Synthesis of Silica-Supported Multidentate Ligands Adsorbents for the Removal of Heavy Metal Ions

Two novel silica-supported multidentate ligands adsorbents were synthesized by the reaction of tetraethylenepentamine-functionalized silica gel (SG) and Schiff's base functionalized SG with carbon disulfide. Fourier transform infrared spectroscopy (FT-IR) analysis and thermogravimetry analysis were used to characterize the synthesized adsorbents. Adsorption characteristics for Pb2+, Hg2+, Cu2+, Zn2+, and Cd2+ were investigated. Results showed that the two adsorbents exhibited good adsorption performance toward Pb2+ and Hg2+, especially toward Hg2+. Effects of adsorption time and initial metal ion concentration on adsorption capacity of the two adsorbents were investigated. Experimental data were exploited for kinetic and thermodynamic evaluations related to the adsorption process. Kinetic data indicated that the adsorption processes of Pb2+ and Hg2+ on the two adsorbents were governed by the film diffusion and followed pseudo-second-order model. The Langmuir model was applied to fit the experimental equilibrium data. The Scatchard model was applied to determine the binding affinity constants and binding sites of the two adsorbents to Pb2+ and Hg2+. The largest adsorption capacity to Hg2+ was found to be 225.8mg/g on the adsorbent containing dithiocarbamate. The adsorbent containing dithiocarbamate and Schiff's base showed strong chelating affinity to Hg2+. Adsorbents synthesized in this work exhibited good performance to Hg2+ and will be conducive to efficient removal of Hg2+ from water bodies.