Zhong Jing, Lin Sen, Yu Jianguo
National Engineering Research Center for Integrated Utilization of Salt Lake Resources, East China University of Science and Technology, Shanghai 200237, China; Engineering Research Center of Salt Lake Resources Process Engineering, Ministry of Education, East China University of Science and Technology, Shanghai 200237, China.
National Engineering Research Center for Integrated Utilization of Salt Lake Resources, East China University of Science and Technology, Shanghai 200237, China; State Environmental Protection Key Laboratory of Environmental Risk Assessment and Control on Chemical Process, East China University of Science and Technology, Shanghai 200237, China.
J Colloid Interface Sci. 2020 Jul 15;572:107-113. doi: 10.1016/j.jcis.2020.03.081. Epub 2020 Mar 23.
Lithium/aluminum layered double hydroxides (Li/Al-LDHs) have been industrially proven to be recyclable lithium adsorbents that do not dissolve upon elution, although they are hypersensitive to lithium deintercalation. In this study, the Li adsorption performances and structural stabilities of Li/Al-LDHs samples with different lithium deintercalation intensities are comprehensively investigated and compared to expose the influence of excessive lithium deintercalation. The characterization results demonstrate that Li/Al-LDHs are inclined to transform to gibbsite under excessive lithium deintercalation. Moreover, this transformation is enhanced by a long deintercalation time at 80 °C in deionized water because the layered structure of Li/Al-LDHs collapses upon reduction of the lithium content. The Li adsorption kinetics and isotherms reveal that excessive lithium deintercalation has no effect on the adsorption pathway and rate, while the adsorption capacity fluctuates with increased lithium loss on account of the conflict between the generation of Li active sites and structural damage. Adsorption experiments at different pH values show that a neutral pH is more favorable because an acidic or alkaline condition leads to the undesirable formation of a gibbsite or amorphous phase in Li/Al-LDHs during adsorption. In addition, the presence of Mg has a significant effect on the lithium adsorption capacity of Li/Al-LDHs. The adsorption capacities of Li/Al-LDHs samples with different lithium deintercalation intensities are all dramatically enhanced by a high Mg concentration, reflecting the promising potential application of Li/Al-LDHs in Li extraction from low-grade brines with high Mg/Li ratios.
锂/铝层状双氢氧化物（Li/Al-LDHs）已在工业上被证明是可回收的锂吸附剂，尽管它们对锂脱嵌高度敏感，但在洗脱时不会溶解。在本研究中，全面研究并比较了具有不同锂脱嵌强度的Li/Al-LDHs样品的锂吸附性能和结构稳定性，以揭示过度锂脱嵌的影响。表征结果表明，在过度锂脱嵌情况下，Li/Al-LDHs倾向于转变为三水铝石。此外，在80°C的去离子水中长时间脱嵌会增强这种转变，因为随着锂含量的降低，Li/Al-LDHs的层状结构会坍塌。锂吸附动力学和等温线表明，过度锂脱嵌对吸附途径和速率没有影响，而由于锂活性位点的产生与结构破坏之间的冲突，吸附容量会随着锂损失的增加而波动。在不同pH值下的吸附实验表明，中性pH更有利，因为酸性或碱性条件会导致Li/Al-LDHs在吸附过程中形成不希望的三水铝石或无定形相。此外，Mg的存在对Li/Al-LDHs的锂吸附容量有显著影响。高Mg浓度显著提高了具有不同锂脱嵌强度的Li/Al-LDHs样品的吸附容量，这反映了Li/Al-LDHs在从高Mg/Li比的低品位卤水中提取锂方面具有广阔的潜在应用前景。
