Study On Modification Of Cation Exchange Membrane Used In The Process Of Metal Electrowinning

To solve the emissions of waste gas and water is one of the most important issues to the development of the metal smelting industry. Along with the development of metallurgical resources reducing increasingly, how to improve the convenient metal purification technology for an environmental friendly is a new topic. The new metal electrowinning method,which apply with two cation membranes sepreated assembly to three components,can solve the problem of the waste in the metal smelting industry. The cation exchange membrane as an important part of the assembly, not only need to intercept the chloride ions which can productce the chlorine, also have the ability to overcome the difficult to run in high temperature, strong acid and oxidizing conditions, but the cation exchange membrane which sells on the market can not reach these requirements, therefore, the choice of the appropriate cation exchange membrane and modified, so that it can meet these requirements.Modified cation exchange membrane using conductive polymer polyaniline, cation exchange membrane as carrier, aniline in protonic acid doping conditions is oxidated Polymerized Polyaniline on the surface of cation exchange membrane.Then test the performance of the modified cation exchange membrane, and the chloride ions interception rate in electrodialysis experiment. Experiments include:(1)At same condition :20℃, the reaction time is 10 minutes, the oxidizing agent is ferric chloride, protonic acid is hydrochloric acid, two kinds of cation exchange membranes are coated the number of coatings. In the coated layer number 5,the chloride ion leakage rate of the modified IONSEP-HC-C is 3.06%, lower 54.12% than to the original membrane; The rate of the modified Nafion 117 is 2.6%, lower 39.53% than to the original membrane.So the focus of the study of perfluorinated cation exchange membrane is Nafion117 which structure is stable and uniform.(2)Discussed the influence of temperature, polymerization time, oxidizing agent, protonic acid in the polyaniline synthesis process of modified Nafion117 membrane performance, the results showed that the optimal conditions of synthesis of polyaniline modified cation exchange membrane is: 40℃, reaction time is 30 minutes, ammonium persulfate as oxidant, hydrochloric acid as protonic acid, the number of coating layer is 3, and electrodialysis experiment of the modified membrane show the chloride ion leakage rate of modified membrane is 1.26%, compared with the original Nafion 117 was reduced by 70.64%.(3)Organic-inorganic composite modified the cation exchange membrane:at first,the cation exchange membrane was modificed by inorganic silica materials with the best conditions,then modificed it with polyaniline film on the surface.This modified method is combine mixing modification with surface modification. The chloride ion leakage rate of the Organic-inorganic composite modified cation exchange membrane is 2.45%, compared with the original Nafion 117 was reduced by 43.02%, and the contrast is found that the chloride ion interception effect of the three kinds of membranes is Nafion/PANi?Nafion/PANi/Si? Nafion/ Si.(4)At the stage of trial production, we do not use the modified cation exchange membrane, the experimental results show that IONSEP-HC-C can reduce chlorine production to 82%~86%, while the Nafion 117 can reduce to 88%~93%, so the application of two cation membranes sepreated assembly to three components in metal smelting process can effectively reduce the chlorine production.