Ferrate(VI)/percarbonate for the oxidation of micropollutants: Interactive activation and release of low-concentration hydrogen peroxide for efficient electron utilization
Zhongjuan Wang, Xi Yang, Qi Du, Tong Liu, Xin Dai, Ye Du, Heng Zhang, Peng Zhou, Zhaokun Xiong, Bo Lai
Abstract
A novel "ferrate/percarbonate (Fe(VI)/SPC) co-oxidation process" was used to treat ciprofloxacin (CIP) and various micropollutants (MPs), which owned better performance than mixture of Fe(VI), Na 2 CO 3 and H 2 O 2 . The mechanism investigation found that the low-concentration H 2 O 2 (1–2 µM) released by SPC can promote the high-valent iron intermediates (Fe(IV)/Fe(V)) of Fe(VI) to the MP oxidation , and Fe(VI) products can also activate SPC to produce hydroxyl radical (·OH). The interactive activation of Fe(VI) and SPC was realized, which retained the high selectivity of Fe(VI) to electron-rich pollutants, and also made up the oxidation of electron-deficient pollutants through •OH, improving the degradation effect of various MPs by 20–30%, and the rate constant was increased by 1 to 3 times. Moreover, non-purgeable organic carbon (NPOC) determination confirmed that •OH participation reduced the NPOC value of CIP from 5.43 mg/L to 4.37 mg/L. The transformation pathway of CIP showed that Fe(VI)/SPC resulted in more hydroxylation intermediates of CIP than Fe(VI) alone. Acute toxicity assays found that the photoinhibition rate of CIP treated with Fe(VI) alone was 14.5%, while the sample treated with Fe(VI)/SPC showed no significant photoinhibition effect, which proved that the new process had good detoxification properties for CIP.