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Now showing items 1 - 4 of 4

  • Adsorption kinetics of a cationic dye from wastewater

    Demirba?, ?zkan   Alkan, Mahir  

    The adsorption kinetics and thermodynamics of Maxilon Blue 5G, a cationic textile dye, onto perlite were investigated in aqueous solution in a batch system for determining the effect of contact time, stirring speed, initial dye concentration, initial solution pH, ionic strength and temperature. Experimental data were evaluated according to the pseudo-first, second-order and the Elovich equation, mass transfer and intra-particle diffusion models, and it was found that adsorption kinetics can be described according to the pseudo-second-order model, from which the rate constant and the adsorption capacity were determined. The thermodynamic activation parameters, such as activation energy, enthalpy, entropy and Gibbs free energy, were determined. The obtained results confirmed the applicability of this mineral as an efficient adsorbent for cationic dyes.
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  • Thermodynamics and kinetics of adsorption of a cationic dye onto sepiolite

    Demirba?, ?zkan   Turhan, Yasemin   Alkan, Mahir  

    The adsorption kinetics and thermodynamics of Maxilon Red GRL (MR-GRL), a cationic textile dye, onto sepiolite were investigated in aqueous solution in a batch system. The effect of contact time, stirring speed, initial dye concentration, initial solution pH, ionic strength, and temperature was studied. The initial tested concentrations of MR-GRL solution were 1.5 x 10(-3), 2.0 x 10(-3) and 2.5 x 10(-3) mol/L. The effect of pH was analyzed in the pH range from 5 to 10. The effect of ionic strength was investigated at 0.001-0.100 mol/L NaCl salt concentrations. The experiments were carried out at 288, 298, 308, and 318 K set with a thermostat. The all parameters significantly influenced the adsorption rate and capacity. Experimental data were fitted to pseudo-first order, second-order, Elovich equation, mass transfer, and intra-particle diffusion models. The adsorption kinetics data showed that this process can be described by the pseudo-second-order model, from which the rate constant and the adsorption capacity were determined. The thermodynamic activation parameters such as the activation energy, enthalpy, entropy, and Gibbs free energy were determined. The value of the standard enthalpy change (19.92 kJ/mol) indicates that the adsorption is physical in nature involving weak forces of attraction and is also endothermic. The results showed the applicability of this clay as an efficient adsorbent for cationic dyes.
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  • Biosorption of zinc ions onto\r Corylus avellana\r L.

    Demirba?, ?zkan   Karada?, Adem  

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  • Adsorption of casein onto some oxide minerals and electrokinetic properties of these particles

    Demirba?, ?zkan   Alkan, Mahir   Demirba?, Aygül  

    In this study, the adsorption properties of casein onto some oxide minerals such as sepiolite, kaolinite and expanded and unexpanded perlites samples were studied as a function of concentrations of casein, sodium phosphate and NaCl, temperature and pH of the aqueous solutions. According to the experimental results, the adsorption of casein increases with temperature from 15 to 45 degrees C and ionic strengths of the solutions over the range of 0.0 and 0.1 mol L-1. The adsorption decreased with increasing pH from 7.00 to 11.00 and the concentration of phosphate ions from 0.02 to 0.10 mol L-1. Maximum adsorption capacity values (q(m)) showed dependence on pH. It was observed that q(e)-pH curves reached a maximum at around neutral pH value. Furthermore, the electrokinetic properties of casein-covered oxide particles were also investigated at similar conditions to those of the adsorption process. The nature of the adsorption process was investigated using Langmuir and Freundlich isotherm models. (C) 2014 Elsevier Inc. All rights reserved.
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