Study On The Efficiency Of A Novel Fenton-like System Dealing With Tannery Wastewater At Neutral PH Conditions

In this paper, leather biochemical tail water and simulated nitrophenol wastewater was treated to study the processing efficiency and mechanism of a novel heterogeneous Fenton reagent method (or Fenton-like Reagent).The Fenton-like reagent method is a new advanced oxidation method. In the system, Fe(â…¢)-PW12O403-complex is set as a catalyst, and can react with H2O2in neutral PH.Oxidizing substances are generated to degrade the organic wastewater.It not only inherits the advantages of high remval efficiency of a general Fenton system but also expands the scope of appropriate PH values.The main conclusions of the thesis are as follows:(1)The novel homogeneous Fenton reagent does good at the tail water treatment, with CODcr being reduced to below100mg/L-a lever to which tail water can be recycled.Through orthogonal experiments,the influence degree of different experiment factors for the organic removal efficiency is obtained:the dosage of H2O2>PH value>the dosage of the catalyst> reaction time.On this basis,the single factor experiment is designed.The best operating conditions for the Fenton-like oxidation process are as follows:the concentration of H2O2was12.5mM, the PH value was6, the concentation of the catalyst was6.25mM,the reaction time was60min. (2)Compared with the general Fenton,the novel heterogeneous Fenton system shows better removal rate and lower H2O2utilization rate.When4mM Fe(â…¢)+PW12O403-was used as the catatalyst, the concentration of H2O2was50mM, the removal rate of0.5mM nitrophenol reached nearly90percent, while the utilization of H2O2was only about50%.(3)The Fenton-like system is suitable in a wider range of PH values.Of the PH values between5.5to8.5,the corresponding p-nitrophenol removal rate was better than the general Fenton system.However, as the PH increases, the removal efficiency declines in both Fenton systems, especially when pH was above7.5.(4)The main oxidizing substances generated during the reaction process was OH-.According to the results acquired by the EPR detection,the OH· signal is significantly stronger in the Fenton-like system than in the general Fenton system under the same conditions.(5)With reference to the reaction mechanism of the general Fenton reagent under acidic conditions, the reaction mechanism of the Fenton-like system is devised as the following reactions: Fe2+-PW12O403-+H2O2â†'Fe3+PW12O403-+·oH+OH-(1) Fe2+-PW12O403-+H2O2â†'Fe2+PW12O403-+HO2·+H+(2) Fe2+-PW12O403-+HO2·â†'Fe2+PW12O403-+O2+H+(3) Fe2+-PW12O403-+HO2·â†'Fe3+PW12O403-+H2O2(4)...