Preparation and characterization of Na-LTA zeolite from Tunisian sand and aluminum scrap

Abstract

Pure Na-A (LTA) zeolite has been prepared from aluminosilicate gel obtained by a mixture of metasilicate and aluminate solutions. Metasilicate sol; used as silica source; was prepared from an alkaline attack of Tunisian sand in an autoclave under agitation at 220 ∘C and pressure of 27 bar. The aluminate solution was obtained by dissolution of aluminium scraps in NaOH solution. The crystallization of Na-LTA zeolite is controlled by the alkalinity of the mixture and the reaction time. At 90 ∘C, well crystallized LTA have been obtained after 3h. The Zeolite LTA converts into the more stable HS after long reaction times according to Ostwald’s law. The alkalinity of the reaction mixture changes the nature of the obtained zeolite. At lower NaOH concentration (0.1 M), Na-X zeolite was obtained; whereas the crystallization of LTA was promoted at higher NaOH concentration (3M).