Spray-assisted biomineralization of a superhydrophilic water uptake layer for enhanced pervaporation dehydration

- Spray-assisted biomineralization of a superhydrophilic water uptake layer.
- The flux with biomineralizing CaCO3 is five times of a polyelectrolyte membrane.
- A new uptake-solution-diffusion pervaporation mechanism was proposed.

The membrane surface wettability is one of the most important factors influencing the solution-diffusion-controlled pervaporation process. In this work, a novel conceptual methodology for the construction of a superhydrophilic water uptake layer is proposed to overcome the limitation of trade-off effects. Rapid implementation of this strategy is possible by spray-assisted biomineralization of calcium carbonate (CaCO3) onto a (poly(acrylic acid)/poly(ethyleneimine))n/polyacrylonitrile ((PAA/PEI)n/PAN) membrane. Scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy confirmed the formation of a hierarchical lotus CaCO3 layer with calcite crystals on the outermost layer. The water contact angle dramatically decreased from 74° to 4.2° after biomineralizing CaCO3 micro-nano-particles. In the pervaporation separation of ethanol/water mixtures, the water content could be enriched from 5 wt% to 98.8 wt% while the permeate flux reached 1317 g/(m2 h), which is almost five times that of a pure polyelectrolyte membrane without biomineralizing CaCO3. This suggests that the CaCO3 water uptake layer plays a very important role in achieving high flux. These results indicate that biomineralization of micro-nano-particles is a facile strategy to fabricate a superhydrophilic surface and, in turn, improve the membrane performance.

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