Equilibrium, kinetic and thermodynamic studies on removal of Cd(II), Pb(II) and As(V) from wastewater using carp (cyprinus carpio) scales

Abstract

Unmodified farming carp (cyprinus carpio) scales were used as a biosorbent for the removal of Cd(II), Pb(II) and As(V) ions from aqueous solutions. The adsorption studies were conducted as a function of pH, contact time and temperature. The best sorption of cadmium, lead and arsenate ions was achieved for pH between 6.0 and 8.0. The adsorption data for cadmium, lead and arsenate at 20, 30 and 40 degrees C are fitted to Langmuir, Freundlich, Sips, Dubinin-Radushkevich (D-R), Jovanovic, Jovanovic-Freundlich (J-F), Temkin, Toth and Koble-Corrigan (K-C) isotherm models. Experimental data were used to model adsorption kinetics using pseudo-first order, pseudo-second order, Elovich and intraparticle diffusion kinetic models. The results showed that the adsorption of Cd(II), Pb(II) and As(V) ions onto carp scale followed the pseudo-second-order kinetic model. Thermodynamic parameters, including the Gibbs free energy (Delta G(0)), enthalpy (Delta H-0), and entropy (Delta S-0) changes, indicated that the present adsorption process was feasible, spontaneous and endothermic in the temperature range of 20-40 degrees C.