High desalination performance, dye retention, and antibacterial properties were achieved with a multifunctional thin-film nanocomposite (MTFN) membrane, fabricated by the incorporation of a novel nanocomposite structure of reduced graphene oxide@TiO2@Ag (rGO@TiO2@Ag) into the polyamide active layer. The specific characteristics of the graphene-based nanocomposite, synthesized by the microwave-assisted irradiation process, favored water channelization and provided superhydrophilicity and antibacterial properties to the MTFN membranes. In comparison with the conventional methods, such as multistep chemical process using strong agents for reduction and long-term energy-consuming hydrothermal process, microwave irradiation facilitated a green, fast, and cost-effective route for the fabrication of GO-based nanocomposites for multifunctional applications. Interfacial polymerization was performed on a polyethersulfone/Si3N4 robust hollow fiber substrate using m-phenylenediamine aqueous solution and 1,3,5-benzenetricarbonyltrichloride organic solution. The structural and chemical characteristics of the synthesized nanocomposites and the MTFN membranes were thoroughly studied by a series of characterization analyses (transmission electron microscopy, field emission scanning electron microscopy, X-ray diffraction, Fourier transform infrared, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy). The physicochemical properties and the nanofiltration performance of the MTFN membranes were investigated after the incorporation of rGO@TiO2@Ag at various concentrations. The water contact angles confirmed the superb surface hydrophilicity of the MTFN membranes. High permeability (52 L·m–2·h–1), desalination (96% for 1 g/L Na2SO4 feed solution), and dye retention (98% for 0.5 g/L rose bengal feed solution) were recorded for MTFN enriched with 0.2 wt % rGO@TiO2@Ag. A 90% reduction in the number of viable bacteria (Escherichia coli), after 3 h of contact with MTFN membranes, confirmed the superior antibacterial activity of the produced membranes.
Li Zhang,Dichao Shi,Baocang Liu,Geng Zhang,Qin Wang,Jun Zhang
A facile hydrothermal etching process was developed to synthesize TiO2/Ag nanocubes for enhanced photocatalytic application. The synthesis was carried out by chemically etching hollow @TiO2 spheres in the presence of an AgF or AgF/NaF solution under hydrothermal conditions. Utilizing F− as a morphology-directing agent and Ag+ as an Ag source during the etching process, TiO2 nanocubes can be easily formed with their active high-energy facets exposed and Ag nanoparticles can be in situ deposited simultaneously on the surface of the TiO2 nanocubes to generate hybrid TiO2/Ag nanocubes. The resulting TiO2/Ag nanocubes were well controlled with Ag nanoparticles uniformly distributed on the surface of the TiO2 nanocubes. The morphologies of TiO2/Ag can be altered from ellipsoidal to cubic shapes depending on the amounts of AgF or AgF/NaF used for chemical etching. Due to the exposure of the active high-energy facets of TiO2 and the uniform deposition of Ag nanoparticles, the obtained TiO2/Ag nanocubes showed superior catalytic performance for the photocatalytic degradation of rhodamine B under visible-light radiation. It is proposed that the surface plasmon resonance effect arisen from Ag nanoparticles on TiO2 nanocubes can effectively enhance the visible-light driven photocatalytic properties of TiO2/Ag photocatalysts. Meanwhile, due to the etching of F ions during the synthetic process, the morphology variation of TiO2 from spherical to cubic shapes may be beneficial to the exposure of high energy {001} facets, which is liable to produce more electron–hole pairs in the photocatalytic process, and electron–hole pairs can combine with OH− to produce large amounts of hydroxyl radicals, eventually accelerating the decomposition of the organic dye.
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