ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Developing a model for sulfadiazine degradation in water using UV alone, Cl alone, UV/Cl, and Cl/O₃: a case study of real water matrix

Asam Shad, Zulfiqar Ahmed Bhatti, Noor Samad Shah, Zahid Hussain, Sajid Hussain Shah, Maha A. Alwaili, Hassan A. Rudayni, Sally M. Khadrawy, and Ahmed A. Allam

Department of Environmental Sciences, COMSATS University Islamabad, Abbottabad Campus, Islamabad, Pakistan

E-mail: Asamshad@cuiatd.edu.pk

Received: 27 February 2025  Accepted: 31 October 2025

Abstract:

This study investigated the degradation of sulfadiazine (SDZ) in real water samples collected from Rawalpindi, Pakistan. The primary objective was to enhance our understanding of adequate water treatment in the study area. The study employed five methods to assess the degradation rates of SDZ: ultraviolet (UV) irradiation alone, chlorine (Cl) alone, ozonation (O₃) alone, the UV/Cl method, and the Cl/O₃ method. Specifically, a UV C (254 nm) lamp was used for UV irradiation, with an SDZ concentration of 5 mg/L and a chlorine dosage of 1.25 mg/L. Notably, with the UV/Cl and Cl/O₃ treatments, 100% degradation was observed in 7 min and 4 min, respectively. The study has further investigated the factors that influence the treatment efficiency of Cl/O₃. The study explored several contributing factors, including pH, scavenger effects, and the effect of real water. For the method studied, the acidic conditions exhibited the highest rate of SDZ breakdown, whereas higher pH showed the lowest rates. The study highlighted the crucial role of free radicals, such as hydroxyl radicals (^.OH) and hypochlorous acid (HOCl), as primary oxidizing agents. For the Cl/O₃ method, theoretical calculations were used for product identification. Theoretical calculation estimates based on Gaussian calculations indicated that the monochlorinated byproduct was the primary byproduct generated. To assess the toxicological evaluations, ECOSAR (ecological structure–activity relationship) software was used. All degradation products generated were found to be nontoxic, and the Cl/O₃ method is recommended for use as an efficient water treatment method.

Keywords: Wastewater; Oxidation; Treatment; Elimination; Toxicity; Identification

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-025-04485-8

Chemical Papers 80 (2) 1733–1744 (2026)