Research On The Synthesis, Characterization And Performance Of The Calcium Sulfate Double Salts

The calcium sulfate double salt is a kind of very important compound in the mineral system of the calcium sulfate. It is very closely with the development and utilization of the calcium sulfate. Nowadays, with the development of national economy, it is more and more urgent to solve the problem of the natural anhydrous calcium sulfate's low hydrous activity. For improving it and utilizing the natural anhydrous calcium sulfate which account for 2/3 of total reserves of the calcium sulfate, it was investigated to the synthesis and performance of the calcium sulfate double salts, what was the vacancy of the hydration theory of the anhydrous calcium sulfate in this paper.In the experiment, synthesis of the calcium sulfate double salt was investigated firstly. Then researched thoroughly to the formulation condition, thermodynamic properties, spectroscopy characterization and solubility idiosyncrasy of the alkali metal calcium sulfate double salt, discussed to the parameters of their preparations, and improved their thermodynamic, spectroscopy files. After that the laws of the thermodynamic transformation and dissolution were analyzed. And in the end, the dissolution kinetics and the crystallization kinetics of the double salts were investigated.1,By mean of the hydrothermal solution method and the high temperature synthetic method, it was investigated to the reactive law of the alkali metal sulfate with calcium sulfate and the synthetic c6ndition of the double salts systematically, and optimized the parameters of the preparations. The main factors of the preparation of the double salt by the hydrothermal solution method were temperature, reactive time and the quantity of the solvent. The influence of the temperature was differently. While the reactions of the alkali metal sulfate with calcium sulfate were studied at various temperature by the high temperature synthetic method. It started at low temperature and transformed to their high temperature modifications gradually. The influence of the temperature was slightly. While the time of the reactions should not too short or too long.2,The thermodynamic stability of the calcium sulfate double salts which were quenched was better, while the transformation of the hydration double salts was complicatedly, K₂Ca₂Cu(SO₄)₄·2H₂O, specially. At 515℃, a new phase (may be K-Cu-SO₄) appeared, and transformated to CaSO₄, K₂SO₄, K₂Ca (SO₄)₃, Cu₂O finally. Then tested their spectroscopy characterization by mean of IR and Raman.3,The solubility idiosyncrasy of the calcium sulfate double salt was researched systematically. The main factors of the solubility transformation were the solvent quantity and the hydration time, the phases of the double salts transformed gradually. Basing on that research, the dissolution kinetics and the crystallization kinetics of the double salts were investigated. And the kinetic equations have been obtained. The progressions of the solubility equations of the hydrate double salts were about 1.1, while the quenched double salts' were about 1.5-1.8. The constants of the kinetics equations were increasing as the center of the third period element. And the CaSO₄·2H₂O phase crystallized in the final stage. Its progression of crystallization kinetic equation was 1.07.