Light-emitting diodes as an emerging UV source for UV/chlorine oxidation: Carbamazepine degradation and toxicity changes

Carbamazepine (CBZ) is a ubiquitous micropollutant in wastewater and reclaimed water. In this study, we evaluated CBZ degradation by light-emitting diode (LED)-driven UV/chlorine oxidation. Under LED irradiation of 280 nm (LED280) and 310 nm (LED310), UV/chlorine could efficiently degrade CBZ. Compared with LED UV/H2O2 treatment, LED UV/chlorine oxidation achieved a CBZ degradation rate that was one order of magnitude higher. The CBZ degradation followed pseudo-first-order kinetics, and the rate constants (k(obs,CBZ)) for LED280 UV/chlorine and LED310 UV/chlorine increased from 0.072 to 0.91 min(-1) and 0.044 to 0.65 min-1, respectively, when chlorine dosage increased from 0.07 to 0.14 mM. Under neutral conditions, the generated center dot OH and center dot Cl accounted for over 80% of the CBZ degraded by LED UV/chlorine. The maximum k(obs,CBZ) for LED UV/chlorine was observed at pH 8.5; k(obs,CBZ) decreased when solution pH increased to 9.5 or decreased to 5.5. This is because the main UV-absorbing chlorine species in the LED280 and LED310 systems is OCl-, which is different from those in low-pressure mercury lamp/chlorine systems. The acute toxicity for CBZ solution treated by LED UV/chlorine increased at lower fluence (<752 mJ/cm(2)) and decreased at higher fluence (>1233 mJ/cm(2)). However, the cytotoxicity to Chinese hamster ovary cells and adsorbable organic halide content of CBZ solution both increased after chlorination and LED UV/chlorine. The lowest electrical cost for the degradation of CBZ by LED UV/chlorine occurred under neutral conditions with a chlorine dosage of 0.4-0.7 mM (28.4-49.7 mg/L). (C) 2016 Elsevier B.V. All rights reserved.