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Chapter II Solution Growth….
The effect of stirring solution on induction period for precipitation of KDP
was studied by Barata and Serrano [118]. They measured induction period as a
function of super-saturation in the agitation range from 50 to 500 rpm by visual
method. The induction periods were constant between 50 to 400 rpm and
decreased later on due to decrease in the Kolmogoroff turbulence micro scale.
The micro-mixing process did not interfere with formation of the new solid
phase, since the micro-mixing time contribution to the induction period was
negligible. The authors concluded that the precipitation mechanism was
primarily nucleation followed by the normal growth in the all agitation intensity
range studied. The interfacial surface tension also did not depend on agitation
intensity.
Qu. et al [119] studied the effect of ethylene diamine tetra acetic acid
(dipotassium salt -EDTA) and potassium pyrophosphate (KPY) on the batch
crystallization of KDP. The crystal growth rates of certain crystal faces were
determined by in-line images taken with MTS particle image analyzer (PIA)
video camera. Nucleation kinetics was studied by measurement of meta-stable
zone width and induction period. A significant promotion effect was found for
nucleation and growth for EDTA, notwithstanding, the KPY exhibited the
inhibitive effect. This was studied by two dimensional nucleation model. It was
concluded by them that the presence of EDTA increased the density of
adsorbed molecules of the crystallizing solute on the surface of crystal.
Apart from this, the advantage of Atomic Force Microscopy (AFM) is
used for 2D nucleation studied on the (100) face of KDP crystal [120]. One of
the most popular and similar system to KDP is the ammonium dihydrogen
phosphate (ADP). The effect of urea on meta-stable zone width, induction
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