| The chemical oxygen demand (COD) removal efficiency for treatment of an oil-water emulsion from the machinery industry using Fenton's reagent was investigated. The optimal [H2O2]/[Fe2+] molar ratio for COD removal was 3. An orthogonal test was designed based on the optimal molar [H2O2]/[Fe2+] ratio to evaluate the significance of four parameters relevant to the treatment process, namely, H2O2 dosage, initial pH, oxidation time and coagulation pH. The influence of the following parameters on COD removal efficiency decreases as follows: H2O2 dosage > oxidation time > coagulation pH > initial pH. The COD removal efficiency was investigated based on the most important single-factor parameter which was H2O2 dosage, as discovered in the orthogonal test. A well-fitted empirical correlation was obtained in the single-factor analysis and up to 98% COD removal was attained using 50 mM H2O2. With the increase of H2O2 dosage up to 50 mM, the COD removal efficiency increased rapidly due to a higher generation of hydroxyl radicals. However, this effect becomes less significant as the dosage of H 2O2 increases. This effect might be attributed to the consumption of hydroxyl radicals with excess H2O2. The coagulation function of Fenton's reagent was confirmed by scanning electron microscope (SEM). Using the doses and conditions identified in this study, the treated oil-water emulsion can be discharged according to Chinese Standard JS-7740-95. |
