Synthesis of polyacrylamide/modified silica composite hydrogels for synergistic complexation of heavy metal ions

Abstract

In this research, polyacrylamide (PAM)/modified silica (SiO₂-NH₂) composite hydrogels have been prepared via in situ free-radical polymerization. The gel fraction of the polymerization was studied by gravimetric method, and the mechanical property of the resultant hydrogels was examined using a tensile tester. It was indicated that both the gel fraction and the mechanical strength increased with the SiO₂-NH₂ content in the formulation. When the pH value of the buffer solution and the SiO₂-NH₂ content increased, the swelling ratio decreased. The composite hydrogels were used to remove heavy metal ions from aqueous solution under the noncompetitive condition. The effects of SiO₂-NH₂ content in the formulation and pH values of the feed solution on the adsorption capacity were investigated. The results showed that the adsorption capacity of the hydrogels decreased with the pH values but increased with SiO₂-NH₂ content in the formulation. Furthermore, the synergistic complexation of metal ions was found in the adsorption studies. The adsorption isotherm of the hydrogels could be well fitted into the Langmuir model. Regeneration studies suggested that metal rebinding capacity of the hydrogels did not change significantly through repeated applications compared with the first run.

Keywords:

• Composite hydrogel
• Heavy metal ion
• Adsorption
• Synergistic complexation

Acknowledgments

This project was supported by China Postdoctoral Science Foundation (No. 2012M520979) and Jiangsu Postdoctoral Science Foundation (No. 1201009B).