Enhanced oxidation of carbamazepine by UV-LED/persulfate and UV-LED/H2O2 processes in the presence of trace copper ions

In this study, the degradation of carbamazepine (CBZ) was comparatively investigated by UV-LED/persulfate (PS) and UV-LED/H2O2 processes in the presence of trace Cu2+ at neutral pH. Results showed that the introduction of trace Cu2+ accelerated CBZ degradation and more favorable performance was achieved in UV-LED/PS process. As oxidants dosage raised from 0.2 to 1.0 mM, the pseudo-first-order rate constant (k(obs)) value of CBZ both linearly increased in UV-LED/PS/Cu2+ and UV-LED/H2O2/Cu2+ processes. The promotion effect of Cu2+ at low level was more significant than that at high level in both processes at neutral pH. With reducing solution pH from 7.2 to 3.1, the k(obs) value dramatically increased from 0.136 to 0.399 min(-1) in UV-LED/PS/Cu2+ process, while its value exhibited the imperceptible change in UV-LED/H2O2/Cu2+ process. (OH)-O-center dot functioned as the major contributor to CBZ degradation in two processes in pH range of 3.1-7.2. The addition of humic acid (HA), HCO3- and Cl- impeded CBZ degradation in UV-LED/H2O2/Cu2+ process. As for UV-LED/PS/Cu2+ process, the k(obs) value significantly increased in the presence of Cl-, while the introduction of HA and HCO3- restrained the removal. Total eleven degradation intermediates of CBZ were identified and a reasonable degradation pathway was proposed based on HPLC-MS/MS analysis and the calculation of Gaussian program. The acute toxicities of reacted solution enhanced in both processes within 15 min, especially in UV-LED/PS/Cu2+ process. In terms of electrical energy per order value, UV-LED/PS/Cu2+ process was found to be more cost-effective than UV-LED/H2O2/Cu2+ process. It was also noticed that UV-LED/PS process was more effective for CBZ removal in natural water in the presence of trace Cu2+.