萃取法从废旧锂离子电池正极材料浸出液中提取锂

Recovery of lithium from leaching solution of anode materials in waste lithium-ion batteries by solvent extraction method

废旧锂离子电池正极材料浸出后,溶液中的镍、钴等有价金属十分容易回收,但一直没有很好的方法来回收锂.实际上,这种浸出液和盐湖卤水都为锂盐溶液,所不同的只是盐湖卤水中锂的浓度往往要低一些,并有大量的氯化钠、氯化镁伴生,因此可将废旧锂离子电池浸出液看做一种特殊的"盐湖卤水",并进一步调整其Cl^-的浓度,进而成功地采用盐湖提锂中常用的萃取法.该方法以磷酸三丁酯(TBP)为萃取剂,磺化煤油为稀释剂,在三氯化铁(FeCl_3)存在的条件下,实现选择性提取锂.TBP首先与FeCl_3-NaCl的酸性溶液接触,形成了锂的专属萃取剂;并将浸出液中氯化钠的浓度进一步调整到250 g/L,在相比(V_O/V_A)为3,温度为室温条件下萃取5 min,锂的单级萃取率可达到75%左右,而Ni^(2+)、Co^(2+)、Mn^(2+)几乎没有被萃取.根据平衡等温线,通过4级逆流萃取,锂的萃取率可达到99%.

After the cathode materials of spent lithium-ion battery have been leached,valuable metals such as nickel and cobalt in solution are easily recycled,but there's been no good way to recycle lithium.In fact,this leaching solution is similar to Salt Lake Brine,the difference is that the concentration of lithium in the Brine is lower,and there is a large amount of sodium chloride,magnesium chloride associated in the Brine.We can treat the leaching solution as a special"Salt Lake Brine",adjusting its chlorine concentration,and then the widely accepted method for extracting lithium from Salt Lake Brine can be successfully applied.With tributyl phosphate(TBP)used as the extractant,sulfonated kerosene as the diluent and ferric chloride(FeCl3)as the co-extractant,lithium is selectively extracted.TBP firstly reacts with the acidic solution of FeCl3-NaCl to form the exclusive extractant for lithium.Then adjust the concentration of NaCl in the leaching solution to more than 250 g/L and conduct the extraction experiment for 5 minutes at room temperature with the organic/aqueous volume ratio(O/A)of 3.It turns out that the extraction rate of single-stage lithium stands at 75%,while Ni2+,Co2+and Mn2+are hardly extracted.According to the equilibrium isotherm,extraction rate of lithium can reach 99%through four-stage countercurrent extraction.