IRON OXIDE-MEDIATED DEGRADATION, PHOTODEGRADATION, AND BIODEGRADATION OF AMINOPHENOLS

The results of the photocatalytic degradation and the influence of photocatalytic pretreatment on the biodegradability of 2-aminophenol using 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 techniques like H-1-NMR studies, CO2 evolution, total organic carbon spectrophotometry, and high-pressure liquid chromatography, the more relevant features of the degradation mechanism observed in aminophenols were established. alpha-Fe2O3 appears to react only with aminophenols having electron-donating character through the formation of a surface complex. No similar degradation was observed when phenol, nitrophenol, or chlorophenol was used as a substrate. The reaction proceeds in the dark and under light and is favored by the amount of oxygen present. The rates of photooxidation were found to vary by about 2 orders of magnitude with different iron oxides. Photocatalysis mediated by alpha-Fe2O3 used as pretreatment step enhanced the biodegradability of 2-aminophenol. A favorable BOD5/COD ratio of 0.40 is achieved when photocatalytic pretreatment is applied as compared to a value of 0.23 found for non-pretreated solutions.