Efficacy of biochar from mixed biomass resources for the removal of pharmaceutical residues from treated domestic wastewater

Biochar-based sorption has gained popularity for pharmaceutical residues removal; nonetheless, its performance is heavily dependent on feedstock selection, biomass characteristics, and operating conditions. Therefore, this study assesses the performance of biochar derived from several mixed biomass resources and addresses its applicability for use in nature-based treatment systems. Batch sorption studies were conducted on eight biochar types derived from softwood, bagasse, and coffee husk to assess their capacity to remove five pharmaceuticals. The experimental study was carried out in two phases. Phase 1 consisted of a screening, where softwood-bagasse biochar (50:50) was found to be the most efficient material among the eight chosen sorbents, with removal efficiencies of up to 97%. In phase two, response surface method (RSM) was employed to evaluate the individual and interactive effects of contact time, sorbent dose, and initial pharmaceutical concentration. The empirical statistical models revealed critical operational trade-offs, with removal efficiencies exceeding 90% at longer contact times (24-30 h) and higher biochar dosages (up to 2 g). The softwood-bagasse biochar's higher sorption performance was attributed to enhanced carbonization and aromaticity, as reflected by a low H/C ratio (0.31). This indicates that condensed carbon structure favours hydrophobic partitioning and π-π interactions with aromatic pharmaceutical molecules.