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[Display omitted] • A heterogeneous catalyst was prepared by wrapping P[BVIM]CoCl 3 around the surface of Fe 3 O 4 @SiO 2. • Coupling of the catalyst with PMS as an oxidant for desulfurization. • A sulfur removal rate of over 98% at room temperature was obtained under optimal experimental conditions. • Identification of a two-step oxidation mechanism of DBT in a tandem reaction. • Obtaining some useful kinetic data for the two oxidation steps, including activation energies and reaction rates. A heterogeneous catalyst was prepared by wrapping a poly 3-butyl vinylimidazole cobalt chloride ionic liquid (P[BVIM]CoCl 3) around the surface of Fe 3 O 4 @SiO 2 magnetic nanoballs. This catalyst was coupled with the oxidant peroxymonosulfate (PMS) for extraction catalytic oxidation desulfurization (ECODS). The prepared desulfurization catalyst had superparamagnetic properties, with a saturation magnetization of 32.5 emu/g. Moreover, this caalyst was multi-porous material, ans it had a specific surface area and pore volume of 8.14 m2/g and 0.018 cc/g, respectively. The average pore diameter of catalyst was 3.9 nm. The optimal experimental conditions were as follows: the initial sulfur content of the oil was 500 ppm, the catalyst dosage was 30 mg, PMS (20 wt%) dosage was 0.6 g, the ACN dosage was 2 g, and the oil sample size was 6 g. After 20 min, a sulfur removal rate of over 98 % was achieved at 20 °C. Furthermore, the unpurified catalyst still maintained high desulfurization activity after being used for 5 times, demonstrating good stability. The desulfurization mechanism was divided into two steps: first, DBT was oxidized to DBTO by SO 4 − free radicals, and second, the DBTO was further oxidized to DBTO 2 by OH free radicals in a tandem reaction. The reaction rates for the two steps at 20 °C were 0.0144 sec−1 and 0.00115 sec−1, respectively. The activation energies associated with these steps were 65.65 kJ/mol and 105.22 kJ/mol, respectively. The quencher t-butanol had no effect on the first step but significantly inhibited the second step, meaning that DBTO became the main oxidation product. One potential application of this study is the utilization of t-butanol to regulate the oxygen content in organic sulfide oxidation products. [ABSTRACT FROM AUTHOR]

• The novel Fe 2 CoTi 3 O 10 -MXene composite was successfully synthesized for PMS activation. • Fe 2 CoTi 3 O 10 -MXene composite exhibited excellent catalytic performance for the 2,4-D removal. • A ternary synergistic degradation was investigated based on Fe, Co and Ti species. • The possible activation mechanism and degradation pathway of 2,4-D were proposed. In this study, a novel Fe 2 CoTi 3 O 10 -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 (HCO 3 − and Cl−) and humic acid (HA) were systematically evaluated. The catalyst with the Fe 2 CoTi 3 O 10 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 (SO 4 −) and hydroxyl radicals (OH) was confirmed based upon electron paramagnetic resonance spectroscopy and radical scavenger tests, while SO 4 − 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. [ABSTRACT FROM AUTHOR]