Study On Ion Exchange Equilibria Of Between The Modified-Clinoptilolite And Aqueous Solutions Of Ca²⁺, Mg²⁺

The new technology for extracting potassium from seawater by modified-clinoptilolite has been industrialized. There are ion exchange equilibrium between clinoptilolite and Na+, K⁺, Mg²⁺, Ca²⁺+, NH4 in this technology. The ion exchange equilibrium between the modified clinoptilolite and the solutions of Ca²⁺-K⁺,Mg²⁺-K⁺²⁺+,Ca-Na,Mg²⁺+²⁺+-Na,Ca-NH4,Mg²⁺+-NH ₄⁺²⁺duality systems and K-Ca-Mg²⁺+²⁺,Na-Ca-Mg²⁺+²⁺,NH4-Ca-Mg²⁺ ternary systems were studied to supply a foundation for further development of this technology and expand the application area of the zeolite.The ion exchange equilibria data between the clinoptilolite and the duality solution systems of Ca²⁺-K⁺, Mg²⁺-K⁺²⁺+, Ca-Na, Mg²⁺+²⁺+-Na, Ca-NH4, Mg²⁺+-NH4 were determined at the temperature of 0℃, 25℃, 50℃and 75℃. The corresponding isotherms of ion exchange were constructed. Diagrams of Kielland were drawn and thermodynamic functions of ion exchange process were calculated. The results show that ion exchange of Ca²⁺-K⁺, Mg²⁺-K⁺, Ca²⁺+-Na, Mg²⁺-Na+²⁺+, Ca-NH4, Mg²⁺+-NH4 are incomplete exchange, low temperature is propitious for the adsorption of Na+, K⁺+, NH4, on the contrary, high temperature is in favor of the selectivity of modified-clinoptilolite to Ca²⁺, Mg²⁺.The ion exchange equilibria between the modified-clinoptilolite and the ternary solution systems were studied. The ion exchange equilibrium data of the systems of K⁺²⁺-Ca-Mg²⁺, Na+²⁺-Ca-Mg²⁺+²⁺ and NH4-Ca-Mg²⁺ were mensurated at the temperature of 0℃, 25℃, 50℃and 75℃, and the corresponding isotherms were plotted. Based on the experimental results, the ternary separation factors of the ions were calculated.The results show that in the K⁺²⁺-Ca-Mg²⁺ system, the value of the is more than 100, the value of ranges from 0.05 to 0.81 and the value of is below 0.5. So the ion exchange selective sequence of clinoptilolite is KKMgCa,αCaMgK,αMgCaK,α+²⁺>Ca>Mg²⁺ in the same temperature; lower temperature is propitious for the adsorption of modified-zeolite to K⁺, on the contrary, higher temperature is in favor of the selectivity of the zeolite to Ca²⁺ and Mg²⁺+²⁺. In the Na-Ca-Mg²⁺ system, the value of the is more than 10, the value of is between 0.4 to 10 and the values of is below 0.4, so ion selectivity sequence of clinoptilolite is NaNaMgCa,αCaCaNa,αMgCaNa,α+>Ca²⁺>Mg²⁺, the higher temperature enhances the adsorption capability of zeolite to Ca²⁺ and Mg²⁺ . It was also fouded that the value of the is more 4,NHMgCaα than 15, the value of is between 0.2 to 1.5 and the value of is below 0.2, so the ion selectivity sequence of clinoptilolite is NHCaMgNH,4αMgCaNH,4α+²⁺4>Ca>Mg²⁺, the higher temperature improves the adsorption capability of zeolite to Ca²⁺²⁺ and Mg.