Investigation of the effect of various impurities on nuclei formation and growth of boric acid and borax pentahydrate in the steady single crystal system

Technical properties expected from a product obtained by crystallization technique in chemical technology; is the production of highly pure, suitable sized, homogeneous and smooth outer appearance crystals. Although it seems quite easy to obtain pure crystals, in some cases there are problems in the crystallization of substances which are susceptible to süper saturation. However, the production of crystals of suitable size and homogeneous structure is possible by knowing the conditions under which the nucleation of the crystallized material will occur and the growth kinetics. MSMPR (mixed suspension mixed product removal) type crystallizers are the most widely used in the industry. However, in the case of many parameters to be examined from such systems, some of these parameters can be eliminated in the single crystal system (the effect of various factors on habit change) and some in the fluidized bed system (such as the effect of hydrodynamic conditions and various impurities). Thus, the optimal conditions for the production of any material by crystallization can be determined using these three systems. In this study, it has been tried to determine the change of habit structures of the crystals formed in the supersaturated solution of boric acid and borax pentehydrate solutions prepared at different temperatures by using pure boric acid and borax pentehydrate crystals under microscope and in the presence of various impurities. As a result of the studies, boric acid crystals both in pure solutions and in the presence of various impurities such as Ca and Mg, the growth of single crystals put in solution medium without nuclei formation was found to be dendritic structure and dentrites were weaker than those formed with nuclei. However, in the presence of various impurities, the dendritic structures are weaker and when a certain süper saturation value is exceeded it is determined that new nuclei are formed in the solution instead of collapsing on the single crystal in the supersaturated medium. Another result obtained in the quiescent single crystal system is that the dendrites formed in the presence of magnesium impurity are less and weaker than those formed in the presence of calcium and sulfuric acid impurities. When borax pentahydrate is observed to grow in the presence of different supersaturation of single crystals placed in saturated solution medium in a stationary medium single crystal system; It was observed that the crystals were grown in uniform structure, no dendritic structures were formed as in boric acid, but a large number of nuclei formed into the solution medium with increasing saturation. In the presence of various impurities, as in boric acid, it was observed that the growth of stagnant medium single crystals was the same as in pure solutions. Another important observation is that with increasing saturation, the twinning becomes more pronounced as boric acid crystals grow. When the linear growth rates of single crystals placed in different supersaturated solution media in constant medium single crystal system were examined due to the variation of the supersaturation, both boric acid and borax pentahydrate crystals showed dispersion at growth rates and this dispersion was also valid in the presence of various impurities.