Growth mechanism of NaClO3 and NaBrO3 crystals from aqueous solutions

Abstract

A study of growth rates of NaClO 3 and NaBrO 3 has been carried out using a small growth cell by in situ observation. Normal growth rates of {100} faces of NaClO 3 and {111} faces of NaBrO 3 along 〈 〈110〉 〉 direction are measured under relatively high supersaturation ranging from 3-8%. In the initial stages of growth, {100}, {110} and {111} faces develop in NaClO 3 and gradually all the faces are replaced by the {100} faces only. In the case of NaBrO 3 , mostly {111} faces develop with occasional occurrence of small {100} faces at the intersection of {111} faces. The growth mechanisms are investigated from growth rate vs supersaturation plots and from the observations of surface features. In the present supersaturation range, the growth mechanism appears to be due to two-dimensional growth mechanism.

Crystal Growth, Dissolution, and Agglomeration Kinetics of Sodium Chlorate

“…Both from visual observation of the fits and SSR values, it can be concluded that the B + S model fits much better the whole experimental dataset as compared to the BCF and PL models. This indicates that at the conditions examined, the B + S growth mechanism describes the observed growth behavior of sodium chlorate more accurately, which is in agreement with previous in situ microscopy studies , in which no growth spirals characteristic of BCF mechanism could be observed, while concentric patterns of growth hillocks typical to two-dimensional nucleation were clearly seen.…”

“…Indicatively, Radisǎ et al 47 measured a growth rate of 3 × 10 −8 m s −1 for σ 1 = 0.015, while Matsunaka et al 44 conclude to a growth rate of 4.8 × 10 −8 m s −1 for σ 1 = 0.029. In addition, Surender et al 46 report a growth rate of approximately 2.5 × 10 −8 m s −1 for σ 1 = 0.025, which is very close to the results of Wojciechowski et al, 50 while for σ 1 = 0.015, the same authors report a value of ca. 1.6 × 10 −8 m s −1 .…”

“…Regarding the growth mechanisms for sodium chlorate, several studies − have been performed, which are summarized in Table S1 of the Supporting Information. It is important to note that most of these studies are based on single-crystal growth experiments using growth cells at flow conditions, which may not be entirely relevant to the flow in stirred crystallizers with crystal populations.…”

“…It is important to note that most of these studies are based on single-crystal growth experiments using growth cells at flow conditions, which may not be entirely relevant to the flow in stirred crystallizers with crystal populations. Most studies conducted at high supersaturations 44,46,51 seem to agree that the B + S mechanism is the dominant one at those conditions, whereas others at lower driving force seem to point out to the BCF mechanism. 45 The latter reflections have been backed up by the observation of growth hillocks and/or spirals during growth at lower supersaturations.…”

Investigation of Growth Mechanisms of Sodium Chlorate Crystals from Aqueous Solutions

“…Ristić et al showed that for sodium chlorate crystals in supersaturation range of 0.1–1.0% ( R , σ) dependence might be parabolic or linear. Surender et al showed that at supersaturations of 3–8% a parabolic trend appeared, suggesting a two-dimensional mechanism.…”