Synergy of morphology and phosphorization for enhanced peroxymonosulfate activation over magnetic Fe3O4 catalysts†

Peroxymonosulfate (PMS) activation is a powerful method for eliminating tetracycline (TC) from water. Herein, the morphology and phosphorization were investigated for efficient PMS activation toward TC degradation over magnetic Fe₃O₄ catalysts. For three kinds of Fe₃O₄ catalyst with different morphologies, phosphorization dramatically enhanced the catalytic performance for TC degradation. A unique morphological effect was also observed for the TC degradation process. By regulation of morphology and phosphorization, the P-RC-Fe₃O₄/PMS system achieved the highest TC degradation efficiency among evaluated catalyst systems. Due to phosphorization, electron transfer occurred from Fe to P, generating a charge imbalance between Fe^δ+ and P^δ−, which reacted with PMS to produce rich active species such as ˙OH, SO₄˙⁻, O₂˙⁻ and ¹O₂ for TC degradation. These active species were confirmed by using quenching experiments with different scavengers and ESR measurements. These results revealed that the nonradical (¹O₂) pathway was dominant in the P-RC-Fe₃O₄/PMS system for TC degradation, but simultaneously the radical (˙OH, SO₄˙⁻ and O₂˙⁻) pathway made a certain contribution. Cyclic experiments demonstrated not only the excellent stability of the P-RC-Fe₃O₄/PMS system for TC degradation but also facile magnetic separation between the catalyst and the reaction system. This work provides an efficient strategy for constructing novel catalytic platforms by regulation of morphology and phosphorization to activate PMS for eliminating TC from water.