偏硼酸镁在氯化锂水溶液中水解的硼物种转化与分布规律

Boron species transformation and distribution law of Mg(BO_(2))_(2) decomposed in LiCl aqueous solution

盐湖卤水含有氯化锂和硼酸盐,而硼又是盐湖提锂过程的主要干扰因素之一。为确定硼在卤水中的存在形态和分布特征,重点对硼物种在氯化锂水溶液中的分布规律开展研究。通过研究偏硼酸镁在氯化锂浓度从零到饱和的系列水溶液中水解的硼物种固液相特征,获得了液相硼物种分布和浓度状态及其随氯化锂浓度的变化规律。结果表明偏硼酸镁在水中的水解固相为多水硼镁石;在低浓度氯化锂溶液中的水解产物为章氏硼镁石和柱硼镁石,但不生成多水硼镁石;在高浓氯化锂水溶液中,只有柱硼镁石生成;虽然偏硼酸镁与水解固相共存,但它不是稳定固相,不能与液相处于固液平衡态。液相硼物种分布不仅与p H相关,还与氯化锂浓度有关,氯化锂浓度较低时B_(3)O_(3)(OH)_(4)^(-)占据液相总硼的55%以上,随着氯化锂浓度的增加,B_(3)O_(3)(OH)_(4)^(-)的分布值减小,而B_(5)O_(6)(OH)_(4)^(-)显著增加。在氯化锂全浓度范围,B(OH)_(4)^(-)和B_(3)O_(3)(OH)_(4)^(-)始终是浓度最高的硼物种。B_(3)O_(3)(OH)_(5)^(2-)、B_(4)O_(5)(OH)_(4)^(2-)、B(OH)_(4)^(-)分别是多水硼镁石、章氏硼镁石、柱硼镁石的阴离子构型,其浓度与固相溶解度有关,而没有对应固相生成的B_(3)O_(3)(OH)_(4)^(-)和B_(5)O_(6)(OH)_(4)^(-)在溶液中能维持较高的浓度。这些结果和大量的物种转化数据,对认知卤水硼的特性和量化表达硼在卤水中的分布提供了重要依据。

Salt lake brine contains lithium chloride and borate,and boron is one of the main interference factors in the pro⁃cess of recovering lithium from salt lake.In order to know the characteristics of boron species distributed in brine,the distri⁃bution law of boron species in lithium chloride aqueous solution was mainly studied.The distribution and concentration state of liquid boron species and their variate behavior with lithium chloride concentration were obtained by studying the solid and liquid boron species produced from the reactions of Mg(BO_(2))_(2) hydrolyzed in a series of aqueous solutions with LiCl con⁃centration from zero to saturation.The results showed that inderite formed when Mg(BO_(2))_(2) was decomposed in water;hun⁃gchsaoite and pinnoite but not inderite would generate when Mg(BO_(2))_(2) was decomposed in LiCl aqueous solution with a lower concentration;and only pinnoite would form in high concentration LiCl aqueous solution.Although Mg(BO_(2))_(2) was co⁃existed with hydrolyzed solid phase,but it was not a stable salt and could not be in phase equilibrium with the liquid phase.The distribution of liquid boron species was not only related to pH,but also to LiCl concentration.When LiCl concentration was low,B_(3)O_(3)(OH)_(4)^(-) was more than 55%of the total liquid boron.The distribute rate of B_(3)O_(3)(OH)_(4)^(-) was decreased and B_(5)O_(6)(OH)_(4)^(-) was increased significantly while LiCl concentration was increased.B(OH)_(4)^(-)and B_(3)O_(3)(OH)_(4)^(-) were the boron species with highest concentration in all the LiCl concentration range.B_(3)O_(3)(OH)_(5)^(2-),B_(4)O_(5)(OH)_(4)^(2-)and B(OH)_(4)^(-) were the an⁃ionic configurations of inderite,hungchsaoite and pinnoite respectively,moreover their concentrations were related to the solubility of the solid phase,while B_(3)O_(3)(OH)_(4)^(-) and B_(5)O_(6)(OH)_(4)^(-) were not corresponding to solid salt,but could maintain higher concentrations.These results and a large number of species data provided an important basis for recognizing the char⁃acteristics of boron in brine and quantifying the distribution of boron in brine.