Emerging contaminants, especially pharmaceuticals, have become a growing concern due to their long-term ecological impacts. These compounds are not effectively removed by conventional wastewater treatment technologies and persist in the environment. The European Union introduced a directive requiring the implementation of quaternary treatment in large-scale wastewater treatment plants capable of removing at least 80% of harmful organic micropollutants, namely pharmaceutical compounds [1-3].
In this study, biochar derived from agro-industrial basil (Ocimum basilicum) residues were used as a low-cost and sustainable adsorbent for removing antidepressants (trazodone and fluoxetine) from water. Particle size was found to significantly influence the biochar performance in different ways, with finer fractions (<0.5 mm) achieving over 70% for trazodone, and the largest size (>2 mm) reaching over 90% for fluoxetine.

Additionally, the biochar was investigated as a catalyst in an electro-Fenton system for the degradation of antidepressants, showing a strong removal efficiency. Notably, pharmaceutical-loaded biochar was also successfully treated using the electro-Fenton process, enabling degradation of the adsorbed contaminants and minimising secondary environmental risks.
The results confirm the dual functionality of basil-derived biochar as an effective adsorbent and catalyst. This approach supports circular economic practice by valorising agricultural waste.

References
[1] N. Morin-Crini et al. (2022). Environ. Chem. Lett., 20, 1333-1375.
[2] European Parliament and Council. Directive (EU) 2024/3019 of the European Parliament and of the council of 27 November 2024 concerning urban wastewater treatment (recast)

Ana Rita Alves, Cristina Soares, Sónia Figueiredo, Cristina Delerue-Matos, Antón Puga ; REQUIMTE/LAQV, Instituto Superior de Engenharia do Porto, Instituto Politécnico do Porto, Porto, Portugal