Study On Preparation And Properties Of Cation Exchange Alloy Membrane

With the excellent performance,the ion exchange membrane has been widely used in various fields.With the emergence of new deposition treatment processes,cation exchange membranes gradually occupy a central position in metallurgical wastewater treatment.Membrane performance is an important factor restricting the application of ion exchange membranes in electrodeposition processes.Improving the selective permeability and acid and alkali resistance of the membrane and preparing a more excellent cation exchange alloy membrane is of great significance for promoting the application of ion exchange membranes in the chemical industry.In this study,based on a semi-interpenetrating network structure system,a PVDF cation exchange alloy membrane with excellent performance was prepared by a blending method that could be easily controlled.The modified materials selected in this study are mainly inorganic materials,supplemented by organic materials.Among them,the selected inorganic materials are heteropoly acids?ammonium molybdopho-sphate,abbreviated AMP?and oxides?nano Al₂O₃?,and the selected organic material is polyvinyl chloride.The cation exchange alloy resin powder was prepared by controlling the mass ratio of different modified materials to PVDF.The PVDF-AMP alloy membrane?PAP alloy membrane?and PVDF/PVC-Al₂O₃ alloy membrane?PPA alloy membrane?are prepared by traditional hot pressing technology.In order to determine the best mass ratio of blended materials,the conventional properties?ion exchange capacity,water content?,electrical conductivity?membrane surface resistance?,mass transfer characteristics?migration number?,physical and chemical stability?antioxidant quality Percentage?and micro-characteristics?Scanning Electron Microscope,Fourier Transform Infrared Spectroscopy?of the prepared alloy membrane are characterized and compared with the original PVDF membrane.According to the characterization results,the alloy membrane with the best performance was selected and used in the"double membrane three-coell"electrodeposition experiment.By simulating an industrial environment?temperature 60?,deposition time 24 h?,controlling different current densities to electrolyze high concentration cobalt chloride solution.Compared with the polyethylene-based heterophasic membrane and the original PVDF membrane,the effect of the alloy membrane on the amount of cobalt deposition,cell voltage,current efficiency,and acid recovery was measured to verify the actual application effect of the alloy membrane.The research results are as follows:?1?The PAP alloy membrane was prepared by blending ammonium molybdopho-sphate.The membrane characterization results showed that:?1?Microscopic characterization results showed that ammonium molybdopho-sphate can be evenly dispersed into the ion exchange membrane.?2?Compared with the characterization results of the original PVDF membrane,when the mass ratio of ammonium molybdopho-sphate is 2%,the performance of the PAP alloy membrane is different,the membrane ion exchange capacity is increased by 15%,and the water content remains the same.Ammonium molybdopho-sphate can effectively increase the membrane migration number?it can be increased by 2.29%?.Due to the high degree of dispersion and limitation of ammonium molybdopho-sphate,excessive uniform dispersion makes the membrane denser and affects ion transmission.The evenly dispersed ammonium molybdopho-sphate increased the membrane surface resistance of the PVDF membrane by 1.4?·cm².?2?The PPA alloy membrane prepared by blending polyvinyl chloride and nano alumina has the following changes:?1?Microscopic characterization results show that the structure of the PPA membrane is clear,and the membrane surface is flat and uniform.After the oxidation of the PPA membrane and the PVDF membrane,the membrane surface of the PPA alloy membrane penetrated the pores less and was smoother than the PVDF membrane surface,indicating that the destruction of the PVDF membrane was more serious.?2?Compared with the original PVDF membrane,when the blending mass ratio of PVC-Al₂O₃ is 2%,the performance of PPA membrane has been improved to varying degrees,such as:the ion exchange capacity is increased from 1.28 mmol/g dry membrane to 1.74 mmol/g dry membrane;Water content increased from 24.3%to 38.1%;Migration number increased from 88.85% to 94.83%;Membrane surface resistance decreased from 20.3?·cm² to 10.7?·cm²;Anti-oxidation percentage decreased to 31.75%.?3?Compared with PAP alloy membrane,the performance of PPA alloy membrane modified by alumina blend is more superior,and it has greater potential in the field of metallurgical wastewater treatment.?3?The electrodeposition experiment results show that:?1?The cobalt deposition amount of the PPA alloy membrane and the polyethylene-based heterogeneous membrane is equivalent.The optimal deposition amounts are 22.31 g and 22.04 g respectively,which is 15%higher than the PVDF original membrane.?2?The voltage stabilization time of the PPA alloy membrane and the polyethylene-based heterogeneous membrane tank are about 8 h,while the PVDF original membrane's stability time is 1.3 times that of the PPA membrane;The maximum current efficiency of the PPA alloy membrane and the polyethylene-based heterogeneous membrane is up to more than 95%;Under the same conditions,the deposition concentration of hydrochloric acid in the PPA alloy membrane,polyethylene heterogeneous membrane and PVDF original membrane deposition process were 2.53 mol/L,2.37 mol/L and 2.05 mol/L respectively.The acid recovery concentration of the PPA alloy membrane is higher than that of the polyethylene-based heterophasic membrane and the PVDF original membrane,indicating that the PPA alloy membrane has better ion selectivity.?3?The PPA alloy membrane performs well in the electrodeposition cobalt process,and the deposition effect is comparable to commercial membranes,indicating that the PPA alloy membrane can meet the basic requirements of the new membrane electrodeposition cobalt process.