Apparent Nucleation Order Research Articles

Determination of Primary Nucleation Kinetics of Acetylsalicylic Acid in Ethanol

AbstractThe metastable zone width (MSZW) for the acetylsalicylic acid‐ethanol system was determined by the polythermal method. Nucleation parameters were calculated applying the self‐consistent Nyvlt‐like approach and the classical three‐dimensional theory approach. The results showed the usual increments in MSZW with increases in the cooling rate, mixed effects when raising the agitation rates, and an unusual behavior that reduced MSZW when the saturation temperature decreased. The apparent nucleation order proved to be independent of all three analyzed variables. The interfacial energy increased with higher saturation temperature and activation energies incremented when agitation rates raised. In general, the two approaches explained closely the experimental results.

Nucleation kinetics from metastable zone widths for sonocrystallization of l-phenylalanine

This study investigates the effect of ultrasound on metastable zone width (MSZW) during crystallization of l-phenylalanine from aqueous solution. The solubility of l-phenylalanine in water was measured gravimetrically in the temperature range of 293.15–333.15K. The MSZW was measured by conventional polythermal method for four different cooling rates at five different saturation temperatures in absence and presence of ultrasound. The MSZW increased with increase in cooling rates and decreased with increase in saturation temperature. The application of ultrasound considerably reduced the MSZW for all the experiments. The obtained MSZW data are analysed using four different approaches to calculate various nucleation parameters. In presence of ultrasound, the apparent nucleation order decreased and nucleation rate constant increased significantly.

Solubility and metastable zone width measurement of 3,4-bis(3-nitrofurazan-4-yl)furoxan (DNTF) in ethanol + water

The solubility and supersolubility of 3,4-bis(3-nitrofurazan-4-yl)furoxan (DNTF) in ethanol+water at different operation were determined by laser monitoring system under atmospheric pressure to study the metastable zone width (MSZW). The modified Apelblat equation was adopted to correlate the experimental solubility data, and the correlation result showed perfect consistent with the experimental data. The standard dissolution enthalpy, standard dissolution entropy and Gibbs energy were calculated according to the experimental solubility data. The effect of the cooling rate, stirring rate, temperature and the concentration of ethanol+water on the MSZW was studied. It was found that the MSZW of DNTF increased with the increasing cooling rate, decreasing temperature, decreasing stirring rate and decreasing ratio of water. And the apparent nucleation order of DNTF in ethanol+water was calculated by the relationship between the cooling rate and the MSZW.

MEDICIÓN DEL ANCHO DE LA ZONA METAESTABLE DE SOLUCIONES DE ÁCIDO ADÍPICO-AGUA

The metastable zone width of adipic acid-water solutions has been determined in a temperature range from 293.15 to 328.15 K and cooling rates from 1 to 30 K·h-1 by means of the conventional polythermal method, using a laser diffraction technique. In addition, it is proposed an alternative method for estimating the metastable zone width based on the solution density measured online. The apparent nucleation order is evaluated using the Nývlt equation. Experimental results showed that initial composition and cooling rate had significant effects on the metastable zone width. An increment in cooling rate increased the metastable zone width and an increment in initial composition decreased the metastable zone width. On the other hand, it was found that online density measurements could be used as an alternate method for estimating the metastable zone width. The comparison of metastable zone width obtained with both methods produced an average difference of 6.75 %. Finally, the apparent nucleation order calculated was 4.3 which is closed to the value 4.2 reported in the literature

Solubility and Metastable Zone Width of Sodium Chromate Tetrahydrate

The solubility of sodium chromate tetrahydrate has been investigated in the temperature range from 290.15 K to 325.15 K using the conventional polythermal method by means of the laser technique. The metastable zone width (MZW) and the apparent nucleation order of sodium chromate tetrahydrate were calculated. The effects of cooling rate, initial composition, stirring rate, and seed particles on the MZW were also studied. The results show that the MZW of sodium chromate tetrahydrate first increases and then narrows with increasing initial composition. The MZW becomes wider by reducing the cooling rate and the mass of seed particles, whereas the MZW will be reduced by enhancing the rotation frequency of stirring and the diameter of seed particles.

Solubility and Metastable Zone Width of Sodium Tetraborate Decahydrate in a Solution Containing Lithium Chloride

The solubility and the metastable zone width of sodium tetraborate decahydrate in solutions containing lithium chloride have been measured at temperature a range of (20 to 35) °C. It is found that the lithium impurity has a salt-in effect on the solubility of sodium tetraborate decahydrate. The metastable zone width broadens with an increase of the impurity concentrations. This increase can be attributed to the absorption mechanism on the crystal surface. The apparent nucleation order of sodium tetraborate decahydrate with and without impurity was calculated by a modified regression method. The results show that the addition of lithium impurity has no great effect on the apparent nucleation order of sodium tetraborate decahydrate.

Effects of Different Organic Acids on Solubility and Metastable Zone Width of Zinc Lactate

Effects of three different organic acids including racemic malic acid, succinic acid, and citric acid, which act as an impurity on the solubility and metastable zone width of zinc lactate (ZnL2), have been studied. The results show that the presence of all examined impurities increases the solution solubility and the values of solubility increase with increasing impurity concentration. The introduction of impurity also leads to a reduction on the metastable zone width, and the reductions are pronounced when the impurity concentration increased. Further, experimental data of metastable zone width were analyzed using the expression of the Nývlt’s approach and self-consistent Nývlt-like approach, which can be expressed in the form: ln(ΔTmax/T0) = Φ + β ln b, with intercept Φ = {(1 – m)/m}ln(ΔHd/RTlim) + (1/m)ln(f/KT0) and slope β = 1/m. Here T0 and Tlim are the saturation and nucleation temperature, respectively. m is the apparent nucleation order, and K is a new nucleation constant related to the factor f defined as the number of stable nuclei per unit volume, ΔHd, the heat of dissolution and R the gas constant. Comparing to the former one, the latter approach provides a more satisfactory estimation for the metastable zone width at varying saturation temperature T0. The constant β for specific system reveals independence of the temperature, while the constant Φ increases with increasing saturation temperature. In addition, both constants are proportional to the impurity concentration. Crystal habits of final products are also influenced in the presence of impurities, but the crystal structures are barely changed.

Solubility and Metastable Zone Width Measurement of Borax Decahydrate in Potassium Chloride Solution

The solubility and ultra solubility of borax decahydrate both in pure and impure solutions have been determined in the temperature range from (0 to 30) °C by means of the conventional polythermal method using the laser technique. The metastable zone width and the apparent nucleation order of borax were calculated. The effects and the action mechanism of KCl on metastable zone property of borax were studied. It was found that the presence of KCl made an increase in the solubility and a decrease in the metastable zones of borax. However, the trends in the changes of metastable zone width at low impurity concentrations were different from high concentrations because of the adsorption equilibria on the crystals.

DETERMINATION OF THE METASTABLE ZONE WIDTH OF GLYCINE AQUEOUS SOLUTIONS FOR BATCH CRYSTALLIZATIONS

The aim of this study was to determine the metastable zone width of aqueous solutions of glycine for non-seeded batch crystallizations. The saturation curve was determined by studying the heating rate influence on the apparent saturation temperatures of several solutions. A linear regression was then applied to obtain the saturation temperatures. The spontaneous nucleation curve was obtained by measuring the crystallization temperatures of several solutions at different cooling rates. The results show that the apparent nucleation order of the glycine aqueous solutions was around 3.5 ± 0.5. Moreover, from the experimental data, a second-order polynomial model was established by using the experimental design method. This model enables the expression of crystallization temperature to be defined as a function of concentration and cooling rate. The results show that the model fits well (R2 > 0.99; Q2 > 0.98) and that the cooling rate is the most influential parameter.

On the Metastable Zone Width of 1,3-Dipalmitoyl-2-oleoylglycerol, Tripalmitoylglycerol, and Their Mixtures in Acetone Solutions

The extensive experimental data reported by Smith et al. (Eur. J. Lipid Sci. Technol. 2005, 107, 583−593) on the metastable zone width of 1,3-dipalmitoyl-2-oleoylglycerol, (POP) tripalmitoylglycerol (PPP), and their mixtures in acetone are analyzed using a novel approach based on classical three-dimensional nucleation theory (Sangwal, K. Cryst. Growth Des. 2009, 9, 942−950) and a self-consistent Nývlt-like approach (Sangwal, K. Cryst. Res. Technol. 2009, 44, 231−247) to obtain quantitative information on the processes of nucleation of these systems. The relevant equations of the above approaches are (i) (T0/ΔTmax)2 = F(1 − Z ln R) and (ii) ln(ΔTmax)/T0) = Φ + β ln R, where T0 is the saturation temperature and F and Φ are, respectively, the values of (T0/ΔTmax)2 and ln(ΔTmax)/T0) when ln R = 0, whereas Z is a parameter characteristic of the crystallizing system and the constant β is inverse of the apparent nucleation order m in the Nývlt approach. It was found that (1) the value of parameters β and Z is relatively insensitive to saturation temperature T0 but depends on the investigated compound and the technique used for the measurement of maximum supercooling ΔTmax and the presence of PPP impurity in POP solutions; (2) the values of β and Z for PPP and POP decrease with an increase in their solubility in acetone; and (3) the data of Φ and ln(F1/2) as a function of saturation temperature T0 follow the Arrhenius-type relation with an activation energy Esat. Analysis of the results revealed that (1) the values of β and Z are directly connected with the solid−liquid interfacial energy γ; (2) the value of Esat depends on the nature of ions/molecules participating in diffusion; (3) maximum supercooling ΔTmax measured by turbidimetry corresponds to a nucleation event alone, but that obtained from growth exotherm includes some contribution of growth of stable nuclei after nucleation; and (4) PPP impurity in POP solutions promotes crystallization by acting as growth centers for heterogeneous nucleation.

Effect of ultrasound on anti-solvent crystallization process

The ultrasonic influence on the anti-solvent crystallization of roxithromycin is investigated. The effect of ultrasound on primary nucleation is studied by measuring the induction time and metastable zone width. The experimental results show that ultrasound has a significant effect on reducing the induction time. After applying ultrasound to the system, the change in the apparent nucleation order is small, however the nucleation rate constant ( k N) increases significantly. The diffusion coefficient also changes significantly; however, the other parameters change slightly or remain constant within the ultrasonic field. This suggests that diffusion acceleration is the main reason for the reduction in the induction time. These observations also suggest that ultrasound can enhance the homogeneous nucleation of roxithromycin significantly. The influence of ultrasound on agglomeration and the crystal habit of roxithromycin is investigated in the second part of this contribution. Introducing ultrasound into the system reduces agglomeration and changes the crystal habit significantly.