Desalination Driven by Temperature Gradient Coupled with Surface Wettability in a Graphene Channel

Faced with the dual challenges of energy crisis and water scarcity, desalination using low-grade heat to obtain freshwater has attracted increasing attention. Here, by coupling the temperature gradient with surface wettability in a nanochannel, an efficient desalination method utilizing low-grade heat energy without phase change is proposed. Driven by a temperature gradient, the liquid water in the nanochannel would undergo directional migration depending on surface wettability. Considering the extremely low wetting pressure in the hydrophilic channel, efficient desalination without an external force can be achieved by controlling the channel size. The influence of channel length and temperature difference on water flux is further studied, and the key role of wetting degree between the interface of nanomaterials and water in this thermal osmosis process was revealed. Typically, for a hydrophilic channel with 6.4 nm length and 0.7 nm slit size, a water flux of 1733 kg/(m2 s) with salt rejection up to 100% can be achieved at a temperature difference of 75 K. The results presented here provide a new strategy for efficient desalination using low-grade heat energy.