Application of Activated Persulfate via Red Mud-Based Catalysts for Dye Removal in Wastewater: Kinetics and Mechanism

Abstract

To alleviate the pollution problem of dye wastewater and the problem of resource utilization of red mud, a novel biochar-loaded red mud catalyst (RM_bc) was synthesized using red mud and pomelo peel biochar by a low-cost coprecipitation method. Due to the high specific surface area and abundant oxygen-containing functional groups of RM_bc, the synthesis process promoted the conversion of Fe₂O₃ to Fe₃O₄ and Fe⁰, which achieved higher catalytic activity. Moreover, the RM_bc system showed better removal effects than raw red mud for methyl orange (MO) removal. Of the MO, 92.50% was removed within 60 min, and scanning electron microscope, X-ray powder diffractometer, fourier transform infrared spectrum, and X-ray photoelectron spectroscopy were applied to characterize the catalyst. The mechanism studies demonstrated that sodium persulfate was mainly activated by Fe⁰ and Fe(II) to produce reactive oxygen species O₂^•− and ¹O₂. The intermediate products of MO were identified, and a probable degradation pathway was proposed. Finally, the performance of RM_bc for mixed dyes and coexisting pollutants was evaluated. The RM_bc was low-cost and high catalytic activities, both showing good application prospects in experimental studies and further applications.