Study On Synthesis Of Sodalite And Its Adsorption Properties

Sodalite was applied in the field of inorganic functionalized material firstly, from which some photochromic materials could be synthesized. In recent years, more studies was focused on using it as the hydrogen adsorbents, and showed that the hydrogen adsorption capacity was higher that other zeolites. Annemieke et. al. pointed out that the volume target could be achieved by sodalite theoretically.Based on the literatures home and abroad about synthesis of zeolites, sodalite was hydrothermal synthesized from sodium aluminate and water glass of industrial purity grade. The parameters in synthesizing process was investigated in detail, such as Si/Al(dosing ratio), alkalinity(H₂O/Na₂O, Na₂O/SiO₂), crystallizing time and temperature, and then the synthesizing parameters and technological conditions was optimized, as well as the phase transition rules. The as-obtained sodalite was characterized by XRD, IR and SEM. What's more, the cation exchange of sodalite was carried out with Fe²⁺, Ni²⁺, Li⁺, K⁺, Mg²⁺ and Ca²⁺ cations. The hydrogen and water adsorption properties of varies cation modified sodalites were also studied.The alkalinity has great effects on the crystallization of sodalite, and so do the crystallizing time and temperature. The optimized conditions for the sodalite of the best quality are listed below.Si/Al=1(dosing ration): 90℃, 12 h, Na₂O/SiO₂=3.75, H₂O/Na₂O=22Si/Al=2(dosing ration): 110℃, 14 h, Na₂O/SiO₂=4.38, H₂O/Na₂O=32Si/Al=3(dosing ration): 110℃, 12 h, Na₂O/SiO₂=2.92, H₂O/Na₂O=32Si/Al=4(dosing ration): 110℃, 8h, Na₂O/SiO₂=2.50, H₂O/Na₂O27The cation exchange process is influenced by the pH value, temperature and the cation concentration of solutions. The hydrogen adsorption capacity of the iron exchanged sodalite after reduction reaches up to 4.8 cm³/g. The water adsorption capacity decreases after Li⁺ exchange and the more the cation exchange processes are carried out, the more the water adsorption capacity was reduced. Whereas K⁺, Mg²⁺ and Ca²⁺, the water adsorption capacity increases by the cation exchanging times.