Study On The Treatment Of Methylene Blue Dye Wastewater And COD Removal Kinetics By Multiple Internal Electrolysis

Compare with other industrial wastewater,dyeing wastewater has the characteristic of deep chroma,high concentration,complicated components,poor biochemical degradation and so on,which make it one of the urgent environmental problems to be solved.The internal electrolysis system was introduced in China from 1980 s.The method is simple in operation,low in cost,and has great achievements in the treatment of refractory wastewater.Methylene blue simulated wastewater was taken as a treatment target in this paper.Based on the traditional binary internal electrolysis system of Fe/C and Fe/Cu,which is constituted by adding metal Al and Cu to ternary or quaternary internal electrolysis system: Fe+Al/C,Fe+Al/Cu,Fe/Cu+C,Fe+Al/Cu+C.The effect of mass ratios,filler dosage,initial pH,reaction time and reaction temperature of each system on COD removal efficiency in the methylene blue wastewater has been researched by single factor experiment and optimized by orthogonal experiment to determine the order of the influencing factors and the optimum reaction conditions can be obtained for the best effect.The COD removal kinetics of methylene blue wastewater in each reaction system was studied in depth.The main research contents and conclusions were as follows:(1)In the traditional binary system of Fe/C and Fe/Cu,the optimum process parameters of COD removal rate by orthogonal experiment analysis were:Fe/C mass ratio of 1:1,filler dosage of 12g/L,initial pH of 6,reaction time of 48 h,reaction temperature of 25℃;Fe/Cu mass ratio of 4:5,filler dosage of 27g/L,initial pH of 6,reaction time of 8h,reaction temperature of 20℃,respectively.The influence of various factors on COD removal efficiency in order were: initial pH> reaction time>reaction temperature> filler dosage;initial pH> reaction time> filler dosage> reaction temperature.(2)In Fe/Cu+C、Fe+Al/C、Fe+Al/Cu、Fe+Al/Cu+C systems,the optimum process parameters of COD removal rate by orthogonal experiment analysis respectively were: Fe/Cu/C mass ratio of4:5:1,filler dosage of 20g/L,initial pH of 6,reaction time of 12 h,reaction temperature of 20℃;Fe/Al/C mass ratio of 5:1:5,filler dosage of 13.2g/L,initial pH of 7,reaction time of 48 h,reaction temperature of 25℃;Fe/Al/Cu mass ratio of 4:0.5:5,filler dosage of 15.2g/L,initial pH of 5,reaction time of 28 h,reaction temperature of 25℃;Fe/Al/Cu/C mass ratio of 4:0.2:5:1,filler dosage of 20.4g/L,initial pH of 7,reaction time of 24 h,reaction temperature of 25℃.By optimizing the conditions with the orthogonal tests,the primary and secondary order of influencing factors respectively were: initial pH> filler dosage reaction time> reaction temperature;initial pH>reaction time> reaction temperature> filler dosage;filler dosage> initial pH> reaction temperature>reaction time;filler dosage> reaction time> reaction temperature> initial pH.(3)Under the optimum process parameters,the COD removal rates of Fe/C、Fe/Cu、Fe+Al/C、Fe+Al/Cu 、 Fe/Cu+C and Fe+Al/Cu+C systems are all higher than 90%.The reason is that the micrometer iron has a larger specific surface area,the micro primary cells between iron and cathode has formed more,and the adsorption and reduction ability of pollutants are also stronger.In addition,the particle size of iron powder,copper powder and aluminum powder used in this study is close to nanometer scale,and it’s inferred that it has some nano-material characteristics,thereby impoving the pollutant removal effect.Taking into account the economic cost and time cost,Fe+Al/Cu is a suitable system for treating methylene blue dye wastewater.(4)Through the analysis of COD removal kinetics,the COD removal of Fe/C、Fe/Cu、Fe+Al/C、Fe+Al/Cu,Fe/Cu+C,Fe+Al/Cu+C systems can not be described by pseudo first-order-kinetic model,but can be well described by pseudo-second-order kinetic model.This indicates that the reaction occurs on the surface of the medium.The liquid-film diffusion was the rate contrilling step of Fe/C、Fe+Al/C、Fe+Al/Cu、Fe/Cu+C、Fe+Al/Cu+C systems,but the COD removal of Fe/Cu system can not be described by liquid-film diffusion model.