Study On The Treatment Of Methylene Blue Simulated Wastewater By The Three-Dimensional Electrode Method

Dyeing wastewater which belongs to high concentration organic wastewater can pollute the environment seriously due to its toxic and harmful substance. The wasterwater have the characteristics of large amount,complex ingredients,high alkaline,deep chromaticity. Therefore, the comprehensive treatment to the dyeing wastewater has become one of the urgent problem.In the field of wastewater treatment,the electrochemical method is a kind of green waste water treatment technology, it has the advantage of high load per unit volume, simple operation, easy operation, fewer by-products, etc. The experimental research used the three-dimensional electrode reactor that was made by myself, Methylene Blue (MB) simulated wastewater was the research object, studyed the three-dimensional electrode method treat the dyeing wastewater.The three-dimensional electrode system use graphite plate as cathode and anode, and activated carbon as particle electrodes. The research discussed the electrode gap, concentration of electrolyte, electrolytic voltage, the amount of activated carbon, electrolytic time and other factors on the effect of MB decolorization rate through single factor experiment, and then optimize the test operation for the best operation parameters, put forward the optimum process conditions of the system.The results of orthogonal test showed that, when the conditions were 20V of electrolytic voltage,4cm of electrode gap, 2.0g/L of Na2SO4 concentration,400g of activated carbon, and 60 minutes of electrolytic time, the decolorization rate and CODcr removal rate of MB wastewater of three-dimensional electrode method were 92.6% and 78.9%, respectively.The selection of anode used several common kinds of material including stainless steel, titanium plate, iron plate, aluminum plate. The stainless steel had the best effect on MB degradation that at 60 minutes of reaction time the removal rate reached 93.62%.While titanium and iron plate had the similar degradation trend and effect, aluminum plate followed. But when using Iron and aluminum plate as anode, the system both had produced the floccules, which were not conducive to the reaction.DAS electrodes including Ti/RuO2-TiO2, Ti/IrO2-Ta2O5, Ti/SnO2 and Ti/RuO2-TiO2-IrO2 which was prepared by the method of thermal oxidation were used, and their surface morphology and structure were characterized by different analytic methods. The results of wastewater treatment showed that the prepared Ti/RuO2-TiO2-IrO2 electrode on MB removal rate was superior to other DSA electrodes, and it belongs to the better anode material. The decolorization rate and CODcr removal rate of MB wastewater were 87.83% and 74.45% respectively in the time of 60 minutes, and the wastewater degradation followed a pseudo-first-order reaction kinetic model.The results of the comparative experiments between the method of three-dimensional and two-dimensional electrodes showed that the effects of three-dimensional electrode method on MB removal rate were better than the two-dimensional electrode method on different factors including initial concentration of MB, current value, electrode gaps, pH value, reaction time. At the same time, three-dimensional electrode method has a great advantage over saving energy consumption. When the MB removal ratereached 80%,the energy consumption of three-dimensional electrode accounted only about 7.5% of the two-dimensional electrode consumption.Processes for actual dyeing wastewater containing MB were took the methods of coagulation/three-dimensional electrode. Three kinds of coagulant including PAC, A12(SO4)3 and Fe2(SO4)3 were tested. PAC had the best CODCr removal rate with optimal dosage of 0.7g/L, A12(SO4)3 and Fe2(SO4)3 followed. Finally PAC was selected. Then the coupling of PAM/PAC was used to reduce coagulation time, CODcr removal rate was 27.85% at 30 mg/L of PAM and 0.7 g/L of PAC. The concentration of CODcr reduced from 3158 mg/L to 2279 mg/L, which was only 3.71% higher than used PAC, but the settling time was shorten from 48 minutes to 21 minutes. The method three-dimensional electrode was treated on the wastewater after coagulation. When the electrolytic time was 60 minutes, the removal rate of CODCr reached 42.36%, and the concentration of CODCr decreased from 2279mg/L to 1314mg/L. The index of BOD5/CODcr increased from 0.1 to 0.37.The biodegradability was significantly improved, which is created a good condition for the subsequent process.