高镁锂比盐湖卤水中锂镁沉淀法的分离研究

Separation of Lithium and Magnesium in Salt Lake Brine with High Ratio of Magnesium to Lithium

采用改进的沉淀法进行锂镁分离,解决我国青海高镁锂比盐湖卤水中提锂的工艺难题。配制镁锂浓度比为44的模拟卤水(含110 g/L Mg^(2+)、2.5 g/L Li^+),以氢氧化钠为主沉淀剂,以吐温-80、聚丙烯酰胺及晶种为辅助沉淀剂,来改进氢氧化镁沉淀的颗粒大小及其形态,使生成的氢氧化镁易于过滤,锂离子吸附损失减小。取10mL模拟卤水,以50mL(2 mol/L)氢氧化钠、0.5mL吐温-80、0.03 g聚丙烯酰胺、0.03 g晶种构成复合沉淀剂,反应温度为60℃,溶液pH 12~13,则沉淀除镁率达99.9%,锂离子吸附损失率低于2%,过滤速度大大提高。采用SEM、XRD、粒度分布、热分析对氢氧化镁晶体的形貌和结构进行了分析,结果表明辅助沉淀剂的加入能有效地改变氢氧化镁沉淀的颗粒大小及其形态。

The improved precipitation is used to solve the problems that lithium is extracted by means of the high ratio of magnesium lithium from brine in Qinghai Salt Lake. In order to improve the size and morphology of magnesium hydroxide precipitate particle,Mg-Li ratio of 44 simulation brine（ containing Mg^2＋ 110 g/L and Li^＋2. 5 g/L） is prepared,and precipitation reaction for magnesium hydroxide was proceeded by using sodium hydroxide as the main precipitating agent,and Tween-80,polyacrylamide regard as auxiliary precipitant,the resulting precipitate of magnesium hydroxide was got with large granular,easy to filter,and lithium ion adsorption loss decreased. The magnesium ion was precipitated with rate of 99. 9%,lithium-ion adsorption loss rate of less than 2%,and the filtration rate is greatly improved when using the simulation brine 10mL,and the compound precipitation agents which being made up of 50mL 2 mol/L of sodium hydroxide,0. 5mL Twain-80,0. 03 g polyacrylamide,0. 03 g crystal seed,and the reaction conditions such as reaction temperature 60 ℃,the solution pH 12 ～ 13. The morphology and structure of magnesium hydroxide crystals were analyzed via SEM,XRD,particle size distribution and thermal analysis. The results show that precipitate particle size and morphology of the magnesium hydroxide could be changed effectively by the addition of an auxiliary precipitant.