A high-purity artificial zeolite is industrially mass produced by carrying out osmosis treatment of fly ash in an alkaline aqueous solution, subsequently carrying out the osmosis treatment again with an acidic aqueous solution of pH 1.0 or less obtained by adding acid to the osmotic aqueous solution of fly ash, then performing solid-liquid separation while water wash and dewatering in a centrifuge, thereby synthesizing a starting composition, and performing hydrothermal reaction treatment to this starting composition.

The present invention relates to a method for preparing LiCa-LSX molecular sieves with mixed cations and applications thereof. The method comprises the following steps; preparing CaLSX molecular sieves; replacing all Na.sup.+ in NaLSX molecular sieves with Ca.sup.2+ by multiple times of exchange with a solution containing Ca.sup.2+; changing CaLSX molecular sieves to LiCa-LSX molecular sieves by exchange with Li.sup.+, wherein a solution containing Li.sup.+ is used, and the exchanged sample is directly filtered in vacuum without washing and dried at normal temperature; and activating and pre-treating the sample to obtain LiCa-LSX molecular sieves with mixed cations. The LiCa-LSX molecular sieves can be used as selective adsorbents for N.sub.2 and O.sub.2 in oxygen production processes by PSA/VPSA. In the present invention, the loss of Li.sup.+ caused by the replacement of Li.sup.+ with H.sup.+ because of hydrolysis is avoided, the cost is reduced and the treatment time is short.

The present invention relates to a method for preparing LiCa-LSX molecular sieves with mixed cations and applications thereof. The method comprises the following steps; preparing CaLSX molecular sieves; replacing all Na.sup.+ in NaLSX molecular sieves with Ca.sup.2+ by multiple times of exchange with a solution containing Ca.sup.2+; changing CaLSX molecular sieves to LiCa-LSX molecular sieves by exchange with Li.sup.+, wherein a solution containing Li.sup.+ is used, and the exchanged sample is directly filtered in vacuum without washing and dried at normal temperature; and activating and pre-treating the sample to obtain LiCa-LSX molecular sieves with mixed cations. The LiCa-LSX molecular sieves can be used as selective adsorbents for N.sub.2 and O.sub.2 in oxygen production processes by PSA/VPSA. In the present invention, the loss of Li.sup.+ caused by the replacement of Li.sup.+ with H.sup.+ because of hydrolysis is avoided, the cost is reduced and the treatment time is short.

A high-purity artificial zeolite is industrially mass produced by carrying out osmosis treatment of fly ash in an alkaline aqueous solution, subsequently carrying out the osmosis treatment again with an acidic aqueous solution of pH 1.0 or less obtained by adding acid to the osmotic aqueous solution of fly ash, then performing solid-liquid separation while water wash and dewatering in a centrifuge, thereby synthesizing a starting composition, and performing hydrothermal reaction treatment to this starting composition.