Factors affecting ultraviolet irradiation/hydrogen peroxide (UV/H₂O₂) degradation of mixed N-nitrosamines in water

Disinfection by-products (DBPs) are a great challenge to our drinking water security. Particularly, nitrosamines (NAms), as emerging DBPs, are potently carcinogenic, mutagenic, and teratogenic, and have increasingly attained public attention. This study was to evaluate the performance of the NAms degradation by the ultraviolet (UV) irradiation (253.7nm) in the presence of hydrogen peroxide (H₂O₂). In the UV/H₂O₂ system, hydroxyl radicals (OH), a type of nonselective and powerful oxidant, was produced to attack the molecules of NAms. Factors affecting the treatment efficiency, including the H₂O₂ dosage, initial NAms concentration, UV irradiation intensity, initial solution pH, and inorganic anions present in water, were evaluated. All the NAms degradation exhibited a pseudo-first-order kinetics pattern. Within 60min, 0.1mg/L of any NAms could be almost decomposed except NDPhA that required 120min for complete removal, at 25μmol/L H₂O₂ and at initial pH 7. Results demonstrate that the UV/H₂O₂ treatment is a viable option to control NAms in water.