Adsorption of mercury species on selected CuS surfaces and the effects of HCl

Mercury removal is a hot topic in environments. The present work investigated the adsorption of Hg species on the surfaces of CuS, which performs excellently in experiments as adsorbents for mercury removal, with the dispersion corrected density functional theory. In this work, a pair of asymmetric surfaces (marked as slab1 and slab2) formed by breaking the weakest bond along (001) direction are chosen to present CuS surfaces. It is found that the HCl modification to the CuS may lead to the isolated Cl atoms and defects in the CuS surface. Hg atom can be adsorbed on the perfect CuS surface weakly. The surface defects and the isolated Cl atoms could strengthen the bonding of the Hg species to the surfaces. However, the mechanisms for the defects and Cl affect the mercury adsorption ability in slab1 and slab2 are quite different. The adsorption of HgCl and HgCl2 is much stronger than the adsorption of Hg, indicating that Hg would be first be released, rather than Cl, from the adsorbent during the desorption process.