Comparative Study Of Fenton And Class Fenton Treatment Of Printing And Dyeing Wastewater

In our country, there are about 600 or 700 million tons of printing and dyeing wastewater discharging into the water environment every year. Its characteristics are complicated composition, deep chromaticity, high toxic substances, high chemical oxygen demand (CODcr), difficult treatment and so on. It has been accounted that 35%of the whole industrial wastewater is discharged, which causes serious damage to water environment, even to the safety of human life. With the development of science and technology, printing and dyeing wastewater treatment are also growing, roughly dividing into physical method, chemical method and biological method. Fenton treatment, as a kind of chemical method, has also been introduced to treat the printing and dyeing wastewater since was found. After continuous in-depth study, on the basis of Fenton technology, the class Fenton technology came into being, and its effect is very good.This paper selected the Fe0 and Fe3+ instead of Fe2+ for the Fenton reaction, which formed class Fenton reagent to treat printing and dyeing wastewater. We found the best reaction conditions and the best effect from class Fenton, and compared with the results of Fenton reagent. This paper studied the factors of pH, H2O2 dose, the different valence state of irons and reaction time on the effect of CODCr removal rate and the decolorization rate of printing and dyeing wastewater by experiment. The results showed that the optimized experimental conditions were:for H2O2/Fe0 system, pH=3.0, [Fe0]=3.0 mmol/L, [H2O2]=9.0 mL/L, reaction time was 40 min; for H2O2/Fe2+ system, pH=3.0, [Fe2+]=6.0 mmol/L, [H2O2]=12.0 mL/L, reaction time was 100 min; for H2O2/Fe3+ system, pH=3.0, [Fe3+]=5.0 mmol/L, [H2O2]=12.5 mL/L, reaction time was 100 min.Under those conditions, CODCr removal rate were 95.99%,95.85%,95.89%, the decolorization rate were all 100%.Through the analysis of the results of Fenton treatment and class Fenton treatment, we could understand their respective advantages and disadvantages. It has been found that different valence irons and H2O2 dose shuld be meeted with a certain ratio in three different reaction system to make a better effect. The certain proportions of different valence state of irons and H2O2 dose for three different reaction systems were:H2O2 (mL):Fe0 (mmol)=3:1, H2O2 (mL):Fe2+ (mmol)=2:1, H2O2 (mL):Fe3+ (mmol)=5:2. Through the comparative analysis by the experiment results, we could find the final effect of H2O2/Fe0, H2O2/Fe2+, H2O2/Fe3+ three distinct reaction system were basically the same in dealing with wastewater. But under the same effect, the advantages of H2O2/Fe0 system were most obvious by the less dose of Fe0 and H2O2, the short reaction time. H2O2/Fe3+ and H2O2/Fe2+ system not only had the same reaction time, but also add the same dose of medicine. Just H2O2/Fe3+ system of decoloring rate is very high, in a very short period of time, and can make wastewater meet good decolorization effect.By analyzing and comparing the differences between the three systems, we could better understand and master the Fenton reagent and class Fenton reagent, which provide some support of using class Fenton treatment wastewater research in future.