Removal of mercury from contaminated saline wasters using dithiocarbamate functionalized-magnetic nanocomposite

In this study, an efficient adsorbent was proposed for the removal of mercury from saline water contaminated with mercury ions. Fe₃O₄ nanoparticles were modified using tetraethylenepentamine and carbon disulfide to incorporate dithiocarbamate functional group on the surface of the adsorbent. CHNS analysis confirmed successful modification of magnetic nanoparticles. The XRD pattern of adsorbent indicated a proper match with the standard XRD pattern of cubic Fe₃O₄. The saturation magnetization of final adsorbent was 27 emu g^-1. The morphology of bare and silica-coated Fe₃O₄ and final product were investigated using FE-SEM analysis. For optimizing the adsorption process, response surface methodology was applied, which was resulted in a significant quadratic model. The effect of adsorbent dosage and initial concentration of Hg (II) was much more significant than that of pH. Different concentrations of dissolved solids up to 2000 mg L^-1 had no adverse effect on the adsorption process due to the strong interaction between dithiocarbamate functional group of adsorbent and Hg (II). The least values of RMSE (0.0950) and χ2 (0.0009) were observed for Radke-Prausnitz, Redlich-Peterson, and UT isotherms. Maximum adsorption capacities calculated using Langmuir and UT models were 109.5 and 95.07 mg g^-1, respectively. The investigation of adsorption isotherm was conducted at the pH range of 2.0-6.5. The results showed an increase in the adsorption capacity by increasing pH. Thermodynamic studies demonstrated that the nature of the adsorption process was spontaneous and endothermic. Recovery of adsorbent was successfully carried out using HCl 0.5 mol L^-1. The prepared adsorbent was successfully applied for mercury removal from a real groundwater.