Relationship between Hg(II) adsorption property and functional group of different thioamide chelating resins

[Display omitted] •The adsorption properties and DFT calculation of three similar thioamide resins were investigated.•All resins have high adsorption capacities and regeneration performance for Hg(II).•Ammonium thiocyanate modified ammoniated polystyrene (ATMCR) exhibits the best adsorption selectivity for Hg(II).•The maximum Hg(II) adsorption capacity of ATMCR was 636.94 mg/g at 318 K. In order to investigate the effects of different electron donor groups on the Hg(II) adsorption properties of thioamide chelating resin, three similar resins were prepared by modifying chloromethylated (CPS) and ammoniated polystyrene (APS) beads with thiourea (TMCR), ammonium thiocyanate (ATMCR) and carbon disulfide (CDMCR). These resins were characterized with Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The factors affecting Hg(II) adsorption such as dosage, solution pH, initial concentration, temperature and contact time were investigated in detail. The adsorption kinetics of three resins obey the pseudo-second-order model. Isothermal adsorption thermodynamics showed that Hg(II) adsorption by TMCR belongs to a multilayer adsorption process, and that of ATMCR and CDMCR belong to chemical processes. Compared to TMCR and CDMCR, ATMCR has outstanding adsorption and regeneration performance. It has the maximum adsorption capacity (636.94 mg/g at 318 K) and the adsorption rate can still reach 94% after ten cycles. Selective adsorption and DFT calculation show that ATMCR exhibits a specific adsorption for Hg(II) with a stronger coordination than TMCR and CDMCR.