Degradation of contaminants of emerging concern in UV/Sodium percarbonate Process: Kinetic understanding of carbonate radical and energy consumption evaluation

UV/sodium percarbonate (UV/SPC) advanced oxidation process is an efficient and green technology to remove contaminants of emerging concern (CECs), with the simultaneous formation of hydroxyl radical ( • OH) and carbonate radical (CO 3 •− ). This study investigated the degradation of eight CECs in UV/SPC process, including phenol, atrazine, bisphenol A, ibuprofen, sulfadiazine, acetaminophen, carbamazepine, and diuron. A model was established to simulate the experimental results, which shows that both • OH and CO 3 •− played crucial roles in UV/SPC process, and the steady-state concentrations of CO 3 •− were much higher than that of • OH. The higher concentration compensates for the low reactivity of CO 3 •− with CECs and the loss of • OH depleting by CO 3 •− . Also, the Hammett constants decreased linearly with increasing natural logarithms of rate constants, indicating the selectivity of CO 3 •− with electron-donating substituents. In real water, CEC degradation was significantly inhibited due to the competition for light absorption from background compounds and scavenging of free radicals, especially CO 3 •− , by water matrix. Further, demethylation, decarbonylation, hydroxylation, amino oxidation, and quinonization were proposed as the main reactions for CEC degradation in UV/SPC process. The minimum electrical energy per order (EE/O) was calculated as 0.152 kWh m −3 , with SPC dose of 0.138 mM and UV intensity of 2.02 × 10 -7 Einstein L −1 s −1 .