Janus composite membranes enable efficient solar-powered desalination and soil remediation

Solar-driven water evaporation offers a sustainable pathway for energy-efficient seawater desalination. However, its further practical performance is limited by salt accumulation during solar saline evaporation. Herein, a novel Janus composite membrane based on the assembly of hydrophilic vermiculite (VMT), multi-walled carbon nanotubes (MWCNTs), and hydrophobic polydimethylsiloxane (PDMS) is designed to function cooperatively for efficient solar absorption and long-term salt-rejection. The unique heterostructure endows the sandwich-like membrane with the capability of decoupling the steam generation process from the solar absorption surface to avoid the mutual interaction between the escaped steam and the incident light. Moreover, the tailorable hydrophilic/hydrophobic channels weaken the interaction between water molecules and layers, as well as reduce interlayer friction and water molecules viscosity to accelerate the flow rate. Benefiting from the above merits, the constructed vertical evaporator exhibits a high solar evaporation rate of 1.48 kg m- 2 h-1 and an energy effi-ciency of 92% in saline water (3.5 wt% NaCl). Solar evaporation-induced soil remediation strategy on the basis of efficient removal of heavy metals and organic pollutants is further proposed, implying its potential applications in sustainable freshwater generation and environmental remediation.

Automated summary

A novel Janus composite membrane is designed to achieve efficient solar absorption and long-term salt-rejection by assembling hydrophilic vermiculite, multi-walled carbon nanotubes, and hydrophobic polydimethylsiloxane. The unique structure of the membrane separates the steam generation process from the solar absorption surface, reducing mutual interaction between escaped steam and incident light. The hydrophilic/hydrophobic channels weaken water molecules interaction, reducing interlayer friction and viscosity to accelerate flow rate. The membrane exhibits high solar evaporation rate and energy efficiency in saline water.