Impurities, effect growth

AIChESymp. Ser. (a) 65 (1969) no. 95, Crystallization from solutions and melts (b) 67 (1971) no. 110, Factors affecting size distribution (c) 68 (1972) no. 121, Crystallization from solutions Nucleation phenomena in growing crystal systems (d) 72 (1976) no. 153, Analysis and design of crystallisation processes (e) 76 (1980) no. 193, Design, control and analysis of crystallisation processes (f) 78 (1982) no. 215, Nucleation, growth and impurity effects in crystallisation process engineering (g) 80 (1984) no. 240, Advances in crystallisation from solutions. 

KlMURAH, H. J. Cryst. Growth 73 (1985) 53-62. Impurity effect on growth rates of CaCl2-6H20 crystals. 

Since the edge free energies, y, are different for the vapor and solution phases, and particularly for solute-solvent interaction energies, the same crystal species will exhibit different Tracht and Habitus in different ambient phases and different solvents. If impurities are present in the system, this affects y and the advancing rates of steps. There are two opposite cases in impurity effects, and, depending on the interface state, some will promote growth, whereas others will suppress growth. 

Whatever the details of the kinetic mechanism, impurities cause crystal habit modification. Buckley [65] has classified many impurity effects on different crystal habit modifications. In most cases, impurities decrease the growth rate of specific crystal faces, which lead to a change in the crystal habit because the slowest growing faces will dictate the crystal morphology. In some exceptional cases, impurities can increase the growth rate of a particular crystal face. For example, 1% Fe added... 

Kaneko, N., T. Horie, S. Ueno, J. Yano, T. Katsuragi, and K. Sato, Impurity Effects on Crystallization Rates of n-Hexadecane in Oil-in-Water Emulsions, J. Crystal Growth 197 263-270 (1999). 

The conditions for stable growth of a crystal are closely associated with segregation of dopants or impurities. Crystal growth theory includes an expression for the effective segregation coefficient K, for a crystal growing from a medium in which the dopant distribution is characterized by a boundary layer of thickness 5 ... 

Harano, Y., and Yamamoto, H. (1982). Impurity Effect of Amino Acids on Formation and Growth of L-Glutamic Acid , Industrial Crystallization, vol. 81 (Jancic, S.J., and de Jong, E.J., eds.), pp. 137-145, North Holland Publ. Co. 

The reported data on impurity action are scattered. There is no generalized unified approach to assess the effect of impurity on growth. Some of them are introduced and qualitatively analyzed with the aid of the model described above. 

The combined influence of supersaturation and impurity concentration on crystal growth can be quite complex, but two basic cases may be considered (Kubota, Yokota and Mullin, 2000) (i) growth is only suppressed in the low range of supersaturation while at higher supersaturations the impurity effect disappears completely and (ii) growth rate suppression occurs throughout a very wide range of supersaturation. The first case may be explained by... 

Equation 6.105 is represented by the dotted line in Figure 6.29a showing that for instantaneous adsorption (r = 0) growth rate suppression occurs over a wide range of super saturation. For the case of very slow adsorption (r = cx)), no impurity effect would be expected, i.e., growth in the presence of impurity would be the same as if no impurity were present, i.e. G = Gq. This is represented by the continuous line in Figure 6.29a. 

Boistelle, R. (1982) Impurity effects in crystal growth from solution. In Interfacial Aspects of Phase Transformations, B. Mutaftschiev (ed.), 621 38, Reidel, Dordrecht. 

Eidelmann, N., Azoury, R. and Sarig, S. (1986) Reversal of trends in impurity effects on crystallization parameters. Journal of Crystal Growth, 74, 1-9. 

Harano, Y., Yamamoto, H. Impurity effect of some amino acids on formation and growth of L-glutamlc acid nuclei by secondary nucleatlon In agitated solution, in Industrial CrystalUzatton 81 (eds. Janeic, S.J., de Jong, E.J.), p. 137, North-Holland, Amsterdam 1982... 

Kuznetsov, V.A., Okhrimenko, T.M. and Rak, M., 1998, Growth promoting effect of organic impurities on growth kinetics of KAP and KDP crystals, J. Crystal Growth, 193,164. 

The growth morphology for several organic materials having various entropies of fusion are shown in Figs. 3-7. The effects of diffusion on each are shown by the addition of various amounts of soluble impurities. These growth forms are typical for the various values of entropy change. 

Kaneko N, Horie T, Ueno S, Yano J, Katsuragi T, Sato K. 1999. Impurity effects on crystallization rates of -hexadecane in oil-in-water emulsions. J Cryst Growth 197 263-270. 

C. Chang and M. Epstein. Identification of batch crystallization control strategies using characteristic curves. In Epstein, editor, Nucleation, Growth and Impurity Effects in Crystallization Process Engineering, New York, 1982. AfChE. 

Burke MW, Leardi R, Judge RA, Pusey ML. Quantifying main trends in lysozyme nucleation the effect of precipitant concentration, supersaturation and impurities. Crystal Growth Des... 

Van Driessche, A.E.S., Otalora, F., Gavira, J.A., and Sazaki, G. (2008) Is agarose an impurity or an impurity filter In situ observation of the joint gel/impurity effect on protein crystal growth kinetics. Cryst. Growth Des., 8 (10), 3623-3629. 

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