Exploring the potential of cashew nut shell biochar for chlorpyrifos pesticide removal

Abstract

India generates over 620 million metric tons of agricultural waste yearly. Agricultural wastes have limited economic worth and are underutilized. Agro-waste recycling into circular economy products is essential for environmental health. In small-scale cashew industries, shell waste generation is 67.5 % of the seed weight. Cashew nut shells (CNS), a residual product of the industry, are burned following the extraction of pulp and oils, resulting in negative environmental impacts. This study focuses on the application of CNS biochar for the removal of chlorpyrifos, a highly toxic organophosphate pesticide. Prepared biochar was analyzed using SEM, BET, and FTIR. After adsorption, the specific surface area of biochar decreased from 111.62 m²/g to 14.00 m²/g. For an initial chlorpyrifos concentration of 15 mg/L, the highest removal efficiency of 94.2 % was obtained with a 120-minute contact time, a biochar dose of 0.5 g/L and a pH of 6. Adsorption studies demonstrated a maximum adsorption capacity of 31.34 mg/g, with results following the Langmuir isotherm and pseudo-second-order kinetics, indicating monolayer chemisorption. The findings highlight CNS biochar as a promising alternative to conventional adsorbents, offering an environmentally friendly solution for water purification. © 2025 Elsevier B.V.