Removal of Cadmium and Chromium Ions Using Modified α, β, and γ-Cyclodextrin Polymers

Abstract

The adsorption of cadmium and chromium from aqueous solutions with epichlorohydrin cross-linked α, β, and γ-cyclodextrin polymers (CDPs) was investigated under a wide range of experimental conditions including pH, metal concentration, and CDP amounts. Recent studies have shown that α, β, and γ-CDPs follow the Freundlich, Langmuir, and Brunauer–Emmett–Teller models and are capable of reducing heavy metal ion concentrations in water to desirable levels with enhanced sorption capabilities. The removal of cadmium and chromium achieved equilibrium in 4 h. The pH of effective cadmium removal was 6.5 to 7.5, and phosphate buffer favored the removal of cadmium in the presence of potassium ion. Chromium removal was optimal at pH 3.6 to 6.5. Current technologies can remove 99% cadmium ions from solution, yet this process is not very efficient for chromium ions. Furthermore, a small amount of CDPs can remove large quantities of heavy metal ions and can then be regenerated with acid for reuse. The present results are promising for using inexpensive CDPs as a low-cost material that is effective in remediating waters contaminated with heavy metal species. The sorption kinetics of CDPs along with the conditions to adsorb cadmium and chromium are reported here for the first time.

Keywords:

• adsorption
• cyclodextrin polymer
• epichlorohydrin
• heavy metal
• remediation

ACKNOWLEDGEMENTS

The authors express their deep gratitude to Kankyo Kogaku Co., Ltd. (Hirosaki, Japan) for their benevolent donation of cyclodextrin polymers. The authors are largely indebted to Prof. Nobuo Sakairi and Dr. Syunichi Kawaguchi, Division of Material Sciences, Faculty of Environmental Earth Science, Hokkaido University, for their useful discussion and guidance with FTIR. The authors would like to thank Mr. Yoshihiro Mihara, Mr. Yusuke Kihara, and Dr. Parvin Begum for their useful discussions, as well as the catalytic laboratory and environmental medical chemistry laboratory of the Graduate School of Environmental Science.