RESUMO
Emulsion poses a greater challenge for the remediation of oily wastewater, which can be effectively resolved by the metal-organic framework of MIL-100(Fe). The formula Fe3O(H2O)2(OH) (BTC)2 pronounces that MIL-100(Fe) suffers from an intrinsic defect of less charged atoms, which limits its demulsification performance for oil-water separation. Herein, cations of the ionic liquid (1-allyl-3-methylimidazolium, Amim+) were encapsulated in the micropore of MIL-100(Fe) in situ to increase the positive charge density of MIL-100(Fe). Zeta potential demonstrated that the encapsulation of Amim+ increased the positive charge amount of MIL-100(Fe). N2 probe isothermal adsorption/desorption and spectral measurements (X-ray photoelectron spectroscopy, ultraviolet-visible diffuse reflection spectroscopy, and attenuated total-reflectance infrared spectroscopy) revealed the host-guest interactions of π···Fe complexation and π···cation electrostatic attraction between Amim+ and MIL-100(Fe) for the composite materials. Amim+ encapsulation greatly enhanced the demulsification performance of MIL-100(Fe) for oil-in-water (O/W) emulsion stabilized by sodium dodecyl sulfate. Amim+-encapsulated MIL-100(Fe) with an Amim+/Fe3+ molar ratio of 1:1 [Amim@MIL-100(Fe)-3:3] showed a demulsification efficiency (DE) of 94% within 30 s, compared with MIL-100(Fe) within 30 min. The maximum DE of Amim@MIL-100(Fe)-3:3 was found to be more than 98% within 5 min. The DE lost by MIL-100(Fe) at the third run decreased from 36 to 17% after encapsulating Amim+. The analysis of surface charge and interfacial tension implied a demulsification mechanism of capturing-fusion, which could be promoted by the greater electrostatic attraction. Finally, the role of Amim+ on the outstanding demulsification performance by Amim+-encapsulated MIL-100(Fe) could be explained by the enhanced nonbonded interaction of electrostatic attraction and van der Waals based on the molecular dynamics simulation.
RESUMO
As for photocatalytic oxidation of nitric oxide (NO), the low NO oxidation activity and generation of by-products (cf. NO2) are the urgent challenge. To tackle these issues, a simple in-situ growing stragegy was employed to constructe Ti3C2/g-C3N4 system. The fabricated Ti3C2/g-C3N4 composite (TC-CN) presented enhanced photocatalytic NO removal efficiency and inhibited toxic NO2 generation. Density functional theory (DFT) calculations and experimental characterizations were combined to demonstrate the presence of strong interface effect between Ti3C2 and g-C3N4, which could greatly improve photo-generated charge carrier separation via the construction of electron transfer channels, and further activate oxygen molecules adsorbed on the side of Ti3C2 layer. As a result, nitrite and nitrate instead of NO2 were the final products during the photocatalytic reaction process through the monitoring by in situ diffuse reflectance infrared spectroscopy (DRIFTS).