Removal of trace amount of metal ions using magnetic graphene oxide

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Selenium and other trace metals are widely distributed in sulfide minerals and coal ash. During mining and mineral processing, selenium could be released into water and soils, and further transferred to organisms and their life cycles. Selenium is an essential trace nutrient, but has an adverse effect at higher concentrations. A guideline value of less than 0.04 mg/L (40 microgram/L or 40ppb) selenium in drinking-water has been set by the World Health Organization. The removal of selenium and other trace metals from water systems is crucial to reduce their environmental impact and maintain sustainable development of natural resources. Selenium is metalloid and has variable valence states from -2 to +6. The selenium species present in water are mainly oxyanions of selenate and selenite, which are more mobile than elemental selenium (Se) and selenide (Se2-). In this proposed research, a new kind of adsorbent, magnetic graphene oxide (MGO) composites will be synthesized to investigate the removal of selenium species in conjunction with the application of an external magnetic field. We propose to combine the magnetic carrier technology with the high specific surface area MGO for the removal of selenium oxyanions and other metal ions in from water. After the magnetic separation, MGO will be recycled and reused by stripping off the adsorbed selenium and trace metals. Our preliminary results show that MGO has a good removal rate for both Se (IV) and Se (VI). The large surface area, large adsorption capacity, and high water dispersibility of MGO make it a promising adsorbent for use in wastewater.