RESUMO
Improving the photocatalytic performance of metal-organic frameworks (MOFs) is an important way to expand its potential applications. In this work, zero-dimensional (0D) Bi2O3 nanoparticles were anchored to the surface of tridimensional (3D) MIL101(Fe) by a facile solvothermal method to obtain a novel 0D/3D heterojunction Bi2O3/MIL101(Fe) (BOM). The morphology and optical properties of the as-prepared Bi2O3/MIL101(Fe) composite were characterized. The photocatalytic activity of the synthesized samples was evaluated by degrading chlortetracycline (CTC) under visible-light irradiation. The obtained BOM-20 composite (20 wt % Bi2O3/MIL101(Fe)) exhibits the highest photocatalytic activity with CTC degradation efficiency of 88.2% within 120 min. The degradation rate constant of BOM-20 toward CTC is 0.01348 min-1, which is 5.9 and 4.3 times higher than that of pristine Bi2O3 and MIL101(Fe), respectively. The enhanced photocatalytic activity is attributed to the formation of a Z-scheme heterojunction between Bi2O3 and MIL101(Fe), which is conducive to the rapid separation of photogenerated carriers and the enhancement of photogenerated electron and hole redox capacity. The intermediate products were analyzed by liquid chromatography-mass spectrometry (LC-MS), and a possible photocatalytic degradation path of CTC was proposed. This work provides a new perspective for the preparation of efficient MOF-based photocatalysts.
RESUMO
A spindle-like monoclinic-tetragonal heterojunction BiVO4 was successfully synthesized by a pressure-controllable microwave method. The as-prepared BiVO4 samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy, transient photocurrent responses and electrochemical impedance spectroscopy (EIS). The visible-light-driven photocatalytic activity of the BiVO4 samples was evaluated for the degradation of Rhodamine B (RhB) and tetracycline (TC). The synthesis process needs microwave irradiation for only 10 min without the addition of any auxiliary reagent, pH adjustment, and calcination. The as-prepared spindle-like monoclinic-tetragonal heterojunction BiVO4 exhibits excellent photocatalytic activity for the degradation of both RhB and TC. The photocatalytic degradation rates of RhB and TC over spindle-like BiVO4 are 1.77 and 1.64 times higher, respectively, than that measured over monoclinic BiVO4. The enhanced photocatalytic activity is mainly attributed to the fact that the existence of a heterojunction effectively promotes the separation of photo-generated carriers and extends the visible-light absorption of BiVO4.
RESUMO
To fully exploit the benefits of N-methylmorpholine-N-oxide (NMMO) in lignocelluloses bioconversion, a compatible system was established for efficient in situ saccharification of cellulose in NMMO-aqueous media in which the NMMO is able to activate and solubilize the cellulose, and the cellulases possess high stability and activity. Cellulase retained its original activity after being pre-incubated in 15% and 20% (w/v) NMMO solutions. After optimization of reaction parameters, high saccharification rate (96.5%) was obtained in aqueous-NMMO media by ultrasound assisted treatment of cellulose. The viscosity and FTIR analysis revealed that NMMO-treated cellulose under ultrasonic condition was porous and amorphous, which led to improved saccharification. The addition of trifle lignin in lower concentration improved the saccharification efficiency of sugarcane bagasse, while higher concentration interferes with hydrolysis. In conclusion, these findings provided great implications to develop a continuous process NMMO-cellulases system for transformation of native biomass.