<b>Fenton and Photo-Fenton oxidation of tannery wastewater</b> - DOI: 10.4025/actascitechnol.v25i1.2254

Abstract

Fenton and Photo-Fenton processes are attractive alternatives in effluent treatment, especially when applied to recalcitrant compounds. The aim of this work was to evaluate the efficiency of Fenton and Photo-Fenton processes for the treatment of wastewater from leather industry, investigating the reduction of COD, ammoniac nitrogen concentration and toxicity in treated wastewaters. The results showed that the kinetic of degradation by Fenton and Photo-Fenton reactions can be divided in two stages: an initial fast process, where approximately 70% of the COD reduction takes place, followed, by a slow process, where a reaction takes up to 4 hours, resulting in about 90% of COD reduction. Different mass ratios of Fé²⁺/H₂O₂ were tested and the results showed that the efficiency of the Fenton and photo-Fenton reactions increases from 65 to 90% as the concentration of hydroxyl radicals (•OH) increases. No significant difference in the ammoniac nitrogen amount reduction for the Fenton and Photo-Fenton processes was observed, either before or after coagulation. The ammonia removal was ascribed to the oxidation of nitrogen organic compounds, possibly forming N2 and nitrate ions. The toxicity biossays using Artemia salina decreased as the wastewater was degraded and increased if the hydrogen peroxide residue at the end of the reaction was high.