Study On The Liquid-Liquid Diffusion And Gas-Liquid Interfacial Mass Transfer

The phenomena of diffusion and mass transfer between phases are widely existed in industrial processes such as the fields of chemical, metallurgy, biology engineering, petroleum chemistry, medicine and environment. In order to get a better understanding of the diffusion process in liquid-liquid system and interfacial mass transfer behaviors in gas-liquid system, experiments were conducted by real-time holographic interferometry to determine the diffusion coefficient of vitamin B6 in aqueous solution and in biologic brine at 298.15K, and to investigate the concentration distribution in the vicinity of the interface of CO2 in aqueous solution and PAA (0.10% by mass) aqueous solution with MEA.Firstly, the reliability of the whole system including holographic interferometer and a liquid-liquid simulator of mass transfer by diffusion was confirmed with literature data. Then the diffusion coefficients of different concentrations vitamin B6 in aqueous solution and in biologic brine were measured at 298.15K, respectively. The results show that, the diffusion coefficient of vitamin B6 in aqueous solution decreases unilaterally with the concentration of vitamin B6, but in biologic brine the diffusion coefficient grows to a maximum and then decreases remarkably with the concentration of vitamin B6. It is mainly due to the special self-structure of vitamin B6 and the effect of different interactions existing in different solutions. Relative explanation and discuss were given in this paper according to the integrated effect of H-bond action, interaction between particles, ion intensity and friction resistance between solute and solvent, etc.The liquid phase concentrations distribution near the interface during the mass transfer process of gas-liquid is of great importance to the study of mass transfer. The real-time records of the absorption process of quiescent CO2 bubble were obtained by holographic interferometry and CCD camera, and a simulator of mass transfer specially designed and established was also applied. According to the standard curve of concentration- refractive index, the concentration distribution of CO₂ was gained. A series of optical qualitative experiments showed the existence of turbulence phenomena near the interface,the formation mechanism of the instable phenomena was analyzed; the effects of bulk velocity, MEA concentration and character of the fluid on the concentration distribution were also discussed; based on the convection-diffusion equation, the interfacial concentration field model of bubble between two phases near the interface was developed. The model was simulated by numerical method for CO₂-H₂O with MEA species, and the calculated results were in well accordance with the experimental ones.