Process Simulation Andanalysis Of Membrane Separation Of Inorganic Salt And Amino Acid

The guiding role of mass transfer model is very important for the development of membrane separation process. The Solution-Diffusion model (SDM) and the Preferential Sorption-Capillary Flow model which are widely used can not accurately predict solute rejection and permeation flux. The Adsorption-Diffusion model(ADM) is a new model of membrane separation process and it contains many influential factors of membrane separation process. A prediction of possible maximum and minimum of membrane separation process is showed theoretically by ADM. But ADM has remained at the theoretical level and lack of practical calculation. It is yet to be proved by experiments.The effect of operation pressure and permeation flux of RO membrane is studied. The separation process of RO membrane is simulated by the first approximation form of ADM and SDM. The simulation results show that the first approximation form of ADM is superior to SDM. Based on mathematical form, SDM contains only one parameter B and the first approximation form of ADM contains two parameters Ki(λ) and b. Based on ADM, the maximal values of solute rejection and permeation flux are caused by charge, membrane porosity, concentration polarization and other facts.Accounting into the volume pressure gradient of solute, a modified Solution-Diffusion model (MSDM) for RO membrane was proposed on the basis of SDM. The range of square deviation calculated by MSDM was from 10-8 to 10-6. It was better than the results calculated by SDM. Based on MSDM, parameter B of SDM is a function of operation pressure. There are some deviation between the calculated value of Vs and the true value of solute molar volume. It indicated that parameterαmight be a function of permeation flux and operation pressure on the basis of ADM. MSDM could be used as a semi-empirical model.Based on the ionization equilibrium of amino acid and charge conservation of the solution under steady state, relationship between the total retention of amino acid and retentions of molecule(zwitterion) of amino acid, and the retention of hydrogen ion and the ionization degree of solute is derived, as well as relative expressions of retentions of a variety of ions in the solution. A phenomenological model for membrane separation of amino acid was established. Based on the model, the total retention of amino acid and retentions of ion components are functions of the pH value. The ionization degree of amino acid cation could be neglected when the pH value is high and the ionization degree of amino acid anion could be neglected when the pH value is low. The calculating curves basically tallied with experimental curves by using the model, and the mathematical model established could provided a reference to the theoretical investigation of the retention of membrane separation of multiple organic acid.