Tiansheng Liu,Na Liu,Shangru Zhai,Shengshuai Gao,Zuoyi Xiao,Qingda An,Dongjiang Yang
Well-ordered core/shell/shell-like Fe 3 O 4 @SiO 2 @PPy microspheres with prominent electromagnetic microwave absorption performance were successfully obtained by microemulsion polymerization method. The morphology, crystal form, functional group, magnetism and microwave absorption properties were investigated. The tailored shell thickness can be tuned from 20 to 60 nm (including SiO 2 layer) via changing the molar ratio of Fe 3 O 4 @SiO 2 to Pyrrole. The absorption peak positions gradually move to low frequency with increment of coating thicknesses. The minimum RL reached −40.9 dB at 6 GHz with the coating thickness of 5 mm. The effective absorption bandwidth could reach 6.88 GHz from 11.12 to 18 GHz, completely covering the whole K (12–18 GHz) band. Meanwhile, it showed excellent wave absorption in 4.4–18 GHz with different coating thickness. The perfect electromagnetic wave absorption properties could be attributed to the dielectric loss from the special core/shell/shell microstructure and natural resonance from the Fe 3 O 4 microspheres. These newly prepared Fe 3 O 4 @SiO 2 @PPy microspheres might be considered as prospective nominees for highly efficient microwave absorption materials with tailored nanostructures .
Wang Kai,Li Aiyuan,Zhou Xiaoyan,Yu Shibeike,Chen Bifen,Sun Xiangdong,Zhang Chenyang
Congo red (CR) is a representative benzidine-based anionic azo dye with high toxicity, carcinogenicity, and poor biodegradability, posing substantial threats to human health and aquatic ecosystems. Therefore, its effective removal from wastewater remains a major environmental challenge. To address this, magnetic Fe 3 O 4 @SiO 2 @PPy-CTAB composite microspheres (PPy: polypyrrole; CTAB: cetyltrimethylammonium bromide) were fabricated using a hydrothermal technique in combination with surface modification and in-situ polymerization. The composite was systematically examined using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), vibrating sample magnetometry (VSM), and X-ray photoelectron spectroscopy (XPS), showing a well-defined core-shell framework, with a specific surface area (SSA) of 52.96 m 2 /g, a saturation magnetization of 42.8 emu·g − 1 , and a positively charged surface as a result of CTAB modification. Under optimal conditions (pH = 5, Fe 3 O 4 :CTAB mass ratio = 1:1.5), the CR adsorption capacity reached a maximum of 612.68 mg/g. Kinetic, isothermal, and thermodynamic analyses indicated that the adsorption process was best described by the pseudo-second-order kinetic model and the Langmuir isotherm model, suggesting a spontaneous, endothermic, and entropy-driven chemisorption process. The adsorption mechanism was primarily governed by electrostatic interactions, synergistic π-π stacking, and hydrogen bonding. After ten desorption-adsorption cycles, the adsorption capacity retained 87.1% of its initial adsorption capacity, demonstrating good reusability. The Fe 3 O 4 @SiO 2 @PPy-CTAB composite demonstrates high CR adsorption capacity (612.68 mg/g) and good reusability (87.1% retention after 10 cycles), making it a promising candidate for magnetic separation-based dye wastewater treatment. However, the use of CTAB and organic solvents limits the designation as “green”, and real-world validation is needed before practical application.
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