The dissolution kinetics of calcined ulexite in ammonium chloride solutions at high solid-to-liquid ratios were investigated. In the experiments, calcination temperature, solution concentration, reaction temperature, ...The dissolution kinetics of calcined ulexite in ammonium chloride solutions at high solid-to-liquid ratios were investigated. In the experiments, calcination temperature, solution concentration, reaction temperature, and pre-hydration were chosen as parameters. It was observed that the dissolution rate increased with increasing calcination temperature, solution concentration, and reaction temperature, whereas it was not affected by pre-hydration. Employing graphical and statistic methods, the dissolution rate, based on homogeneous reaction model, can be given as: (1-X(B2O3))-1-1= k(c(NH4Cl))1.982t. The activation energy for the dissolution of the ulexite sample calcined at 160 ℃ was found to be 84.04 kJ·mol-1.展开更多
For the purpose of developing an alkali leaching solvent extraction directly from alkali solution process, the extraction of niobium from alkali solution by long chain alkyl quaternary ammonium salt (methyltrioctylamm...For the purpose of developing an alkali leaching solvent extraction directly from alkali solution process, the extraction of niobium from alkali solution by long chain alkyl quaternary ammonium salt (methyltrioctylammonium chloride R 4NCl) in toluene was investigated. The experiments were carried out under conditions of 25 ℃, Nb(Ⅴ) concentration 0.01 mol/L, pH 10.7 13.8, R 4NCl concentration 0.02 0.14 mol/L. It has been found that the distribution ratio of niobium increases with increasing R 4NCl concentration and with decreasing KCl concentration, but it shows maximum value at pH value of about 12 and decreases below or above this pH value. Distribution ratio of niobium goes up to over 1 000 in appropriate conditions, and so it has been proved that R 4NCl is an effective extractant for extraction of niobium from alkali solution.展开更多
文摘The dissolution kinetics of calcined ulexite in ammonium chloride solutions at high solid-to-liquid ratios were investigated. In the experiments, calcination temperature, solution concentration, reaction temperature, and pre-hydration were chosen as parameters. It was observed that the dissolution rate increased with increasing calcination temperature, solution concentration, and reaction temperature, whereas it was not affected by pre-hydration. Employing graphical and statistic methods, the dissolution rate, based on homogeneous reaction model, can be given as: (1-X(B2O3))-1-1= k(c(NH4Cl))1.982t. The activation energy for the dissolution of the ulexite sample calcined at 160 ℃ was found to be 84.04 kJ·mol-1.
文摘For the purpose of developing an alkali leaching solvent extraction directly from alkali solution process, the extraction of niobium from alkali solution by long chain alkyl quaternary ammonium salt (methyltrioctylammonium chloride R 4NCl) in toluene was investigated. The experiments were carried out under conditions of 25 ℃, Nb(Ⅴ) concentration 0.01 mol/L, pH 10.7 13.8, R 4NCl concentration 0.02 0.14 mol/L. It has been found that the distribution ratio of niobium increases with increasing R 4NCl concentration and with decreasing KCl concentration, but it shows maximum value at pH value of about 12 and decreases below or above this pH value. Distribution ratio of niobium goes up to over 1 000 in appropriate conditions, and so it has been proved that R 4NCl is an effective extractant for extraction of niobium from alkali solution.
