Adsorption mechanisms of sulfamethoxazole and trimethoprim using phosphoric acid activated white-rot fungus biochar

The continual release of sulfamethoxazole (SMX) and trimethoprim (TMP) into aquatic environments, combined with their incomplete removal during wastewater treatment, results in their sustained environmental presence. This persistence contributes to ecological risks and spread of antibiotic resistance. This study evaluated the performance of activated biochar (WR700), synthesized from white-rot fungus ( Ganoderma applanatum ) through phosphoric acid activation followed by pyrolysis at 700 °C, for the removal of SMX and TMP from water. Characterization using scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), elemental analysis, proximate analysis, and zeta potential analysis confirmed that WR700 possesses desirable properties as an activated biochar. This includes well-developed pores, O-H, C O, C C, and C O functional groups, and high carbon content. At an initial antibiotic concentration of 1000 μg g -1 and adsorbent dosage of 4 g l -1 , batch adsorption experiments resulted in maximum removal efficiencies of 99.5% (SMX) and 89.8% (TMP). These conditions yielded adsorption capacities of 216.72 μg g -1 and 220.33 μg g -1 , respectively, which are consistent with the relatively low initial loading and the concentration-dependent behavior of the adsorption system. The adsorption kinetics were analyzed using pseudo-first-order, pseudo-second-order, Elovich, and Intra-particle diffusion models. The Adsorption kinetics of each antibiotic were best described by the pseudo- first-order and pseudo-second-order model, indicating that both physisorption and chemisorption were involved in the process. Isotherm analyses indicated that the Sips model best described SMX adsorption, while the Temkin, Dubinin-Radushkevich, and Freundlich models provided good fits for TMP adsorption. The Sips, Dubinin-Radushkevich, and Freundlich models suggested a heterogeneous surface of WR700. Reusability tests showed that WR700 removed 80.21 ± 1.26% and 81.17 ± 2.19% of SMX during the second and third adsorption cycles, respectively. Overall, these findings highlight the potential of white-rot fungus-derived activated biochar as an effective adsorbent for antibiotic removal in aqueous solutions.