Study On The Mass Transfer Performance Of Extracting Boric Acid By 2-Ethyl Hexanol

The mass transfer process of complexometric extracting boric acid was studied with 2-ethyl hexanol as complexing agent and toluene as diluent. The results can be used to provide theory for selecting the appropriate extracting equipment and realize industrial scale-up of extracting boric acid from strong acid brine with high concentration of magnesium and low concentration of boron.The effects of concentration of complexing agent 2-ethyl hexanol and different dilution agents(kerosene, toluene and methyl-phenol) on extraction efficiency and phase splitting time were investigated. Studies show that toluene as diluent was superior to kerosene and methyl-phenol, which have a connection with diluents viscosity and solvophobic effect between extracted complex and diluents.The kinetics of extracting boric acid from salt lake brine were studied on the conditions of different initial concentrations of boric acid and 2-ethyl hexanol, temperature and the interfacial area of two-phase. The method of rising drop technique was used in the experiment with 2-ethyl hexanol as complexing agent and toluene as diluent. The result shows that the extraction rate of boric acid increases with the increasing of the initial concentrations of boric acid in aqueous phase and 2-ethyl hexanol in organic phase, the interfacial area of two phase. The extraction reaction between boric acid and 2- ethyl hexanol is quick reaction, which occurred in the interfacial area of two-phase. The extraction process is diffusion-controlled mode by the calculation of the apparent activation energy. The kinetics equation of extracting boric acid with 2-ethyl hexanol regressed from the experimental data with linear least square method can be expressed at pH=1(aqueous phase) and T=318.15 K, and the relative deviation of rate constant is 5.318%.The mass transfer performance of extracting boric acid with 2-ethyl hexanol was studied, centered on single droplet mass transfer. It is known, through mechanic analysis on single droplet, that flow pattern of the single droplet is in the transition region when the droplet flow in the free motion stage. The calculation model of the total mass transfer coefficient was established, according to two-film theory model and the empirical correlation of sub-transfer coefficient both within and outside the drop, then the calculated and experimental value of the model was compared, the average relative error was 8.380%, which showed that the model can be used to design the extraction equipment. The overall mass transfer coefficient was affected by the individual mass transfer coefficient inside the droplets. In order to enhance the mass transfer inside droplets, the main controlling parameter is input flux when the extraction equipment is designed.