Removal of sulfamethoxazole at relevant concentrations from wastewater by a magnetic regenerable waste-based activated carbon

Environmental contamination by pharmaceuticals has become an emerging concern, with the discharge of effluents from urban wastewater treatment plants (WWTPs) being one of the most significant pathways for these contaminants to enter aquatic environments. In this study, a magnetic waste-based activated carbon (MAC), produced by microwave pyrolysis of paper mill sludge, was investigated for its ability to remove sulfamethoxazole at relevant concentrations found in wastewater. Adsorption kinetics and equilibrium were assessed in both ultrapure water and real WWTP effluent. Subsequently, MAC was thermally regenerated using microwave radiation and reutilized over successive regeneration/adsorption cycles. MAC achieved equilibrium within 60 min in WWTP effluent and 180 min in ultrapure water. Adsorption isotherms indicated a Langmuir maximum adsorption capacity of 6.2 ± 0.3 mg g −1 in effluent and 54 ± 2 mg g −1 in ultrapure water. The adsorption performance in effluent was influenced by competition with dissolved organic matter and electrostatic interactions. Microwave-assisted regeneration successfully restored MAC adsorption performance for two cycles. Further regeneration resulted in a significant decrease in adsorption efficiency due to textural deterioration and phase transformation of magnetic iron oxides, reducing its magnetic response. These findings highlight the potential of MAC for sustainable wastewater treatment and the benefits of microwave-assisted regeneration in extending its lifespan.