Biosorption of nickel and zinc ions on wheat straw

Abstract

This study investigates the potential use of wheat straw (Tritium sativum) which is an agricultural by-product for the removal of Ni²⁺ and Zn²⁺ from the waste water discharges. Scanning Electron Microscope was used to obtain images of the surface of wheat straw (WS) and Electron Disperive Spectroscopy was employed in elemental analysis of wheat straw, Fourier Transform Infrared Spectroscopy was used to get informations about the chemcial interaction of the wheat straw surface with the sorbed metallic ions. Simulated wastewater containing Ni²⁺ and Zn²⁺ was subjected to biosorption by WS. The effect of initial concentration, pH and temperature on the removal of metal ions on WS was investigated. For varied initial metal concentrations from 5 to 150 ppm the biosorption equilibrium was achieved between 2.5 to 5 hours. The percentage removal of sorption decreases with increasing concentration. The experimental data were fitted to Langmuir, Freudlich and Temkin isotherms model fits better than the other two of single ionic system. For binary ionic system IAS-Freudndlich model served best. In addition the sorption by wheat straw conformed to pseudo second order kinetics with a good value of coefficient of determination (r² > 0.99). Free energy of biosorption ΔG°, enthalpy ΔH° and entropy ΔS° changes were also estimated and used to predict the nature of biosorption. The capacity of the sorption of wheat straw was compared with other common available sorbent. On the basis of sorption capacity, regenerate ability and the cost analysis we can conclude that WS could be used as a sorbent material for removal N²⁺ and Zn²⁺ from an aqueous solution.