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Vacuum membrane distillation (VMD) is a promising technology for high salinity wastewater treatment. One of the key issues in VMD research is improving the antifouling performance of the hydrophobic porous membrane under proper interface modification theory and approach. In this work, the polypropylene (PP) composite membrane coated with SiO2 nanoparticles and fluorinated modification was fabricated to simultaneously enhance the interface roughness and superhydrophobicity. The fabricated superhydrophobic PP membrane was then applied to treat highly concentrated NaCl (15 wt%)/MgCl2 (from 3 to 9 wt %) saline solution in VMD process under various flow conditions. The model concerning the surface roughness and surface nucleation free energy was constructed to predict the influence of membrane surface structure on potential anti-fouling and anti-wetting properties. Classical heterogeneous nucleation theory was introduced to illuminate the improved performance of developed membrane with targeted surface morphology on inhibiting the initial interfacial nucleation process. The experimental results illustrated the fabricated superhydrophobic PP membrane exhibited unique anti-fouling and anti-wetting abilities, as well as extremely stable permeating flux even under low feed rate and highly concentrated salt solution system during the continuous operation. In addition, it was also indicated that sodium ion and magnesium ion with distinct features in the structure of water-ion solution system had the potential impact on the permeate flux decline and concentration polarization effect, which was helpful for further improving the stability and durability of this series modified membrane when treating the high concentrated multiple solution system.

Droplet evaporative crystallization on a micro-structured platform with limited interfacial area has potential applications in crystallization theory, bioengineering, and particle drug preparation. Here, an efficient and versatile approach is discussed for multiple drop-evaporative crystallization processes on a micro-crystallization chip fabricated via three-dimensional printing. A chip with limited interfacial area could be fabricated on a highly controlled crystallizer interface. During liquid injection, various drop locations and evaporative conditions can be used, which enables flexible and distinct crystallization processes. This reveals controlling mechanisms and identifies nucleation locations and growth paths. Various classic crystallization systems were introduced to evaluate the chip performance. Controlled nucleation and growth mechanisms at stable evaporative rates were revealed. From the final crystal morphologies, particle locations, and distributions, the effects of the initial concentration and droplet contact conditions at the triple-phase interface could be investigated with high adjustability. Moreover, the results can provide insights into the 'coffee ring' formation during evaporative crystallization, dendritic crystal growth, and hydrate crystallization mechanisms. In the limited microstructure, the capillary flow of a liquid drop can spontaneously drive the crystal distribution and morphology. Finally, incorrect liquid drop locations that led to unpredictable crystal formation and distributions were discussed to improve repeatability and efficiency. Applications include the manufacture of particle drugs and flow chemistry.