Mechanism of degradation of nitrilotriacetic acid by heterogeneous photocatalysis over TiO2 and platinized TiO2.

C. A. EMILIO; R.T. GETTAR; M. I. LITTER, M. C. APELLA

JOURNAL OF APPLIED ELECTROCHEMISTRY

SPRINGER

Lugar: Londion; Año: 2005 vol. 35 p. 733 - 740

0021-891X

TiO2-heterogeneous photocatalysis of NTA at pH 2.5 was studied to establish the kinetic regime and the mechanism of the reaction. Pure Degussa P-25 and Hombikat UV100 commercial samples were compared. A Langmuirian behavior was observed over P-25. Platinization of the Hombikat sample (0.5 wt.%) caused an important increase on the photocatalytic rate with a change in the kinetics from zero order in the pure precursors to first order in the platinized sample. The nature of the intermediates and their evolution with time were compared on all systems. Glycine, iminodiacetic and oxamic acids have been identified in different proportions, together with ammonium and glycolic acid, depending on the catalyst used. The rapid depletion of NTA was not accompanied by a corresponding TOC reduction, but 84% of TOC decrease was obtained on P25 after 24 h, a very reasonable result for refractory compounds. A detailed mechanism is proposed for the photocatalytic reaction, suggested to be the same over the three catalysts here tested.