Abstract
The adsorption and electroadsorption of arsenic from a natural water has been studied in a filter-press electrochemical cell using a commercial granular activated carbon as adsorbent and Pt/Ti and graphite as electrodes. A significant reduction of the arsenic concentration is achieved when current is imposed between the electrodes, especially when the activated carbon was located in the vicinity of the anode. This enhancement can be explained in terms of the presence of electrostatic interactions between the polarized carbon surface and the arsenic ions, and changes in the distribution of most stable species of arsenic in solution due to As(III) to As(V) oxidation. In summary, electrochemical adsorption on a filter press cell can be used for enhancement the arsenic remediation with activated carbon in the treatment of a real groundwater.
Highlights
Thanks to the combination of high surface area, chemical and physical stability, adjustable surface chemistry, and reduced production costs, activated carbon is the preferred adsorbent for the removal of organic and inorganic pollutants from polluted waters
The application of a controlled electric potential to the adsorbent can enhance adsorption by enabling the formation of an electric double layer, which can be partially formed by heavy metal ions, on the surface of the activated carbon in a process known as electroadsorption (Ban et al, 1998)
The Granular activated carbon (GAC) utilized in this study is a commercial material used in the water treatment plants
Summary
Thanks to the combination of high surface area, chemical and physical stability, adjustable surface chemistry, and reduced production costs, activated carbon is the preferred adsorbent for the removal of organic and inorganic pollutants from polluted waters. The availability of different techniques for tuning their surface chemistry and their pore size distribution makes possible to adapt their surface characteristics in order to match the requirements to enhance as much as possible the adsorption of a given component from a water or gas mixture Adsorption treatments using these kind of porous carbon materials are known to combine a high degree of efficiency with a reasonable cost (Derbyshire et al, 2001; Radovic et al, 2001). In these conditions, activated carbons are reported to be an ineffective adsorbent for water treatment (Pattanayak et al, 2000; Babicet al., 2002) In those cases, the application of a controlled electric potential to the adsorbent can enhance adsorption by enabling the formation of an electric double layer, which can be partially formed by heavy metal ions, on the surface of the activated carbon in a process known as electroadsorption (Ban et al, 1998). This phenomenon shares the same fundamentals as the energy storage in supercapacitors (Ghosh and Lee, 2012) and the capacitive deionization for water purification (Gabelich et al, 2002; Noked et al, 2009), and it is only possible in materials with adequate pore size distribution and acceptable conductivity, such as activated carbons
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