Degradation of the Antibiotic Sulfamethoxazole by Ozonation: A Comprehensive Review

Abstract

Sulfamethoxazole (SMX) is an antibiotic widely used for the treatment of several diseases, especially respiratory and urinary. Due to its widespread use, its presence in the environment has been on the rise. This study discusses the degradation of the antibiotic SMX through the ozonation process. SMX is preferentially degraded by the direct action of O₃ on the molecule, starting by breaking the double bonds in the aromatic ring. Through ozonation it is possible to obtain complete SMX degradation within 10 min, but the mineralization of the solution is not achieved, reaching total organic carbon removal efficiencies of 5%–60%, depending on the reaction time. Factors such as the presence of organic matter (OM) and the pH of the solution interfere with the degradation of SMX. The OM acts as a radical scavenger, decreasing the efficiency of degradation, while the pH interferes with the decomposition of O₃ into radicals and the dissolution of the oxidant in the medium, in addition to influencing the state of ionization of the SMX making it more or less prone to reactions. In general, most other remediation processes are carried out on a laboratory scale. To increase the level of these processes to a full scale, more pilot-scale studies are needed. In addition, it is necessary to focus on the practice of reusing materials, avoiding the generation of secondary pollution, and increasing the useful life of the material. The review also discusses the reaction mechanisms, intermediate compounds formed, mineralization of the solution, and factors that influence the process, which can help in making decisions for future studies to be carried out in the area. Prospects in the research area revolve around using metal–organic frameworks as molecular imprinting technology to modify heterogeneous catalysts, integration of external energy, bimetallic systems, and evaluation of deactivation mechanisms.