Fluoride ions enhanced cobalt ferrite for peroxymonosulfate activation with efficient performance and active oxygen yield regulation.

The activation of peroxymonosulfate (PMS) by cobalt-based catalysts for the degradation of organic pollutants has been widely studied, while the role of coexisting anions has received little attention. In this study, the performance of atrazine (ATZ) degradation by the addition of fluoride ions (F) in the activation of PMS by cobalt ferrite (CoFeO) was investigated. The addition of F to the CoFeO/PMS system increased ATZ degradation effect from 82 % to 98 % within 10 min, and the rate increased from 0.172 min to 0.431 min. At the same time, F could also enhance the degradation of organic substances such as sulfamethoxazole (SMX), ibuprofen, and iohexol. Based on generating SO, HO and Co(IV)=O in the CoFeO/PMS system, F enhanced the generation of SO. When coexisting with common substances in water (i.e., inorganic anions, humic acid, hemoglobin and dextran), F can still increase the reaction rate and reduce their negative impacts. Ion dissolution and control tests verified Co as a valid active site. A potential reaction mechanism was proposed for the complex Co(II)F formation with Co by F, which enhanced the activation of the PMS by CoFeO and regulated the active species. Finally, it was verified that the low concentration of F could enhance ATZ degradation within two hours and the remaining F could be effectively removed by flocculation and precipitation. This research takes utilization of F in wastewater to promote advanced oxidation processes based on PMS, which provides a new direction for the treatment of actual water pollution.