| As a large textile production country,China emits about 1.6×109m3dye wastewater every year.Printing and dyeing wastewater emissions accounted for 80%.Printing and dyeing wastewater is characterized by high chroma,high organic content,complex composition,strong toxicity and degradation-resistant.With the increase of denim varieties year by year,the demand for indigo dyes is always high.Therefore,indigo wastewater is one of the most serious water pollution.The purpose of this project is to explore the influence of cell device,electrode material,additive concentration,decolorization time and voltage on degradation efficiency in the electrochemical treatment of indigo wastewater.The degradation conditions were optimized by range analysis,grey clustering analysis and response surface analysis.Firstly,the influence of electrode materials on electrochemical degradation of indigo wastewater in double pools was discussed.Stainless steel and graphite were selected as anode and cathode electrode materials to design orthogonal experiments to explore the influence of Fe Cl3 and Na Cl concentration,decolorization time and voltage on decolorization rate.The decolorization efficiency and the effect of various factors were analyzed by means of mean and range,and the COD and BOD values were measured under the condition of optimized decolorization efficiency to evaluate the biodegradability of wastewater.The results showed that when the wastewater was degraded by a single anode,the decolorization efficiency was the best,reaching 99.01%,COD removal rate was 63.40%,and B/C value was 2.7.Range analysis showed that Na Cl concentration had the most significant effect on decolorization.When the cathode electrode stainless steel and anode electrode graphite were used for degradation at the same time,the decolorization efficiency was the best,which was 98.71%,the COD removal rate of anode wastewater was 57.41%,the B/C value was 2.7,the COD removal rate of cathode wastewater was 88.81%,and the B/C value was as high as 7.1.Range analysis showed that Fe Cl3 concentration had the most significant effect on the decolorization of cathode wastewater,and voltage had the most significant effect on the decolorization of anode wastewater.Secondly,the effects of different chlorine systems,electrode materials,decolorization time,voltage and p H value on the electrochemical degradation of indigo wastewater in a single cell were studied.The results showed that,when the Na Cl massconcentration was 5 g?L-1,the voltage was 7 V,the decolorization time was 60 min and the p H value was 11,the decolorization rate reached 97.88% and the B/C value was 2.1,indicating the best biodegradability.It is concluded from range analysis that p H value has the most significant effect on decolorization rate.Thirdly,the degradation efficiency of indigo wastewater was compared between single and double pools.The experiment showed that the degradation efficiency of single pool wastewater was better than that of double pools.Then,response surface was used to optimize the electrochemical oxidation degradation conditions in a single cell.Finally,analysis and calculation of each element in the flocculation precipitation were carried out,and the following conclusions were obtained: RSM method was used to optimize the conditions of single cell electrolysis.The experiment shows that voltage has the greatest influence on decolorization rate,flocculation precipitation and COD removal rate.The optimized conditions obtained through RSM were as follows: voltage was 9 V,Na Cl concentration was 7.9 g?L-1,decolorization time was 60 min,electrolysis was 200 m L indigo wastewater under this process,decolorization rate of wastewater was 99.01%,COD removal rate was up to 80.34%,and flocculation rate was up to 74.2%.EDS analysis showed that Na,S,K,Fe and other elements change significantly,and Na content in wastewater before treatment was 17.585%,decreased to 5.457%.The content of element S decreased from 8.187% to 1.761%.The potassium content in the wastewater was reduced to 0.The main element added in the wastewater was Fe,which was mainly distributed in the precipitation and neutralization solution.The content of Fe in the precipitation was 54.64% and that in the aqueous solution was 45.36%.The ratio of Fe3+to Fe2+was 4.68?1,indicating that most of the iron dropped from the electrode was converted into Fe3+.Finally,the influence of three-dimensional electrode on electrochemical degradation was explored.Activated carbon was added into the electrolytic cell to form a three-dimensional electrode system,and the degradation efficiency of indigo wastewater by two-dimensional electrode method and three-dimensional electrode method was compared.The decolorization rate of 2-d electrode method was 96.71%,and that of 3-d electrode method was 98.01%.Through orthogonal test design,the influence of Na Cl concentration,activated carbon dosage,electrolysis time and voltage on wastewater absorbance,COD and biodegradability(BOD/COD)was further analyzed.Under the optimal process conditions,indigo wastewater was treated.The three indexes of wastewater absorbance,COD and B/C were analyzed by grey clustering,and theoptimized process conditions were obtained as follows: voltage was 5 V,Na Cl concentration was 10 g?L-1,activated carbon was 1.2 g?L-1,electrolysis was 60 min.At this time,the decolorization rate of wastewater reached 95.84%,COD removal rate reached was 87.5%,and B/C was 1.57. |
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