Remediations of Thiophenes from Liquid Fuel via Ultrasound-assisted Oxidative Desulfurization by Magnetic MgFe₂O₄@CQD Nanocatalyst

Abstract

Magnetic MgFe₂O₄@CQD was developed as a novel nanocatalyst for ultrasound-assisted oxidative desulfurization (UAOD) of thiophenes from fuel. The nanocatalyst was synthesized using an oxidative co-precipitation method and characterized. The XRD and XPS confirmed the formation of carbon quantum dots and MgFe2O4 @CQD and its paramagnetic character was confirmed by VSM technique. The UAOD tests were designed by Box–Behnken type of response surface methodology (RSM) and the process modelled and optimized. The optimum conditions were predicted to be 50 ppm, 0.62, 0.5 g.L-1 and 24 min, respectively for sulfur concentration, volumetric ratio of H2O2/fuel, Catalyst dosage/fuel, and sonication time led to 67% removal rate. The order of independent factor’s importance by Pareto analysis was as follows: sonication time > nanocatalyst dosage/fuel > sulfur concentration > volumetric ratio of oxidant/fuel. The kinetic of the DBT oxidation over MgFe2O4 @CQD followed a pseudo-first order reaction rate with an activation energy of 33.94 kJ. Mol-1, revealing easy oxidation of DBT. The results of thermodynamic studies exhibited a ΔG~82 kJ.mol-1 and ΔS~ -0.17 kJ.mol-1.K-1 at 298 K, indicating a non–spontaneous reaction. The results demonstrate that magnetic MgFe₂O₄@CQD is a cheap, green, highly effective and recyclable nanocatalyst in UAOD process for fuel purification.