Study On Concentration Of Acetic Acid By Electrodialysis

The process of the concentration of acetic acid by electrodialysis is studied in this paper, which used JM homogeneous ion exchange membranes. Main works are as follows:1. Determined the mass transfer coefficient of anode membrane and cathode membrane: K CM= 1.223×10^-4m /h, K AM= 4.467×10^-4m /h,the linear relationship between the total mass-transfer coefficient of acetic aqueous and different flow rate: K AM + K CM= 0.0014Q + 0.0095.2. Calculated the limiting current density and determining the empirical relationship between the limiting current density and the volumetric flow rate and acetic acid concentration in small ED unit (100×300): i lim = 0. 051Cb0.95ν0.56.3. Described the water transport behavior during concentrating acids, determine electrodialytic coefficient of water under the limiting current density:βA +βC = 0.0309c m /( mA.min)4. A mathematical model was established to simulate the transfer process. The calculated results of Conc. ratio and current efficiency lower than experimental results'.5. The factors influencing the concentration and current efficiency are investigated, such as current density, flow rate and the concentration difference between the concentrated and dilute solution chambers. The experimental results indicate that: Firstly, the concentration of acetic acid and current efficiency increase with the increase of electric current density under lower current density and begin to decrease as the current density reaches its limiting value; Secondly, the acetic acid concentration rate and the current efficiency decrease with the increase of the feed acetic acid concentration; Thirdly, as the feed flow rate increases, the current efficiency is increased, however concentration is decreased; Finally, if the difference of the acetic acid concentration between both sides of membrane is increased, the current efficiency decreases.6. Using ED separation unit investigate the factors influencing the concentration and current efficiency: when electricity applied to ED unit, the concentration of acetic acid, flow rate of dilute stream and concentrate stream are settled at 0.96A, 6.2%, 120l/h and 2.8l/h, the acetic acid concentration rate and current efficiency can reach to 10.4% , 84.9%.While are settled at...