Comparative study of various advanced oxidation processes for the treatment of tannery wastewater

The leather tanning process generates a large amount of residue. The present work aims to apply an experimental design to assess several parameters of different advanced oxidation processes for tannery residue treatment, such as UV/H2O2, Fenton, photo-Fenton and sono-Fenton, using 70% hydrogen peroxide. As an optimization strategy, chemometric techniques were applied to evaluate the reaction factors: volume of H2O2, HNO3, Fe(II) and reaction time. The evaluated response was the absorbance at 375 nm, which is the maximum absorbance wavelength for this wastewater. Thus, the optimum conditions obtained by response surface methodology for Fenton method were 10.30 mL of 70% H2O2 and 0.124 mL of 0.06 g mL(-1) Fe(II). Under these conditions, 96% decrease in absorbent species and 95% of COD removal occur in 30 min using the sono-Fenton process at pH 3.0 and 298 K. This result for discoloration is approximately 5.4-fold higher than that obtained with the use of UV/H2O2 with 0.87 mL of HNO3 at 298 K and 1.65 h of reaction with 60% of COD removal.