The Applications of Graphene and Its Derivatives for Heavy Metal Removal

Heavy metal pollution is very prevalent in our environment. The entire removal of heavy metal and organic contaminants in natural water resources will not only affect the environment itself, but also can block the toxic contaminant transfers in food chains. Currently, there are many studies being done to remove these heavy metal ions from our water, such as reduction reactions, chemical precipitation, reverse osmosis and electrolytic recovery. One of the promising techniques is adsorption. The focus of this research is using graphene and its derivatives, such as silylated graphene oxide (GO), to adsorb heavy metals, specifically, lead. This research describes chemical modification techniques to modify the GO surface with functional groups, and the modified graphene will be used as a functional sorbent for waste water treatment and natural water resource protection, especially for heavy metal removal. In this study, N-(trimethoxysilylpropyl) ethylenediaminetriacetic acid (EDTA-silane) was linked to the graphene oxide (GO) surface through a silanization reaction. EDTA is a widely used chelating agent, and modifying the surface of GO with EDTA will add a chelating ability to GO. The results demonstrate that the EDTA-GO compound is an ideal adsorbent for heavy metal removal with a higher adsorption capacity than the carbon-based adsorbents currently in use. EDTA modification enhanced the adsorption capacity of GO due its chelating ability. At pH 6.0 ~7.2, the adsorption capacity for Pb(II) removal was found to be 486 mg/g, with adsorption completed within 20 minutes. A Langmuir adsorption model agrees well with experimental data. The effects of solution conditions such as pH and metal ion concentrations were investigated, along with adsorption and desorption behaviors of heavy metal cations. The desorption behavior predicts that GO can be reused after washing with 0.10 M HC1. My results have demonstrated potential applications for uses in the environmental restoration