Removal of Heavy metals and Hormones from Wastewater Using Rice husk and Rice straw Biochar Packed Columns

This research work investigates the effectiveness of rice husk and straw derived biochar as a low-cost adsorbent for domestic wastewater containing both organic and inorganic contaminants. Continuous laminar flow adsorption columns packed with biochar were used to investigate the immobilization of the contaminants at four different flow rates: 1, 2, 4 and 10 mL/min. Filtrate samples were collected at different time intervals and analyzed for constituents (heavy metals and hormones) as well as chemical oxygen demand (COD) and orthophosphate (PO4). Biochar characterization including elemental composition, surface functional groups, thermal analysis, surface morphology and surface area were carried out using CHSN-O analyzer, FT-IR, TGA, SEM-EDS and BET analysis, respectively. Repeated measurement analysis using statistical analysis system (SAS) was carried out to investigate the significance of type of biochar, flow rate, and adsorption time on the remediation of contaminants in wastewater. The results showed that the adsorption potential of biochar was greatly influenced by the flow rate, type of biochar used and treatment time. Additionally, competitive adsorption of heavy metals was observed in all types of biochar. At a flow rate of 1 mL/min, the breakthrough point for lead (Pb) was achieved after seven hours using rice husk biochar (RH-340) and twelve hours for rice straw biochar (RS-340). At a flow rate of 2 mL/min, the breakthrough point was achieved after four hours for RS-340 and three hours for RH-340. At a flow rate of 10 mL/min, breakthrough points were not attained due to the high velocity flow within the biochar extrinsic pores.