Water treatment by adsorption with electrochemical regeneration using graphene based materials

Date
2018-01-22
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Abstract
Adsorption is a simple and effective process for the removal of organic contaminants with low concentration from water. However, the disposal of adsorbent loaded with toxic contaminants may not be feasible, especially for adsorbents which are not available in large quantities or are expensive to produce. In order to meet these challenges, an economical process to treat water contaminated with dissolved organics is to utilize adsorption coupled with electrochemical oxidation. The adsorbents employed in adsorption-electrochemical regeneration processes have a low adsorptive capacity (ca. 1 mg g-1), low electrochemical regeneration efficiency (<100 %) or high energy consumption. There was thus a need to produce new materials that have both good regeneration efficiency and adsorptive capacity. This PhD project focuses on an investigation of graphene adsorbents to be utilized in adsorption and electrochemical regeneration. In this regard, different graphene nanocomposite namely graphene / iron oxide, graphene / TiO2 and graphene / SnO2 have been synthesized, characterized, and applied in adsorption and regeneration process. Reduced graphene oxide / iron oxide showed good capability to adsorb the organic contaminants with adsorptive capacity of 39 mg g-1 and be regenerated electrochemically with a regeneration efficiency of 100% for a charge passed of 39 C per mg-1 adsorbate. However, the surface of the rGO was observed to be corroded during electrochemical regeneration. On the other hand, Graphene / TiO2 showed a lower absorptive capacity, but with lower required charge passed of 21 C per mg-1 adsorbate. TEM studies revealed that the bare graphene was rapidly corroded, while graphene / TiO2 could tolerate more cycles of adsorption and electrochemical regeneration. Unlike graphene / TiO2, graphene / SnO2 showed higher adsorptive capacity combined with a low required charge for 100% regeneration of 21 C per mg-1 adsorbate. Graphene / SnO2 nanocomposites also showed good performance in presence of sodium sulphate as the electrolyte. The effect of the synthesis conditions on the graphene prepared by electrochemical exfoliation was also investigated. The results show that graphene synthesized using ammonium phosphate possessed higher electrocatalytic activity and thermal stability than the graphenes synthesized using other salt solutions.
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Keywords
Graphene, water treatment, electrochemical regeneration
Citation
Sharif, F. (2018). Water treatment by adsorption with electrochemical regeneration using graphene based materials (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.