Photodegradation of Butyl 4-Hydroxybenzoate in the Presence of Peroxides and Mediated by Dissolved Organic Matter

Dissolved organic matter can be a photosensitizer in photodegradation processes. It can produce hydroxyl radicals, singlet oxygen, and triplet-state dissolved organic matter, which promote pollutant degradation. This study investigated to what extent the triplet substances and other active substances can, under irradiation, stimulate peroxides to produce more reactive species (RS), which accelerate the degradation of pollutants. The photodegradation of butyl 4-hydroxybenzoate (BP) was studied in the presence of dissolved organic matter (DOM) and persulfate (PDS), peroxymonosulfate (PMS), or hydrogen peroxide (H2O2). The peroxides promoted the photodegradation in the order PDS > H2O2 > PMS. The degradation rates were peroxide > DOM-mediated peroxide > DOM. The interaction of DOM with peroxide produced more RS to promote the degradation. Chlorella vulgaris were used to evaluate the toxicity of the treated effluent and the ecological risk was found to be low. The findings explain the mechanism of the photodegradation of BP in the presence of dissolved organics and peroxides.