The destruction of trichloroethylene by zinc dioxide using a modified Fenton reaction: Performance and a preliminary mechanism

The use of zinc dioxide (ZnO 2 ) powder as a source of H 2 O 2 in a modified Fenton reaction catalyzed with Fe(II) to destroy trichloroethylene (TCE) was investigated. The experimental results showed that the optimum molar ratio of ZnO 2 /Fe(II)/TCE in ZnO 2 /Fe(II)/TCE system was 20/20/1 with a TCE removal of up to 99.6%. TCE degradation was significantly inhibited by the low reaction temperature and influenced by the initial solution pH, in which ZnO 2 /Fe(II)/TCE system was suited for high temperature and low pH settings. Both Cl − and HCO 3 − anions showed a detrimental effect on TCE elimination with HCO 3 − being more significant. The addition of a high concentration (100 mg/L) of HA in solution inhabited TCE degradation performance, while the effect was negligible at low concentrations (1–10 mg/L). The tests with hydroxyl radical (HO·) scavengers elucidated that TCE was mainly degraded by HO· radicals in ZnO 2 /Fe(II)/TCE system. TCE degradation and the dechlorination proceeded simultaneously, but the final release of Cl − was less than the degraded TCE, indicating the occurrence of chlorinated intermediates in the reaction process. Graphical abstract