Removal of ionic mercury from gasoline using zeolite 13X impregnated with KI: Adsorption mechanisms and simulation

Abstract Mercury (Hg) removal from natural gas condensates is a hot topic due to its importance in petroleum refineries. Unfortunately, though much attention has been paid to the adsorption efficiency of sorbents in industry, mercury adsorption mechanisms are rarely addressed. This paper studies the adsorption mechanisms of zeolite 13X impregnated with potassium iodide (KI) on ionic mercury (Hg(II)) from gasoline. The effects of different KI loading amounts, initial mercury concentrations, and adsorption times of mercury removal were investigated by adsorption experiments. The adsorption efficiency increased from 15% to 91%, and the adsorption amount increased by 18 times after the addition of pristine zeolite loaded with 2% KI. The preferential adsorption sites of potassium (K), iodine (I), and Hg atoms in zeolite were calculated by the grand-canonical Monte Carlo (GCMC) method. The center of the super cage (center 1) and interface between the super cages (center 2) provided the main I active sites for Hg capture. In addition, the adsorption energies between I and Hg were analyzed by density functional theory (DFT), and partial density of states (PDOS) analysis indicated that Hg interacts strongly with I in the super cage. Hence, during the adsorption process, mesopores served as an entrance for active materials. Hg(II) in gasoline diffused to the micropore channels via mesopores and were captured by I, forming HgI2. These results cast a new light on the development of novel sorbents for mercury removal.