IRON OXIDE-MEDIATED DEGRADATION, PHOTODEGRADATION, AND BIODEGRADATIONOF AMINOPHENOLS

The results of the photocatalytic degradation and the influence of pho tocatalytic pretreatment on the biodegradability of 2-aminophenol usin g iron oxides are reported. Various reaction parameters like substrate concentration, alpha-Fe2O3 content, amount of oxygen present, type of iron oxide, pH of the solution, temperature, and contribution of the dark reaction were investigated. By the use of several experimental te chniques like H-1-NMR studies, CO2 evolution, total organic carbon spe ctrophotometry, and high-pressure liquid chromatography, the more rele vant features of the degradation mechanism observed in aminophenols we re established. alpha-Fe2O3 appears to react only with aminophenols ha ving electron-donating character through the formation of a surface co mplex. No similar degradation was observed when phenol, nitrophenol, o r chlorophenol was used as a substrate. The reaction proceeds in the d ark and under light and is favored by the amount of oxygen present. Th e rates of photooxidation were found to vary by about 2 orders of magn itude with different iron oxides. Photocatalysis mediated by alpha-Fe2 O3 used as pretreatment step enhanced the biodegradability of 2-aminop henol. A favorable BOD5/COD ratio of 0.40 is achieved when photocataly tic pretreatment is applied as compared to a value of 0.23 found for n on-pretreated solutions.