Construction of CoTiO3/TiO2/Ti composite catalytic membrane for degradation of tetracycline via peroxymonosulfate activation: Reactive oxygen species and electron transfer pathways

Abstract

The advanced oxidation processes based on peroxymonosulfate (PMS) has shown great promise for the removal of emerging contaminants in water reuse applications. Constructing cobalt-based composite nanomaterials is an effective strategy to achieve electron transfer and reduce the leaching of cobalt ions. Here, a CoTiO3/TiO2/Ti (CTT) catalytic membrane was fabricated using TiO2 nanotubes as both template and reactant, and then was applied to activate PMS for tetracycline (TC) degradation in a continuous flow-through reactor. The CTT/PMS system showed a remarkable TC degradation efficiency of 96.99%, exhibiting anti-interference performance towards Cl−, HCO3– and humic acid in water (>90.00% degradation efficiency). It has been proved that OH, SO4−, and 1O2 existed in the CTT/PMS system, and the CTT membrane served as a medium for mediating the electron transfer from TC to PMS. Density functional theory calculations indicated that the construction of a composite structure of CoTiO3 and TiO2 successfully enhanced the activation of PMS by the electron transfer from Ti atoms of TiO2 to Co sites. We proposed three potential degradation pathways for TC, followed by toxicity analysis of the intermediate products. After being exposed to an initial TC concentration of 20 mg/L and a membrane flux of 600 LMH for 30 hours, the CTT catalytic membrane exhibited a TC degradation rate exceeding 92.23% and mineralization rate surpassing 64.43%. This work supplied a new approach for fabricating cobalt-based catalytic membrane for PMS activation, with potential applications in water reuse.