Thermochemical modification of lignocellulosic Moringa oleifera seed husks for atrazine biosorption

This study demonstrates a combined thermochemical modification - acid treatment (0.1 M HNO₃) followed by calcination (300 °C) - to engineer Moringa oleifera seed husks into a high-performance biosorbent (MCT). This treatment induced a profound restructuring of the lignocellulosic matrix, increasing the specific surface area by nearly 700 % (from 9.47 to 73.66 m² g^-1) and shifting the structure to be predominantly microporous. Consequently, the maximum atrazine adsorption capacity (q_max) increased by over 150 % compared to the raw material, reaching 9.14 mg g^-1, with 99 % removal achieved in 60 min. Mechanism elucidation revealed a multi-step, entropy-driven process governed by non-electrostatic interactions. The increased surface aromaticity of MCT promotes initial capture via hydrophobic and π-π stacking, followed by anchoring through hydrogen bonding. Kinetic (pseudo-second order) and thermodynamic data corroborate this mechanism. In conclusion, this surface engineering strategy effectively transforms a low-cost agricultural residue into a highly efficient biosorbent, showcasing a significant improvement over the pristine biomass and offering a promising solution aligned with circular economy principles.