Removal of meropenem from hospital wastewater using biochar derived from grape stalks

This study focuses on synthesizing biochar from grape stalks and its application for removing the antibiotic meropenem (MRP) from aqueous solutions. The raw biochar was chemically activated with NaOH under mild conditions and thoroughly characterized to elucidate its adsorption mechanisms. Preliminary tests confirmed the need for activation to enhance the adsorption efficiency. The effect of initial MRP concentration, biochar dosage, solution pH, kinetics, and equilibrium were investigated. Furthermore, the adsorption of MRP contained in simulated hospital wastewater (HWW) was also evaluated. Characterization revealed a honeycomb pore structure, high mineral content, and surface functional groups relevant for adsorption. Kinetic data fitted the pseudo-second-order model, and equilibrium isotherms fitted the Freundlich model. Thermodynamic analysis indicated spontaneous adsorption in ultrapure water, with an enhanced spontaneity observed in HWW due to the presence of competing ions. Desorption tests showed 90 % MRP removal after five cycles. In simulated HWW, the activated biochar achieved complete MRP removal at low (5 mg dm^-3) and high (100 mg dm^-3) concentrations and concurrently reduced salinity. The maximum adsorption capacity (80 mg g^-1) was reached at an initial concentration of 100 mg dm^-3, under optimal conditions of pH 3 and 1.0 g dm^-3 of biochar. These findings highlight the potential of grape stalk-derived biochar as an effective and reusable adsorbent for hospital wastewater treatment.