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•The degradation efficiency of TC over the 0.3-p-Ag2S/n-BiVO4 can be achieved 90.2%.•Ten intermediate products for TC degradation were verified by the GC-MS.•The enhancing ...photocatalysis mechanism was attributed to the facilitated charge transfer.
Three-dimensional microsphere p-Ag2S/n-BiVO4 p-n heterojunction photocatalyst was successfully fabricated via depositing p-type Ag2S on n-type BiVO4, which showed excellent photocatalytic performance, compared with BiVO4 and Ag2S, for the photocatalytic degradation of tetracycline under visible light irradiation. The enhancing photocatalytic performance can be attributed to the facilitated charge transfer, and the increased lifetime of the charge carriers confirmed by the results of time-resolved fluorescence spectra and photoelectrochemical measures. Moreover, 10 photocatalytic degradation intermediates and products were also identified by the gas chromatography-mass spectrometer. Finally, the photocatalytic enhancement mechanism over p-Ag2S/n-BiVO4 was discussed. The strategy to form three-dimensional microspheres p-n heterojunction photocatalyst may open a new opportunity to design highly efficient photocatalyst for environmental treatment to control pollution.
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•Lifetime of the charge carriers was obtained by time-resolved fluorescence spectra.•Ag/p-Ag2O/n-BiVO4 plasmonic photocatalyst exhibits excellent photocatalytic activity.•The band ...structure was revealed via the valence band XPS and CASTEP code.•The enhancing photocatalysis mechanism was discussed.
Herein, we demonstrate the successful construction of a novel flowerlike Ag/p-Ag2O/n-BiVO4 plasmonic photocatalyst for the photocatalytic oxidation of BPA and reduction of chromium(VI) simultaneously under visible light irradiation. Among these samples, 2mM-Ag/p-Ag2O/n-BiVO4 exhibits the highest photocatalytic performances. The photocatalytic reduction and oxidation efficiency can achieve 69.8 and 91.9%, respectively, after 100 min visible-light irradiation. The enhancement mechanism for the plasmonic photocatalyst is explored, which can be attributed to the enhanced absorbance in the visible light region, and the facilitated charge transfer and the suppressed recombination of electron-hole pairs in the Ag/p-Ag2O/n-BiVO4. The results of the electrochemical impedance spectroscopy, the fluorescence emission spectra and the time-resolved fluorescence emission decay spectra indicate the enhanced charge separation in the Ag/p-Ag2O/n-BiVO4 plasmonic photocatalyst. In addition, the free radical scavenging test shows that h+ and OH radicals play crucial roles in the photocatalytic oxidation reaction. The photogenerated electrons in the photocatalytic reduction process, are confirmed by the DMPO spin-trapping technology. Moreover, the band structures of various photocatalysts are revealed via the valence band XPS spectra and the Fermi level obtained by CASTEP code.
Herein, a novel amorphous/crystalline contact Bi2S3/Bi4O7 heterostructure was constructed by in-situ sulfidation and proved to be an effective photocatalytic Cr(VI) reduction and RhB oxidation.
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Constructing a heterojunction photocatalyst is a significant method to enhance photocatalytic activity because it can promote the separation of photogenerated carriers. Herein, amorphous/crystalline contact Bi2S3/Bi4O7 heterostructure was successfully synthesized by in-situ sulfidation of Bi4O7. The amorphous Bi2S3 is diffused on the surface of Bi4O7 rod, enhancing the visible light response and improving the transport of photogenerated carriers. Various characterizations confirm that the rapid separation of photogenerated carriers leads to increased photocatalytic performance. The optimized Bi2S3/Bi4O7 heterostructure photocatalyst (BiS-0.15) exhibits the highest Cr(VI) reduction (0.01350 min−1) and RhB oxidation (0.08011 min−1) activity, which is much higher than that of pure Bi4O7 and Bi2S3/Bi4O7 mixture under visible light irradiation. This work provides new insights into the construction of efficient novel photocatalysts.
Biological treatment can remove more than 89.8% of total organic carbon (TOC) and 94.4% of fluorescent dissolved organic matter (DOM) in the coking wastewater, thereby affecting the migration, ...transformation and bioavailability and binding characteristics of heavy metals (HMs). The results of parallel factor analysis (PARAFAC) show that protein-like materials accounted for 97.53% in the coking wastewater DOM, a large number of humic-like substances are produced and accounted for more than 55.40% after biological treatment. A new spectral data processing method, the 1/n-th power transformation after two-dimensional correlated spectroscopy (2D-COS) in combination with synchronous fluorescence spectra (SFS), can identify small features obscured by strong peaks, and reveal more binding sites as well as preserve the sequential order information. The result indicates that the preferential bonding of Cu(II) is at 306 nm (protein-like) for coking wastewater DOM, and at 514 nm (humic-like) for effluent DOM. The C−O group of esters and alcohols can preferentially complexate with Cu(II) in the coking wastewater and effluent DOM. The log KM values of PARAFAC components with Cu(II) are in the range of 3.59–5.06 for coking wastewater DOM, and in the range of 4.80–5.64 for the effluent DOM. Log KM values for protein-like materials with Cu(II) are higher than these for fulvic- and humic-like substances. Humic-like substances can form more stable complexes with Cu(II) in the effluent DOM. Biological treatment increases the chemical stability of DOM-Cu(II) complexes, thereby further reducing the environmental risk of Cu(II).
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•Protein-like materials play a crucial role in coking wastewater DOM.•Biological treatment can affect the complexation of DOM and HMs.•DOM-Cu(II) shows higher chemical stability in the effluent.•The 1/n-th power transformation can reveal more binding sites.
Herein, a comprehensive review on different MOFs for heterogeneous photoelectrocatalysis is carried out and, in particular, the application of this technique to CO2 conversion and water splitting is ...discussed. The challenges and development prospects of MOFs in photoelectrocatalysis are also presented.
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Semiconductor-based photoelectrocatalytic processes have attracted considerable research interest for solar energy collection and storage. Photoelectrocatalysis is a heterogeneous photocatalytic process in which a bias potential is applied to a photoelectrode, and thus the photoelectrocatalytic performance is closely related to the photoelectrode prepared by semiconductors. Among various semiconductors, metal-organic frameworks (MOFs) have attracted more and more attention because of their unique properties such as optical properties and adjustable structure. Herein, a comprehensive review on different MOFs (Ti-based, Zn-based, Co-based, Fe-based, Cu-based, and mixed metal-based MOFs) for heterogeneous photoelectrocatalysis is carried out and, in particular, the application of this technique for CO2 conversion and water splitting is discussed. In addition, the challenges and development prospects of MOFs in photoelectrocatalysis are also presented.
The fluorescent components of dissolved organic matter (DOM) in biogas slurry can react with heavy metals (HMs) and affect the migration, transformation, toxicity, and bioavailability of HMs in soil. ...Fluorescence quenching titration combined with two-dimensional correlation spectroscopy (2D-COS) can reveal the binding mechanism between HMs and different fluorescent components of biogas slurry DOM. The logarithmic-transformed (log-transformed) 2D-COS can be used to decrease the difference in the fluorescence intensity between low-intensity and high-intensity fluorophores that provides a better insight into the binding mechanism between biogas slurry DOM and HMs. Synchronous maps suggest that protein-like substances are more susceptive to the variation of the concentration of metal ions than fulvic-like substances. Asynchronous maps show that the preferential bonding of Cu(II) and Cr(III) to humic-like substances can be found in the biogas slurry DOM, as well as Fe(III) and Pb(II) to protein-like materials. DOM-Cu(II) may lead to an increasing risk of the migration of Cu(II) from soil to water environment due to the low log K values in the range from 2.93 to 3.46. Protein-like substances can also increase the environmental risk of HMs when these low-stable complexes occur migration and transformation. The potential environmental risk of protein-like with HMs follows the order: Pb(II) > Cu(II) > Cr(III). Here we demonstrate that the log-transformed 2D-COS can also identify fluorescence components at longer wavelength with relatively low content and reveals their preferential binding sequence and the number of binding sites. The study on the complexation between biogas slurry DOM and HMs provides a scientific basis for the environmental chemical behavior of HMs after the application of biogas slurry in agricultural soils.
A novel 3-D heterojunction photocatalyst Ag2CO3/BiVO4 was successfully fabricated. It exhibits excellent photocatalytic performances for the photocatalytic oxidation of crystal violet and reduction ...of Cr6+, which is ascribed to the suppression of charge recombination, and increasing lifetime of the charge carriers confirmed by the result of time-resolved fluorescence emission decay spectra and photoelectrochemical measures. The electron spin resonance result also suggests that heterojunction structure can improve separation efficiency of photogenerated carriers and favor to form •OH radicals. Moreover, ten intermediates and products for the photocatalytic oxidation degradation of crystal violet are identified by GC-MS.
•A novel 3-D heterojunction photocatalyst Ag2CO3/BiVO4 was successfully fabricated.•Heterojunction plays the role for increasing lifetime of the charge carriers.•EPR result suggests that the heterojunction structure favor to form OH radicals.•The photocatalytic enhancement mechanism for Cr6+ reduction and CV oxidation was discussed.
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•EmimDP was effective to disrupt the shields formed by lignin inside rice straw.•The cellulase from Trichoderma aureoviride showed high stability in EmimDP.•The coupling of ...IL-activation and subsequent enzymatic hydrolysis process.•An efficient IL-cellulase media for in situ enzymatic saccharification of biomass.
Although ionic liquids (ILs) have emerged as a promising type of solvent for lignocellulose pretreatment, the enzymatic saccharification of regenerated lignocellulose must occur in a separate step due to the toxicity of ILs to cellulase. It is critical to develop a compatible IL-cellulase system in which the IL effectively activates the lignocellulosic biomass, while the enzyme remains highly stable. In this context, an exploration of ILs with high lignin-extraction capacity, for the first time showed 1-ethyl-3-methyl-imidazolium dimethylphosphate (EmimDP) to be effective in disrupting the lignin-based shield within rice straw, thus enhancing the biodegradability of this plant material. The cellulase obtained from Trichoderma aureoviride showed high stability in this IL. After incubation in EmimDP for 24h, more than 40% of the lignin was successfully leached from the rice straw. The spectroscopic and morphological analyses showed that the synergistic effect of delignification and the partial dissolution of cellulose during the activation process significantly changed the crystalline molecular structure of rice straw. When the activated straw slurry was enzymatically hydrolyzed in IL diluted to 15% (w/v), a high yield of reducing sugars, 61%, was obtained. Thus, an efficient system coupled the activation and subsequent enzymatic hydrolysis of a native biomass in a one-pot procedure was successfully developed.
Soil samples were collected from the areas surrounding Wuliangsuhai Lake in China. Dissolved organic matter （DOM） was extracted from the samples and characterized by fluorescence and UV-Vis spectra. ...Spectral properties and humification degree of DOM were studied. The results indicated that both humic- and protein- like fluorophores were present in the DOM spectra, and the former was the dominant component. The analysis of humification （HIX） and r （A, C） indices revealed that the maximum humification degree in three agricultural soils （AAF, ASC, and ASW） was presented in the second soil layer （20-40 cm）. However, the humification degree of the two Halophytes soils （SSE and GKF） decreased with increasing depth. One index, I344/270, showed that humification degree increased gradually with an increasing proportion of humic-like acid. There was a significant positive correlation between humification degree （HIX） and aromaticity （SUVA254）, indicating that a higher aromaticity corresponded to a higher humification degree. Land use was an important factor responsible for the major difference of cation exchange capacity （CEC） in different soils, which led to a higher CEC value in the second soil layer for the three agricultural soils. CEC values and humification degree had the same trend for all five soils. The correlation analysis showed that there was a significant positive correlation between HIX and CEC,and a negative correlation between the r （A, C） index and CEC, indicating that humification degree increases gradually with increasing CEC values.
A novel three-dimensional microspheres Ag/p-AgBr/n-BiVO4 plasmonic p–n heterojunction photocatalyst was successfully obtained for the first time; the photocatalytic performance of the as-prepared ...sample was systematically examined via the photocatalytic reduction of Cr6+ and oxidation of bisphenol S under visible-light irradiation. Among these samples, 3 mM-Ag/p-AgBr/n-BiVO4 exhibits the highest photocatalytic performances; the photocatalytic reduction and oxidation efficiency can be achieved at 76.9 and 98.8%, respectively. Enhancing photocatalytic performance is attributed to the increasing lifetime of the charge carrier confirmed by the results of time-resolved fluorescence spectra and photoelectrochemical measures. Moreover, based on the results of free radical scavenging activity test, and EPR experiments, we verify that h+ and •OH radicals are the main reactive species. Furthermore, the theoretical understanding of the underlying mechanism was also supported; we systematically calculated the energy band structure and Fermi level using the density functional theory approach. The results show that the matched positions of the CB and VB band edge between BiVO4 and AgBr are beneficial for efficiently separating electron–hole pairs. The strategy to form a three-dimensional microspheres plasmonic p–n heterojunction photocatalyst may offer a new strategy for applications in the field of solar energy conversion.
