Determination of dissolution kinetics of K2SO4 crystal with ion selective electrode

Prediction of In Vitro Drug Dissolution into Fed-state Biorelevant Media: Contributions of Solubility Enhancement and Relatively Low Colloid Diffusivity

A model was previously derived to predict in vitro dissolution of drug into surfactant solution and showed good predictability for pharmaceutical surfactants, where surfactant-mediated enhanced drug dissolution was several fold less than enhanced solubility (about 3-fold or less) due to drug-loaded micelles exhibiting slower diffusivity than free drug. The present objective was to quantitatively assess the contributions of biorelevant media-mediated solubility and diffusivity on enhanced drug dissolution in FeSSGF and FeSSIF-V2. Three poorly water soluble drugs were subjected to dissolution into FeSSGF and FeSSIF-V2, as well as their corresponding "surfactant-free" media. Solubility and laser diffraction analysis of drug in FeSSGF and dynamic light-scattering studies (DLS) of drug in FeSSIF-V2 were conducted. Results showed drug-saturated FeSSGF globules and FeSSIF-V2 mixed micelles were large and slow diffusing (diffusivities of about 1×10^-9 and 7×10^-8 cm²/s, respectively), compared to free drug (about 7×10^-6 cm²/s) and drug-bound micelles from pharmaceutical surfactants (about 0.5-1×10^-6 cm²/s). Of the three drugs, griseofulvin exhibited the greatest biorelevant media-enhanced solubility and dissolution (652-fold and 6.23-fold respectively in FeSSGF, and 190-fold and 12.7-fold respectively in FeSSIF-V2), but slow colloid diffusivity markedly attenuated large solubility benefits, particularly in FeSSGF.

Purification and rapid dissolution of potassium sulfate in aqueous solutions

Water soluble potassium sulfate dissolves rapidly and completely in water. Its main characteristics are purity and dissolution rate. In this study, the purification and rapid dissolution of potassium salt (K₂SO₄) separated from potassium brine deposits collected from Lop Nur basin of China (referred to as LN K₂SO₄) were studied for utilization in agricultural farming as a potash fertilizer. First, the dissolving-crystallizing process was conducted to remove the insoluble content and improve the purity of K₂SO₄. Second, physical modification of K₂SO₄ surfaces was accomplished based on the Noyes–Whitney equation. The results showed that the water insoluble content could be completely removed and the purity of K₂SO₄ reached 100% in the purification process. The dissolution rate was significantly improved with the help of environmentally-friendly additives such as sodium tripolyphosphate (STPP)/urea phosphate (UP). These additives ameliorated the diffusion coefficient (D) and the diffusion layer thickness (h) for K₂SO₄. Results also demonstrated that a larger K₂SO₄ surface area (S) induced a higher dissolution rate.

Water soluble potassium sulfate dissolves rapidly and completely in water.

Determination of the ion exchange process of K2Ti4O9 fibers at constant pH and modeling with statistical rate theory

The ion exchange kinetics of K₂Ti₄O₉ fibers at constant pH was determined precisely by ion-selective electrodes, and activity coefficients of ions in solutions were calculated by the Lu–Maurer equation.

Hydrolysis of iron and chromium fluorides: mechanism and kinetics

Fluoride complexes of metallic ions are one of the main problems when processing industrial effluents with high content of fluoride anion. The most important case is derived from pickling treatment of stainless steel, which is performed with HNO3/HF mixtures to remove oxides scale formed over the metal surface. Waste from this process, spent pickling liquor, must be treated for recovering metallic and acid content. Conventional treatments produce a final effluent with high quantity of fluoride complexes of iron and chromium. This work proposes a hydrolysis treatment of these solid metal fluorides by reacting them with a basic agent. Metal oxides are obtained, while fluoride is released to solution as a solved salt, which can be easily recovered as hydrofluoric acid. Solid iron and chromium fluorides, mainly K2FeF5(s) and CrF3(s), obtained in the UCM treatment process, were employed in this work. Optimal hydrolysis operating conditions were obtained by means of a factorial design: media must be basic but pH cannot be higher than 9.5, temperature from 40 to 70 degrees C and alkali concentration (potassium hydroxide) below 1.1 mol L(-1). Secondary reactions have been detected, which are probably due to fluoride adsorption onto obtained oxides surface. Mechanism of reaction consists of several stages, involving solid fluoride dissolution and complexes decomposition. Hydrolysis kinetics has been modeled with classical crystal dissolution kinetics, based on mass transfer phenomena.