Strategic synthesis of biowaste-derived magnetic hydrochar for adsorption and photocatalytic removal of Chlorpyrifos herbicides from simulated wastewater

This study presents the synthesis of a magnetic hydrochar composite (ZMMHC) from Zea mays biowaste, integrating CoFe2O4 nanoparticles (5-20 wt%). Characterization techniques included BET, XRD, FESEM, HRTEM etc. The ZMMHC composite with 15 wt% CoFe2O4 exhibited the highest surface area of 162.89 m2/g. Saturation magnetization (Ms) values for composites with 5 %, 10 %, and 15 wt% CoFe2O4 were 34.70 emu/g, 42.73 emu/ g, and 54.40 emu/g, respectively, indicating magnetic properties. The composite displayed a band gap of 2.18 eV, enabling visible light activity. For wastewater, ZMMHC achieved 97.4 % CPF adsorption in 120 min at pH 6.0, following the Langmuir model (R2 = 0.99). Photocatalytic degradation removed 94.2 % CPF in 180 min, with the rate k1 0.0161 min-1. Radical scavenging experiment confirmed the photoexcited electrons as key contributors to CPF degradation. Its high surface area, magnetization, visible-light activity, and reusability make it promising for wastewater treatment.