Application of Rice Husk and Rice Straw Biochar in Decontamination of Waste Streams

Biochar from rice residues was investigated as a low cost material to remediate heavy metals and female sex hormones in wastewater. Therefore, the biomass including rice husk and rice straw were used in the production of biochar at 340, 400 and 500 °C. In this study, continuous flow adsorption columns packed with rice derived biochars were used to evaluate the removal efficiency of six heavy metals and three hormones at different operating conditions. Then effluent samples were collected and analyzed for each type of biochar. Besides, the spent biochars were examined by thermogravimetric analysis and surface morphology to assess the weight loss for biochar. Results showed that the adsorption potential of biochar was significantly influenced by the hydraulic retention time, type of biochar and carbonization temperature. Rice straw derived biochar had a higher adsorption capacity and lower ash content compared to rice husk biochar. At flow rate of 1mL/min, sorption capacity of heavy metals indicated the order Fe > Pb > Cu > Cd > Zn > Cr. Additionally, after seven hours of continuous flow in rice straw derived biochar at 500 °C, the concentrations of 17-ß estradiol, estrone, and progesterone were decreased by 78, 75 and 99%, respectively. Therefore, rice straw derived biochar could be a feasible renewable tool for wastewater remediation.