Study On Utilization Of Sodium Chloride By-product Salt Resource By Composite Diaphragm Electrolysis Technology

Industrial by-product salt is difficult and costly to dispose due to its large amount,variety,complex composition and high toxicity.Enterprises can only solve the environmental pressure caused by by-product salt through landfill or temporary storage,which affects the sustainable development of enterprises.It is an important issue in chemical production to realize the reduction,harmless and resource utilization of by-product salt.At present,the best way to recycle sodium chloride by-product salt is to produce chlorine gas,hydrogen gas,sodium hydroxide and other valuable products by electrolytic method,and then apply them again to form green circular economy.Because the toxic and harmful substances in by-product salt can not be completely removed,the risk of treating by-product salt by ionic membrane electrolysis increases.Due to the low requirements for brine in diaphragm electrolysis,the treatment of sodium chloride by-product salt is relatively simple.The utilization of sodium chloride by-product salt as a resource through diaphragm electrolysis has broad development prospects.In this paper,PTFE emulsion and talc were used as raw materials to prepare composite diaphragm,which avoided the harm of asbestos diaphragm to human body and environment.The effects of the ratio of raw materials,heat treatment technology and diaphragm thickness on the properties of composite diaphragm were studied respectively.The dosage of raw material,heat treatment temperature and appropriate thickness of diaphragm were determined.A composite diaphragm was prepared using vacuum adsorption method,and its electrochemical performance was studied from the aspects of current density,electrolysis temperature,alkali concentration,current efficiency,chlorine purity,and diaphragm stability.The process for preparing composite diaphragms has been determined through research:PTFE and talc were prepared into composite materials in a ratio of 2:4,using 14%sodium hydroxide/sodium chloride solution as solvent to prepare slurry,and a diaphragm was formed through vacuum adsorption.The optimum thickness of the diaphragm was 3mm.After drying the diaphragm at 90℃for 12 h,the composite diaphragm was sintered by stepwise heating method.The optimum sintering temperature was 336℃～350℃,the sintering time was 30 min,and the diaphragm was cooled naturally.When by-products of glyphosate,2,4-D byproducts and byproducts of hazardous waste disposal enterprises were treated by oxidation technology,the total organic carbon（TOC）content in the brine was reduced to 9 mg·L^-1,22 mg·L^-1,22 mg·L^-1,and three kinds of by-products were electrolyzed by composite diaphragm electrolysis technology.The electrolytic operation was safe and stable.Electrolytic energy consumption was 23 KWh·t^-1,1 KWh·t^-1,71 KWh·t^-1 higher than electrolytic purified brine,respectively.The composite diaphragm electrolysis technology can be used to recycle the by-product salt of other industries and help enterprises to develop sustainably.