Abstract: Dissolution kinetics of sodiumcarbonate is investigatedwith the image analysismethod at the approach of single particle. The dissolution experiments are carried out in an aqueous solution under a series of controlled temperature and pH. 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 sodiumcarbonate increases significantly with the rising of temperature, but decreases with the increasing of pH conversely.

Key words: Sodium carbonate, Single particle, Dissolution rate constant, Image analysis

摘要： Dissolution kinetics of sodiumcarbonate is investigatedwith the image analysismethod at the approach of single particle. The dissolution experiments are carried out in an aqueous solution under a series of controlled temperature and pH. 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 sodiumcarbonate increases significantly with the rising of temperature, but decreases with the increasing of pH conversely.

关键词: Sodium carbonate, Single particle, Dissolution rate constant, Image analysis