Biosorption of hexavalent Chromium by the agricultural wastes of the cotton and barberry plants

Hexavalent chromium, a highly toxic metal ion employed in industrial activities, is considered as a first priority pollutant. In this study, the capsule walls of the boll of cotton (cotton waste, CW) and the waste obtained from pruning barberry bushes (barberry waste, BW) were investigated as cheap and locally available adsorbents for Cr (VI) removal. The adsorption behavior, equilibrium, and kinetic properties have been studied through batch experiments. Specifically, the sample pH showed a significant effect and an initial pH of 2.0 was most favorable for the effective removal of chromium. The equilibrium adsorption data were well fitted to the Langmuir adsorption equation with the maximum adsorption capacities of 20.7and 15.5mg/gfor CW and BW, respectively. The kinetic evaluations showed a rapid rate of adsorption (within 10 min) that followed the pseudo-second order kinetic model. In competitive adsorption tests, Cl̶ had the least effect on the adsorption efficiency of Cr (VI), especially for CW. The results indicate the potential for the application of the studied agricultural wastes as adsorbents to reduce Cr (VI) concentration in aqueous samples.