Scavenging arsenate from contaminated water using solid supported chemical receptors

Arsenic contamination of drinking water is problematic across the globe, with a serious effect on human health. The WHO guideline of 10 μg L-1 maximum concentration for arsenic in drinking water is regularly exceeded in developing countries in South East Asia, and many other countries across the world including the USA and Japan. Aqueous arsenic is commonly found in two oxidation states, AsV (arsenate) or AsIII (arsenite). Arsenate exists in water as a tetrahedral oxyanion, analogous to phosphate. Recently there has been great interest in developing new materials than can remove arsenate from drinking water. Specifically, chelating resins loaded with transition metal cations have shown potential for use in arsenate remediation. This Thesis describes the synthesis of two series of metal complexes that were evaluated as arsenate receptors and subsequent development of one of these receptors into a novel arsenate adsorbent. Firstly, a range of bridging di-metallic complexes was synthesised. The aqueous phase oxyanion binding properties of these receptors were investigated by indicator displacement assays, isothermal titration calorimetry and in the solid phase by X-ray crystallography. Metallo-receptors containing boronic acid binding sites were also synthesised and arsenate binding was studied by isothermal titration calorimetry, UV-vis spectroscopy and NMR spectroscopy. An arsenate sorbent was prepared by immobilising a phenolate di-zinc(II) complex onto a polystyrene resin. The novel material thus obtained was studied as an arsenate adsorbent in a range of batch adsorption experiments. The effects of solution pH and presence of competing ions on arsenate uptake were investigated and the Langmuir adsorption capacity was obtained. These results were compared with those of a commercially used arsenic adsorbent, Bayoxide E33. Finally the novel adsorbent was packed into a glass column and its ability to adsorb arsenate in flow through experiments was studied.Open Acces