Reaction pathways and kinetics of butylated hydroxyanisole with UV, ozonation, and UV/O3 processes

The chemical degradation of the endocrine disrupting chemical, butylated hydroxyanisole (BHA), was investigated by different treatment processes including ultraviolet (UV) irradiation, ozonation (O3), and UV/O3. O demethylation, dimerization, and oxidation have been found to be the main degradation mechanisms. A systematic decay pathway was proposed based on ten identified intermediates in the studied processes, including a unique pathway leading to the formation of precipitates in the ozonation process. An unconventional minimum-type variation of BHA decay rate constants from acidic to caustic range has been found for both ozonation and UV/O3 processes. The precipitates formed during ozonation can be removed during the process to optimize the treatment, while the UV/O3 process can offer a relatively fast and clean process to degrade BHA and its associated intermediates.