From Thyme to Treatment: Green‑Engineered ZnO Photocatalyst for Light‑Driven Removal of Sulpiride

Benzamide derivative sulpiride (SUL) is commonly used to treat schizophrenia, dysthymia, depressive disorder, peptic ulcers, and vertigo. The occurrence of this antipsychotic in the environment is problematic, since SUL can disrupt the usual dopamine–serotonin feedback loops in non-patients. Therefore, finding green and sustainable water remediation technologies is of vital importance.

Heterogeneous photocatalysis, an advanced oxidation process, based mainly on the formation of highly reactive hydroxyl radicals, offers an eco-friendly approach to eliminating antipsychotics from the aquatic environment. This process can become even more green with the assistance of diverse plant extracts during the photocatalyst synthesis. Various phytochemicals, naturally found in different parts of plants, are used as reducing, capping and/or stabilizing agents, consequently substituting toxic chemicals.

Thus, for this research, Thymus serpyllum (Breckland thyme) extract (TSE) was used to obtain ZnO nanoparticles (ZnO/TSE). Its photocatalytic activity was evaluated in the removal of SUL from the aqueous medium after studying the influence of catalyst loading, initial SUL concentration, and irradiation type on SUL removal efficiency. Ultrafast liquid chromatograph with a fluorescence detector was used to quantify SUL at each stage of the photocatalytic process.

After the 75-min-treatment and achieving 30% SUL removal, it was concluded that the optimal photodegradation conditions were 0.5 mg/cm³ ZnO/TSE, 0.05 mmol/dm³ SUL, and simulated solar irradiation. Such preliminary results leave the space for further improvements of the photocatalytic process.

Acknowledgements: The authors acknowledge the financial support of the Ministry of Science, Technological Development and Innovation of the Republic of Serbia (Grant Numbers: ‪451-03-33/2026-03/200125 & 451-03-34/2026-03/200125).