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Xiaoyu Lin,Leli Wang,Shi Jiang,Longzhe Cui,Gui-Ping Wu 한국화학공학회 2019 Korean Journal of Chemical Engineering Vol.36 No.7
Iron-doped chitosan microsphere was prepared successfully and employed for effective adsorption of As(III). The results showed that the adsorption capacity benefited from the increase of iron content, and the maximum adsorption capacity was achieved at pH=8. According to the study of adsorption kinetics, adsorption rate was controlled by liquid film diffusion at a lower rotational speed, while it was controlled by chemical reaction rate at a higher rotational speed. The Freundlich and Temkin models exhibited a better fit to adsorption isotherm data, which indicated the adsorption of As(III) on iron-doped chitosan microsphere was chemisorption and the active sites of adsorbents were non-uniform distributed. Adsorption process was a spontaneous exothermic reaction because its ΔG and ΔH were negative. In presence of cations (Cd2+, Pb2+ or Zn2+) in solution, the iron-doped chitosan microsphere also showed the significant removal of As(III). However, the existence of anions (NO3 , SO4 2 or PO4 3) inhibited the As(III) removal at different level. PO4 3 showed the most significant side effects on the removal of As(III) by iron-doped chitosan microsphere. The used iron-doped chitosan adsorbent can be effectively regenerated using 1.0mol·L1 NaOH solution, and the adsorption efficiency decreased only 15.69% after being reused three times. The results of XPS, FT-IR showed that the adsorption was mainly achieved by the coordination interaction between As (III) and doped Fe in adsorbent.
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Thickness Effect on Thermal Stability by Phase Transition of Single Crystal Hematite Nanorings
Le Li,Fagen Li,XiaoPing Zhang,JUN WANG 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2015 NANO Vol.10 No.6
Single-crystal hematite (α-Fe2O3) nanorings with three different thicknesses were synthesized by a hydrothermal method. The results of X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) show that the nanorings are single-crystal and have relatively uniform outer diameters of 160 nm, and heights of about 100 nm. Magnetic measurements up to 920K have been performed on hydrothermally synthesized α-Fe2O3 nanorings and nanoparticles using a quantum design vibrating sample magnetometer. A high temperature phase transition of thermal stability ( α-Fe2O3 to Fe3O4) occurs when magnetic measurement was performed under high vacuum ( < 9.5 x 10-5 Torr). The phase transition temperature is 670 K for nanorings with thickness of ~30 nm, 718 K for nanorings with thickness of ~50 nm, 678 K for nanorings with thickness of ~65 nm, and 640 K for ~35 nm nanoparticles. This data show better thermal stability of nanorings with the thickness of ~50 nm than the other two kinds of nanoring samples The Néel temperature (TN) of α-Fe2O3 nanorings with the thickness of ~50 nm is determined to be 937.2 K by magnetic measurement for the first time, about 22.8 K below the bulk value. The small reduction of the TN of the α-Fe2O3 nanorings is consistent with the finite-size scaling theory.
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