Catalytic ozonation performance and mechanism of Mn-CeOx@γ-Al2O3/O3 in the treatment of sulfate-containing hypersaline antibiotic wastewater

Abstract

Herein, we attempted to apply an alumina-based bimetallic (Mn-Ce) catalyst as an O3 activator and explored the feasibility of the treatment of hypersaline organic wastewater. Compared with independent O3 (35.00 ± 4.20%), mineralization of ciprofloxacin (CIP) under the Mn-CeOx@γ-Al2O3/O3 (MCAO) process was elevated to 76.04 ± 2.30%. The synergetic corporation among multivalence redox pairs of Mn (III)/Mn (IV), Ce (III)/Ce (IV) promoted the protonation of the surface hydroxyl group (S-OH2+), and subsequently the dominant reactive oxygen species in the MCAO process, OH and O2−, were generated rapidly. However, the mineralization of CIP decreased in MCAO/SO42− system due to the formation of SO4−, which reacted with CIP more slowly (8.4 × 108 M−1 s−1) than OH (4.1 × 109 M−1 s−1). In MCAO/SO42−/Cl− mixture saline conditions, mineralization of CIP was improved at low Cl− concentration (0.5 wt%) due to the generation of Cl, while inhibited with excessive Cl− (≥1.5 wt%) owing to the formation of residual chlorides (Cl2, Cl2− and ClO−). Meanwhile, the MCAO process possessed promising capability to remediate hypersaline wastewater containing dyes, phenol and pesticides, as well as actual salinity-rich wastewater. Based on the above, the present study would provide new insights into hypersaline organic wastewater treatment by the MCAO process.