Study On The Complexation Extraction Of Valeric Acid By Triethylamine Aqueous Solution

In this paper,the triethylamine was used as complexation extractant and water as diluent to separate valeric acid from n-butyl ether solution.At the molar concentration of 0.3776?0.6847 mol·L^-1 of valeric acid,the extraction equilibrium,kinetics was analysised and the total mass transfer coefficient model was established on the basis of experimental data,which could provide the theoretical basis for rational selection of extraction equipment.By analyzing different stirring time on the equilibrium distribution coefficient,we determined the extraction equilibrium time was 30min.The effects of valeric acid concentration,triethylamine concentration,diluent and temperature on extraction equilibrium were researched.It indicated that the equilibrium distribution coefficient has a good synchronization with the triethylamine,With the increase of extraction temperature,the equilibrium partition coefficient was decreased,and the reaction enthalpy of the extraction process was calculated as-7.18 kJ·mol^-1,which indicated that this complex extraction was an exothermic process,therefore,extraction experiments were carried out at room temperature?298K?.The influence of the specific surface area of different concentration of valeric acid on the extraction rate was investigated by using the rising droplet method,with capillary nozzles of different diameters respectively at the conditions of T = 298K,which determined this complex extraction occurs at the interface of two phases.When fixed nozzle diameter as 1mm,the extraction rate of the droplet increased with the concentration of triethylamine in the aqueous phase and the concentration of valeric acid in the organic phase,and it showed a great linear relationship.It was found that this complexation extraction was an ion association mechanism mostly by the analysis of IR.Based on the above experiments,we studied the mass transfer performance of the complex extraction.It was known,through the mechanic analysis on single droplet,that flow pattern of which was in the transition region when the droplet flow in the free motion stage.The model of total mass transfer coefficient was established according to the two-film theory and the empirical correlation of sub-transfer coefficient of the droplets,The calculated values of the model were compared with the experimental ones.The average error of this model was small,which indicated that it could be used for the reference of extraction equipment design.We found that the mass transfer resistance was mainly concentrated on the inside of the droplet.Therefore we should reduce the droplet size or increase the escape rate of organic liquid droplets to enhance the degree of turbulence in the interface,so as to intensify degree of mass transfer within the droplet.