Magnetic iron nanoparticles (Fe3O4) supported on activated carbon as a hybrid adsorbent for desulphurisation of liquid fuels

Abstract

ABSTRACT In this work, efficient hybrid adsorbents were developed through surface modification of commercial activated carbon with magnetic iron nanoparticles (Fe3O4). These modified adsorbents were characterised for their texture, morphology, and other surface properties and investigated for sulphur removal from model fuel consisting of thiophene (T), benzothiophene (BT), and dibenzothiophene (DBT) in liquid phase using hexane as a solvent. The effect of temperature and contact time was studied to understand the thermodynamics and kinetics of the adsorption process, and experimental adsorption data were interpreted using standard isotherms such as Langmuir, Freundlich, and Temkin model. The findings showed that the iron-loaded activated carbon could effectively remove the DBT (a representative sulphur compound) much better than the precursor nascent carbons in single and multicomponent models fuels under the optimised dosage of 30 g.L−1 and operating temperature of ~ 40°C. The kinetic analysis revealed that the pseudo-second-order model could represent the surface binding mechanism of DBT. The rate-limiting step, as indicated by the Weber-Morris plot, involved several steps. It was observed that the adsorption potential of the prepared materials increased with the increasing initial DBT concentration, exhibiting a maximum capacity of 29 mg.g−1, and the adsorption process was well described by the Freundlich isotherm (R2 = 0.95 to 0.99). Fe@AC-2 also demonstrated their ability to satisfactorily remove T, BT, and DBT from multi-component model fuel systems with higher selectivity for the more refractory DBT. Thermal regeneration of Fe@AC-2 saturated with DBT at 350°C could be recycled till the fourth cycle, and loss in adsorbent mass was observed in each cycle. Analysis of real diesel fuel pre- and post-adsorption with Fe@AC-2 showed a negligible change in the gross calorific value, density, and kinematic viscosity of the treated diesel from the untreated diesel.