Sunlight-driven photocatalytic process for pharmaceutical removal in complex water matrices: Implications for treatment under Global South conditions

The development of effective treatment technologies for the removal of pharmaceutically active compounds (PhACs) under realistic environmental conditions remains a major challenge in water engineering. In this study, a sunlight-driven photocatalytic process using bismuth oxybromide (BiOBr) was assessed for the degradation of carbamazepine (CBZ) and atenolol (ATL) in pure water, tap water, and secondary effluent under natural solar irradiation in Tunisia (average irradiance: 765 W m −2 ). Complete removal of CBZ and ATL was achieved in pure water within 90 and 60 min, respectively, with apparent rate constants of 0.0406 and 0.0669 min −1 . Matrix-dependent effects were observed, with reduced performance in tap water (CBZ: 85%; ATL: 95%) and enhanced degradation in secondary effluent (CBZ: 94%; ATL: 100%). This was attributed to the dual role of dissolved organic matter, which may either inhibit degradation or enhance it through photosensitization. Mineralization yields reached 44.11% for CBZ and 83.19% for ATL in pure water. Photo-holes were the dominant reactive species in the catalytic process, although radical-mediated pathways also contributed to degradation. Catalyst deactivation was observed after the first reaction cycle due to surface reduction and defect accumulation; however, the activity of BiOBr was successfully restored through mild thermal regeneration. Transformation product analysis indicated divergent pathways, with CBZ leading to persistent intermediates, such as acridine, while ATL followed more favorable oxidative routes. Sunlight-driven photocatalytic processes can effectively remove pharmaceuticals under realistic conditions, although their performance is strongly influenced by water matrix composition, catalyst stability, and the formation of transformation products.