In this work, oxygen vacancies were introduced onto the surface of BiFeO₃ nanoparticles by NaBH₄ reduction method to yield oxygen-deficient BiFeO
samples. Comprehensive analysis on the basis of ...high-resolution transmission electron microscopy (HRTEM) observation and X-ray photoelectron spectrum (XPS) confirms the existence of surface oxygen vacancies on the BiFeO
nanoparticles. The photocatalytic activity of as-prepared BiFeO
samples was evaluated by the decolorization of rhodamine B (RhB) under simulated sunlight irradiation. The experimental results indicate that the photocatalytic activity of samples is highly related to the NaBH₄ reduction time, and the BiFeO
sample reduced for 40 min exhibits the highest photocatalytic efficiency, which is much higher than that of pristine BiFeO₃ nanoparticles. This can be explained by the fact that the surface oxygen vacancies act as photoinduced charges acceptors and adsorption sites suppress the recombination of photogenerated charges, leading to an increasing availability of photogenerated electrons and holes for photocatalytic reaction. In addition, the obtained BiFeO
sample exhibits good photocatalytic reusability.
In this work, Ag
3
PO
4
microparticles were decorated onto the surface of BiFeO
3
microcuboids through a precipitation method to obtain p-Ag
3
PO
4
/n-BiFeO
3
heterojunction composites. The ...composites were employed for the degradation of acid orange 7 (AO7) under visible-light irradiation. It is found that the composites exhibit much higher photocatalytic efficiency than bare BiFeO
3
. Meanwhile, the intrinsical visible-light-driven photocatalytic activity of Ag
3
PO
4
/BiFeO
3
composites was further confirmed by the degradation of phenol. In addition, the photo-Fenton-like catalysis property of the composite was also evaluated. The photocurrent analysis indicates that the combination of BiFeO
3
with Ag
3
PO
4
leads to the inhibition of recombination of photoinduced electrons and holes. The obvious enhancement in the photocatalytic activity of the composite is mainly ascribed to the efficient photogenerated charge separation and interfacial charge migration caused by the formation of Ag
3
PO
4
/BiFeO
3
p-n heterojunctions.
•EC process was successfully used for Zn2+ removal at various concentrations.•The influence mechanisms of main parameters on Zn2+ removal were discussed.•Zn2+ removal kinetic model highly depends on ...initial ion concentrations.•Electrochemical reduction facilitated Zn2+ removal at high initial concentrations.
In this work, the research focused on the Zn2+ removal from the synthetic wastewater by electrocoagulation (EC) with aluminum electrodes. The effects of current density (2.1–12.5 mA/cm2), initial concentration (50–2000 mg/L), solution pH (2.9–7.4) and conductivity (0.15–14.11 mS/cm) on the removal efficiency and energy consumption were systematically investigated. It indicated that Zn2+ removal efficiency increased with the increasing of current density and residence time. With a relatively low energy consumption of 0.35 kWh/m3, all of Zn2+ (50 mg/L) was removed in 20 min EC treatment, 8.3 mA/cm2 for current density, and 5.3 for pH. With an energy consumption of 0.88 kWh/m3, all of Zn2+ (250 mg/L) were removed in 50 min. In addition, kinetic study was applied to analyze Zn2+ removal rate at different current densities and initial concentrations. Different mechanisms of Zn2+ removal were implied by comparing the results of low initial concentration (≤250 mg/L) and high one (≥500 mg/L). It was reasonable to conclude that, besides the precipitation effect of aluminum hydroxide flocculation, electrochemical reduction of Zn2+ at the cathode also contributed to Zn2+ removal, especially at a high initial concentration.
A novel membrane surface modification approach was proposed to successfully obtain a poly(vinylidene fluoride)-poly(acrylic acid)-ZnO (PVDF-PAA-ZnO) membrane with super-high water permeability and ...great oil rejection through cold plasma-induced PAA graft-polymerization followed by simple nano-ZnO self-assembly. The experimental parameters of modification were optimized and their optimal combination was identified using Taguchi orthogonal array (OA) design method. The PVDF-PAA-ZnO membrane was comprehensively characterized and the mechanism of nano-ZnO self-assembly was explored by contact angle measurement, scanning electron microscope (SEM) images, elemental analysis, tension test, Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy (ATR-FTIR) and synchrotron-based X-ray analyses. It was revealed that ZnO nanoparticles were immobilized onto membrane surface through the adsorption of PAA layer to form a PAA-ZnO coating without valence change. The carboxyl groups of PAA layer provided complexing ligands to coordinate with Zn2+ and form bidentate species on the nano-ZnO surface. The firm PAA-ZnO coating on PVDF membrane surface converted its hydrophobic nature to hydrophilic, bringing about the dramatically improvement of membrane performance both in water permeation flux and oil rejection rate. The permeation flux of the PVDF-PAA-ZnO membrane was more than 10 times as great as that of the pristine PVDF membrane.
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•A super-hydrophilic PVDF-PAA-ZnO membrane was obtained by plasma-induced polymerization and nano-ZnO assembly.•The permeation flux for oily wastewater treatment was increased more than 10 times.•The experimental parameters were optimized using Taguchi OA design method.•The mechanisms of nano-ZnO self-assembly were revealed through synchrotron-based X-ray analyses.
Graphitic carbon nitride (g-C3N4) has gained enormous attention for water and wastewater treatment. Compared with g-C3N4 nanopowders, g-C3N4 based hybrid membranes have demonstrated great potential ...for its superior practicability. This review outlines the preparation and characterization of g-C3N4 based hybrid membranes and presents their representative applications in water and wastewater treatment (e.g., removal of organic dyes, phenolic compounds, pharmaceuticals, salt ions, heavy metals, and oils). Meanwhile, g-C3N4 based films for the removal of contaminants through photocatalytic degradation is also summarized. In addition, the corresponding mechanisms and relevant findings are discussed. Finally, the challenges and research needs in the future and application of g-C3N4 based hybrid membranes are highlighted.
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•Water and wastewater can be effectively treated through g-C3N4 based hybrid membranes.•Porosity and photocatalytic ability of g-C3N4 result in desirable removal performance.•Various integrated membrane systems are summarized and discussed.•Prospects of g-C3N4 based hybrid membranes are presented.
In this work, ternary all-solid-state Z-scheme g-C₃N₄/carbon nanotubes/Bi₂Fe₄O₉ (g-C₃N₄/CNT/BFO) composites with enhanced photocatalytic activity were prepared by a hydrothermal method. The ...morphology observation shows that ternary heterojunctions are formed in the g-C₃N₄/CNT/BFO composites. The photocatalytic activity of the samples for the degradation of acid orange 7 was investigated under simulated sunlight irradiation. It was found that the ternary composites exhibit remarkable enhanced photocatalytic activity when compared with bare BFO and g-C₃N₄/BFO composites. The effect of the CNT content on the photocatalytic performance of the ternary composites was investigated. The photocatalytic mechanism of g-C₃N₄/CNT/BFO was proposed according to the photoelectrochemical measurement, photoluminescence, active species trapping experiment and energy-band potential analysis. The results reveal that the introduction of CNT as an excellent solid electron mediator into the ternary composites can effectively accelerate the electron migration between BFO and g-C₃N₄. This charge transfer process results in highly-efficient separation of photogenerated charges, thus leading to greatly enhanced photocatalytic activity of g-C₃N₄/CNT/BFO composites. Furthermore, the g-C₃N₄/CNT/BFO composites also exhibit highly-efficient photo-Fenton-like catalysis property.
In this paper, a high-affinity ssDNA aptamer binding to Salmonella typhimurium was obtained by a whole-bacterium-based Systemic Evolution of Ligands by Exponential Enrichment (SELEX) procedure. After ...nine rounds of selection with S. typhimurium as the target, a highly enriched oligonucleotide pool was sequenced and then grouped into different families based on primary sequence homology and secondary structure similarity. Eleven sequences from different families were selected for further characterization via flow cytometry analysis. The results showed that the sequence ST2P demonstrates affinity for S. typhimurium much more strongly and specifically than other sequences tested. The estimated Kd value of this particularly promising aptamer was 6.33 ± 0.58 nM. To demonstrate the potential use of the aptamers in the quantitative determination of S. typhimurium, a fluorescent bioassay with the aptamer ST2P was prepared. Under optimal conditions, the correlation between the concentration of S. typhimurium and fluorescent signal was found to be linear within the range of 50-10(6) cfu/mL (R2 = 0.9957). The limit of detection (LOD) of the developed method was found to be 25 cfu/mL. This work demonstrates that this aptamer could potentially be used to improve the detection of S. typhimurium.
Z-scheme Ag₂S/BiFeO₃ heterojunction composites were successfully prepared through a precipitation method. The morphology and microstructure characterization demonstrate that Ag₂S nanoparticles (30⁻50 ...nm) are well-decorated on the surfaces of polyhedral BiFeO₃ particles (500⁻800 nm) to form Ag₂S/BiFeO₃ heterojunctions. The photocatalytic and photo-Fenton catalytic activities of the as-derived Ag₂S/BiFeO₃ heterojunction composites were evaluated by the degradation of methyl orange (MO) under visible-light irradiation. The photocatalytic result indicates that the Ag₂S/BiFeO₃ composites exhibit much improved photocatalytic activities when compared with bare Ag₂S and BiFeO₃. The optimum composite sample was observed to be 15% Ag₂S/BiFeO₃ with an Ag₂S mass fraction of 15%. Furthermore, the addition of H₂O₂ can further enhance the dye degradation efficiency, which is due to the synergistic effects of photo- and Fenton catalysis. The results of photoelectrochemical and photoluminescence measurements suggest a greater separation of the photoexcited electron/hole pairs in the Ag₂S/BiFeO₃ composites. According to the active species trapping experiments, the photocatalytic and photo-Fenton catalytic mechanisms of the Ag₂S/BiFeO₃ composites were proposed and discussed.
Government subsidy for waste incineration is an effective measure to promote the economic growth of the waste management system. It is of vital importance to formulate optimal management strategies ...for decision-makers by considering conflicting objectives among system cost and environmental risk under complex uncertainties. In this study, an inexact two-stage multi-objective planning (ITMOP) model is proposed for supporting municipal solid waste (MSW) management. This model advanced existing optimization methods through integrating interval linear programming and two-stage stochastic programming within the multi-objective programming framework, where various uncertainties expressed as interval value and probability distributions were effectively reflected. The environmental risks associated with exhaust gas and leachate emission from incineration and landfill are quantitively assessed. The economic performance of these two waste disposal facilities is evaluated through the introduction of different energy recovery and subsidy policy scenarios. The ITMOP-based municipal solid waste management model is applied to a case study of MSW management planning in the Baotou city of China. Ten scenarios integrated with different economic incentives are designed for analyzing the optimized solutions. The generated waste flow allocation pattern and facility expansion capacity results provide scientific waste management strategies for local authorities. Moreover, the obtained total system cost and environmental risks under different scenarios can help policymakers resolve eco-economic conflicts according to their preferences. Waste incineration will gradually replace landfilling as the mainstream of waste treatment in the future. Revenues from energy recovery and financial subsidies for incineration can compensate for its high economic cost and promote waste resource utilization. The results indicate that the local government can use the subsidy policy to encourage waste disposal to proper facilities and simultaneously reduce environmental emissions.
•Economic and environmental oriented solid waste management model is developed.•Environmental risk is introduced to express air and water pollutants emissions.•Financial subsidies for WTE are designed for promoting solid waste utilization.•Multiple uncertainties and objectives are reflected through ITMOP model.
Female and latent genital tuberculosis (FGTB and LGTB) in young women may lead to infertility by damaging ovarian reserve function, but the regulatory mechanisms remain unclear. In this study, we ...investigated the effects of FGTB and LGTB on ovarian reserve function and potential regulatory mechanisms by untargeted metabolomics of follicular fluid, aiming to provide insights for the clinical management and treatment approaches for afflicted women. We recruited 19 patients with FGTB, 16 patients with LGTB, and 16 healthy women as a control group. Clinical data analysis revealed that both the FGTB and LGTB groups had significantly lower ovarian reserve marker levels compared to the control group, including lower anti-Müllerian hormone levels (FGTB: 0.82 0.6, 1.1 μg/L; LGTB: 1.57 1.3, 1.8 μg/L vs. control: 3.29 2.9, 3.5 μg/L), reduced antral follicular counts (FGTB: 6 5.5, 9.5; LGTB: 10.5 7, 12.3 vs. control: 17 14.5, 18), and fewer retrieved oocytes (FGTB: 3 2, 5; LGTB: 8 4, 8.3 vs. control: 14.5 11.5, 15.3). Conversely, these groups exhibited higher ovarian response marker levels, such as longer gonadotropin treatment days (FGTB: 12 10.5, 12.5; LGTB: 11 10.8, 11.3 vs. control: 10 8.8, 10) and increased gonadotropin dosage requirements (FGTB: 3300 3075, 3637.5 U; LGTB: 3037.5 2700, 3225 U vs. control: 2531.25 2337.5, 2943.8 U). All comparisons were statistically significant at P < 0.05. The results suggested that FGTB and LGTB have adverse effects on ovarian reserve and response. Untargeted metabolomic analysis identified 92 and 80 differential metabolites in the control vs. FGTB and control vs. LGTB groups, respectively. Pathway enrichment analysis revealed significant alterations in metabolic pathways in the FGTB and LGTB groups compared to the control group (P < 0.05), with specific changes noted in galactose metabolism, biotin metabolism, steroid hormone biosynthesis, and nicotinate and nicotinamide metabolism in the FGTB group, and caffeine metabolism, primary bile acid biosynthesis, steroid hormone biosynthesis, and glycerophospholipid metabolism in the LGTB group. The analysis of metabolic levels has revealed the potential mechanisms by which FGTB and LGTB affect ovarian reserve function, namely through alterations in metabolic pathways. The study emphasizes the importance of comprehending the metabolic alterations associated with FGTB and LGTB, which is of considerable relevance for the clinical management and therapeutic approaches in afflicted women.
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