Research On The Process Of Electrodialysis For Salt Recovery From Membrane Concentrate Of Printing And Dyeing Wastewate

Double membrane technology is widely used in the reuse of printing and dyeing wastewater.Although this technology improves the utilization of water resources,it produces more difficult membrane concentrate.The membrane concentrate contains reusable sodium salt.Direct pipe discharge of wastewater will lead to waste of salt resources.Taking electrodialysis as the core,this paper innovatively developed a set of treatment process for the reuse of membrane concentrated salt of printing and dyeing wastewater,and carried out the following research work.The effects of hardness,organic pollutants and initial temperature of membrane concentrate of printing and dyeing wastewater on the concentration of electrodialysis salt were investigated.The results show that hardness will lead to inorganic pollution of electrodialysis system.Organic pollutants reduce the salt concentration efficiency of electrodialysis.The initial temperature of solution in electrodialysis system has little effect on salt concentration.The effects of different operating parameters of Electrodialysis on salt concentration were studied by orthogonal experiment.The order of influence from large to small is the concentration dilution chamber flow ratio,voltage and concentration chamber flow.The process scheme of using electrodialysis concentrated chamber solution as concentrated brine to reuse dyed cloth was designed.The alkalinity in concentrated brine can be effectively removed by acid-base neutralization method.The alkalinity of concentrated brine can be removed from the initial 17170 mg/L to a minimum of 647 mg/L.The minimum color difference can be reduced to 0.18,meeting the requirements of national standard color difference.In the pilot test stage,a set of electrodialysis process for the reuse of membrane concentrated solution salt of printing and dyeing wastewater was studied.This process has been successfully operated in a printing and dyeing plant in Zhejiang Province.Electrodialysis was used as the core process to concentrate the membrane concentrate of printing and dyeing wastewater.Electrodialysis concentrated chamber solution is used as concentrated brine.After the alkalinity is removed by acid-base neutralization method,the concentrated brine can directly replace the sodium sulfate and reuse the dyed cloth.The dyeing and proofing experiments were carried out in Zhejiang A printing and dyeing factory,B printing and dyeing factory and C textile factory.The color difference of recycled dyed cloth with concentrated brine was measured.The results show that the color difference of cloth dyed with concentrated brine meets the requirements of national standard.The final water produced by the pilot process can be directly reused as concentrated brine for dyeing cloth.The operation cost of pilot process is the total cost of equipment electricity and reagent,totaling 85.33 yuan.Operating expenses are basically the same as the total profit.