Comparative and competitive adsorptive removal of Ni2 + and Cu2 + from aqueous solution using iron oxide-vermiculite composite

Abstract

In this study, iron oxide-vermiculite composite (Iovc) with a high specific surface area (SSA) was prepared to remove Ni2+ and Cu2+ from aqueous solution. It was characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), Fourier-transform infrared (FTIR), and scanning electron microscopy (SEM). The effects of initial pH of the solution, contact time and adsorbent concentration on the adsorption efficiency were investigated systemically. Equilibrium adsorption isotherms were measured for the single component by using various models. The homogenous adsorption of Ni2+ and Cu2+ was confirmed in the single system by Langmuir and Koble–Corrigan models. For the binary adsorption of Cu2+ and Ni2+ ions have been analyzed by using non-modified Langmuir, modified Langmuir, extended Langmuir, extended Freundlich and Sheindorf–Rebuhn–Sheintuch (SRS) models. The competitive extended Langmuir model described well the competitive adsorption of Ni2+ and Cu2+. Maximum adsorption capacities for Ni2+ and Cu2+ in the binary system are 101.3 and 59.7mg/g, respectively.In the kinetic study, the experimental data fitted well the pseudo-second-order kinetics for Ni2+ and Cu2+ adsorption data. Furthermore, calculated thermodynamic parameters, ΔG°, ΔH° and ΔS° of adsorption showed that the adsorption of Ni2+ and Cu2+ was feasible, spontaneous and an exothermic process.