• GAC regeneration
• Fenton reaction
• iron oxide

Granular activated carbon (GAC) is widely used as an adsorbent of various organic contaminants due to its high surface area and porous structure. It can be used over a wide range of pH and be modified by chemical treatment to increase its adsorption capacity. Once the GAC is saturated, it is regenerated for reuse, replaced with virgin carbon, or disposed. Thermal, biological and chemical regeneration methods applied worldwide all have significant drawbacks. Advanced oxidation processes (AOPs) have the ability to degrade a wide range of organic pollutants by generation of the very reactive and non selective hydroxyl radicals. Hence, its potential to regenerate spent GAC. Fenton reagent is one of the AOPs at which hydroxyl radicals are generated by decomposition of hydrogen peroxide with an iron catalyst (H2O2/Fe). Fenton reactions have the advantages of being performed at ambient temperature without requiring illumination, the reagents are readily available, easy to store, relatively safe to handle, and non–threatening to the environment.
Iron oxides immobilized in the GAC could potentially improve the carbon regeneration by producing hydroxyl radicals in situ (i.e. within the GAC particle). The short lived radicals produced in the bulk solution are unable to diffuse into the GAC pores and react with the adsorbed pollutant. Hence, the oxidation reaction is limited to the bulk and film near the GAC surface.
Phenol is frequently used as a model compound to study adsorption processes since it is relatively simple and well characterized. Phenolic compounds are present in the environment as a result of their uses and the processes in which they are implicated. Industrial processes, including production of drugs, textiles, dyes, pesticides and paper, are the main source of these compounds in the environment. Phenolic compounds are toxic and potentially carcinogenic and they can affect the taste and odor of drinking water at very low concentrations.
In this research regeneration of phenol saturated charcoal virgin and iron loaded granular activated carbon by Fenton oxidation was investigated. Virgin and pre-oxidized charcoal GAC were loaded with ferric chloride salt and characterized by Mössbauer spectroscopy, High Resolution Scanning Electron Microscopy (HR-SEM), and nitrogen adsorption analyses for Brunauer-Emmett-Teller (BET) surface area. Regeneration was evaluated in expanded bed continuous system using various weight ratio of hydrogen peroxide to iron. Finally, mineralization of desorbed phenol from saturated GAC bed, using Fenton reaction, in aqueous solution was studied.