Modification Of PVDF Cation Exchange Alloy Membrane

At present,ion exchange membranes used in chemical metallurgy,medicine,environmental protection and other fields include heterogeneous membranes and homogeneous membranes.Although the cost of heterogeneous membranes is low,heterogeneous membranes have the disadvantages of “holes” and “de-powdering”;Although the homogeneous film has excellent performance but high cost,it is not suitable for application.In view of this background,based on the preparation of a PVDF semi-interpenetrating network cation exchange alloy membrane with lower cost but better performance than heterogeneous ion exchange membrane,the PVDF cation exchange alloy membrane was studied in this experiment.Modification,improve the electrochemical index of the alloy film and other basic indicators.In order to solve the above problems,in this experiment,a blended polyaniline particle with high conductivity was selected as the modified material,and the surface infiltration modification method was used to increase the amount of doped polyaniline in different proportions.The self-made PVDF cation exchange alloy membrane was modified;in order to obtain the performance of the better ion exchange alloy membrane,the second modification scheme was designed and compared with the scheme one,and the most effective modification scheme was selected.In scheme 2,The film-modified common material-nano-silica is used as the modifying substance,and considering that the nano-silica does not have conductivity,the nano-silica and the doped polyaniline are mixed to form a polyaniline-In order to determine the optimum mass ratio of the composite particles,nano-silica composite particles were prepared by mixing several different mass ratio composite particles to the self-made PVDF cation exchange alloy film.In order to determine the effect of the modification,the membrane properties of the ion exchange alloy membrane modified by the two schemes and the unmodified PVDF cation exchange alloy membrane were characterized.The characterization indexes include: ion exchange capacity(IEC),migration number.Film resistance,water content,hydrophilic angle,scanning electron microscopy(SEM),and Fourier transform infrared spectroscopy(FT-IR).Finally,by comparing the experimental data,the optimal addition ratio of doped polyaniline in the surface infiltration modification scheme is determined;and the optimum mixture ratio of the composite particles is prepared in the composite particle blending modification experiment;The results of the two experimental schemes were compared to select a modification scheme that maximized the performance of the PVDF cation exchange alloy membrane.According to the experimental data,the performance of the ion exchange alloy membrane modified by the surface infiltration of polyaniline has undergone the following changes:(1)The microscopic morphology of the membrane was observed by scanning electron microscopy and it was found that the surface was infiltrated and modified.The doped polyaniline particles were successfully introduced into the surface of the alloy film.(2)By comparing the characterization results of the modified cation exchange alloy film before and after modification,it was found that the cation exchange was carried out after the surface infiltration modification of the doped polyaniline particles.The exchange capacity of the alloy film increased by 0.855 mmol/g,and accordingly,the moisture content of the alloy film increased from 25.3% to 34.3%;however,this modification scheme could not effectively improve the selective permeability of the film and the migration of the alloy film.The number is only increased by 0.02;(3)the doped polyaniline can effectively improve the conductivity of the ion exchange alloy film.According to the measured film surface resistance data,the film surface resistance is greatly reduced by 14.1 cm 2 · ?;(4)Finally,through the comparative analysis of the experimental data,it can be determined that when the added mass of the doped polyaniline particles is 10% of the mass of the methanol used as the solvent,the surface infiltration modification can be taken.Get the best results.Through the characterization of each performance,the blending modification method using the mixed state/nano-silica composite particles can obtain the following conclusions:(1)The film surface of the alloy film can be visually observed by electron microscopy scanning analysis.The morphology and the structure of the membrane changed.(2)The blending modification scheme has different degrees of improvement for the five major indexes tested.The most obvious modification effects are ion exchange capacity and water content.The increase of 1.445mmol/g and 12.7%,and the migration number of the alloy film increased from 0.89 to 0.95,and the permeability was also greatly improved.On the index of membrane surface resistance,the blending modification was obtained.The effect is also excellent,which is reduced by 11.2 cm2·?;(3)after comparative analysis,when the doping polyaniline/nano silica composite particles with a mass ratio of 1:2 are blended and modified,the chemical for the film For the modification of indicators,the effect is the best.Comparing the experimental steps and modification effects of the two schemes,it can be concluded that although there are many disadvantages in the experimental steps,the blending modification scheme is compared with the surface infiltration modification in the modification of the cation exchange alloy membrane.The program has a greater advantage.Firstly,the doping state/nano silica conforming to the particle modification of the alloy film can improve the performance of the ion exchange alloy film as a whole,and can more fully exert its advantages in the subsequent application;secondly,because of the first The preparation of the composite particles results in a multitude of steps for the blending modification scheme,but the preparation of the composite particles is simple and easy to obtain various raw materials.In summary,the blending modification of PVDF ion exchange alloy membranes using blended polyaniline/nano-silica composite particles is the most effective modification in this study.