Preparation And Properties Of Polyvinylidene Fluoride (PVDF) Ion Exchange Membrane

With the great development of science and technology and the pursuit of material spirit in all aspects of human life,it is more necessary to protect the environment in the case of satisfying human needs.In wet metallurgy industry,most of cobalt production are used cobalt electric deposition process at present.It is used deposition in inert electrode as anode,pure cobalt plate as cathode,and cobalt chloride solution as the electrolyte to produce cobalt.Chlorine gas is inevitably caused in such the production condition.Chlorine is a toxic and harmful substance to the human body,and it can cause great pollution to the environment.Ion exchange membrane is suitable for electrolysis because of its specific selectivity,good conductivity,high stability and plane structure.It is applied in the electrodeposition process of film and cobalt,and the cobalt is deposited from the cobalt system of the cobalt chloride system,and the generation of chlorine gas will be avoided.The two membrane tri-cell electrolytic cells are divided into three compartments by the cathode and anode ion exchange membrane: the anode chamber,the middle compartment and the cathode chamber.Cationic exchange membrane as the core component in the electrodeposition process of film,its important role is self-evident.Therefore,the preparation of a cationic exchange membrane with excellent comprehensive properties and suitable for the electrodeposition process of film is the focus of the research.Polyvinylidene fluoride(PVDF)has good chemical properties,such as corrosion resistance,oxidation resistance and high temperature resistance.At present,there are more and more researches on the membrane research field.Through a lot of research and experiments,it is found that it is a good substrate for the preparation of homogeneous ion exchange membrane.Therefore,PVDF cation exchange membrane was prepared by chemical grafting method in this paper.The preparation process was: PVDF base film preparation,PVDF basement membrane alkalization,initiation of grafting and sulfonation.With ion exchange membrane key performance indicators(ion exchange capacity,burst degrees,chloride ion leakage rate,the membrane resistance and the oxidation resistance of membrane)is a standard,the stages of experimental conditions are analyzed and the optimal conditions are discussed in the process of preparation.Under the optimum conditions of preparation,doped nano-inorganic particles(Si O2 and Ti O2 nanometer)are modified to improve the performance of the modified membrane.The modified membrane and the commercial membrane are applied to the electrodeposition process of the film,and the effect of the self-made film and the film barrier is compared.When PVDF cation exchange membrane is prepared,the control film thickness is0.15 mm.The optimum conditions in each preparation stage are determined by experimental analysis.In the preparation stage of PVDF base film,when the mass concentration of PVDF is26%,the resistance of the base film can meet the experimental requirements well.During thealkali treatment phase,when the concentration of alkali solution was 0.08mmol/L,and the temperature was 65 degrees,and the time was 75 min,the grafting rate of the PVDF substrate under this condition is very high and the mechanical strength of the basement membrane is not destroyed.In the stage of the trigger grafting,when the concentration of BPO is 0.6 g/(100ml),the temperature is 65 ℃,time of 9 h.In this condition,the grafting rate of the PVDF alkali membrane is 30.57%.In the stage of sulfonated best sulfonated condition is that temperature is 65 ℃ and time is 8 h.The ion exchange capacity(IEC)of PVDF positive film made under this condition is 1.87mmol/g,the bursting degree is 0.4876 MPa,the chloride leakage rate is 8.70%,the film resistance is 10.17 and cm2,and the antioxidant is 12 d.In the preparation of PVDF cationic exchange membrane,it is found that the color of each stage is different,and the reason of the change of the membrane color is analyzed by SEM.In comparison with the performance of the above homemade PVDF cationic exchange membrane and the commercial film,the PVDF Yang film has been found to have the function of the commercial film,but there is still a certain gap.In the doping of inorganic nanoparticles(Si O2 and Ti O2 nanometer total doping amount accounts for 1.5% of PVDF quality of casting solution)of the PVDF cation exchange membrane is modified research.It is found that more excellent performance of the modified membrane.When Si O2 / Ti O2 ratio of 2:1,the modification of PVDF Yang membrane performance is best.In the condition of the PVDF Yang membranes modified burst degree is0.4621 MPa,the oxidation resistance is 15 d,ion exchange capacity is the IEC = 2.34mmol/L,chloride ion leakage rate is 3.89%,and the membrane resistance is 8.03 Ω cm2.SEM analysis shows that the addition of nano-inorganic particles can effectively block the large pore channels in PVDF positive film,which make the film pores smaller and the membrane become more dense.The effect of blocking chloride ion in the small test experiment is remarkable,and the other performance indexes are similar to that of the commercial film.Therefore,the electrodeposition process has great application value in the cobalt industry.