Degradation of Organic Pollutants by the Photo-Fenton-Process

Abstract

The Photo-Fenton-Process utilizing the combinations Fe(II)/H 2 O 2 /UVA and Fe(III) oxalate/H 2 O 2 /UVA was employed with success to degrade biorefractory organic pollutants in landfill leachate. The rate of degradation of the organic pollutants depends on the concentrations of hydrogen peroxide and the iron catalyst, the pH value and the concentration of dissolved oxygen. A comparison of the Photo-Fenton-Process with the H 2 O 2 /Fe(II) process and the H 2 O 2 /UVC process shows that the Photo-Fenton-Process gives a higher COD degradation and a reduced energy consumption of at least 30% compared to the H 2 O 2 /UVC process. By using photogenerated Fe(II) the amount of the iron catalyst required and the volume of sludge produced are strongly reduced. Advanced oxidation processes (AOPs) generate hydroxyl radicals (*OH) in solution and have attracted interest for the degradation of biorefractory or hazardous organic compounds in wastewater. The organic pollutants are oxidized by free radicals and mineralized to water and carbon dioxide. Recently, various oxidation processes which produce hydroxyl radicals using ultraviolet light have been applied in wastewater treatment. This will result in high energy requirements. The utilization of the metal salt Fe(II) as Fenton′s reagent produces inorganic sludge that may cause a waste disposal problem. A combination of H 2 O 2 and UVA radiation with Fe(II) or Fe(III) oxalate, the so-called Photo-Fenton-Process, produces more hydroxyl radicals in comparison with the systems Fe(II)/H 2 O 2 or H 2 O 2 /UVC, thus promoting the rate of degradation of organic pollutants.