Removal of Pb(II), Cu(II) and Cd(II) ions from aqueous solution using polyazomethineamides: Equilibrium and kinetic approach

Abstract

The removal of Pb(II), Cu(II) and Cd(II) ions onto polyazomethineamides (PAMA) has been investigated using batch adsorption techniques. The extent of adsorption was investigated as a function of pH, adsorbent dose, contact time and initial metal ion concentration. The metal ion removal was pH-dependent and reached maximum at pH 6.0. Experimental data were analysed by Langmuir, Freundlich, Redlich-Peterson and Temkin adsorption isotherms. The characteristic parameters for each isotherms and related correlation coefficients have been determined using MATLAB 7.1. The maximum adsorption capacities of PAMA for Pb(II), Cu(II) and Cd(II) ions were calculated from the Langmuir isotherm 452.1, 470.7 and 462.3mg/g respectively. Pseudo-first-order, pseudo-second-order, Elovich kinetic and intraparticle diffusion models were used to fit the experimental data. Kinetic parameters, rate constants, equilibrium sorption capacities and related correlation coefficients, for each kinetic model were calculated and discussed. The kinetic studies showed that the pseudo-second-order rate equation was better described by the adsorption process. The FT-IR spectra of the adsorbent indicated that the amide, amide carbonyl and azomethine groups were major binding sites with the metal ions. The adsorption of PAMA for heavy metal is selective, and the adsorption capacity is in the order of Cu(II)>Cd(II)>Pb(II).