Effect of L-aspartic acid on formation and growth of L-glutamic acid nuclei by secondary nucleation in agitated solution.

概要

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From the changes of the light transmittance and the electrical conductivity of solution with elapsed time and from the size distribution of the final product crystals, the impurity effect of L-aspartic acid on the heading process was studied kinetically, under the following conditions: agitation rate, nr [rpm]=567, 630, 730; temperature [°K]=298; initial solute concentration C0[g-mol/l] = 1.12×10-1-1.67×10-1; supersaturation ratio, S[-] (=C/CS) =1.5-3.0; impurity concentration, Cimp, 0 [g-mol/l]=0-1.48×10-2; ξimp, o [%]=0-10. The impurity content in the crystal, Wimp, increased linearly with increase in ξimp, 0, accompanying changes of crystal form from neeedle-like to granular, and suggesting the chemical incorporation of impurity in the crystal lattice. The rates of crystallite growth and nucleation were markedly suppressed by impurity. They were given by dr/dt=k1''Sm'' and dN/dt=knNm2Snn, respectively, where m'' is the solute number in a two-dimensional critical nucleus, from which the two-dimensional nucleation parameters such as free edge energy, radius of critical nucleus, and activation energy were obtained. Nm is the number of crystals with radius larger than rmin, which is the smallest radius among the crystals breeding the secondary nucleation and was estimated as 14-135 μ, depending on S, nr, and Wsimp.
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