Fabrication of MgO-nanoparticle-modified zeolite from rice husk ash for efficient adsorptive desulfurization: Experimental studies, process parameter optimization, and reusability potential

In this study, pristine zeolite (PZ) was synthesized from rice husk ash (RHA) and food-grade aluminum foil (FGAF) via hydrothermal route, while magnesium oxide nanoparticles (MgO-NPs) were green-synthesized using onion peel extract (OPE). The produced MgO-NPs were impregnated onto the zeolite framework to produce MgO-NP-modified Zeolite (MZ). Batch adsorptive desulfurization experiments were designed using Definitive Screening Design (DSD) to optimize the effects of initial dibenzothiophene (DBT) concentration, adsorbent dosage, contact time and temperature. Both adsorbents (PZ and MZ) were characterized using FTIR, XRD, SEM–EDX and BET analyses before and after DBT adsorption to evaluate their physicochemical properties and structural stability. The maximum DBT removal efficiencies obtained were 69.43% for PZ at 221 mg/L DBT, 235 mg adsorbent, 115 min and 31 °C while 93.56% was obtained for MZ at 281 mg/L DBT, 249 mg adsorbent, 57 min and 30 °C. Equilibrium data were best described by the Freundlich isotherm model, indicating adsorption on energetically heterogeneous surfaces, while the pseudo-second-order kinetic model provided the best fit for both adsorbents. Thermodynamic analysis confirmed that DBT adsorption was spontaneous, feasible and endothermic. Regeneration studies showed that PZ and MZ retained approximately 55.6% and 88.0% of their initial adsorption efficiencies, respectively, after five adsorption-desorption cycles. Furthermore, FTIR, XRD, SEM–EDX and BET analyses of the regenerated adsorbents confirmed that the zeolitic framework remained largely intact, with MZ exhibiting superior structural stability and textural property retention. Overall, this study demonstrates an effective integration of waste valorization, green nanotechnology and statistical optimization for the development of a sustainable, low-cost and highly reusable adsorbent for deep desulfurization of model oil.