Preparation of 3D Fe, Mn-MOF and Its Performance for Tetracycline Removal by Adsorption and Activating Persulfate

Persulfate-based advanced oxidation processes (PS-AOPs) hold significant promise for antibiotic remediation in wastewater, wherein the adsorption capacity of catalyst plays a pivotal role in facilitating subsequent catalytic degradation. In this study, a three-dimensional (3D) Fe/Mn bimetallic framework (Fe, Mn-MOF) was synthesized via a facile room-temperature stirring method using Fe/Mn salt and 1, 4-phthalic acid (1, 4-BDC) as precursors. The as-prepared material was employed for simultaneous adsorption and PS activation toward tetracycline (TC) removal from aqueous solutions. Optimal adsorption and catalytic performance were achieved at an Fe/Mn molar ratio of 1∶0.1 (designated Fe, Mn-MOF_0.1), which exhibited an abundant void structure with a specific surface area of 202.01 m²·g^-1 and numerous accessible active sites. The maximum adsorption capacity of 3D Fe, Mn_0.1-MOF for TC reached 293 mg·g^-1 at 298 K with an initial TC concentration of 45 mg·L^-1. In the integrated Fe, Mn-MOF_0.1/PS system, 80% removal efficiency was achieved within 45 min. The material also demonstrated efficacy in treating naturally contaminated water matrices. Moreover, the Fe, Mn-MOF_0.1/PS system retained ≥64% TC removal efficiency after three consecutive cycles, indicating satisfactory operational stability. Adsorption kinetics and isotherm analyses reveal that TC uptake followed a pseudo-first-order kinetic model and corresponded to a spontaneous, endothermic process governed by monolayer surface adsorption. Quenching experiments elucidated the dominant role of radical species, including sulfate radicals (SO₄^·-), hydroxyl radicals (·OH), singlet oxygen (¹O₂), and superoxide anions (O₂^·-), in TC degradation. This work provides mechanistic insights into the coupled adsorption-catalytic function of MOF-based materials in PS systems, establishing a theoretical foundation for their application in antibiotic-contaminated water remediation.