Experimental and theoretical studies for the mechanism of mercury oxidation over chlorine and cupric impregnated activated carbon

Highlights: • CuCl₂ modified activated carbon for Hg removal was studied in experiment and theory. • Dispersed cupric could promotes mercury oxidation and provides adsorption sites. • The reaction pathway of heterogeneous Hg transformation was expressed. Experimental and theoretical studies were conducted to investigate the roles of cupric and chloride in CuCl₂ impregnated activated carbon for mercury removal. Solution impregnating was used to add cupric, chlorine and copper chloride on activated carbon respectively. Experiment results show that combination of chlorine and cupric possesses stable and high efficiency in mercury removal. In CuCl₂ impregnated activated carbon, besides chlorine existence promotes the mercury oxidation and adsorption, dispersed cupric could accelerate the process and provide adsorption sites for oxidated mercury. Theoretical calculations based on density functional theory (DFT) were carried out to elucidate the mechanism of mercury adsorption and oxidation. Models of CuO and CuCl₂ doped on monolayer graphene were established to simulate the sorbents surfaces. There is a weak physisorption for Hg adsorption on CuO doped sorbent, but for CuCl₂ doped sorbent, it could oxidate mercury and generated HgCl₂ with the energy barrier of 121.83 kJ/mol. More than that, the correlation between CuCl₂ doped sorbent and CuO doped sorbent pretreated with HCl has been graphene reflected in simulation results. Experimental and theoretical results both evidenced that the cooperation of chlorine and cupric is favorable to remove mercury.