Fenton oxidation treatment of tannery wastewater and tanning agents: synthetic tannin and nonylphenol ethoxylate based degreasing agent

In the present experimental work, the degradation and detoxification of two commercially important products being widely used in the tannery industry as synthetic tannin (ST) and degreasing agent (EP) containing 0.1% of nonylphenol ethoxylate (NPE) as well as degreasing wastewater from re-tanning was investigated using Fenton (FO) and Photo-Fenton (PFC) oxidation processes. FO and PFC oxidation experiments were performed in batch reactors for 30 min at pH 3 +/- 0.2 and 40-45 degrees C, considering the actual temperature and pH values of retanning bath effluents. For the FO experiments the effect of varying Fe(2+) and H(2)O(2) concentrations and UV-C light irradiation on oxidation measured by the parameters COD, UV(254) and UV(280) absorbancies was studied. Toxicity of untreated and FO, PFC-treated synthetic solutions to the freshwater cladoceran Daphnia magna was also tested. PFC provided appreciably high COD (>80%) and UV(254) and UV(280) (>90%) removals for ST. The toxicity could be drastically reduced in the PFC-treated ST samples. A maximum COD removal of 57% for FO and 77% for PFC was obtained for EP samples. However, the FO process resulted in 90% toxicity even after 30 min of oxidation, while the effluent of PFC exhibited 10% of immobilization to D. magna. FO carried out on degreasing wastewater allowed resulted in 72% COD removal as well as 86% and 77% of UV(254) and UV(280) removals, respectively.