•Synthesis of amino-functionalized Fe3O4@SBA-15 core–shell microspheres with ordered mesostructure.•Good adsorptive capability of the amino-functionalized Fe3O4@SBA-15 composite.•Magnetically ...recoverable property of the amino-functionalized Fe3O4@SBA-15 composite.•The magnetic amino-functionalized Fe3O4@SBA-15 composite can be regenerated by acid treatment.
Magnetic mesoporous SBA-15 microspheres were fabricated by a colloidal chemical method. The prepared microspheres were hydrated with steam at 40°C and then functionalized with aminopropyltriethoxysilane, resulting in a large amount of amino groups (2.77mmol/g) grafted on the microspheres with ordered mesostructure. The amino-functionalized magnetic mesoporous composite showed excellent adsorptive capability toward heavy metal ions and the adsorption capacity was as high as 243.9mg/g for Pb2+ at room temperature. The adsorbent could be easily removed from solution by an external magnetic field and regenerated easily by acid treatment. These results suggest that this kind of composite is potentially useful for effectively adsorbing heavy metal ions in aqueous solution.
Perovskite oxides with formula ABO3 or A2BO4 are a very important class of functional materials that exhibit a range of stoichiometries and crystal structures. Because of the structural features, ...they could accommodate around 90% of the metallic natural elements of the Periodic Table that stand solely or partially at the A and/or B positions without destroying the matrix structure, offering a way of correlating solid state chemistry to catalytic properties. Moreover, their high thermal and hydrothermal stability enable them suitable catalytic materials either for gas or solid reactions carried out at high temperatures, or liquid reactions carried out at low temperatures. In this review, we addressed the preparation, characterization, and application of perovskite oxides in heterogeneous catalysis. Preparation is an important issue in catalysis by which materials with desired textural structure and physicochemical property could be achieved; characterization is the way to explore and understand the textural structures and physicochemical properties of the material; however, application reflects how and where the material could be used and what it can solve in practice, which is the ultimate goal of catalysis. This review is organized in five sections: (1) a brief introduction to perovskite oxides, (2) preparation of perovskite oxides with different textural structures and surface morphologies, (3) general characterizations applied to perovskite oxides, (4) application of perovskite oxides in heterogeneous catalysis, and (5) conclusions and perspectives. We expected that the overview on these achievements could lead to research on the nature of catalytic performances of perovskite oxides and finally commercialization of them for industrial use.
Abstract
The development of efficient catalysts for Fischer–Tropsch (FT) synthesis, a core reaction in the utilization of non-petroleum carbon resources to supply energy and chemicals, has attracted ...much recent attention. ε-Iron carbide (ε-Fe
2
C) was proposed as the most active iron phase for FT synthesis, but this phase is generally unstable under realistic FT reaction conditions (> 523 K). Here, we succeed in stabilizing pure-phase ε-Fe
2
C nanocrystals by confining them into graphene layers and obtain an iron-time yield of 1258 μmol
CO
g
Fe
−1
s
−1
under realistic FT synthesis conditions, one order of magnitude higher than that of the conventional carbon-supported Fe catalyst. The ε-Fe
2
C@graphene catalyst is stable at least for 400 h under high-temperature conditions. Density functional theory (DFT) calculations reveal the feasible formation of ε-Fe
2
C by carburization of α-Fe precursor through interfacial interactions of ε-Fe
2
C@graphene. This work provides a promising strategy to design highly active and stable Fe-based FT catalysts.
Purple soil bunds are embankments constructed along the contour on purple soil sloping farmlands, and play a key role in controlling soil erosion. The soil shear strength makes a significant ...influence to the bund stability; however, few reports have documented how purple soil shear strength responds to the soil physical properties. The main goal of the present study was to determine how indicators of soil shear strength vary with the soil water content and dry density. In this study, we collected soil samples from 3 purple soil bunds in Zhong County, in the Three Gorges Reservoir Area in China, and performed an unconsolidated undrained triaxial compression test to study the soil shear strength in terms of the cohesion (c), internal friction angle (φ), and the principal stress difference (σ1–σ3). The test results show that when the dry density was constant and the soil water content increased, the soil cohesion increased and then decreased, and the results fitted to a quadratic curve. As the soil water content increased, the internal friction angle of the soil bunds decreased and displayed a first-order exponential decay. As the soil water content increased and the confining pressure remained constant, the principal stress difference decreased rapidly. When the soil water content was constant and the dry density increased, the soil cohesion, internal friction angle, and the total principal stress difference increased, although at different rates. In general, the water content had a greater effect on the cohesion, internal friction angle, and the principal stress difference than the dry density, but there were little or no interaction between water content and dry density. Furthermore, except when the water content was 6%, the stress–strain characteristics were similar across the range of water contents. For a low water content, fixed confining pressure, and an increasing dry density, the curves gradually changed from the hardening type to the weak hardening type and then to the softening type. In most cases the curves corresponded with the hardening type as the confining pressure increased.
•Soil shear strength of purple soil bund responds to water content and dry density.•Increasing dry density increase soil cohesion, internal friction angle•Water content affects soil shear strength greater than dry density.•Stress–strain curves dominated by hardening type as confining pressure increases.
•Photocatalytic activity of porous TiO2 nanoparticles is higher than that of P25.•Effects of morphology and calcination temperature on photoactivity were discussed.•A modified L–H kinetic model has ...been used to describe the photodegradation process.•The degradation mechanisms were discussed in detail.
The photocatalytic activity of a mesoporous anatase TiO2 catalyst, which was prepared using a solvothermal method, was studied for the degradation of gaseous benzene under UV irradiation. The optimal synthesis conditions, which utilised acetic acid/butyl titanate (5:1 v/v) with calcination at 400°C, were determined, and nanopores in the prepared samples were found. The newly prepared TiO2 powders were characterised using X-ray diffractometer (XRD), scanning electronic microscopy (SEM), Brunauer–Emmett–Teller (BET) N2 adsorption, transmission electronic microscopy (TEM) and high resolution transmission electronic microscopy (HRTEM). The effects of the different morphologies, sizes and calcination temperatures on the photocatalytic activity of the prepared samples were discussed in detail. Nano-sized TiO2 particles that were synthesised under optimal conditions show the largest specific surface area (130.3m2/g), which is nearly two times that of Degussa P25. These particles also have the highest efficiency, which is significantly higher than was observed with Degussa P25. A modified Langmuir–Hinshelwood kinetic model was used considering a pseudo-steady state approach in order to explain the dependence of the apparent reaction rate constant and the apparent Langmuir adsorption constant on light intensity. Different intermediates in the samples used during the photocatalytic degradation of benzene have been identified using GC–MS analysis. A detailed reaction mechanism is proposed to explain their formation.
In order to understand the role of Co catalysts with different phases on Fischer–Tropsch synthesis, single-phase face-centered-cubic (fcc) and hexagonal-close-packed (hcp) Co were synthesized via a ...two-step approach, involving the formation of single-phase CoO materials followed by reduction in H2. The physicochemical properties of Co catalysts were thoroughly characterized by XRD, SEM, TEM, TPR, and H2 chemisorption. It was found that hcp-Co exhibits higher activity on hydrocarbon formation than fcc-Co in Fischer–Tropsch synthesis. For both catalysts, CO dissociation was suggested as the rate-determining step, on which hcp-Co presents ca. 40 kJ mol–1 lower activation energy than fcc-Co, in agreement with a reported computational study. As a result, hcp-Co is concluded to be the preferable phase for rational catalyst design.
Covalent triazine framework (CTF) is a good adsorbent material for organic dyes comparing to the traditional ones such as AC and SBA-15 (A). It can be reused for at least four cycles without losing ...the adsorption ability (B) and is applicable to various organic dyes. Display omitted .
•Covalent triazine framework (CTF) is used as adsorbent to remove organic dyes in aqueous solution.•CTF shows adsorption capacity of 1.01mmol/g for Rhodamine B.•CTF can be regenerated for at least four cycles without losing the adsorption capacity.•Kinetics and mechanism of dyes adsorbed on CTF are investigated.•CTF is efficient for adsorption removal of various organic dyes.
Covalent triazine framework (CTF) with microporous structure and high surface area are synthesized and used as adsorbent for adsorption removal of organic dyes in aqueous solution. It shows adsorption capacity of 1.01mmol/g for Rhodamine B (RhB), which is far higher than that reported for traditional adsorbents such as activated carbon (AC), which shows adsorption capacity of 0.36mmol/g for RhB under otherwise identical conditions. Within 55min the material shows uptake of 0.48mmol/g for RhB at weight ratio of RhB/CTF=0.24, and the initial pH can be adjusted in a wide range, from 1 to 11, without significantly affecting the uptake. Further studies indicate that the CTF can be regenerated and no appreciable loss in the uptake of RhB is observable even after four cycles. Mechanism and kinetic investigations indicate that the adsorption of RhB onto CTF obeys the Langmuir isothermal adsorption model with pseudo-second-order equation. Besides, the CTF is also applicable to adsorption removal of other organic dyes including reactive brilliant red X-3B and direct scarlet 4BS, with uptake of 0.43mmol/g for X-3B and 0.18mmol/g for 4BS within 55min.
Abstract
Background
To enhance teleconsultation management, demands can be classified into different patterns, and the service of each pattern demand can be improved.
Methods
For the effective ...teleconsultation classification, a novel ensemble hierarchical clustering method is proposed in this study. In the proposed method, individual clustering results are first obtained by different hierarchical clustering methods, and then ensembled by one-hot encoding, the calculation and division of cosine similarity, and network graph representation. In the built network graph about the high cosine similarity, the connected demand series can be categorized into one pattern. For verification, 43 teleconsultation demand series are used as sample data, and the efficiency and quality of teleconsultation services are respectively analyzed before and after the demand classification.
Results
The teleconsultation demands are classified into three categories, erratic, lumpy, and slow. Under the fixed strategies, the service analysis after demand classification reveals the deficiencies of teleconsultation services, but analysis before demand classification can’t.
Conclusion
The proposed ensemble hierarchical clustering method can effectively category teleconsultation demands, and the effective demand categorization can enhance teleconsultation management.
Ecological and environmental protection is essential to achieving sustainable and high-quality development, which highlights the important role of environmental governance. In terms of the practical ...actions of environmental governance, the central government in China has carried out continuous rating and praise campaigns, and local governments have actively promoted this effort. However, the related performance consequences have not been empirically investigated. We aimed to verify whether this incentive policy can improve the efficiency of environmental governance and whether this governance method has long-term effects. In addition, we sought to identify mechanisms through which the policy can improve environmental governance. We take the rating and praise campaign of the Establishment of National Sanitary Cities (EONSCs) as a quasi-natural experiment and use the panel data for 174 cities from 2004 to 2016 and the propensity score matching-difference in differences (PSM-DID) method to test the impact of rating and praise campaigns on environmental governance efficiency. EONSCs campaign can improve the efficiency of environmental governance by 0.7595 (p<0.01), which is significant at the 1% level; the effects are clearly significant during the evaluation process and the year in which cities are named National Sanitary Cities (NSCs) but decrease annually thereafter. The EONSCs campaign has a significant promoting effect on public services provision, such as public infrastructure investment, public transportation and education. (1) The rating and praise campaigns can effectively improve the efficiency of environmental governance; (2) the incentive effect is distorted and is not a long-term effect; (3) the impact of the rating and praise campaign of EONSCs on the efficiency of environmental governance is mainly realized through the provision of corresponding public services that are closely related to environmental protection. The findings of this paper provide empirical support for the effectiveness of the central government's rating and praise campaigns and could motivate local governments to actively participate in environmental governance. Moreover, the findings provide an important reference for further improving the rating and praise campaigns and the level of environmental governance.
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