Contaminant adsorption and oxidation via Fenton reaction

A ground-water treatment process is described in which contaminants are adsorbed onto granulated activated carbon (GAC) containing fixed iron oxide. Hydrogen peroxide (H2O2) is amended to the GAC suspension and reacts with the iron, forming hydroxyl radicals ((OH)-O-.). The radicals react with and oxidize sorbed and soluble contaminants regenerating the carbon surface. Laboratory results are presented in which 2-chloro-phenol (2CP) was first adsorbed to GAC and subsequently oxidized via the Fenton-driven mechanism. Transformation 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 oxide and 2CP on the GAG. The extent of 2CP oxidation increased with H2O2 concentration. Lower treatment efficiency was evident at the highest H2O2 concentration utilized (2.1 M) and was attributed to increased (OH)-O-. scavenging by H2O2. Aggressive oxidation procedures used in sequential adsorption/oxidation cycles did not alter the GAC surface to a degree that significantly interfered with subsequent 2CP adsorption reactions. Although process feasibility has not yet been established beyond bench-scale, experimental results illustrate the potential utility of the adsorption/oxidation process in aboveground systems or permeable reactive barriers for the treatment of contaminated ground water.