Effect of extraction parameters on the synergistic reaction mechanism for arsenic and mercury removal from natural gas condensate via LLE, vibrational spectroscopy and DFT calculations

Abstract

Poisonous metals are often found as the basic constituents of natural gas condensate. Both arsenic (As) and mercury (Hg) have a negative effect on the processes and control criteria in diesel production. Liquid-liquid extraction (LLE) is a simple and widely used method for developing processes to remove such toxic substances. In this paper, LLE investigates the extraction yield of As and Hg from natural gas condensate using HCl-MeOH, HCl-Thiourea and HCl-TMAH, at a temperature range of 303.15–323.15 K. In all cases, temperature leads to an increase in reaction rate and activation energy, thus affecting the ability to extract target ions. Density function theory (DFT) is used to examine the reaction mechanism along with the resulting vibration spectra in the removal of As and Hg, using HCl-Thiourea. LLE employs two different procedures based on the use of either an individual of combination of extractants. Enthalpy change (As = 0.9557, Hg = 1.3522 kJ/mol) indicates the endothermic reaction of the extraction process. Both the positive entropy change (As = 0.0202, Hg = 0.0286 kJ/mol) and Gibbs free-energy (As = -5.5548, Hg = −7.8961 kJ) indicates that extraction occurs spontaneously in the forward direction. This research shows promise for the development of high-yield and toxic free diesel production from natural gas resources.