In this study, porous sandwich structure Fe 3 O 4 nanoparticles coated by polyhedral oligomeric silsesquioxanes and β-cyclodextrin were prepared by surface polymerization and were used as the magnetic solid phase extraction adsorbent for the extraction and determination of carbaryl and carbofuran. The Fe 3 O 4 nanoparticles coated with polyhedral oligomeric silsesquioxanes and β-cyclodextrin were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, vibrating sample magnetometry, and scanning electron microscopy. After optimizing the extraction conditions, a method that combined magnetic solid phase extraction with high-performance liquid chromatography was developed for the determination of carbaryl and carbofuran in apple. The method exhibited a good linearity in the range of 2-400 μg/kg for carbaryl and carbofuran (R 2 = 0.9995), respectively. The limits of detection were 0.5 μg/kg of carbaryl and 0.7 μg/kg for carbofuran in apple, respectively. Extraction recoveries ranged from 94.2 to 103.1% with the preconcentration factor of 300 and the relative standard deviations were less than 5.9%. These results indicated that the method combined magnetic solid phase extraction with high-performance liquid chromatography and was promising for the determination of carbaryl and carbofuran at trace amounts.
In this work, adsorption behaviors of pyrene (PYR), fluoranthene (FLT), phenanthrene (PHE), and fluorene (FLU) on the coordination cluster [Zn 5 (H 2 L n ) 6 ] -(NO 3 ) 4 ]•8H 2 O•2CH 3 OH (Zn 5 ) were studied. The adsorption mechanism and spectrum analyses revealed that the synergistic effect of hydrophobic interaction, π−π stacking, and N−H•••π interaction played a crucial role during the adsorption process. The maximum adsorption capacities of PYR, FLT, PHE, and FLU were 406.4, 399.7, 153.7, and 114.3 mg g −1 , respectively, resulting from the Langmuir isotherm model. Quick removal of PYR and FLT was found in kinetic experiments with the adsorption equilibrium being reached within 1 min. Competitive adsorption indicated that the adsorption sites for PYR, FLT, PHE, and FLU on Zn 5 were identical, and synergistic effects also existed in the adsorption process. Therefore, Zn 5 has the potential to be used as an adsorbent in the field of wastewater treatment.
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