Study On Production Process Of 4A Zeolite From Mother Liquor Of Bayer Seeding Process

Focused on high cost of sintering production by refined sodium aluminate solutions within Chalco Shandong Branch, the author kept seeking for other low-cost aluminum sources, and innovated the synthesis of 4A zeolite by seeding mother liquor which is by-produced in Bayer process of alumina. The initial laboratory tests showed that most of the key specifications, such as calcium exchange rate and particle size could reach to the inner quality standard, except the low whiteness with high b value together, which mainly due to the coloring matters, induced by any oxalates and other organic salts containing in the seeding mother liquor of Bayer process.To solve the problem of low whiteness, various de-coloring experiments on seeding mother liquor were conducted successively, and the hydrogen peroxide was designated as the decolorizing agent eventually. The whiteness of de-coloring treated products can be reached to more than 96%, and its b value not more than 1.0, without significant effect on other quality indicators, including calcium exchange rate and particle size, etc.The synthesis technology of 4A zeolite which produced by Bayer seeding mother liquor were optimized sequentially, with the optimal conditions obtained from a series of industrial tests. The ratio of SiO2 and Al2O3 is 1.8～2.0, the slurry temperature is 45～50℃, the crystallization temperature is 75～80℃for 3 hours, and the de-coloring agent's addition from 1% to 1.4%.Compared to the original sintering process with refined sodium aluminate solutions, the production cost was reduced significantly by Bayer seeding mother liquor, while the economy benefit is remarkable. The key quality indicators of the qualified product, such as calcium exchange rate, particle size and whiteness, etc were equal to the national standard QB1768-93.