Fengyu Wei

BiVO4/MIL-101 composite having the synergistically enhanced visible light photocatalytic activity

In this study, a novel composite containing a Cr based metal–organic framework (MOF), MIL-101 and BiVO4 was successfully synthesized by hydrothermal method, and was fully characterized by X-ray diffraction, transmission electron microscopy, thermogravimetric analysis, UV-vis diffuse reflectance absorption spectra and photoluminescence emission spectra. Moreover, the photocatalytic activities of BiVO4/MIL-101 composite and the pure materials were evaluated by measuring the degradation of Rhodamine B under visible light. The results show that the composite exhibits better photocatalytic activities than pure materials, which can be ascribed to the big adsorption capacity of MIL-101 and the enhanced separation of photogenerated charge carriers from assembly of MIL-101 on BiVO4. The synergistic effect between BiVO4 and MIL-101 was evaluated by the proposed synergistic factor, which is bigger than 1 for various ratios of BiVO4 to MIL-101, suggesting there exists positive interactions between pure materials for enhancing photocatalytic activities.

Synergistic effects in N-K2Ti4O9/UiO-66-NH2 composites and their photocatalysis degradation of cationic dyes

Abstract N-K 2 Ti 4 O 9 /UiO-66-NH 2 composites synthesized by a facile solvothermal method have a core-shell structure with UiO-66-NH 2 forming the shell around a N-K 2 Ti 4 O 9 core. Their photocatalytic activities in the degradation of dyes under visible light irradiation were investigated. The N-K 2 Ti 4 O 9 / UiO-66-NH 2 composites exhibited higher photocatalytic activity than the pure components. This synergistic effect was due to the high adsorption capacity of UiO-66-NH 2 and that the two components together induced an enhanced separation efficiency of photogenerated electron-hole pairs. The mass ratio of N-K 2 Ti 4 O 9 to ZrCl 4 of 3:7 in the composite exhibited the highest photocatalytic activity. Due to the electrostatic attraction between the negatively charged backbone of UiO-66-NH 2 with the positively charged groups of cationic dyes, the composites were more photocatalytically active for cationic dyes than for anionic dyes.

The excellent photocatalytic synergism of PbBiO2Br/UiO-66-NH2 composites via multiple coupling effects

PbBiO2Br/UiO-66-NH2 composites synthesized by a facile solvothermal method have a core–shell structure with UiO-66-NH2 forming the shell around a PbBiO2Br core. Their photocatalytic activities in the degradation of Rhodamine B (RhB) dye solution and colorless phenol solution under visible light irradiation were investigated. For both model organic pollutants, the PbBiO2Br/UiO-66-NH2 composites exhibit higher photocatalytic activity than the pure components. This synergistic effect is due to the high adsorption capacity of UiO-66-NH2 and the compounding induced an enhanced separation efficiency of photogenerated electron–hole pairs. The composite with a 3 : 2 mass ratio of PbBiO2Br to ZrCl4 exhibits the highest photocatalytic activity for RhB degradation, in which trapping experiments confirm that the photogenerated holes and O2˙− radicals are the main active species.

Modification of abandoned fine blue-coke: optimization study on removal of p-nitrophenol using response surface methodology

Abandoned fine blue-coke was modified with a physicochemical method including nitric acid (HNO3) treatment and nitrogen gas (N2) calcination, and used as an adsorbent for p-nitrophenol (PNP) removal. The preparation process was optimized to improve the adsorption ability based on the 2IV6–2 fractional factorial design, steepest ascending method and the Box–Behnken design (BBD) of the response surface methodology (RSM) technique. The significant factors on each experimental design response were identified by means of analysis of variance (ANOVA). The predicted adsorption capacity of PNP on MFBC was found to agree with the experimental values. The optimum experimental conditions were as follows: HNO3 concentration: 4.46 mol L−1, modification temperature: 87.8 °C, modification time: 20.3 h, impregnation ratio of HNO3 to MFBC: 10 mL/1 g, calcination time: 2 h, and calcination temperature: 716 °C. Moreover, surface roughness of the MFBC was found to increase obviously after the modification by FESEM and HRTEM analysis, and the total pore volume and specific surface area increased by 0.8 and 1.2 times, respectively. The PNP equilibrium adsorption capacity of MFBC was found to be 156.9 mg g−1 at 328 K, which highlights its potential application in wastewater treatment.

Synthesis and photocatalytic activity of N-K2Ti4O9/UiO-66 composites

N-K2Ti4O9/UiO-66 composites synthesized by a facile solvothermal method possess a hierarchical core–shell structure with UiO-66 forming the shell around the N-K2Ti4O9 core. Photocatalytic activity of N-K2Ti4O9, UiO-66 and the composites were investigated by the degradation of rhodamine B (RhB) under visible light irradiation. The synergistic effect induced by compounding was quantitatively evaluated by the proposed synergistic factor. The results show that N-K2Ti4O9/UiO-66 composites exhibit higher photocatalytic activity as compared with the pure materials, and this is due to the high adsorption capacity of UiO-66 and the compounding induced higher separation efficiency of photogenerated electron–hole pairs. In particular, when the molar ratio of N-K2Ti4O9 to ZrCl4 is 3 : 7, the composite exhibits the highest photocatalytic activity, and the synergistic factor is 4.90.

Synergistic Photocatalysis of Bi 2 Fe 4 O 9 /g-C 3 N 4 /UiO-66 Ternary Composites

Bi 2 Fe 4 O 9 /g-C 3 N 4 /UiO-66 ternary composites synthesized by a facile hydrothermal method possess synergistically enhanced visible-light photocatalytic performance for degradation of both RhodamineB dye and colorless phenol solutions as compared with purity materials of g-C 3 N 4 , Bi 2 Fe 4 O 9 and UiO-66. The ternary composite materials show increased visible light absorption, efficient separation of charge carriers, strong redox capability via Z-scheme Bi 2 Fe 4 O 9 /g-C 3 N 4 heterojunction and high adsorption ability.

Kinetic study of application of graphene oxide as a catalyst to accelerate extraction of total flavonoids from Radix Scutellaria

A new kinetic model, Sos three-step kinetic model, was used to study the kinetics of graphene oxide (GO)-assisted ethanol reflux extraction (GERE). An experimental design to investigate the effect of five single factors (extraction temperature, dosage amount of GO, concentration of ethanol aqueous solution, the ratio of liquid to solid, rotating speed) on the kinetic extraction of total flavonoids was materialized. From the single factors experiments, we found that the extraction process is mainly controlled by internal diffusion, and the extraction rate increases with the growth of GO dosage, ethanol concentration and liquid–solid ratio at 30–70 °C; moreover, the rotating speed had little effect. The effective internal diffusion coefficient (D′) and the activation energy (Ea) of total flavonoids extracted by ERE and GERE were also studied, respectively. Results showed a good prediction of Sos three-step kinetic model for extraction kinetics in all experiments, which gave the possibility for estimating the initial rate and extent of GERE.