Heterogeneous activation of persulfate by metal and non-metal catalyst for the degradation of sulfamethoxazole: A review

Sulfamethoxazole (SMX) is a high-priority pharmaceutical that is widely used as an antibiotic and fungicide. It can be partially metabolized by animal and human bodies, hence a large portion is excreted through urine and feces, eventually contaminating surface water and groundwater. Owing to its high water solubility, high chemical stability, strong bacterial resistance, potential carcinogenicity, apparent ecological toxicity, and high resistance to natural attenuation processes. SMX posed a crucial threat to water safety and environmental sustainability. Therefore, persulfates (peroxymonosulfate (PMS) and peroxydisulfate (PDS)) activated with heterogeneous metal and non-metal catalysts are widely used to degrade SMX due to the generation of highly reactive oxygen species (ROS). Hence, this review aims to summarize the development of several heterogeneous metals and non-metal catalysts used for persulfate activation for SMX degradation. Heterogeneous persulfate activators were classified into metals (single-metals, bi-metals, mixed metals, and layered double hydroxides), metal-free materials, and metal-non-metal (includes metal-supported and/or metal-doped) materials. The SMX degradation mechanisms by different heterogeneous persulfate activation systems were summarized. It was found that the type, nature, and composition of different heterogeneous metal and non-metal catalysts influenced the SMX degradation mechanism. The degradation mechanism affects the type of degradation products found in the persulfate-activated process. However, the reactivity of the heterogeneous catalysts can be influenced by changes in pH, as well as the co-existence of inorganic ions and organic matter. The toxicity of SMX degradation products was considered. Finally, the conclusion and future perspectives were proposed.