrate (CAN) initiator. Infrared spectroscopy and acid–base titration were used to confirm graft copolymer formation and carboxylate functionalization. SEM studies of CBS clearly indicated that adsorbent has rough and porous surface caused by rigid and hydrophobic nature of acrylonitrile cross-links. Thermal stability of the CBS was studied using thermogravimetry. The cationic exchange capacity (CEC) of the CBS was determined to be 1.68 mequiv. g⁻¹. The sorptive potential of the CBS for mercury(II) from aqueous solutions was examined by the batch technique. The optimum pH range for the maximum removal of mercury(II) was 6.0–9.0. The CBS was observed to have high adsorptive capacity for mercury(II) with 99.3% from a solution containing 10 mg L⁻¹ of mercury(II) with 0.2% (w/v) concentration of CBS. The experimental kinetic data for the mercury(II)–CBS system were analyzed using the linearised form of the Elovich model, a second-order kinetic equation. The isotherm data were correlated reasonably with the Langmuir isotherm and the mercury(II) adsorption capacity was found to be 90.88 mg g⁻¹ at 30 °C. The quantitative removal of 10 mg L⁻¹ mercury(II) in 50 mL chlor-alkali industry wastewater by 125 mg of CBS was observed at pH 6.0. The mercury(II)-loaded CBS can be regenerated by 0.1 M HCl treatment without altering the adsorbent properties.

Keywords: Graft Copolymerisation, Banana Stem, Mercury(II) Removal, Adsorption Isotherm, Regeneration

? Crini, G., Peindy, H.N., Gimbert, F. and Robert, C. (2007), Removal of C.I. Basic Green 4 (Malachite Green) from aqueous solutions by adsorption using cyclodextrin-based adsorbent: Kinetic and equilibrium studies. Separation and Purification Technology, 53 (1), 97-110.

Full Text: 2007\Sep Pur Tec53, 97.pdf

Abstract: Batch sorption experiments were carried out for the removal of C.I. Basic Green 4 (Malachite Green), a cationic dye from its aqueous solution using cyclodextrin-based material (CD/CMC material) as adsorbent. The operating variables studied were adsorbent mass, particle size, agitation speed, solution pH, contact time and initial dye concentration. Adsorption experiments indicated that the adsorption capacity was dependent of operating variables and the process was strongly pH-dependent. Kinetic measurements showed that the process was uniform and rapid. Sorption of dye reached equilibrium in 120 min. In order to investigate the mechanism of sorption, adsorption data were modeled using the pseudo-first-order and pseudo-second-order kinetic equations, and intraparticle diffusion model. On the basis of the non-linear chi-square test, it was found that the adsorption kinetics followed a pseudo-second-order model for the dye concentration range studied in the present work, suggesting that the rate-limiting step may be chemisorption. Equilibrium isotherm was analyzed using the Langmuir and the Freundlich isotherms. The characteristic parameters for each model have been determined. The Langmuir model yields a much better fit than the Freundlich model. The maximum sorption capacity was 91.9 mg/g at 25 °C and the negative value of free energy change indicated the spontaneous nature of adsorption.

Keywords: C.I. Basic Green 4, Cyclodextrin, Adsorbent, Adsorption, Batch Mode, Kinetic Modeling, Isotherms

? Hashim, M.A. and Chu, K.H. (2007), Prediction of protein breakthrough behavior using simplified analytical solutions. Separation and Purification Technology, 53 (2), 189-197.

Full Text: 2007\Sep Pur Tec53, 189.pdf

Abstract: The predictability of the breakthrough behavior of lysozyme on the strong cation exchanger SP Sepharose FF was evaluated using two different but related analytical solutions. The first solution, known as the Thomas equation, assumes that adsorption can be represented by a pseudo second-order reaction rate law which translates into a Langmuir isotherm at equilibrium. The second solution, known as the Bohart–Adams equation, assumes that adsorption can be described by a quasi-chemical rate law which reduces to a rectangular isotherm at equilibrium. The Bohart–Adams solution can be regarded as a limiting form of the Thomas solution. The equilibrium and rate parameters embedded in the two solutions were extracted from batch experiments. Predictions using the two simplified solutions agreed with experimental breakthrough data. When the isotherm is highly favorable the simpler Bohart–Adams solution can be used as a practically useful modeling tool in lieu of the mathematically complicated Thomas solution.

Keywords: Adsorption, Adsorption-Kinetics, Affinity-Chromatography, Batch, Batch Experiments, Bed Adsorption, Behavior, Bohart-Adams, Breakthrough, Breakthrough Curve, Cation, Cation Exchanger, Data, Design, Equilibrium, Experimental, Experiments, First, Fixed Bed, Ion-Exchange Chromatography, Isotherm, Langmuir, Langmuir Isotherm, Law, Ligand, Lysozyme, Media, Membrane Chromatographic Columns, Modeling, Performance, Protein, Pseudo, Pseudo Second Order, Pseudo Second-Order, Pseudo-Second-Order, Purification, Rate Law, Rights, Second Order, Second-Order, Solution, Solutions, Thomas, Tool

? Janoš, P., Sypecká, J., Mlčkovská, P., Kuráň, P. and Pilařová, V. (2007), Removal of metal ions from aqueous solutions by sorption onto untreated low-rank coal (oxihumolite). Separation and Purification Technology, 53 (3), 322-329.

Full Text: 2007\Sep Pur Tec53, 322.pdf

Abstract: Naturally occurring kind of weathered and oxidized young brown coal called oxihumolite was used for an adsorptive removal of heavy metal cations (Cd²⁺, Cu²⁺, Co²⁺, Ni²⁺, Pb²⁺, Zn²⁺) from waters. A working range for the oxihumolite as a sorbent is in a slightly acidic medium (pH ca. 3.5–4.5), where it exhibits a sufficient stability and sorption capability. Typical sorption capacities estimated from equilibrium measurements (sorption isotherms) ranged from ca. 0.1 to 0.4 mmol g⁻¹. The kinetic dependencies for the metal sorption were measured in a batch arrangement and evaluated using both pseudo-first- and pseudo-second-order kinetic models. The metal sorption was a quite rapid process that may be characterized by half-times ranging from ca. 10 to 80 min. The intraparticle diffusion was identified as the main mechanism controlling the rate of the sorption. Various extraction tests, namely the standardized leaching test with water and the three-step sequential BCR test, were used to examine a leachability of the heavy metals from the loaded sorbents and to assess potential risks of their subsequent liberation into the environment. Certain differences in the sorption and extraction behaviours of the examined metal ions (e.g. a high sorption capacity and low leachability of Pb²⁺) can be related to the well-known ‘selectivity sequences’ (or stabilities of the metal–humate complexes) as published in literature.

Keywords: Binding, Capacity, Coal, Complexes, Cu²⁺, Diffusion, Dyes, Environment, Equilibrium, Extraction, Extraction Tests, Heavy Metal, Heavy Metals, Heavy-Metals, Humic Acids, Isotherms, Kinetic, Kinetic Models, Kinetics, Leaching, Measurements, Mechanism, Metal, Metal Ions, Metal Sorption, Metals, Model, Models, Multicomponent Adsorption, Natural Organic-Matter, Peat, pH, Pseudo-Second-Order, Range, Removal, Risks, Sorption, Sorption Capacity, Sorption Isotherms, Stability, Test, Waste-Water, Water, Waters, Young Brown Coal, Zn²⁺

? Weng, C.H., Tsai, C.Z., Chu, S.H. and Sharma, Y.C. (2007), Adsorption characteristics of copper(II) onto spent activated clay. Separation and Purification Technology,