Laccase–Biochar Synergy for Efficient Removal of Trimethoprim, Clindamycin, and Fipronil from Wastewater

The presence of organic micropollutants such as pharmaceuticals and pesticides in aquatic systems poses risks to environmental and public health, as conventional wastewater treatment plants are often ineffective at removing them, highlighting the need for alternative solutions. This study evaluates the combined use of biochar and laccase to remove trimethoprim, clindamycin, and fipronil, selected for their ubiquity, persistence, and physicochemical properties. Commercial wood-derived biochar was used, and removal performance was assessed through adsorption isotherms, time-dependent evaluation of removal efficiency, and quantification by UPLC-MS/MS. Toxicity after treatment was evaluated using bacterial growth assays with Escherichia coli and Rhodococcus erythropolis. Adsorption of trimethoprim and clindamycin followed the Langmuir model (Qmax 2.27 and 1.49 mg/g), while that of fipronil followed the Temkin model (Qmax 0.98 mg/g). The combined biochar–laccase system enabled up to 99% removal of trimethoprim and clindamycin within one hour, demonstrating synergy between adsorption and enzymatic removal. Enhanced removal was also observed for clindamycin and fipronil in mixtures. Bacterial assays showed partial restoration of growth after treatment, suggesting reduced antibacterial activity of transformation products, although effects remained species-dependent. Overall, the biochar–laccase system shows promise for micropollutant removal, supporting green remediation strategies, but further work is required to characterize transformation products and assess ecological impacts.