Study On The Semi-impregnation Preparation,Characterization And Application Of The Bipolar Membranes

On the basis of the cation exchange homogeneous membrane, we prepared bipolar membranes with excellent performances by semi-impregnation method. The properties of bipolar membrane(including the thickness, ion exchange capacity, water content, dimensional stability, ability of producing acid and alkali, Ⅰ-Ⅴ curve) were measured. The effects of the impregnation ratio, the DVB content and the conditions of amination reaction on the physical and electrochemical properties of the prepared bipolar membranes were investigated. Moreover, the actually performances of the bipolar membranes in the electrodialysis were operated and evaluated. At last, two application cases of the prepared bipolar membranes were studied.The bipolar membranes were prepared by semi-impregnation method successfully. The FTIR spectra indicated the successful introduction of chloromethyl groups as well as quaternary amine and tertiary amine ion exchange groups after amination reaction. Electron microscopy pictures showed that both the anion exchange and the cation exchange of the bipolar membrane were dense and homogeneous with a combined closely structure. At the same time, the concentrations of acid and alkali first increased and then decreased with increasing of the impregnation ratio and DVB content. Meanwhile, the potential across the membrane presented the trend of first decline then up. The study also indicated that the temperature of amination reaction was not too high and the content of quaternary amine groups increased with the increasing of the concentration ratio between trimethylamine and dimethylamine.Japanese and Germanic bipolar membranes showed the best electrodialysis performances by comparing the electrodialysis performances of bipolar membranes with different structures. Domestic bipolar membrane, by contrast, had the highest energy consumption. Some properties indicators of prepared bipolar membranes had reached the level of commercial bipolar membranes. At the same time, the lithium hydroxide, sulfuric acid and ammonia all were successfully obtained by using the prepared bipolar membranes electrodialysis. The results showed that the lithium hydroxide concentration reached 3.14 mol/L and the concentration of sulfuric acid reached 2.58 mol/L. Moreover, current efficiency and energy consumption reached the level of commercial bipolar membranes. All the results illustrated that the prepared bipolar membranes had good practical application effect.