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

[Display omitted] •A kinetic model was established to predict contaminants removal.•Carbonate radical played crucial roles with high selectivity.•Contribution of carbonate radical was significantly inhibited in real water.•Energy consumption was calculated based on the model.•The degradation pathway of acetaminophen was determined. 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 (CO3•−). 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 CO3•− played crucial roles in UV/SPC process, and the steady-state concentrations of CO3•− were much higher than that of •OH. The higher concentration compensates for the low reactivity of CO3•− with CECs and the loss of •OH depleting by CO3•−. Also, the Hammett constants decreased linearly with increasing natural logarithms of rate constants, indicating the selectivity of CO3•− 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 CO3•−, 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.