Recovery Of Boron From East Taijinar Salt Lake Brine By Solvent Extration

With the rapid development of modern industry,boron has been widely used in chemical catalysis,building materials,electronic equipment,nuclear energy,etc.Hard-rock ores and salt lake brines are major boron resources.Between them,salt lake brines account for more than 30%of the total boron reserves in China.Currently,both the reserves and grades of boron-magnesium ores are declining rapidly,leading to a serious shortage of boron ore resources.Therefore,effective and environmentally friendly extraction of boron from salt lake brines has become an important research topic.Solvent extraction is a more promising technology applied for boron recovery from salt lake brines,and the key to solvent extraction is to find suitable extraction systems in the research of different types of salt lakes in recent years.In this paper,different aliphatic alcohol extraction systems were used to extract boron from East Taijinar Salt Lake.Through optimization and integration of process parameters,an efficient boron extraction process was established.The main research contents were as follows:Nine commercially available monohydric alcohols with different structures were selected for boron extraction from a salt lake brine with high magnesium content.Passing through the optimization,isodecanol was finally selected for the detailed study on boron recovery from the brine due to its moderate viscosity,lower solubility and water entrainment.Under the optimized extraction conditions:the organic phase containing 2.5 mol/L isodecanol was mixed with brine at O/A ratio of 1:1,293 K,equilibrium pH was adjusted to 3.5,the single-stage extraction efficiency of boron was 81.67%and the saturated extraction capacity was 8.56 g/L.Additionally,the mechanism of boron extraction by isodecanol was investigated using both slope analysis method and Fourier transform infrared spectroscopy(FTIR).The stoichiometric ratio of isodecanol to boron required to form boric acid ester was found to be 1.268.At the same time,the thermodynamic experimental results showed that the process of boric acid extraction by isodecanol was an exothermic reaction with reduced entropy,and low temperature was conducive to the extraction of boron.In order to further improve the extraction efficiency of boric acid,various readily available dibasic aliphatic alcohol extracting agents were introduced and compared.And 2,2,4-trimethyl-1,3-pentanediol/isodecanol/sulfonated kerosene extraction system was selected for boron extraction from East Taijinar Salt Lake.Under the optimized extraction conditions:the organic phase containing 0.6 mol/L 2,2,4-trimethyl-1,3-pentanediol and 1 mol/L isodecanol was mixed with brine at O/A ratio of 1:1,293 K,equilibrium pH was adjusted to 4.5,the singlestage extraction efficiency of the mixed alcohols was 96.09%,and the saturated extraction capacity was 11.08 g/L.Compared with the isodecanol extraction system,the mixed alcohol extraction system was less affected by the salting out effect,and the saturated extraction capacity was significantly increased.The mechanism analysis showed that 2,2,4-trimethyl-1,3-pentanediol and isodecanol react with boric acid at stoichiometric ratios of 1.280 and 0.751,respectively.By comparing the differences between the theoretical calculation and experimental results of boron extraction.The use of multi-stage counter-current extraction has higher economic feasibility.Therefore,2.5mol/L isodecanol was selected for three-stage counter-current extraction and four-stage countercurrent stripping,and the total recovery efficiency of boron was 97.79%.The boric acid crystal was obtained after evaporation and concentration of the stripping solution,which proved that the isodecanol/sulfonated kerosene extraction system was feasible for boron extraction from East Taijinar Salt Lake brine.