Accelerated Photocatalytic Degradation of Sulfamethoxazole and Cefixime: A Comprehensive Study of Biotoxicity, Degradation Kinetics and Pathway

This study aimed to accelerate photocatalytic treatment of sulfamethoxazole (SMX) and cefixime (CFM) and alleviate the toxicity of photocatalysis effluents to improve further biodegradability. An efficient and fast reactive photocatalyst (Fe₂O₃/ZnO@VC) was synthesized, characterized and applied for photocatalytic removal of the targeted compounds. Results further confirmed the complete removal of SMX (1 mgL^-1) within 30-min photocatalytic treatment. Acidic condition favored SMX removal due to the formation of negative ions, which were attracted by the surface of the catalyst comprising positive charge in pH values below the point of zero charge. The ideal degradation environment for CFM (1 mgL^-1) was at neutral pH, and 97.2±0.1% of CFM was degraded over 60-min. A quenching test revealed that superoxide radial (^•O₂⁻) and e⁻ played a major role in the photocatalytic degradation of SMX, while hydroxyl radical (^•OH) showed an identical effect during photocatalytic treatment of CFM. The degradation efficiency of SMX was marginally reduced in synthetic wastewater (SWW) and CFM in tap water (TW) due to the quenching effects of phosphates and carbonates anions in SWW and chloride ions in TW, respectively. As a result of the excellent mineralization properties of the photocatalyst, the photocatalysis effluents were highly detoxified, reaching 93.5±11.8% and 87.0±5.1% for SMX and CFM, respectively.