Biosorption of cadmium and copper ions from aqueous solution by chemically modified wheat straw

ABSTRACT

Increased environmental pollution caused by toxic metals is a great concern because of their carcinogenic, non-biodegradability and bio-accumulation properties. Cadmium [Cd] and copper [Cu] are two of the most common heavy metals in the environment. The objective of this study was to assess the effect of modified wheat straw promoted by sodium bicarbonate for removal of cadmium and copper from aqueous solution. Adsorption process was accomplished in a laboratory-scale batch with emphasis on the effect of various parameters such as pH, contact time, arsenic concentration and adsorbent dosage on adsorption efficiency. In order to understand the adsorption process, equilibrium isotherms were also determined. The results of this study showed that adsorption of the Cd and Cu was influenced by several parameters such as arsenic initial concentration, adsorbent dosage and solution pH. Maximum adsorption efficiency was achieved at a pH of 7. The adsorbed amount of metal ions increased with the initial concentration of the metals. Among the isotherm models tested, i.e., the Langmuir, Freundlich, and Dubinin Radushkevich, the adsorption equilibrium of both Cd and Cu was best described by the Langmuir and Freundlich models. Mean values of the free energies of adsorption [11.1 kJ mol-1 for Cd and11.4 kJ mol-1 for Cu] indicated that adsorption of Cd and Cu ions by wheat straw might follow a chemisorption mechanism. We concluded that adsorption by modified wheat straw is an efficient and reliable method for removal of Cd and Cu from aqueous solutions