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

Abstract

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 Pb 2 + , Hg 2 + , Cu 2 + , Zn 2 + , and Cd 2 + were investigated. Results showed that the two adsorbents exhibited good adsorption performance toward Pb 2 + and Hg 2 + , especially toward Hg 2 + . 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 Pb 2 + and Hg 2 + 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 Pb 2 + and Hg 2 + . The largest adsorption capacity to Hg 2 + was found to be 225.8 mg/g on the adsorbent containing dithiocarbamate. The adsorbent containing dithiocarbamate and Schiff's base showed strong chelating affinity to Hg 2 + . Adsorbents synthesized in this work exhibited good performance to Hg 2 + and will be conducive to efficient removal of Hg 2 + from water bodies.

A Chelating Resin of EDTA-Type Modified Cross-Linking Polystyrene to Preconcentrate Trace Metals for Seawater Detection

“…However, the structures of commercial adsorption resins are not uncovered, and the performance robustness for the long-term use of the adsorption/desorption process of trace metal ions is not elucidated clearly. Ethylene diamine tetraacetic acid (EDTA) was a good chelating agent in chemistry, and EDTA-like or EDTA-modified recyclable resins had been designed and applied in removal of trace metal ions for purification of water [18,19]. e stability of the obtained resins through polymerization by using acrylate monomers is insufficient for long-term use because there will be decomposition of the esters of acrylate to a certain extent when purged by acid or buffer solution during desorption, which may lead to the disintegration of the resin system.…”