Heterogeneous catalytic Wet Peroxide Oxidation Systems for the Treatment of an Industrial Pharmaceutical Wastewater

Abstract

The aim of this work was to assess the treatment of a wastewater coming from a pharmaceutical plant through a continuous heterogeneous catalytic wet peroxide oxidation (CWPO) process using a Fe2O3/SBA-15 nanocomposite catalyst. This catalyst was preliminary tested in a batch stirred tank reactor (STR), to elucidate the influence of significant parameters on the oxidation system, such as temperature, initial oxidant concentration and initial pH of the reaction medium. In that case, a temperature of 80ºC using an initial oxidant concentration corresponding to twice the theoretical stoichiometric amount for a complete carbon depletion and initial pH of ca. 3 allow obtaining TOC degradation around 50% after 200 minutes of contact time. Thereafter, the powder catalyst was extruded with bentonite to prepare pellets that could be used in a fixed bed reactor (FBR). Results in the up-flow FBR indicate that the catalyst shows high activity in terms of TOC mineralization (ca. 60% under steady-state conditions), with an excellent use of the oxidant and high stability of the supported iron species. The activity of the catalyst is kept constant, at least, for 55 hours of reaction. Furthermore, BOD5/COD ratio is increased from 0.20 up to 0.30, whereas the Average Oxidation Stage (AOS) changed from 0.70 to 2.35. These two parameters show a high oxidation degree of organic compounds in the outlet effluent, which enhances its biodegradability, and favours the possibility of a subsequent coupling with a conventional biological treatment.