1,3-二元脂肪醇萃取硼酸的平衡特性

摘要

基于1,3-二元脂肪醇的溶剂萃取法在盐湖卤水提硼方面有广阔的应用前景,系统研究了两种1,3-二元脂肪醇萃取剂:2-乙基-1,3-己二醇(EHD)和2-丁基-2-乙基-1,3丙二醇(BEPD)对硼酸的萃取性能,分别考察了萃取剂浓度、原料液pH、硼酸浓度、氯化镁浓度以及温度等因素对硼酸分配系数的影响.实验结果表明,温度为303.15 K,原料液中硼酸浓度为0.0185 mol·L-1,EHD和BEPD甲苯溶液中浓度均为0.4 mol·L-1时,硼酸的分配系数分别达到9.43和8.25.高浓度的萃取剂和较低的原料液pH条件对提高分配系数有利；分配系数随原料中硼酸浓度和反应温度的升高而降低,1,3-二元脂肪醇萃取硼酸的过程为放热过程；氯化镁存在下的盐析效应也有利于硼酸的萃取分配.%Solvent extraction based on aliphatic 1,3-diols is a promising technique for the recovery of boric acid from salt lake brine. In this work, two diols, 2-ethyl-1, 3-hexanediol (EHD) and 2-butyl-2-ethyl-1,3-propanediol (BEPD),were selected as extractants and toluene was used as diluent. The effects of extractant concentration, pH of brine, initial boric acid concentration, magnesium chloride concentration, and temperature on the distribution coefficients of boric acid were systematically investigated. Distribution coefficients of boric acid up to 9. 43 and 8. 25 were obtained from the boric acid aqueous solutions with the initial concentration of 0. 0185 mol · L-1 when using toluene containing 0. 4 mol · L-1 EHD and BEPD, respectively, as organic phases at 303. 15 K. Higher extractant concentration or lower pH is favorable to the extraction. However, the distribution coefficients decrease gradually with the increase of boric acid concentration and temperature. The extraction of boric acid with aliphatic 1, 3-diols is an exothermic process. The salting-out effect of magnesium chloride enhances the extraction performance.