| Popis: |
The objective of the present work was to study transformation of Georgian natural zeolites, analcime and phillipsite, during their recrystallization in the aim to obtain zeolites A and X, widely used for adsorption, separation, ion exchange and catalysis. It is found that phase-pure zeolite NaA (Na11.25(25) (K,?Ca,?Mg)0.7(1) (Al11.95(25)Si12.3(3)O48).18H2O) can be prepared in the form of cubic/rhombus crystallites with uniform micrometric (3-5 μm) dimensions by hydrothermal crystallization (95oC) of aged (72 hr) at room temperature gel (4.5Na2O: 0.45Al2O3: 1SiO2: 178H2O) obtained from natural analcime, treated with hydrochloric acid before suspending in water and mixing with sodium hydroxide. Phase-pure zeolite NaX (|Na66(3) [K,?Ca,?Mg,?Cu,?Zn]12(1) (H2O)248(10)| (Al78(3)Si114(4)O384)) with specific surface area of 589 m2/g and total pore volume of 0.578 cm3/g can be prepared in the form of octahedral crystallites with uniform micrometric (2-7 μm) dimensions by hydrothermal crystallization (95oC) of aged (96 hr) at room temperature gel (2.9Na2O: 0.26Al2O3: 1SiO2: 150H2O) obtained from water suspension of natural phillipsite, treated with hydrochloric acid and mixed with sodium hydroxide. The resulting zeolites in their characteristics are competitive with commercially available materials. |
