The thermodynamic properties of the most important NaOH-NaAI（OH）4-H20 system in Bayer process for alumina production were investigated. A theoretical model for calculating the equilibrium constant of gibbsite dissol...The thermodynamic properties of the most important NaOH-NaAI（OH）4-H20 system in Bayer process for alumina production were investigated. A theoretical model for calculating the equilibrium constant of gibbsite dissolved in sodium hydroxide solution was proposed. New Pitzer model parameters and mixing parameters for the system NaOH-NaAI（OH）4-H20 were yielded and tested in the temperature range of 298.15-373.15 K. The results show that the proposed model for calculating the equilibrium constant of gibbsite dissolution is applicable and accurate. The obtained Pitzer model parameters of β（0）（NaAl（OH）4）、β（1）（NaAl（OH）4）和CΦ（NaAl（OH）4）,Al（OH）4 for NaAI（OH）4, the binary mixing parameter of θ（OH-Al（OH）4-） with OH-, and the ternary mixing parameter of ψ（Na＋OH-Al（OH）4-） for AI（OH）4- with OH- and Na＋ are temperature-dependent. The prediction of the equilibrium solubility of gibbsite dissolved in sodium hydroxide solution was feasible in the temperature range of 298.15-373.15 K.展开更多
Dissolution kinetics of sodium carbonate is investigated with the image analysis method at the approach of single particle.The dissolution experiments are carried out in an aqueous solution under a series of controlle...Dissolution kinetics of sodium carbonate is investigated with the image analysis method at the approach of single particle.The dissolution experiments are carried out in an aqueous solution under a series of controlled temperature and p H.The selected sodium carbonate particles are all spherical with the same mass and diameter.The dissolution process is quantified with the measurement of particle diameter from dissolution images.The concentration of dissolved sodium carbonate in solvent is calculated with the measured diameter of particle.Both surface reaction model and mass transport model are implemented to determine the dissolution mechanism and quantify the dissolution rate constant at each experimental condition.According to the fitting results with both two models,it is clarified that the dissolution process at the increasing temperature is controlled by the mass transport of dissolved sodium carbonate travelling from particle surface into solvent.The dissolution process at the increasing pH is controlled by the chemical reaction on particle surface.Furthermore,the dissolution rate constant for each single spherical sodium carbonate particle is quantified and the results show that the dissolution rate constant of single spherical sodium carbonate increases significantly with the rising of temperature,but decreases with the increasing of pH conversely.展开更多
At pH = 8, the complex formation process of Ni（Ⅱ） ions with FA was studied by the solubility method. FA were separated from the river Mtkvari by the adsorption-chromotographic method. The charcoal （BAU, Russia） w...At pH = 8, the complex formation process of Ni（Ⅱ） ions with FA was studied by the solubility method. FA were separated from the river Mtkvari by the adsorption-chromotographic method. The charcoal （BAU, Russia） was used as a sorbent. The old suspension of Ni（Ⅱ） hydroxide was used as the solid phase, on which was added the increasing quantity of standard solution of FA. In diluted solutions, at pH = 8.0 the dominant form of Ni（Ⅱ） is nickel dihydroxocomplex Ni（OH）2^0. It was established that in the Ni（OH）2（solid）-Ni（OH）2^0（solution）-FA2-H20 system dominates nickel dyhydroxofulvate complex with the structure 1：1, [Ni（OH）2FA]2-. The average stability constant of nickel dyhydroxofulvate complex was calculated based on experimental data flNi（OH）2FA2＂ = 5.3 × 105.展开更多
基金Project (2005CB6237) supported by the National Basic Research Program of China
文摘The thermodynamic properties of the most important NaOH-NaAI（OH）4-H20 system in Bayer process for alumina production were investigated. A theoretical model for calculating the equilibrium constant of gibbsite dissolved in sodium hydroxide solution was proposed. New Pitzer model parameters and mixing parameters for the system NaOH-NaAI（OH）4-H20 were yielded and tested in the temperature range of 298.15-373.15 K. The results show that the proposed model for calculating the equilibrium constant of gibbsite dissolution is applicable and accurate. The obtained Pitzer model parameters of β（0）（NaAl（OH）4）、β（1）（NaAl（OH）4）和CΦ（NaAl（OH）4）,Al（OH）4 for NaAI（OH）4, the binary mixing parameter of θ（OH-Al（OH）4-） with OH-, and the ternary mixing parameter of ψ（Na＋OH-Al（OH）4-） for AI（OH）4- with OH- and Na＋ are temperature-dependent. The prediction of the equilibrium solubility of gibbsite dissolved in sodium hydroxide solution was feasible in the temperature range of 298.15-373.15 K.
基金the Institute of Particle and Science Engineering,University of Leeds and Procter&Gamble Newcastle Innovation Centre(UK)for partially funding the project
文摘Dissolution kinetics of sodium carbonate is investigated with the image analysis method at the approach of single particle.The dissolution experiments are carried out in an aqueous solution under a series of controlled temperature and p H.The selected sodium carbonate particles are all spherical with the same mass and diameter.The dissolution process is quantified with the measurement of particle diameter from dissolution images.The concentration of dissolved sodium carbonate in solvent is calculated with the measured diameter of particle.Both surface reaction model and mass transport model are implemented to determine the dissolution mechanism and quantify the dissolution rate constant at each experimental condition.According to the fitting results with both two models,it is clarified that the dissolution process at the increasing temperature is controlled by the mass transport of dissolved sodium carbonate travelling from particle surface into solvent.The dissolution process at the increasing pH is controlled by the chemical reaction on particle surface.Furthermore,the dissolution rate constant for each single spherical sodium carbonate particle is quantified and the results show that the dissolution rate constant of single spherical sodium carbonate increases significantly with the rising of temperature,but decreases with the increasing of pH conversely.
文摘At pH = 8, the complex formation process of Ni（Ⅱ） ions with FA was studied by the solubility method. FA were separated from the river Mtkvari by the adsorption-chromotographic method. The charcoal （BAU, Russia） was used as a sorbent. The old suspension of Ni（Ⅱ） hydroxide was used as the solid phase, on which was added the increasing quantity of standard solution of FA. In diluted solutions, at pH = 8.0 the dominant form of Ni（Ⅱ） is nickel dihydroxocomplex Ni（OH）2^0. It was established that in the Ni（OH）2（solid）-Ni（OH）2^0（solution）-FA2-H20 system dominates nickel dyhydroxofulvate complex with the structure 1：1, [Ni（OH）2FA]2-. The average stability constant of nickel dyhydroxofulvate complex was calculated based on experimental data flNi（OH）2FA2＂ = 5.3 × 105.
