Heterogeneous Fe2CoTi3O10-MXene composite catalysts: Synergistic effect of the ternary transition metals in the degradation of 2,4-dichlorophenoxyacetic acid based on peroxymonosulfate activation

Abstract

In this study, a novel Fe2CoTi3O10-MXene (FCT-M) composite was synthesized and employed as a heterogeneous catalyst for the oxidative degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) based on peroxymonosulfate (PMS) activation. The effects of catalyst dosage, PMS dosage, pH of the initial solution, 2,4-D concentration, and the co-existing inorganic ions (HCO3− and Cl−) and humic acid (HA) were systematically evaluated. The catalyst with the Fe2CoTi3O10 loading (FCT-M-2) of 6.72% demonstrated superior catalytic performance. The results showed that around 98% of 2,4-D degraded in 15 min on using 0.2 g/L FCT-M-2 composite, 0.2 g/L PMS, and 20 mg/L 2,4-D with an initial pH of 7. The co-existence of sulfate radicals (SO4−) and hydroxyl radicals (OH) was confirmed based upon electron paramagnetic resonance spectroscopy and radical scavenger tests, while SO4− was identified as the main reactive species in the FCT-M/PMS catalytic system. The superior performance of FCT-M based on PMS activation was achieved due to remarkable synergistic effect of the active sites of three transition metals (Fe, Co, and Ti) on the catalyst surface. According to the identified intermediates, a possible 2,4-D degradation pathway is proposed. Overall, this study widens the scope of employing heterogeneous catalysts towards PMS activation and sheds light on the degradation of organic pollutants in aqueous solutions.