TheTeffstraw: a novel low-cost adsorbent for quantitative removal of Cr(VI) from contaminated aqueous samples

Abstract

In the present study, removal of Cr(VI) from aqueous solutions was investigated utilizing Teff straw, the agricultural solid waste product of Tef [Eragrostis tef (Zucc.) Trotter]. The characteristic surface chemistry of the Teff straw was analyzed by FT-IR analysis and the adsorption efficiency of this novel adsorbent was studied using the batch adsorption technique. Different experimental parameters including pH, contact time, adsorbent dose, initial metal ion concentration, and agitation speed were optimized. Equilibrium and kinetic models for Cr(VI) sorption were studied by considering the effects of concentration and contact time at the optimum pH (pH = 2) and agitation speed of 150 rpm. Results of the sorption equilibria were found to fit better to the Langmuir isotherm (R²= 0.9739) than the Freundlich isotherm (R²= 0.9187) and maximum Cr(VI) loading capacity of 3.51 mg/g was determined. On the other hand, kinetics of Cr(VI) sorption on the Teff straw was well defined by the pseudo-second order model (R²= 0.9999). The results obtained showed that the use of Teff straw can be considered as one of the most promising, natural, easily accessible, and low-cost adsorbent for efficient and quantitative removal of Cr(VI) from contaminated wastewaters released from leather industries.