Process optimization of rice straw-derived activated biochar and biosorption of heavy metals from drinking water in rural areas

Abstract

The Indo-Gangetic plain of northern India is known for prevalent rice farming. Due to the lack of a rice straw waste management system, a large volume of rice straw is burned in the field. Therefore, we add value to rice straw by converting it into activated biochar and utilizing it to remove toxic metals from natural water. In this work, single-step physical activation (CO2 and H2O) of rice straw was planned and optimized the activation process parameters to get better biochar yield and surface area. The biochar activation parameters were optimized using the central composite design method. The CO2 activated biochar has an optimum surface area and product yield of 399.99 m2/g and 26.79 %, whereas H2O activated biochar has an optimum product yield and surface area of 31.53 % and 300 m2/g. The SEM analysis shows that CO2 activated biochar has a more uniform porous structure than H2O activated biochar. Cost analysis revealed that CO2 and H2O activated biochar had a lower manufacturing cost of 1.287 and 1.672 U.S. $/kg, respectively compared to other adsorbents. Arsenic and manganese removal efficiency in natural water was found to be greater than 95 % for both activated biochar.