锂铝层状双金属氢氧化物的制备及其锂脱嵌过程

Preparation of lithium aluminum layered double hydroxides and their lithium deintercalation performance

锂铝层状双金属氢氧化物(Li/Al-LDHs)是一种适用于高镁锂比卤水中提锂的吸附剂,但其存在吸附容量偏低、吸附机理与适用条件不够清晰等问题。本工作以铝粉、氢氧化锂为原料制备Li/Al-LDHs,考察了适用条件下溶液中阴阳离子对吸附过程的影响并进行了不同溶液组成下的提锂性能测试,结合红外光谱测试和X射线光电子能谱等表征明晰了锂脱嵌机理。结果表明,Li/Al-LDHs在卤水中的最大吸附容量为8.350mg/g,阳离子选择性顺序为Li^(+)>Na^(+)>Mg^(2+)>Ca^(2+)>K^(+)。Li/Al-LDHs对Li^(+)的吸附符合Langmuir等温吸附模型和准二级吸附动力学模型,吸附过程主要是基于尺寸筛分效应进行的,Li^(+)进入吸附剂层间的空位后需要等量的阴离子(Cl^(-)、SO_(4)^(2-)等)进行电荷平衡,其吸锂容量随溶液体系总离子浓度的增加而变大,因此更适用于从高含盐量卤水中提锂。研究结果可为后续废旧金属铝制取Li/Al-LDHs用于盐湖卤水提锂提供技术参考。

lithium/aluminum layered double hydroxides(Li/Al-LDHs)is an adsorbent suitable for lithium extraction from high magnesium to lithium ratio brine.However,there are issues such as low adsorption capacity,unclear adsorption mechanism and insufficient understanding of applicable conditions.In this work,Li/Al-LDHs were prepared using aluminum powder and lithium hydroxide as raw materials.The applicable conditions and the influence of anions and cations in the solution on the adsorption process were investigated.The lithium extraction performance under different solution compositions was tested and the lithium desorption mechanism was characterized by FTIR and XPS.The results showed that the maximum adsorption capacity of Li/Al-LDHs in brine was 8.350mg/g,and the cation selectivity order was Li^(+)>Na^(+)>Mg^(2+)>Ca^(2+)>K^(+).The adsorption of Li^(+)by Li/Al-LDHs followed the Langmuir isotherm adsorption model and the pseudo-second-order adsorption kinetics model.The adsorption process was mainly based on the sieving effect of size.When Li^(+)entered the interlayer space of the adsorbent,an equal amount of anions(Cl^(-),SO_(4)^(2-),etc.)was needed to maintain charge balance.The lithium adsorption capacity increased with the increase of the total ion concentration in the solution,making it more suitable for lithium extraction from high salt content brines.This research findings can serve as valuable technical references for the subsequent utilization of Li/Al-LDHs derived from discarded aluminum metal in lithium extraction from salt lake brines.