More effective peroxymonosulfate activation for tetracycline removal by Co–FeN/@BC assisted by micro-electrolysis: performance and mechanism

Abstract

Preparation of N-doped bimetallic (Co/Fe) MOFs and their loading on biochar (Co–FeN/@BC) was reported. The micro-electrolytic co-catalyst activated PMS for the efficient degradation of tetracycline (TC). The mechanism was comprehensively investigated by EPR analysis, free radical quenching experiments and electrochemical measurements. The results showed that micro-electrolysis prompted the catalyst to synergize with peroxymonosulfate (PMS) activation to degrade TC, and the pathways of TC degradation included free radical, non-free radical and high-valent metal pathways. Microelectrolysis accelerates electron transfer, Fe/Co activates PMS to become a high-valent metal after electron transfer, and PMS is activated to produce ¹O₂ and SO₄·⁻. The main active substances for TC degradation by PMS activation were ¹O₂, SO₄·⁻, Fe^IVO²⁺ and Co^IVO²⁺. The active substances attacked the TC molecules to form intermediates, which were eventually mineralized into CO₂ and H₂O.