Synthesis of Graphene for Wastewater Treatment by Adsorption and Electrochemical Regeneration
Date
2021-03-24
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Abstract
Adsorption of pollutants in water is one of the most feasible techniques for water treatment. Several carbon materials have been used as an adsorbent, with graphene being one of the most attractive materials due to its high specific surface and conductivity. In this study, two electrochemically synthesized graphenes were used to investigate the adsorption capacity as well as the corrosion resistance of doped graphene. Electrochemically exfoliated nitrogen-phosphorous-doped graphene (EEG-N-P) showed a higher adsorption capacity compared to electrochemically exfoliated nitrogen-sulfur-doped graphene (EEG-N-S) resulting in a good adsorbent. However, EEG-N-S showed higher charge efficiency, with a shorter time required for electrochemical regeneration. A regeneration efficiency of more than 100 % was achieved after the first cycle of regeneration using EEG-N-P; this was likely due to the creation of new adsorption sites, due to corrosion of the material. Accelerated corrosion tests and electrochemical techniques were used to analyze the oxidation resistance. Cyclic voltammetry (CV) provided information about the changes of the graphene surface before and after oxidation. A higher increase in gravimetric capacitance was obtained for EEG-N-P, according to CV data, and the calculated corrosion mass loss was greater for EEG-N-P than EEG-N-S based on potential step data. Therefore, EEG-N-S showed a higher corrosion resistance in the two different media used in these studies. Although air oxidation protection was provided by phosphorous doping, this doping did not protect the graphene from electrochemical corrosion. The increase of electrode dimensions in electrochemical synthesis was also studied in this work. The effect of operating conditions including the current density, electrode area and pH on the yield, energy consumption and quality of graphene obtained were investigated. A higher yield was achieved in all cases with the use of larger electrodes. The pH was found to affect the yield and energy consumption, with bettery performance at higher pH. Exfoliation with constant current and constant voltage was compared, resulting in a higher graphene doping and higher thermal stability when constant current was used. Different current densities were studied, showing a more cost-effective exfoliation when 100 and 200 mA cm–2 was used compared to higher current density.
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Keywords
graphene, nanomaterials
Citation
Lopez Pablos, M. F. (2021). Synthesis of Graphene for Wastewater Treatment by Adsorption and Electrochemical Regeneration (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.