A porous composite membrane for spontaneous moisture adsorption

Highly humid air is harmful to human health. The solution dehumidification can easily cause salt solution droplets release into the air while membrane dehumidification requires a significant driving force. This work aims to investigate the moisture adsorption performance of as-synthesized composite porous membranes in the absence of pressure driving force. Here, a series of PVDF/PVA/CaCl2 membranes were prepared. An open core-shell skeleton with a porous surface and PVA aggregated core was obtained, which serves as a permeation channel for mass transfer. Due to the uniform distribution of CaCl2 adsorption sites, the hydrophilic nature of PVA, and the porous structure, the membranes exhibited outstanding hygroscopic properties with the highest initial moisture adsorption rate of 0.053 g·g−1·min−1 and moisture adsorption capacity of 2.36 g·g−1 in the spontaneous state. The water vapor adsorption data of the M-4-5 sample was best fitted using the double constant kinetic model. Moreover, the core-shell skeleton provided excellent strength and a stable structure. The maximum dry strength of the composite membrane was 1.6 MPa and the maximum wet strength was 0.92 MPa. This work provides a new concept for designing the dehumidified membrane material, especially for non-pressure-driven condition.