RESUMEN

A unique hybrid of Zr-based metal-organic framework (UiO-66) with graphitic carbon nitride (g-C3N4) nanosheets was synthesized by a facile annealing method. Photocatalytic effect was measured by the photodegradation of methylene blue (MB) under visible light irradiation. The morphology, structure, and porous properties of the as-synthesized composites were characterized by using transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), the thermogravimetric and differential scanning calorimetry analysis (TG-DSC), diffuse reflectance UV-vis spectroscopy (UV-vis DRS), photoluminescence (PL), and N2 sorption-desorption isotherms (BET). The results showed that about 100% of MB (200 mL of 10 mg L-1) photodegradation was achieved by the UiO-66/g-C3N4 hybrids (UC 10:10) in 240 min under visible light. The enhanced photocatalytic activity could be attributed to the heterojunction between UiO-66 and g-C3N4 therefore the photoelectron transfers efficiently from the conduction band (CB) of g-C3N4 to the CB of UiO-66 through the inner electric field generated by the heterojunction resulting the decreasing of recombination of electron/hole and the porous structures which enhance adsorption of the dye molecules on the catalyst surface thereby facilitates the electron/hole transfer within the framework. The trapping experiment and electron spin resonance (ESR) results showed that superoxide radicals (•O2-) was the main oxidative species in the photodegradation of MB and the enhanced photocatalytic mechanism of UiO-66/g-C3N4 heterojunction hybrids was also proposed.

Asunto(s)

Nanopartículas Calcificantes/química , Azul de Metileno/química , Adsorción , Catálisis , Luz , Oxidación-Reducción , Fotólisis

RESUMEN

Food safety issues closely related to human health have always received widespread attention from the world society. As a basic food source, wheat is the fundamental support of human survival; therefore, the detection of pesticide residues in wheat is very necessary. In this work, the ultrasonic-assisted ionic liquid-dispersive liquid-liquid microextraction (DLLME) method was firstly proposed, and the extraction and analysis of three organophosphorus pesticides were carried out by combining high-performance liquid chromatography (HPLC). The extraction efficiencies of three ionic liquids with bis(trifluoromethylsulfonyl)imide (Tf2N) anion were compared by extracting organophosphorus in wheat samples. It was found that the use of 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([OMIM][Tf2N]) had both high enrichment efficiency and appropriate extraction recovery. Finally, the method was used for the determination of three wheat samples, and the recoveries of them were 74.8-112.5%, 71.8-104.5%, and 83.8-115.5%, respectively. The results show that the method proposed is simple, fast, and efficient, which can be applied to the extraction of organic matters in wheat samples.