Venlafaxine Removal from Water and Wastewater Using Activated Carbons from Spent Brewery Grains Produced by Conventional vs. Microwave Pyrolysis

<b>Background/Objectives:</b> The recent increase in antidepressant consumption, particularly venlafaxine, combined with the limited effectiveness of conventional wastewater treatment processes, has led to rising environmental concentrations. Adsorption methods have emerged as effective strategies for removing persistent pharmaceuticals without generating harmful by-products. This study aimed to develop and assess two activated carbons (ACs) derived from spent brewery grains as an efficient material for venlafaxine removal from wastewater. <b>Methods:</b> Two pyrolysis methods, conventional and microwave-assisted, were evaluated to assess their influence on the adsorption properties. The materials were characterized through nitrogen physisorption and scanning electron microscopy to evaluate surface area (<i>S</i>_BET), porosity, and morphology. Their adsorption properties were examined through batch adsorption experiments to analyze kinetic and equilibrium behavior, and the efficacy was evaluated in both ultrapure water and real wastewater. <b>Results:</b> The obtained AC exhibited high porosity, with the <i>S</i>_BET ranging from 1080 to 1197 m² g^-1. Kinetic studies indicated that adsorption followed a pseudo-second-order model, achieving equilibrium within 2 h. The equilibrium data were optimally described by the Langmuir isotherm, indicating monolayer adsorption, with the maximum adsorption capacity of microwave-assisted AC reaching 74 ± 6 mg g^-1. Microwave-assisted AC has shown higher efficiency than conventionally produced AC, demonstrating that this pyrolysis technique can produce materials with enhanced adsorption properties. <b>Conclusions:</b> This study evidences that microwave-assisted pyrolysis of an abundant agro-industrial residue yields high-performance materials capable of efficiently removing an antidepressant, included in the revised Urban Wastewater Treatment Directive, from complex effluents even at low doses, highlighting a sustainable route to mitigate pharmaceutical contamination in aquatic environments.