Synergistically boosting sulfamerazine degradation via activation of peroxydisulfate by photocatalysis of Bi2O3-TiO2/PAC under visible light irradiation

Photocatalysis-activated sulfate-radical advanced oxidation process (SR-AOP) is an effective approach to remove organic micropollutants from water. Here, we tested a photocatalysis-activated SR-AOP in which peroxydisulfate (PDS) was activated by composites of Bi2O3-TiO2 photocatalyst supported onto commercial powdered activated carbon (Bi2O3-TiO2/PAC) under visible light irradiation. This Vis-Cata-PDS treatment exhibited outstanding degradation performance (97.96% removal) towards sulfamerazine (SMZ) following optimized reaction conditions of 0.1 g/L Bi2O3-TiO2/PAC and 0.1 g/L PDS at pH of 7. Synergistic effects were observed between the visible-light photocatalytic activation of PDS via direct electron transfer and nonradical PDS activation over pristine PAC within Bi2O3-TiO2/PAC. Both active radicals (SO4 center dot-, h + , center dot O-2(-)) and nonradical singlet oxygen (O-1(2)) and the mediated electron transfer of pristine PAC within Bi2O3-TiO2/PAC were contributed to SMZ degradation. Based on intermediates identified by Liquid Chromatograph-Mass Spectrometer (LC-MS) combined with density functional theory (DFT) calculations, three degradation pathways were proposed and that were mostly attributed to SO2 extrusion/Smiles-type rearrangement and S-N bond cleavage, and toxicity of intermediates were effectively alleviated. An inhibitory effect on SMZ degradation was observed for presence of HCO3, whereas presence of SO42- was less inhibitory and Cl- had no effect. The Bi2O3-TiO2/PAC composite displayed excellent reusability and stability, and it was effective towards a number of tested micropollutants (sulfadiazine, sulfamethoxazole, ciprofloxacin, bisphenol A and methyl orange) and in real water matrixes. This work offers deep insights into the nonradical oxidation mechanism and application of Vis-Cata-PDS over a Bi2O3-TiO2/PAC composite for removal of organic micropollutants.

Automated summary

The study investigated a photocatalysis-activated sulfate-radical advanced oxidation process, using Bi2O3-TiO2 photocatalyst supported on commercial powdered activated carbon for efficient removal of organic micropollutants from water. The treatment showed excellent degradation performance and synergistic effects between different activation mechanisms, contributing to the degradation of target pollutants. The composite material displayed high reusability and stability, making it a promising approach for water treatment.