THE FATE OF ORGANIC NITROGEN UNDER PHOTOCATALYTIC CONDITIONS - DEGRADATION OF NITROPHENOLS AND AMINOPHENOLS ON IRRADIATED TIO2

The photocatalytic transformation of 2-, 3- and 4-nitrophenol (NP) and 2-, 3- and 4-aminophenol (AP) over irradiated titanium dioxide was in vestigated in aerated aqueous solution. At pH < 6, extensive mineraliz ation (more than 90%) of the substituted phenols occurs, whereas, at p H 11, organic carbon is persistently observed. Photocatalysis converts 80% of the nitro group in nitrophenols to NO3- through the intermedia te formation of NO2- ions; the remaining 20% is transformed into NH4ions. This implies that, even in aerated solutions, reductive pathways are significant, as confirmed by the detection of aminophenol. By con trast, photocatalytic degradation of aminophenols converts the NH2 gro up into about 60%-70% NH4+ ions and only about 10% NO3-, when about 20 % of the organic carbon remaining. A slow transformation of the ammoni um ions into NO3- ions is observed at longer irradiation times. (C) 19 97 Elsevier Science S.A.