Adsorption of Pharmaceutical Contaminants from a Real Hospital Effluent Using Açaí Biomass-Derived Biochar Modified via Magnetron Sputtering

Abstract

A novel aluminum-coated biochar derived from açaí waste was successfully engineered via physical vapor deposition (magnetron sputtering) to remove the emerging pharmaceutical contaminants clorazepate (Clz) and diclofenac (Dic) from synthetic and real aqueous systems. Aluminum deposition at 200 W significantly altered the biochar’s surface morphology and chemistry, introducing Al-related active sites that enhanced interactions with anionic drug species. Kinetic studies revealed that the PSO model best describes the data (R2 = 0.995 for Clz and 0.993 for Dic), with rapid adsorption equilibrium reached within 120 min for Clz and 80 min for Dic. Equilibrium data were best fitted by the Sips model, indicating heterogeneous adsorption. Increasing temperature from 298 to 328 K enhanced the maximum adsorption capacity (Qms) from 260 to 437.8 mg g–1 for Clz and from 277 to 442.8 mg g–1 for Dic. Thermodynamic parameters confirmed spontaneous adsorption and a weakly exothermic process. The application in a real hospital wastewater demonstrated 95% removal of Dic and >88% removal of other pharmaceuticals, reducing total drug concentration from approximately 50–5 mg L–1. Regeneration tests showed stable performance in the sixth cycle (250–270 mg g–1), with a gradual loss of efficiency in subsequent cycles due to partial aluminum leaching. These results highlight AlAB_200W as a promising, high-capacity, and scalable adsorbent for pharmaceutical remediation in complex aqueous matrices.