Influence of impurities on the growth kinetics of epsomite from low temperature aquaeous solutions

Abstract

In this thesis, the gro\\1h mechanism of epsomite aml its different physical properties have been ;tuclied. In this regard, lhe pure and doped ep,omites were grown al low temperature by slow cooling technique as well a; by nalural evaporalion method with potassium chloricle KCI as a dopant. The mass growths as well as the growth rates with respect to time of all the grown crystals were estimated. tvlass growth increases with the KCI concenlration 10 a certain limit and lh~n decreases with the higher eoncentralion ofKCI Highly transparcnl and "ell faceted large single cryslals have bcen grown successfully by isothermal evaporation process and 510" cooling proceS8. The crystals have well defined shape wilh length of about 2.5-3 2cln for pure epsomite, 3,3-3,5 cm for O,land 0.2M KCI doped crystals, 2.5-3.0 cm for 0.4:;'1KCl doped, 2.4-2.9 cm for O.6MKCI doped crystals. Thc mixed crystals arc smaller in 8ile with length of about 1.3-1.5 em. The addition of KCI incre08es the qualil) of the crystals by decreasing the di8locmions, which is apparent in thc tranoparenC) of thc crystaL The increa,e in the quality of the epoomite crystal in pre;ence of KCI is due to the complexion of trace metal ion by cr ion, These complex melal iOll8cannot gel into the erystallauice. The morphological studie, of the doped and pure magneSium ;ulphate were done to observe the change of the structure of the crystal. A sharp habit modif.eation is observed as lhe orthorhombic shape of pure epsomite change, to tetragonal due 10 the impurities KC!. Higher the impurities higher the shape change. l'or KCI of 25- 33% by vol. change is fully letragonal. The phase of pure crystals changes in dry en, ironment due to the loss of crystalline water. Crystals with high KCI content (25- 33% by vo!.) are stable in dry environment.