The Study On The Synthesis Of Disc-shaped Potassium Ion Sieve Membrane And Its Separation Performance Of Potassium In Seawater In Electrodialysis Process

Because of lack of terrestrial potassium resources in China,the import dependence of potassium fertilizer is higher.But seawater reserves of 550 trillion tons of potassium resources,the development of potassium resources in seawater is of great significance.At present,although the extracting potassium from seawater method with zeolite method had put into industrial application,the efficiency is low in the intermittent ion exchange process and large area were occupied.Therefore,the study on the plate potassium ion sieve membrane and its electric sieve membrane module,could improve the separation efficiency of ions,and has a great significance to further improve the technology of extracting potassium from seawater.This study was based on the previous research on potassium ion sieve membrane.The plate?-Al₂O₃ supported potassium ionic sieve membrane was synthesized by the secondary hydrothermal growth method with the synthetic liquid ratio of n?Si?:n?Al?:n?template?:n?KOH?:n?H₂O?=36.8:8:1:24.8:771 and potassium ion sieve for seed with n-butyl amine and diethanolamine mixed template agent under 200?in 24 h.Further studies on the placement,synthetic time,number of synthesis,template agent and the flow field of the influence on the potassium ion sieve membrane crystal growth were carried.Then it was characterized by XRD,SEM,EDS and gas permeation.It turns out that the potassium ion sieve membrane about 30?m thickness was synthesized successfully.The permeability of H₂ is 20.6×10^-6mol·m^-2·s^-1·Pa^-1 while N₂ 8.1×10^-6 mol·m^-2·s^-1·Pa^-1.And the separation factor of??H₂/N₂?is 2.54.The differential coefficient of permeability is 0.6180 cm³/?h·atm·cm²?.The results of the electric drive experiments show that the permeation flux of K⁺,Na⁺,Ca²⁺and Mg²⁺are 852.61 mmol/?m²·h?,112.38 mmol/?m²·h?,12.44 mmol/?m²·h?,5.26mmol/?m²·h?respectively.The separation factors of K⁺/Na⁺,K⁺/Mg²⁺and K⁺/Ca²⁺are equal7.25,69.85,166.06.So the disc-shaped ion sieve membrane for the separation of potassium ion has a good performance under the effect of DC field.Voltage,temperature and concentration were researched on the influence of the permeation flux and separation factors of potassium ion sieve membrane.The migration rates and permeation flux of K⁺,Na⁺,Mg²⁺and Ca²⁺were increased with the increase of voltage and the separation factors of K⁺/Na⁺,K⁺/Mg²⁺,K⁺/Ca²⁺were also increased.The ion thermal motion increased with Temperature,so the migration rates and permeation flux were increased but ion selective declined.And the migration rates and permeation flux of K⁺,Na⁺,Mg²⁺and Ca²⁺were increased with the increase of concentration.Ion selective were declined but still had a good selectivity.The potassium ion sieve membrane still has a better performance in the seawater and concentrated water.In the process of electrodialysis,potassium ion sieve membrane combined with anion-exchange membranefilm show a good application performance on extracting potassium from seawater and concentrated water.