Gas adsorptive desulfurization of thiophene by spent coffee grounds-derived carbon optimized by response surface methodology: Isotherms and kinetics evaluation

Abstract

Abstract The elimination of sulfur compounds in the FCC gasoline is indispensable to protect downstream equipment. Researchers are trying to find technological innovations to produce the famous “zero sulfur” fuel. Many adsorbents, such as spent coffee grounds-derived carbon (SCG-AC), have been claimed to be effective in H2S removal. However, no study has been conducted to exploit its ability to eliminate the organo-sulfur compounds present in FCC gasoline such as thiophene. This work involves the optimization by the response surface methodology (RSM) of different operating conditions of activated carbon (AC) production by the chemical activation (H3PO4) of SCG. RSM was used to estimate the variables considered in the preparation of AC using the Box–Behnken Design (BBD). The optimized SCG-AC was used for the adsorption of thiophene through batch tests at ambient conditions. The equilibrium experimental data of the thiophene adsorption were analyzed by Langmuir, Freundlich, and Langmuir–Freundlich isotherms. The adsorption isotherm data fit the Langmuir–Freundlich isotherm where the adsorption’s kinetics were described by the Elovich model. The optimum SCG-AC exhibited the highest adsorption capacity, with up to 2.23 mmol/g. These results revealed that SCG-AC is a promising and economical adsorbent for the elimination of thiophenic sulfur compounds.