Potential of rice straw derived activated biochar to remove arsenic and manganese from groundwater: A cleaner approach in the Indo-Gangetic Plain

Abstract

Heavy metal pollution in groundwater has become a public health concern due to its non-degradable and poisonous nature. Several research studies were conducted using various adsorbents to extract heavy metals from water. However, the removal of As and Mn using rice straw-derived activated biochar in a binary metal system was found to be limited. This study examined a comparative analysis of As and Mn adsorption by CO2-activated biochar derived from rice straw in a single and binary metal approach. Findings showed that the maximal sorption capacity of As and Mn in single metal systems was 18.26 and 12.18 mg g−1 and 8.51 and 5.42 mg g−1 in binary metal systems. PSO kinetic model (R2> 0.99) and Langmuir isotherm model (R2> 0.95) show good agreement with experimental data. The highest removal efficiency of As (99.53%) and Mn (96.23%) was achieved in naturally contaminated water (Sahibganj, India). Health risk assessment indicates chances of cancer (CR> 1 × 10−4 and HQ>1) in humans due to the high concentration of As (192 μg L−1). Water treated with 0.1 g activated biochar had lower CR and HQ values, and metal concentration was below the WHO safe drinking water standard.