Abstract:
Pharmaceutical residues, particularly antibiotics, are emerging contaminants of environmental concern because of their persistence in aquatic environments and their contribution to antibiotic resistance. Adsorption using biochar has attracted considerable attention as a sustainable and cost-effective treatment technology. This study evaluated the removal of sulfamethoxazole (SMX) and trimethoprim (TMP) from aqueous solutions using phosphoric acid-activated white-rot fungus biochar (WR700), corncob biochar (CB700), and their mixtures. Specifically, the study characterized the physicochemical properties of WR700 and CB700, evaluated their adsorption behavior using kinetic and equilibrium studies, and assessed the performance of their mixtures under varying operating conditions using a Taguchi L25 orthogonal array. Biochar characterization using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), elemental analysis, proximate analysis, and zeta potential analysis confirmed that both WR700 and CB700 possessed porous structures, oxygen-containing functional groups, and favorable surface characteristics for adsorption. Batch adsorption experiments showed that WR700 achieved maximum removal efficiencies of 99.5% for SMX and 89.8% for TMP, while CB700 achieved maximum removal efficiencies of 89.8% for SMX and 87.7% for TMP. The maximum adsorption capacity of WR700 was 0.22 mg g⁻¹ for both antibiotics, whereas CB700 achieved adsorption capacities of 0.12 mg g⁻¹ for SMX and 0.15 mg g⁻¹ for TMP. Adsorption was influenced by solution pH, contact time, and adsorbent dosage, with kinetic and equilibrium analyses indicating that both physical and chemical interactions contributed to antibiotic removal. The mixtures of WR700 and CB700 did not improve adsorption performance. Instead, maximum removal efficiencies of 65.56% for SMX and 27.37% for TMP were obtained, indicating an antagonistic interaction between the two biochars. Overall, the study demonstrates that WR700 and CB700 are effective adsorbents for the removal of sulfamethoxazole and trimethoprim from aqueous solutions, whereas combining the two biochars does not enhance adsorption performance. These findings provide useful information for the development of sustainable biochar-based technologies for antibiotic removal from contaminated water.
