Research On Extraction Of Boron From Brine

As an important chemical raw material, solid boron ore resource is in shortage seriously nowadays, however salt lake brines contain abundant liquid boron resources. Can ease the shortage of born and promote the comprehensive utilization of salt lake resources. This study applied the extraction technic, the most prospected boron removal method of industrial application, and studied systematically.Firstly, screened out potential boron extraction agents from monohydric aliphatic alcohol, aliphatic diol, aromatic alcohol and glycerin acid ester, made a preliminary evaluation and selected two1,3-diols, i.e.,2-ethyl-1,3-hexanediol (EHD) and2-butyl-2-ethyl-1,3-propanediol (BEPD) as the best extractants, constructed extraction system.The results of boric acid extraction equilibrium showed that, Higher extractant concentration or lower pH was favorable to the extraction. However, the distribution coefficients decreased gradually with the increase of boric acid concentration and temperature. The extraction of boric acid with aliphatic1,3-diols was an exothermic process. Furthermore, the salting-out effect of magnesium chloride enhanced the extraction performance. Distribution coefficients of boric acid up to4.50and3.96were obtained from the boric acid aqueous solutions with the initial concentration of0.0185mol/L when using toluene containing0.2mol/L EHD and BEPD, respectively, as organic phases at303.15K. Stripping boron loaded organic phase with aqueous solution of pH=13can acquired one-stage back-extraction efficiency and total extraction yield of83.94%and68.69%respectively, after five-stage, the back-extraction efficiency and total extraction yield can promoted to99.98%and81.81%significantly.In order to strengthen the effect of boron extraction, multilevel cross-flow extraction and multi-stage countercurrent extraction were calculated and verificated with experiments. The results showed that cross-flow extraction had higher extraction efficiency, acquired lower boric acid concentration in raw material and boron-loaded organic phase, the experimental operation was also simpler. However the countercurrent extraction was fit for industrialization application. This research applied this extraction method in centrifugal extraction plant.The research then studied the split phase performance and mass transfer performance in single stage extractor, obtained the optimal process parameters. The flow flux both in water and organic phase was10ml/min, rotating speed was3510rpm, in this condition, the stage efficiency was49.70%when using BEPD as extractant, after four stage centrifugal extraction, the total extraction efficiency was just90.38%, with9.34%relative error. However the stage efficiency and total extract efficiency can be achieved to85.68%and98.12%respectively when using EHD, it’s because of better dynamic process of this extractant. This result can be confirmed in extraction equilibrium experiment. For further research extraction kinetics of boric acid showed that, it was first-order reaction and occurred in two phase interface. The apparent activation energy was28.568kJ/mol, confirmed its diffusion and reaction hybrid control mechanism.