Physicochemical Evaluation of Calotropis procera Fruit-Derived Biochar for Carbofuran Adsorption: Kinetic, Isotherm, and Diffusion Studies

Carbofuran, a toxic carbamate pesticide, frequently contaminates aquatic environments due to its high solubility and persistence. This study evaluates the adsorption performance of acid-treated (ABCP) and alkaline-treated (ALBCP) biochars derived from Calotropis procera fruits for carbofuran removal from aqueous solution. The biochars were characterized using SEM, BET, EDX, and FTIR analyses, confirming well-developed porous structures, high surface areas, and enriched oxygen-containing functional groups after chemical modification. Batch adsorption experiments were conducted to investigate the effects of pH, contact time, adsorbent dosage, and initial concentration. Maximum removal efficiencies were achieved at pH 7, with optimal dosages of 0.5 g (ABCP) and 0.3 g (ALBCP). Equilibrium data fitted both Langmuir and Freundlich isotherm models, indicating combined monolayer and heterogeneous adsorption behavior. Kinetic analysis showed excellent agreement with the pseudo–second-order model, suggesting chemisorption as the dominant mechanism, while intra-particle diffusion contributed partially in the case of ABCP. Overall, the findings demonstrate that chemically modified Calotropis procera biochars are efficient, low-cost, and sustainable adsorbents for carbofuran remediation in pesticide-contaminated water systems.