Silicalite Nanosheet Laminated Membranes: Effects of Layered Structure on the Performance in Pervaporation Desalination

Silicalite nanosheet (SN) laminated membranes are promising for pervaporation (PV) desalination of concentrated brines for water purification and critical material concentration and recovery. However, scaling up the SN-based membranes is limited by inefficient synthesis of monodispersed open-pore SN single crystals (SNS). Here, we report a scalable approach to fabricate multilayered silicalite nanosheet plate (SNP) laminated membranes on porous alumina and PVDF substrates and demonstrate their excellent PV desalination performance for simulated brines containing lithium and high total dissolved salts (TDS). At 73 ± 3 °C, the SNP laminated membrane on alumina support achieved a remarkable water flux (Jw) of nearly 20 L/m²·h, significantly outperforming the alumina-supported SNS laminated membrane (Jw = 9.56 L/m²·h), while both provided near-complete salt rejection (ri ~99.9%) when operating with vacuum pressure on the permeate side. The PVDF-supported SNS and SNP laminated membranes exhibited excellent Jw (14.0 L/m²·h) and near-complete ri (>99.9%), surpassing the alumina-support SNP laminated membranes when operating by air sweep on the permeate side. However, the ri of the PVDF-supported membranes was found to decline when operating with vacuum pressure on the permeate side that was apparently caused by minimal liquid permeation through the inter-SNP spaces driven by the transmembrane pressure. With scalable SNP production, SNP-A membranes show potential for PV desalination of high-TDS solutions, especially in harsh environments unsuitable for polymer membranes.