Contaminant adsorption and oxidation via Fenton reaction

A ground-water treatment process is described in which contaminants are ads orbed onto granulated activated carbon (GAC) containing fixed iron oxide. H ydrogen peroxide (H2O2) is amended to the GAC suspension and reacts with th e iron, forming hydroxyl radicals ((OH)-O-.). The radicals react with and o xidize sorbed and soluble contaminants regenerating the carbon surface. Lab oratory results are presented in which 2-chloro-phenol (2CP) was first adso rbed to GAC and subsequently oxidized via the Fenton-driven mechanism. Tran sformation of 2CP was indicated by the formation of carboxylic acids and Cl (-)release. The treatment efficiency of 2CP, defined as the molar ratio of Cl(-)released to H2O2 consumed, increased with increasing amounts of iron o xide and 2CP on the GAG. The extent of 2CP oxidation increased with H2O2 co ncentration. Lower treatment efficiency was evident at the highest H2O2 con centration utilized (2.1 M) and was attributed to increased (OH)-O-. scaven ging by H2O2. Aggressive oxidation procedures used in sequential adsorption /oxidation cycles did not alter the GAC surface to a degree that significan tly interfered with subsequent 2CP adsorption reactions. Although process f easibility has not yet been established beyond bench-scale, experimental re sults illustrate the potential utility of the adsorption/oxidation process in aboveground systems or permeable reactive barriers for the treatment of contaminated ground water.