ABSTRACT
Membrane distillation (MD) is considered a promising technology for desalination. In the MD process, membrane pores are easily contaminated and wetted, which will degrade the permeate flux and salt rejection of the membrane. In this work, SiC ceramic membranes were used as the supports, and an Al2O3 micro-nano structure was constructed on its surface. The surface energy of Al2O3@SiC micro-nano composite membranes was reduced by organosilane grafting modification. The effective deposition of Al2O3 nanoflowers on the membrane surface increased membrane roughness and enhanced the anti-fouling and anti-wetting properties of the membranes. Simultaneously, the presence of nanoflowers also regulated the pore structures and thus decreased the membrane pore size. In addition, the effects of Al2(SO4)3 concentration and sintering temperature on the surface morphology and performance of the membranes were investigated in detail. It was demonstrated that the water contact angle of the resulting membrane was 152.4°, which was higher than that of the pristine membrane (138.8°). In the treatment of saline water containing 35 g/L of NaCl, the permeate flux was about 11.1 kgâ m-2â h-1 and the salt rejection was above 99.9%. Note that the pristine ceramic membrane cannot be employed for MD due to its larger membrane pore size. This work provides a new method for preparing superhydrophobic ceramic membranes for MD.
ABSTRACT
Separation membranes with underliquid dual superlyophobicity have recently caused widespread concern due to their switchable separation of oil-water mixtures and emulsions. However, the fabrication of the reported underliquid dual superlyophobic membranes is difficult, and the design of the underliquid dual superlyophobic surface of these membranes is challenging because of their complex surface composition. Theoretically, underliquid dual superlyophobicity is an underliquid Cassie state attainable by the synergy of the underliquid dual lyophobic surface and the construction of a high-roughness surface. Herein, we fabricated an underliquid dual superlyophobic membrane by combining underliquid dual lyophobic polyvinylidene fluoride (PVDF) and TiO2 nanowires. PVDF-modified TiO2 nanowire membranes with underliquid dual superlyophobicity were prepared via a simple adsorption and filtration approach. PVDF was coated onto TiO2 nanowires to form a PVDF layer with a thickness of 6 nm. The PVDF modification provided flexibility to the fragile TiO2 nanowires membrane and changed its wettability from underwater superoleophobicity/underoil superhydrophilicity to underliquid dual superlyophobicity. The PVDF-modified TiO2 nanowires membrane efficiently separated both oil-in-water and water-in-oil emulsions. The binary cooperative effect between the TiO2 nanowires and the coated PVDF layer was responsible for the underliquid dual superlyophobicity.
ABSTRACT
W18O49 with a tunable oxidation state was prepared by addition of NaNO3 or NaBH4 as a redox agent in the solvothermal system. The addition of redox agents has no influence on the crystallization of W18O49. The obtained W18O49 structures keep their morphology as a bundle of nanowires with a regular hexagonal on the cross-section. W18O49 exhibits strong valence-dependent absorption features in the near-IR region. Reduced W18O49 with more W5+ has a higher concentration of oxygen vacancies, which enhances the localized surface plasmon resonance effect. Reduced W18O49 exhibits a high photothermal conversion efficiency of 59.6 % and has good photothermal stability.
ABSTRACT
Porous TiO2 were assembled by evaporating or refluxing TiO2 colloid, which was obtained by dispersing the TiO2 nanoparticles with a crystallite size (d XRD) of 3.2 nm into water or ethanol without any additives. Porous transparent bulk TiO2 was obtained by evaporating the TiO2-C2H5OH colloid at room temperature for 2 weeks, while porous TiO2 nanospheres were assembled by refluxing the TiO2-H2O colloid at 80 °C for 36 h. Both of the porous TiO2 architectures were pore-size-adjustable depending on the further treating temperature. Porous TiO2 nanospheres exhibited enhanced photocatalysis activity compared to the nanoparticles.
