Adsorptive mercaptan removal of liquid phase using nanoporous graphene: Equilibrium, kinetic study and DFT calculations.

This research investigated the adsorption of tertiary butyl mercaptan (TBM) from liquid phases by using nanoporous graphene. Nanoporous graphene synthesized through chemical vapor deposition method was characterized using Brunauer-Emmett-Teller method, transmission electron microscopy, field-emission scanning microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy techniques. The TBM adsorption equilibrium was investigated by using Langmuir, Freundlich, and Tempkin models. The obtained results were in good agreement with the Freundlich isotherm. The adsorption kinetics of this process was modeled by the pseudo-first-order, pseudo-second-order, and intraparticle models. The adsorption rate was obtained according to the pseudo-second-order model. The satisfactory results indicated that nanoporous graphene can be used as a good carbon nanostructure sorbent in mercaptan removal. The process reduced the sulfur content from 300 ppm to less than 10 ppm which was the standard level in environmental regulations. The capacity for TBM removal was achieved at 4.4 gr S/gr adsorbent. The desulfurization efficiency was revealed about 96.3% for nanoporous graphene at 298 K and 24 h. Moreover, density functional theory calculations were used to determine the stable configuration, adsorption energy, and electronic structure of different configurations of TBM adsorbed onto a graphene surface. TBM physically adsorbed onto the graphene surface with adsorption energies of approximately - 25 kJ/mol was indicated from DFT calculations.