Simultaneous removal of imidacloprid, carbendazim, and bispyribac sodium using zinc and bentonite functionalized rice husk biochar composite.

The increasing use of pesticides in intensive cultivation practices poses significant environmental risks due to their persistence, leaching, and adverse impacts on non-target organisms. Rice husk, an agricultural by-product, was functionalized with zinc chloride and bentonite for the removal of three commonly used pesticides; imidacloprid, carbendazim, and bispyribac sodium. Engineered rice husk biochar (ERHB) was produced via the co-pyrolysis of 10 g of rice husk, 5 g of bentonite and 5 g of ZnCl2 at 500 °C for 2 h, and it removed 96.43, 84.47 and 78.94% of spiked bispyribac sodium, carbendazim, and imidacloprid, respectively, from water through sorption. Physico-chemical characterization revealed significant structural and surface chemistry changes upon modification and their role in enhancing adsorption. Elemental analysis of ERHB confirmed the incorporation of clay minerals along with Zn. Adsorption experiments showed that pesticide removal was mainly influenced by initial concentration, contact time, and adsorbent dosage, while solution pH had little effect. Kinetic and isotherm models further explained the adsorption mechanisms. ERHB could remove 86.37 82.52 and 85.82% of spiked imidacloprid, carbendazim, and bispyribac sodium from the mixed-pesticide solution under optimized sorption conditions. ERHB could also remove over 95% of 50 pesticides and three synthetic dyes including bromocresol green (44.6%), allura red (75.3%), and methylene blue (89.7%) from water. Thus, the ERHB can be used as a multi-class pesticide and dye removal agent from aqueous media, offering potential for integrated water remediation strategies in agro ecosystems.