A New Method of Producing High Purity 4A-Molecular Sieve from High Modulus Sodium Silicate Liquor Purified by Carbonization

Abstract

A new technology for producing high purity 4A-molecular sieve was developed with high modulus sodium silicate liquor and sodium aluminate liquor extracted from coal fly ash as starting materials. The sodium silicate liquor extract was purified by precipitating ferrous, titanium, and other impurities by carbon dioxide injection. Concentration of carbon dioxide in the extract was maintained at 48%, and the pH value of the extract controlled in the range of 11 and 11.2. After that, the purified sodium silicate liquor was mixed with sodium aluminate liquor in the ratios of SiO2/Al2O3=2.0, Na2O/SiO2=1.6 and H2O/Na2O=60. The mixture was then heated to 90°C and kept for 2 h. A high purity 4A-molecular sieve product was obtained after washing and drying the crystals obtained from the reaction mixture. The molecular sieve product has a purity of 99% and aperture of 0.4nm. Its calcium absorption capacity is about 290mg/g. The product was also characterized by SEM, BET, XRD and IR analysis.