Oxalic acid destruction at high concentrations by combined heterogeneous photocatalysis and photo-Fenton processes

N. QUICI, M. E. MORGADA, G. PIPERATA, P.A. BABAY, R.T. GETTAR, M. I. LITTER

Barcelona, España

Congreso; 3rd. European Meeting on Solar Chemistry and Photocatalysis: Environmental Applications (SPEA3); 2004

In this work, OxH2 degradation at pH 3.7 at relatively high concentrations (0.032 M) using HP, photo-Fenton (PF) and their combination (HP-PF), is described. An annular photoreactor with recirculation, equipped with a black-light tubular lamp (350-400 nm, P0 = 8 meinstein dm-3 s-1), was used. Air was constantly bubbled. In HP, TiO2 Degussa P-25 (1 g L-1) was used. In the homogeneous and combined cases, H2O2 and iron salts (either Fe(II) or Fe(III)) were added  in different molar ratios with respect to OxH2. In the early experiments, OxH2 concentration was measured by capillary electrophoresis and the mineralization degree was followed by Total Organic Carbon (TOC). As it was demonstrated that oxalic acid degradation matched TOC decrease (identical degradation profiles), indicating that probably no intermediates were formed in the reaction, the extent of decomposition in all remaining experiments were followed only by TOC. In all experiments with H2O2, periodical addition of the reagent was made to keep the same initial concentration as long as the reagent was consumed. pH was kept constant at the initial value by periodical addition of diluted HClO4.