Hierarchically oriented carbon nanotubes/fly ash Janus membrane with open, straight pores for enhanced solar desalination performance

Seawater desalination via the solar photothermal membrane distillation technology is an effective way to solve the fresh water shortage, and it is very important to prepare a Janus membrane with excellent solar desalination properties to improve the water permeability. In this work, three typical hydrophobic carbon nanotubes/hydrophilic fly ash (CNTs/FA) Janus asymmetric membranes with different membrane support structures are prepared for solar desalination by the conventional tape casting or phase inversion tape casting techniques. It is demonstrated that nitrogen permeability is significantly enhanced from (4.81±0.17)×10⁵ L m^-2 h^-1 bar^-1 for the tortuous CNTs/FA Janus membrane to (9.28±0.10)×10⁶ L m^-2 h^-1 bar^-1 for the hierarchically oriented CNTs/FA Janus membrane with open, straight pores by manipulating the microstructure of the fly ash membrane support. Moreover, the corresponding evaporation rate is strongly increased from 0.633±0.010 to 1.669±0.010 kg m^-2 h^-1, which is greatly ascribed to the accelerated water permeation in the hierarchically oriented FA membrane support with open, straight pores. Additionally Our findings proves that the solar desalination performance can be greatly improved by the microstructure manipulation of the membrane support, and guide the development of novel membranes for efficient solar desalination.