Utilizing agricultural wastes to remove hexavalent chromium from aqueous solutions

Abstract The purpose of this study was to determine the hexavalent chromium (CrVI) biosorption capacities of several agricultural wastes from aqueous solutions. Samples were tested unaltered and after hydrochloric acid (HCl) treatment. Additional parameters tested include sample dose, contact time, particle size, mixing temperature, and the concentrations and pH of the CrVI solutions. Desorption studies were performed to determine if the removed CrVI could be recovered. In addition, tests were conducted to determine if the agricultural waste samples (AWS) could be reused for additional CrVI biosorption cycles. The results of this study demonstrate a wide range of CrVI biosorption proficiencies ranging from 13 to 98 percent removal. The parameters that resulted in higher CrVI removal include HCl treatment, higher sample dose, lower CrVI solution concentration, and lower mixing temperature. Desorption results showed an 8 to 25 percent CrVI recovery rate. Reused AWS were effective at removing CrVI during subsequent trials. Therefore, all AWS can be reused for additional CrVI biosorption cycles. Hence, these could reduce hazardous waste disposal inefficiencies and costs by avoiding disposing of spent AWS following each CrVI biosorption cycle.