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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 °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 (ΔG0), enthalpy (ΔH0), and entropy (ΔS0) changes, indicated that the present adsorption process was feasible, spontaneous and endothermic in the temperature range of 20-40 °C. [ABSTRACT FROM AUTHOR]

Multi-wall carbon nanotubes (MWCNTs) was functionalized with 6-arm amino polyethylene glycol (PEG), and synthesized PEG-MWCNTs was used as adsorbent in order to study adsorption characteristics with respect to Cd(II), Pb(II) and As(V) ions. In batch tests, the influence of contact time, initial metal ion concentration and temperature on the ion adsorption on PEG-MWCNTs was studied. Adsorption of Cd(II), Pb(II) and As(V) on PEG-MWCNTs strongly depends on pH. Time dependent adsorption can be described by intra-particular Weber-Morris kinetic model, and adsorption process was modelled by Koble-Corrigan isotherm, respectively. The maximum adsorption capacities of Cd(II), Pb(II) and As(V) on PEG-MWCNTs, for initial concentration of 10 mg dm-3 and at pH=4, were 77.6, 47.5 and 13 mg g-1 at 25°C, respectively. The competitive adsorption studies showed that the adsorption affinity of ions towards PEG-MWCNTs showed largest adsorption of Cd(II) at pH 8, following by Pb(II) at pH 6, and As(V) at pH 4. Thermodynamic parameters showed that the adsorption of Cd(II), Pb(II) and As(V) ions was spontaneous and endothermic. [ABSTRACT FROM AUTHOR]