Adsorption of an Al (III) Impurity onto the (100) Face of a Growing KDP Crystal in Supersaturated Solution

Abstract

The growth-starting supercooling ∆T G , defined as a supercooling at which a crystal starts to grow on cooling, was measured for the (100) face of a potassium dihydrogen phosphate (KDP) crystal on which an Al (III) impurity had been adsorbed beforehand. When adsorption was made onto the nongrowing (100) face at a low supercooling value of ∆T A ) 0.6 °C, the measured values of ∆T G were successfully explained with a mathematical model considering the Langmuir equilibrium (or instantaneous) adsorption. On the contrary, smaller values of ∆T G were obtained when adsorption was made on the growing (100) face at a high supercooling value of ∆T A ) 6.0 °C. These smaller values obtained for the adsorption at ∆T A ) 6.0 °C are concluded to be due to an insufficient amount of the adsorbed Al (III) impurity, and the adsorption is shown to proceed more slowly onto the growing (100) face compared to the nongrowing face.

Adsorption Isotherms of Citric Acid Acting as a Growth‐Suppressor onto the (100) and (111) Faces of Sodium Chloride Crystals in Supersaturated Aqueous Solution

“…The experimental procedure, which was basically the same as in previous papers [5,6], is briefly summarized. Initially, the solution was kept at 34.3°C (T A ), a temperature of 0.7°C lower than the saturated temperature 35°C, for a period of t A , as shown in Fig.…”

“…In previous studies, we measured the growth-starting supercooling DT G , a degree of supercooling at which a crystal starts to grow when the solution is cooled continuously, for the (100) face of a KDP (potassium dihydrogen phosphate) crystal in aqueous solution in the presence of an Al(III) impurity [5], and the (100) face of a sodium chloride crystal in aqueous solution in the presence of a Pb(II) impurity. The measured values of DT G were analyzed theoretically using a model [5,6], and the Langmuir constants were deduced for the adsorption of the impurities Al(III) and Pb(II), respectively, for the (100) faces of KDP and sodium chloride crystals.…”

“…The measured values of DT G were analyzed theoretically using a model [5,6], and the Langmuir constants were deduced for the adsorption of the impurities Al(III) and Pb(II), respectively, for the (100) faces of KDP and sodium chloride crystals. In this study, we measured the growthstarting supercooling DT G for the (100) and (111) faces of a sodium chloride crystal, respectively, on which a growth-suppressor -citric acid -had been adsorbed beforehand.…”

Multi-Impurity Adsorption Model for Modeling Crystal Purity and Shape Evolution during Crystallization Processes in Impure Media

“…The non-estimated kinetic parameters, which are used in the model were previously determined by Gunawan et al 26 , , Kubota et al 47 , and Maeda et al 70 . (23) [ ] …”

“…Langmuir's adsorption isotherm [24][25][26] . This model was further improved and combined with population balance modelling and mass balance to describe the dynamic variation of crystal purity as well as shape distribution by Majumder and Nagy, in order to investigate and control the shape evolution of KDP crystals 27 .…”