Potash alum, crystallization

Garside, J. and Jancic, S.J., 1976. Growth and dissolution of potash alum crystals in the sub-sieve size range. American Institution of Chemical Engineers Journal, 22, 887. 

Jones, A.G. and Mydlarz, J., 1990b. Slurry filtrability of potash alum crystals. Canadian Journal of Chemical Engineering, 68, 513-518. 

Ristic, R.I., Sherwood, J.N. and Shripathi, T., 1991. The role of dislocations and mechanical defonuation in growth rate dispersion in potash alum crystals. In Advances in Industrial Crystallization. Eds. J. Garside, R.J. Davey, and A.G. Jones. Oxford Butterworth-Heinemann, pp. 77-91. 

Amara N, Ratsimba B, Wilhelm A, Delmas H (2004) Growth rate of potash alum crystals comparison of silent and ultrasonic conditions. Utrason Sonochem 11 (1) 17—21... 

The effect of US power on formed crystals was studied at 0, 10 and 100 W by suspending potash alum crystals in a potash alum saturated solution for 3 h. Conductivity measurements showed that there was neither dissolution nor crystallization, but electron scanning microscopy revealed that the shape of the crystals changed due to erosion. Also, crystal size decreased with increasing US power. Size analysis confirmed the appearance of small particles upon application of US. The amount of smaller crystals formed was modest at a low power (10 W) but increased dramatically with increasing US power an abrasion effect was therefore clearly involved [146]. 

J. Garside and S. F. Jencid. Growth and Dissolution of Potash Alum Crystals in the Subsieve... 

Direct observation of impact-induced microattrition at the surfaces of potash alum crystals immersed in supersaturated solution (Garside, Rush and Larson, 1979) indicated that the majority of the fragments produced were in the 1-10 pm size range and had a supersaturation-dependent size distribution. Impact energy and the frequency of impact also have an important influence on the number of crystals resulting from contact secondary nucleation (Larson, 1982). 

The results in Figure 6.16 show the effects of both solution supersaturation and velocity on the linear growth rates of the (111) faces of potash alum crystals at 32 °C. This hydrated salt [K2SO4 Al2(S04)3 24H2O] grows as almost perfect octahedra, i.e. eight (111) faces. 

Figure 6.17. Effect of solution velocity on the 111) face growth rate of potash alum crystals at 32 °C. After Mullin and Garside, 1967)...

Figure 6.18. Extrapolated growth rates of potash alum crystals at limiting velocities 0 = u cxD, =w 0) After Mullin and Gar side, 1967)...

Data plotted in accordance with equation 6.65 for the dissolution of potash alum crystals yield the relationship (Garside and Mullin, 1968)... 

Another possibility for reducing supersaturation levels, and hence nucleation rates, is to use an air-diluted precipitant. This is quite easy to arrange if the precipitant is a volatile organic liquid. A practical example of this technique is the foam column described by Halasz and Mullin (1987) which was used for the controlled precipitation of potash alum crystals from aqueous solution using air saturated with 2-propanol Figure 8.11). 

Table 9.2. Size analysis of potash alum crystals ...

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