Synthesis of a novel silica-supported dithiocarbamate adsorbent and its properties for the removal of heavy metal ions

Highlights: → A new silica-supported dithiocarbamate adsorbent (Si-DTC) was synthesized following a novel synthesis route by anchoring the chelating agent of macromolecular dithiocarbamate (MDTC) to the chloro-functionalized silica matrix(SiCl). → By adopting this method, it could make more efforts to increase the nucleophilic reactivity of polyamine with carbon disulfide under strong alkaline condition and avoid the degradation of silica matrix. → The new adsorbent were used to absorb Pb(II), Cd(II), Cu(II) and Hg(II) which are known to be common heavy metal ions from polluted aqueous solutions. → The dithiocarbamate groups and the amino groups in Si-DTC both take part in the adsorption process for M(II) from aqueous solutions but the adsorption mechanism of Hg(II) onto Si-DTC is quite different from that of Pb(II), Cd(II) or Cu(II) onto Si-DTC, which is testified by the XPS and FT-IR results. - Abstract: Silica-supported dithiocarbamate adsorbent (Si-DTC) was synthesized by anchoring the chelating agent of macromolecular dithiocarbamate (MDTC) to the chloro-functionalized silica matrix (SiCl), as a new adsorbent for adsorption of Pb(II), Cd(II), Cu(II) and Hg(II) from aqueous solution. The surface characterization was performed by FT-IR, XPS, SEM and elemental analysis indicating that the modification of the silica surface was successfully performed. The effects of media pH, adsorption time, initial metal ion concentration and adsorption temperature on adsorption capacity of the adsorbent had been investigated. Experimental data were exploited for kinetic and thermodynamic evaluations related to the adsorption processes. The characteristics of the adsorption process were evaluated by using the Langmuir, Freundlich and Dubinin-Radushkevich (D-R) adsorption isotherms and adsorption capacities were found to be 0.34 mmol g-1, 0.36 mmol g-1, 0.32 mmol g-1 and 0.40 mmol g-1 for Pb(II), Cd(II), Cu(II) and Hg(II), respectively. The adsorption mechanism of Hg(II) onto Si-DTC is quite different from that of Pb(II), Cd(II) or Cu(II) onto Si-DTC, which is demonstrated by the XPS and FT-IR results.