Adsorptive desulphurization of model oil by Ag nanoparticles-modified activated carbon prepared from brewer’s spent grains

Abstract

This study reports removal of dibenzothiophene (DBT) from model oil (DBT dissolved in n-heptane) by silver nanoparticles modified activated carbon prepared from brewer’s spent grains using wet impregnation (WI) method. The removal efficiency follows the order AgNPscw/AC>AgNPskp/AC>ACB. The AgNPskp/AC and AgNPscw/AC exhibit higher adsorption capacities for DBT with maximum values of 25.7 and 29.8mg DBT/gAds at 25°C respectively, than ACB with 13.9mg DBT/gAds. The two-fold enhancement in the DBT uptake capacities of modified ACs can be attributed to the introduction of Ag(1) ion, a weak Lewis acid as an additional adsorption site. A significant decrease from 212.9 to 136.2m2/g in the Brunauer–Emmett–Teller surface area of AgNPscw/AC is observed following the loading of DBT. The equilibrium adsorption data is adequately represented by Freundlich isotherm. The adsorption kinetics of DBT by these adsorbents followed pseudo second-order (PSO) model and the mechanism of adsorption was controlled by film and intra-particle diffusion. The change in entropy and heat of adsorption for DBT adsorption by these adsorbents range from 0.18 to 0.19kJ/molK and 21.5 to 23.9kJ/mol, respectively. The results indicate that Ag nanoparticles-modified ACs from brewer’s spent grains can be used as adsorbent for the removal of DBT from model oil.