Fenton-type heterogeneous oxidation of paper mill effluent in batch and continuous reactors

Abstract

The application of heterogeneous Fenton-type systems was studied, using an industrial paper mill effluent and a model solution of sodium acetate. The reaction was investigated in a batch and a fixed bed reactor, at 70 °C. Different copper-based catalytic materials were supported on commercial spheres of gamma alumina. Besides, Zn, Fe, and Ce-containing catalysts were prepared and preliminarily tested for the acetate peroxidation, with comparative purposes. All the catalysts were calcined at 900 °C to improve the anchorage of active species on the support. For the experiments performed with acetate solution in the batch system with Cu2+/Al2O3 catalyst (C1 and C2), the TOC conversions were approximately 20%. With the industrial effluent, the TOC conversions were close to 45%, with leaching levels below 0.1 ppm Cu. In the continuous system, TOC reductions of the effluent were 20- 30% after 4 h of operation. The decolorization degrees and oxidant consumptions were complete and the estimated reductions in aromatics content were near 70% (SUVA 254 nm), with a COD reduction of ca. 40%. The impact of two reaction parameters (oxidant concentration and residence time) was investigated, with a slightly positive effect.