Polyacrylonitrile and its TiO 2 composites were electrospun into nanofibers in N, N'-dimethylformamide for photocatalysis and antifouling experiments. The resultants nanofibers were characterized using field emission scanning microscope, Fourier transform infrared spectroscopy, x-ray diffraction, x-ray photoelectron spectroscopy and contact angle analyses. Fourier transform infrared spectroscopy confirmed the formation of polyacrylonitrile-TiO 2 composite nanofibers with their diameter ranging from 10 to 340 nm. The x-ray photoelectron spectroscopy results indicate the formation of O-Ti-C bonds on polyacrylonitrile-TiO 2 matrix. polyacrylonitrile-TiO 2 and polyacrylonitrile nanofiber surfaces showed superhydrophobicity with water contact angle of 155 ± 1 and 154 ± 1, respectively at 120 s. The photocatalytic properties of polyacrylonitrile nanofibers and polyacrylonitrile-TiO 2 nanofibers were investigated under a simulated visible light source of 1000 W/m 2 using methylene blue. About 90% of methylene blue was degraded within 3 h of exposure using polyacrylonitrile-TiO 2 nanofibers while 55% methylene blue degradation was achieved for polyacrylonitrile nanofibers. Photoluminescence experiment conducted on both materials showed that polyacrylonitrile-TiO 2 could produce OH radicals 10-fold compared to polyacrylonitrile nanofibers. Antimicrobial tests were conducted using E. coli and Bacillus sp. The results showed that only polyacrylonitrile-TiO 2 under visible light hindered the growth of these bacteria with a greater effect on the Gram-positive bacterium, Bacillus sp. The photo-degradation and microbial growth inhibition properties of polyacrylonitrile-TiO 2 showed that the material could be used as an antifouling material under visible light.
a b s t r a c tThe rare-earth elements (REEs) remain very important due to the growing increase in their demand and for their critical and indispensable use in many high-tech industries today. This growing demand for REEs has led to an increased environmental exposure and water pollution from numerous REEs commercial products and as a result, the recovery of REEs is a significant issue that requires appropriate consideration. There are diverse and various strategic techniques available to remove metal ions from aqueous solutions, but nanofiber adsorbent appears to be quite innovative due to their outstanding characteristics such as cost effectiveness, flexibility, high surface area, porosity, and the portable nature which makes them a better choice for potential adsorbent applications. This review presents a brief view on several typical removal techniques, new developments and applicable examples of the various technologies used for the removal of rare earth elements from water/ wastewater solutions. The review highlights these developments with a particular focus on innovative physicochemical removal processes like adsorption as the process techniques most widely used.
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