Dongyu Hao,Yinghui Hu,Fang Wang,Debin Xia,Dakang Wang,Ruiqing Fan,Yulin Yang,Kaifeng Lin
In this work, a novel Al2O3-free core-shell structured nAl@aluminum-perfluorooctanoate (F-x) nanocomposite has been prepared via a self-assembly approach. The Al2O3 shell was first removed by hydrofluoric acid (HF) solution, and then the perfluorooctanoic acid (PFOA) was coated on the surface of nAl by a self-assemble reaction. The thickness of the obtained F-x layer can be easily tuned by using different amount of PFOA based on the chemical interaction between nAl and PFOA molecules. The obtained nAl@F-x nanocomposite showed an enhanced exothermic and combustion performance due to the synergetic effect between F-x and nAl and the mesoporous structure in situ formed during the combustion process. This work demonstrated that nAl@F-x nanocomposite prepared by PFOA coating on nAl could effectively solve the detrimental effect of in situ formed Al2O3, thus enhancing the combustion and thermal reaction performances, which showed great potential to be applied in solid rocket propellant.
Covalent surface grafting of fluorinated methacrylate is shown to be able to impart intrinsically hydrophilic foam with oleophobic-hydrophilic property. The determining factor in generating this unique wettability is the amount of surface-grafted poly(fluoro-methacrylate). The results well support the mechanisms behind the oleophobic-hydrophilic wetting behavior. Array of fluorinated chains provides oil repellency, whereas water molecules can penetrate through the defects in fluorolayer to reach the hydrophilic subsurface and meanwhile fluorinated chains may reorientate to facilitate this penetration. When the fluorolayer is thick or has no defects, water molecules cannot penetrate through anymore. The oleophobic-hydrophilic foam shows high contact angle (>140°) for a variety of oils including hexadecane , soybean oil, sunflower oil , waste engine oil and diesel, but it can absorb water. Using the foam, it is possible to continuously remove water from oil-water mixture under assistance of an external pump. Potential applications include water removal from diesel to protect engines and from collected oil spills for further purification.
Ao Xian,Changlong Wei,Zhiwen Tang,Yao Zhang,Qing Wang,Zhiyong Han,Xin Song
Layered double hydroxides have been proved to be effective adsorbents for the removal of per- and polyfluoroalkyl substances (PFASs) from aqueous solutions. In this study, a novel layered double hydroxides modified by perfluorooctyltriethoxysilane (LDHs-PFOTES) was synthesized at room temperature, demonstrating rapid and selective sorption of perfluorooctane sulfonic acid (PFOS). The covalent grafting of fluorosilane groups onto the LDHs surface enhanced hydrophobicity and introduced fluorine functional groups, while preserving the positive charge essential for electrostatic interactions. LDHs-PFOTES removed 97.21 % of PFOS from water within 5 min, with a sorption capacity of 1530.33 mg/g, nearly doubling the capacity of unmodified LDHs (831.79 mg/g). The thermodynamic analysis of PFOS sorption on LDHs-PFOTES revealed that the process is spontaneous and endothermic. LDHs-PFOTES maintained over 90 % PFOS removal efficiency under varying pH levels, ionic strengths, and the presence of competing compounds. Furthermore, the C-F structure on the LDHs-PFOTES enabled fluorine-fluorine (F-F) interactions with PFOS, further improving selective sorption. It was concluded that the combined effects of electrostatic interactions, hydrophobicity, F-F interactions, and ion exchange resulted in the efficient and selective removal of PFOS from water. LDHs-PFOTES demonstrated 95.37 % sorptive efficiency in removing PFOS when treating a mixture of 11 PFAS compounds. Additionally, LDHs-PFOTES effectively desorbed PFOS using a mixed solution of NaCl and methanol, maintaining approximately 95.08 % removal efficiency over three regeneration cycles. This fluorination strategy to modify LDHs offers a novel approach for selectively and efficiently removing PFASs from water.
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