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

Chemical resources are rich in seawater, and the total reserves of potassium are500billion tones. From the perspective of sustainable development, the extraction ofpotash from seawater has bright prospects. The defects such as discontinuity, longcycle and large ground occupation of the granular potassium ion sieves can beovercome through using potassium ion sieve membrane which is suitable forcontinuous separation. So studying on the noval potassium ion sieve membrane hasimportant application value for improving the market competitiveness for extractionof potash from seawater.The potassium ionic sieve membranes were synthesized on porous α-Al₂O₃support employing secondary hydrothermal growth using NaAlO2, soluble glass,KOH as the raw materials. In the synthesis aspect of potassium ionic sievemembranes, the influencing factors of seeding concentration, mean pore size ofsupports, water content, alkali content, templates content and etc were investigatedrespectively. The prepared membranes were characterized by means of SEM andsingle-gas permeability. The results show the optimum synthetical conditions of thepotassium ionc sieve membranes are as follows: synthesizing on the outer surface ofα-Al₂O₃tube support with1.0μm mean pore size, seeding beforehand by vacuummethod, employing secondary hydrothermal synthesis in the synthetic liquid andusing C16H36BrN as templates. The results show that the prepared membranes waspotassium ionc sieve membranes. From the SEM images, the continuous and densezeolite membranes were formed on the seeded supports. The ideal separation factor is4.56at room temperature in comparing with Knudsen diffusion ratio of3.74for N2/H2,which means that the membranes have good performance for selective separation.The separation selectivity of the ionic sieve membranes to K⁺, Na⁺, Ca²⁺andMg²⁺were measured by ionic exchange experiment. The results show that the separation factors of K⁺/Na⁺，K⁺/Ca²⁺，K⁺/Mg²⁺are respectively equal to18.06，32.10，118.45, which mean that the potassium ionic sieve membranes have certainselectivity to K⁺. For futher study on the separation selectvity of potassium ionic sievemembranes, the dependence of separation factor on the conditions of flow weremeasured. It was found that low flow are benefit to separation of K+, the process ofions exchange can take place spontaneously without any adscititious energy.