Facile synthesis and exfoliation of micro-sized LDH to fabricate 2D membranes towards Mg/Li separation

Abstract

Two-dimensional (2D) membranes have demonstrated potential for molecular separation; however, their applicability for Li/Mg ion separation has been restricted by their negatively-charged and easily-swellable properties in water. Moreover, their practical application has been hindered by the challenge of producing significant quantities of single-layer nanosheets. To overcome these challenges, we have developed a scalable method for synthesizing micro-sized nitrate ZnAl layered double hydroxide (LDH) and subsequent exfoliating to yield monolayer nanosheets for the construction of 2D membranes. The sub-nanometer channels of the LDH membrane is positively charged, which prevents the passage of magnesium ions. These channels also impede the flow of magnesium ions that are more difficult to dehydrate. As a result, the LDH membranes exhibit robust lithium–magnesium separation ability, with a separation ratio of 6 (Li/Mg). This work provides a method for producing high-quality LDH nanosheets and validates the enormous potential of LDH membranes in the field of lithium–magnesium separation.