Synergistic effect of nitrogen and molybdenum on activated carbon matrix for selective adsorptive Desulfurization: Insights into surface chemistry modification

Abstract

This study reports the synthesis of mesoporous metal-modified nitrogen doped activated carbon (AC-N-Mo) from date seeds by ZnCl2 activation and its applicability for selective adsorptive desulfurization of dibenzothiophene (DBT). The AC-N-Mo exhibits higher adsorption capacity for DBT at 100 mg-S/L with the maximum removal percentage of 99.7 % corresponding to 19.94 mg-S/g at room temperature than the unmodified carbon with 17.96 mg-S/g despite its highest surface area and pore volume of 1027 m2g−1 and 0.55 cm3g−1 respectively. The adsorption capacity breakthrough follows the order AC-N-Mo > AC-Mo > AC > AC-N. Also, AC-N-Mo displays excellent selectivity in the presence of aromatics (toluene, naphthalene, and 1-methylisoquinoline). The enhancement in the DBT uptake capacities of AC-N-Mo is attributed to the synergistic effect of nitrogen heteroatom that aids the dispersion of molybdenum nanoparticles on carbon surface thereby improving its surface chemistry and promising textural characteristics. The kinetic studies showed that the DBT adsorption proceeds via pseudo-second order kinetics while the isotherm revealed that Langmuir fit the data more accurately for the adsorbents. The physical properties (surface area, pore volume, particle size, etc.) and chemical properties (carbon content, etc.) of as-prepared adsorbents namely; AC, AC-N, AC-N-Mo, and AC-Mo were characterized by N2– physisorption, X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Spectroscopy/Energy Dispersive Spectroscopy (SEM/EDS), Raman Spectroscopy (RS), Fourier Transform Infrared Spectroscopy (FTIR) and Ammonia-Temperature-Programmed Desorption (NH3-TPD).