Degradation Mechanism Research Of The Organics And Heavy Metals Using Microwave-Fenton Method

Chelating heavy metal wastewater is often of wide sources, complex composition, a large amount of toxic and harmful organic pollutants and heavy metal, and poor biodegradation performance, which has become the focus of the industrial wastewater treatment. In this dissertation, microwave was used to strengthen the Fenton method in the treatment of analog chelating heavy metal wastewater. The orthogonal test and single factor optimization experiment were carried out to obtain the optimal condition. And the ESR technology and Ferron hourly colorimetric method were adopted to explode the distribution of Fe(III)and the flocculation and oxidation mechanism in the Microwave-Fenton reaction system. By the contrast experiment between Microwave-Fenton and Microwave-H2O2in the treatment of different chelating metal solutions, the synergistic effect of the heavy metal and the degradation of the EDTA were studied. In the end, the remained sludge was treated by microwave and the product was tested by XRD.Apparent analysis results of the orthogonal test show that:the main factors in the Microwave-Fenon reaction are the dosage of Fe2+, dosage of H2O2, initial pH value and the reation temperature, and the reaction will be almost complete when it lasted for9minutes. And the orders in the removal rates of the CODCr and Ni ion are the same, like dosage of Fe2+>initial pH value> dosage of H2O2>reaction temperature>reaction time.But the order of the removal rate of Cu ion is different, like the dosage of Fe2+>dosage of H2O2＞reaction temperature>initial pH value>reaction time.Results of the single factor experiment show that: when Microwave Fenton method treat the EDTA-Cu-Ni water for9minutes, the optimal conditions of this reaction are as follow:0.5mmol/L Fe2+, initial pH value was2.5,185mmol/L H2O2, T=80℃. The quality ratio of CODCr:Fe2+: H2O2is1:0.06:15(mg/L). When the initial pH value is above2.5, it is found that the removal rate of Cu ion doesn’t influenced by the increasing initial pH value, while the removal rates of CODCr and Ni ion decreased.And the removal rates of those presented a three-stage change with the temperature. In the experiment of Ferron hourly colometic, the species distribution of Fe(III) in the Microwave-Fenton system was studied. And the results show that the initial value, reaction temperatue and the dosage of H2O2affect the distribution strikingly. While the initial pHvalue is below2.5or the reaction temperature is below65℃or the H2O2addition is not enough, the degradation of the organics are low, then the Fe ion will chelate with the organics, and the flocculation and oxidation are restrained. The removal rate of the Cu ion is due to the effect of flocculation and oxidation.Concerted catalysis experiment indicate that:the removal rate of CODCr in the EDTA solution by Microwave-Fenton method is the lowest; the chelating function of the heavy metal with EDTA will change the degradation process of EDTA and promote the degradation; Cu ion have Like-Fenton catalisis effect in the Microwave-H2O2reaction, however the initial rate is slow;Moreover, when the Microwave-H2O2reaction includes both Cu ion and Ni ion, the removal rate of Ni ion is depend on the displacement of Cu ion; it’s unfavourable when the degradation of EDTA produce NH4+, which will chelate with Cu ion and lead to the decreasing removal rate of that.ESR technic hasdeteched the·OH in the Microwave-Fenton system.The XRD result shows that it’s available to produce ferrite with remained sludge by Microwave hydrothemol. The EDTA degradation process may be produce the unsable organics, like ethylene and Carboxymethyl methylamine carboxymethyl formaldehyde schiff s base, which were oxidated into amino acetic acid, oxalic acid, formaldehyde and formic acid in the following reactions.The detection results of the product in the microwave-Fenton reaction show that the products are low molecular weight organics as formic acid, methanol, oxalic acid and glycine.