Innovative Hollow Fiber Membranes Decorated with Cobalt-Doped Mn3o4: Sustainable Solution for Effective Tetracycline Removal from Wastewater

Abstract

In this study, we developed an innovative oxygen-based membrane reactor decorated with cobalt-doped Mn₃O₄ (cobalt-doped O₂-MMnfR) to enable efficient TC oxidative degradation. Comprehensive physicochemical characterization confirmed uniform cobalt doping and structural modifications in Mn₃O₄. Under optimal conditions (pH7 and 0.06MPa oxygen pressure), the cobalt-doped O₂-MMnfR achieved a TC removal efficiency of 92.9% (at a TC concentration of 15mg/L), following pseudo-first-order kinetics (kobs = 0.1962 h⁻¹), and markedly outperformed the undoped O₂-MMnfR. In multi-cycle stability tests, the Mn leaching rate of the cobalt-doped O₂-MMnfR was one-sixth of the undoped system. Electron paramagnetic resonance (EPR) analysis and radical scavenging experiments confirmed that superoxide radicals played a crucial role in TC degradation. Mass spectrometry analysis indicated that cobalt doping altered the TC degradation pathways, leading to less toxic transformation products and an increased mineralization rate (25.3%). Building on these findings and supported by extensive characterization methods, we propose the TC degradation mechanism in this system: cobalt substitution of unstable trivalent manganese mitigates Jahn-Teller effects and stabilizes the higher oxidation states of manganese, thus enhancing the stability and rate of Mn₃O₄ on hollow fibers for TC degradation. This study offers a highly effective and sustainable approach to antibiotic removal from wastewater.

Keywords: Hollow fiber membrane, Manganese oxides, Oxidative degradation, Tetracycline