Removal of toxic chlorpyrifos from agricultural effluents using highly porous biochar and its magnetic derivative

This work reports the presence of a significant percentage of toxic chlorpyrifos (CPS) (approximately 16 ppm) in the agricultural wastewater emanating from the local farmlands, largely producing seasonal vegetables, and its effective mitigation using highly porous biochar (BC) and its magnetic derivative synthesized from a combination of waste materials (viz., low-grade coal and municipal sludge) available in abundance locally via low temperature pyrolysis. Detailed material characterization was performed using FE-SEM, Transmission Electron Microscopy (TEM), PXRD, BET, XPS, Vibrating Sample Magnetometer (VSM), and other techniques to understand the surface morphology and chemical composition of the synthesized materials. Surface morphology confirmed good porosity, crystallinity, and high specific surface areas (1107 m²/g for BC and 550 m²/g for its magnetic derivative). Batch adsorption results with real agricultural wastewater showed promising CPS removal of 81.5% and 92.8% with BC and magnetic BC (MBC), respectively. The regeneration study was encouraging, where between the freshly used samples (batch 1) and the final 7th batch (spent adsorbent), for BC, a drop of 31.35%, and for MBC, 32.2% in terms of removal percentage was observed. The proposed valorization of waste and underutilized indigenous materials holds promise for developing novel adsorbents that can be effective in scaled-up operations.