Efficient degradation of m-cresol by MnO-doped red mud catalyst activating peroxymonosulfate process: Performance and mechanism

M-cresol, one of phenolics, is highly toxic, refractory, and threatens human health and ecological safety. The study on the efficient m-cresol degradation technologies is crucial and helpful to restrain its discharge into water body. A composite of MnO-doped red mud (RM) to activate peroxymonosulfate (PMS) for the m-cresol degradation was fabricated and employed, favorable to the recycling and utilization of RM. Considering the catalytic activity and cost, 0.1M/RM@G exhibited an excellent degradation capacity attributing to strong Fe₃O₄ and MnO synergy and was considered as the best catalyst among the investigative catalysts. 100% of m-cresol and 71.4% of COD could be degraded within 90min under 2g/L catalyst, 10mM of PMS, 3-8 of initial pH and 50mg/L m-cresol in the 0.1M/RM@G/PMS system. The reaction rate constant (0.045min⁻¹) of 0.1M/RM@G was much larger than RM@G (0.012min⁻¹), ARM (0.0048min⁻¹) and WRM (0.0028min⁻¹). Main Mn and Fe active components and abundant mesoporous structures on the catalyst surface could efficiently drove electron transfers, and further accelerated the redox cycles of Mn(III)－Mn(II) and Fe(III)－Fe(II) for activating PMS. ¹O₂ played a crucial role in degrading m-cresol. Based on the experiment data, the generation mechanism of radicals and the possible pathways of m-cresol degradation were proposed in the 0.1M/RM@G/PMS system. This finding provides a new way for the synthesis of the efficient catalyst with RM and optimal operating strategies for the treatment of m-cresol wastewater.