Study On The Preparation Of Lithium Ion Sieve Membrane And Its Application Performance

The extraction of lithium carbonate from seawater has great prospects,in the resource use of sustainable development. At present, the work has focused on the synthesis of spinel-type manganese oxide. The weak points such as bad permeation, flowability,discontinuity, long period and large ground areas will not problems, when lithium ion sieve membrane used to extract lithium. So the research on the lithium ion sieve membrane has theoretical and applicative values for extraction of lithium carbonate from seawater. The synthesis condition, characterization and performance on permeability of lithium ion sieve membrane were studied.First, study the conditions of the lithium ion sieve membrane synthesis,which were painted silica sol as transition layer.The transition layer was synthesized via sol-gel using TEOS, H₂O, EtOH, HNO₃ and CTAB as the raw materials. The factors of the template agents, dilution of the silica sol, TEOS / H₂O and the painting times on the surface of theα- Al₂O₃ eramic tube were inspected. The calcination temperature and the rate on the tube painted silica sol as transition layer were also researched.After those workes,the lithium ion sieve membrane was synthesized with the raw materials of Mn(NO₃)₃, LiOH and H₂O₂. To compound lithium ion sieve membrane, when using CTAB as template agent to make the silica sol, and with the molar ratio of 1(TEOS):6(H₂O):3.8(EtOH):0.085(HNO₃),after, theα- Al₂O₃ ceramic tube was painted three times using the sol diluted by EtOH, dryed, calcinated, and at last, lithium ion sieve membrane was obtained via the hydrothermal synthesis for three times. From the SEM images, the continuous and dense lithium ion sieve membranes were formed on the seeded supports. The gas permeability was well, and the ideal separation factor achieved 0.7157 as to the nitrogen and the hydrogen.The second condition to obtained the lithium ion sieve membrane was using the synthesized zeolite membranes as transition layer. It was synthesized with the above molar ratio of 36.8Si:8Al:1template:24.8KOH:771H₂O by the secondary growth hydrothermal method, and the reaction lasts for 24 hours at 200℃. In this method,the optimal condition for ion sieve membrane synthesis is to be synthetized for three and four times. via the hydrothermal synthesis. When lithium ion sieves the membrane were synthesized three time or four time, the abilities of single gas permeability determination were well, and the ideal separation factors were 1.161 and 1.520 respectively. So this method to synthesize ion sieve membrane was better than the first method. In addition, if use the high molar ratio of SiO₂/Al₂O₃ to synthesized the zeolite membranes, it can be found a lot of crackes on the surface of the lithium ion sieve membrane. And, that is not a good condition to obtained the lithium ion sieve membrane.It was found that the ion-exchange properties can be performanced, the process of ions exchange can take place spontaneously without any adscititious energy, but its stability should be further studied.