Exploratory Study On Synthesis Of Zeolites By Diatomite

Zeolites are widely used as absorbents, ion exchanges and catalysts. There are many shortcomings in synthesizing zeolites from chemical materials, such as high cost, and serious pollution from reactant liquids and so on. Based on lots of literatures of zeolites synthesis, a series of zeolites are hydrothermally synthesized successfully from diatomite. Besides, the influence of treatment conditions is studied systematically.Using diatomite and alkali solution directly, this paper synthesizes a series of zeolite products (NaP, NaA and NaY type) through the hydrothermal method. It is discussed in depth the effects on synthesis of zeolites, including the composition of the reaction mixture and the hydrothermal conditions. Then the technical parameters of hydrothermal treatment of zeolites are optimized.In existing of the structure directing agent (SDA), Zeolite NaY of high crystallinity is hydrothermally synthesized by diatomite, which is calcined with alkali in advance. The crystal phase is identified by X-ray diffraction. And the static water absorption capacity data of zeolite NaY is gained. The reaction conditions are discussed and the results show that the alkali fusion, the action of SDA and the composition of reactant system are the main impacting factors on zeolite NaY synthesis. The optimum technical conditions are as follows. Diatomite is calcined with sodium hydroxide under the Na₂O/SiO₂ ratio of 1:1 at the temperature of 550℃. Afterwards, the composition of reactant mixture is 6SiO₂: Al₂O₃: 6Na₂O: 219.6H₂O, with adding little amounts of SDA composed of 15SiO₂:Al₂O₃:21.6Na₂O: 569H₂O. And then the reactants are crystallized 10h at the temperature of 100℃. The crystallinity of product reaches to the maximum, and its water absorption capacity comes to 27.3%.