Cocoa pod-derived biochar for Ibuprofen and Diclofenac adsorption: a low-cost and reusable adsorbent

Abstract

This study investigates the adsorption potential of biochar derived from cocoa pod husks, both in its raw form and after nitric acid-functionalization, for the removal of two common pharmaceutical pollutants, diclofenac and ibuprofen, from aqueous solutions. The biochars were characterized using BET, XRD, SEM, FTIR, and TGA-DTG techniques. Acid modification significantly enhanced the surface area (235.50 m2 g-1 vs. 213.77 m2 g-1), thereby increasing the availability of active sites for adsorption. Morphological analysis revealed irregular, porous structures favorable for pollutant trapping. Adsorption kinetics followed a pseudo-second-order model, suggesting chemisorption as the dominant mechanism, while isotherm modelling indicated a combination of physical and chemical interactions, suggesting multi-mode adsorption. Maximum adsorption occurred under highly acidic conditions (pH = 1 for diclofenac, pH = 2 for ibuprofen). Notably, the biochar recovered 63% of its capacity in the first reuse cycle, though performance declined progressively to 39% by the third cycle. These findings position cocoa pod biochar as a cost-effective, sustainable, and reusable adsorbent for pharmaceutical-contaminated water, offering a high-value application for agricultural waste in water purification systems. This research underscores the value of transforming agricultural waste into innovative adsorbents that can help address pollution challenges in wastewater management on a practical scale. Keywords : Cocoa pods biochar ; Pharmaceutical pollutants ; Adsorption kinetics ; Water treatment ; Biochar regeneration.