Density Functional Theory Studies of Sulfur Compounds Removal by Zinc Oxide Nanotube

Abstract

Selective adsorption of sulfur compounds is one of the most widely used methods. The most important advantages of this method are the desulfurization reaction at ambient temperature and pressure, which reduces the costs of refining operations. In this study, the reduction and elimination of sulfur pollutants (diethyl sulfide and benzothiophene) on zinc oxide nanotubes (ZnO-NT) has been investigated using DFT computational method. First, the geometric structures of the studied compounds were optimized and then the probabilities of approaching (passing through the central axis, adsorption on the top and wall of the nanotube) and adsorption and reduction of diethyl sulfide and benzothiophene to the oxidized nanotube were simulated in five steps. B3LYP/6-31++G* method was used to study the structural properties, thermodynamic parameters, and QSAR. The results showed that nanotubes show a high tendency to interact with both sulfur compounds in all spatial positions, so that the energy of the gap (Eg = 9.48 eV) decreases with the approach of the pollutant (4 ˂ Eg ˂ 5), which indicates the transfer of electrons between them. By studying the obtained structural properties and thermodynamic parameters, the tendency of ZnO-NT to adsorption of diethyl sulfide is higher than benzothiophene. While for both compounds, the position approaching the end of a ZnO-nanotube is more likely to pass through the central axis and adsorb on the outer wall of the nanotube. In general, this nano-adsorbent has the ability to adsorption of sulfur compounds and can reduce them, solving the problem of the oil industry.