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

To alleviate the pollution problem of dye wastewater and the problem of resource utilization of red mud, a novel biochar-loaded red mud catalyst (RMbc) 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 RMbc, the synthesis process promoted the conversion of Fe2O3 to Fe3O4 and Fe0, which achieved higher catalytic activity. Moreover, the RMbc 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 RMbc for mixed dyes and coexisting pollutants was evaluated. The RMbc was low-cost and high catalytic activities, both showing good application prospects in experimental studies and further applications.