Mining Critical Metals from Seawater by Subnanostructured Membranes: Is It Viable?

The continuous demand for energy-critical elements such as lithium, cobalt, uranium and so on will soon exceed their availability increasing further their significance of geopolitical resources. Seawater is a relevant, not conventional source of critical metals. Synthetic membranes with subnanometer pores are the core of processes such as desalination for separating solutes from water. These membrane processes have achieved remarkable success at industrial level. However, state-of-the-art desalination membranes cannot selectively separate a single metal ion from a mixture of ions. In this review the challenges of membranes with subnanometer pores to selectivity discriminate among different metal ions are briefly discussed. The key points of the molecular-level mechanism that contribute to energy barrier for ions transport through subnanometer pores are highlighted to provide guidelines for the design of single-metal ion selective membranes.