Simulation Study On The Growth Habit Of Calcium Sulfate Crystal

With the increasing awareness of environmental protection,the process of flue gas desulfurization is concerned,and the use of calcium sulfate is directly related to the selection and cleaner production of desulfurization process.While the dissolution and recrystallization behavior of calcium sulfate directly affects its crystal structure and morphology change,it not only relates to the application field of calcium sulfate,but also affects the difficulty of the solid-liquid separation of calcium sulfate.Therefore,the systematic research on the dissolution and recrystallization behavior of calcium sulfate in the solution system is of great significance to control the crystal structure of calcium sulfate.With the development of quantum chemistry and electronic information technology,the method of molecular dynamics simulation applied to study the growth behavior of crystals in solution system become practical.In this paper,with the help of the Materials Studio simulation software,the crystal surface-solution two-layer structure model was constructed.The growth habit was simulated of the calcium sulfate crystals in different solution systems,and the interface structure stability of the calcium sulfate crystal was calculated.Under the condition of this experiment,the following conclusions were drawn:(1)The crystal structure of CaSO4·2H2O in the natural environment is a flat structure which is composed of(020),(021),(11-1)and(110)crystal surface and its symmetrical crystal surface.The stability sequence of the crystal surface is(020)>(11-1)>(110)>(021)crystal surface.While the structure of CaSO4·0.5H2O crystal is a club-like structure which is composed of(200),(002),(110)and(1-10)crystal surface and its symmetrical crystal surface.The grain surface stability sequence is(1-10)>(110)>(200)>(002)crystal surface.(2)With the increase of sodium chloride and magnesium chloride concentration,the association between Na+,Mg2+ and Cl-in solution was enhanced,while the hydration of Na+ and Mg2+ was weakened.The increase of temperature is favorable for the hydration of Na+ in solution,but unfavorable to the association between Na+ and Cl-.With the increase of sodium chloride concentration and the decrease of temperature at the same time,the self-diffusion coefficient of Na+and Cl+ in solution gradually decreased.(3)With the increase of the concentration of sodium chloride and the decrease of temperature,the crystal of the CaSO4·2H2O is transformed from the plate to the coarse crystal,in which the crystal surface disappears.(4)With the increase of sodium chloride concentration and temperature,the crystal of CaSO4·0.5H2O is gradually growing to the X axis and Y axis from the rod.With the increase of concertation of magnesium chloride,it is beneficial to the growth of CaSO4·0.5H2O crystal to the Z axis and then form the fibrous crystal.And with the increase of temperature,the crystal grows first toward the Z-axis,and then towards X and Y axis.