| The integration of acidizing crystallization-solvent is an efficient method for the extraction of boron from salt lake brine containing high Mg2+.Acidizing crystallization-solvent extraction which used for extraction of boron has become a more mature technology.The key is the choice of extraction system in solvent extraction stage.However,there are some problems which volatilization of volatile organic solvent,high solution loss in aqueous phase,emulsification and environmental pollution so on,in the process of conventional extraction systems.Ionic liquids,the high thermal stability,non-volatile,non-flammable and unique solubility properties are a new kind of green solvents,which are used in the extraction and separation process of organic,natural product and metal ion so on.In this paper,the extraction systems of ionic liquid were constructed by three kinds ionic liquids,which were used to extract boron from boron mother liquor of acidified brine.The effects of water phase pH,ionic liquid volume fraction,phase ratio and temperature on boron extraction rate were investigated.The extracted complex stoichiometry was determined using a slope analysis method,and the main functional groups of the organic phase before and after extraction were characteried by infrared spectrum.The extraction mechanism of boron extraction by ionic liquid system was discussed preliminarily.The major conclusions of research are as following:1.The extraction system of Tributylhexylphosphonium bis?trifluoromethyl sulfonyl?imide[P4,4,4,6][NTf2]-isooctyl alcohol-butyl acetate was used for extraction of boron from boron mother liquor of acidified brine.The optimum extraction conditions were obtained by single factor variable method:At room temperature,the volume ratio of[P4,4,4,6][NTf2],isooctanol and butyl acetate was 1:5:4,the water phase pH=1.5,phase ratio?O/A?1:1,the extraction efficiency of boron can reach99.7%with four stages cross-current extraction,and the saturated extraction capacity is about 28.7 g·L-1?by H3BO3?.Deionized water is the reverse extraction agent,the reverse extraction phase ratio?O?/A??is 1:1,and the efficiency of three cross-current stripping extraction is 99.6%.The total recovery of boron was 99.3%.Meanwhile,the separation factor(?B/Li,?B/Mg,?B/K)was 100.63,301.35,206.50,respectively.The separation coefficient of boron and Magnesium is high,and the selected system is suitable for the separation of boron and Magnesium in high-Magnesium brine.A slope analysis method and the infrared spectrum showed that the stoichiometry of the extracted complex is 1.556.Esterification reaction is taken between isooctyl alcohol and boric acid,generating monobasic and binary borate complex.The thermodynamic function of the extration system was calculated by temperature experiment,?Ho=-22.957 kJ·mol-1 and?Go=-5.722 kJ·mol-1,which showed that the extraction of boron was spontaneous exothermic reaction.2.A new extraction system of hydrophobic ionic liquid Cyphos IL 104-toluene was establelished to extract boron from boron mother liquor of acidified brine.Cyphos IL 104 has a certain extraction capability for boron in aqueous phase.The extraction efficiency on boron increases with the increase of Cyphos IL 104 volume fraction,and decreases with the increase of pH in aqueous phase.Acid environment is more favorable to the extraction of boron.A slope analysis method and the infrared spectrum showed that the stoichiometry of the extracted complex between Cyphos IL 104 and boric acid is 1:1,the extracted complex was formed by interaction between P=O and boron which was in aqueous phase.The thermodynamic parameters of Cyphos IL 104 system,?Hoand?Go,were determined by changing the extraction temperature,?Ho=-10.454 kJ·mol-1 and?Go=-2.244 kJ·mol-1.The extraction of boron was spontaneous exothermic reaction.3.Hydroxyl-functionalized ionic liquids,[OHEtN1,1,1][NTf2],was researched for extraction of boron from boron mother liquor of acidified brine.The better extraction efficiency of boron was obtained for[OHEtN1,1,1][NTf2].The extraction efficiency on boron decreases with the increase of pH,and decreases with the increase of temperature.Acid environment and low temperature are more favorable to the extraction of boron.The infrared spectrum showed that the hydroxyl groups-OH on the cations of[OHEtN1,1,1][NTf2]may have a esterification reaction with-OH of H3BO3 which was in aqueous phase. |
PDF Full Text Request