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

## TL;DR

This study shows that activated carbon made from spent brewery grains using microwave pyrolysis can effectively remove the antidepressant venlafaxine from wastewater.

## Contribution

Microwave-assisted pyrolysis of spent brewery grains produces activated carbon with enhanced venlafaxine adsorption capacity compared to conventional methods.

## Key findings

- Microwave-assisted AC achieved a maximum adsorption capacity of 74 ± 6 mg g−1 for venlafaxine.
- Adsorption followed a pseudo-second-order kinetic model and reached equilibrium within 2 hours.
- Microwave-assisted AC outperformed conventionally produced AC in venlafaxine removal efficiency.

## Abstract

Background/Objectives: 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. Methods: 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 (SBET), 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. Results: The obtained AC exhibited high porosity, with the SBET 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. Conclusions: 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.