This article analyses centralizing trends that may be able to reduce the negative influence of local protectionism on environmental law enforcement in China. The article finds that as centralizing ...trends unfolded, enforcement over time has become stricter and more frequent, however with only minor effects in reducing pollution. Moreover it finds a situation of uneven enforcement with richer and more urbanized areas having much stronger and more frequent enforcement than inland areas. Centralizing trends may thus have spurred stronger enforcement, but concurrently allowed for an uneven enforcement. At the same time, the article finds a continued local influence, keeping enforcement too weak to have much effect in reducing pollution and allowing for local interests to shape enforcement into unequal outcomes. 文章旨在分析中央集权化的趋势是否有可能减少地方保护主义对于中国环境执法所产生的负面影响。研究发现, 随着中央集权化趋势所呈现出来的执法实践正变得更加严格和频繁, 但是对于减少污染所起到的作用甚微。此外, 研究发现, 执法存在不均衡的情形, 即相对于内陆地区, 较富裕、城市化程度较高的地区执法强度更高、更频繁。因此, 中央集权化的趋势有可能刺激出较强的执法, 但同时也可能催生出不均衡的执法实践。与此同时, 研究发现, 地方性的影响仍然持续存在, 使得执法太弱而无法对减少污染产生显著作用, 并且使得地方性的利益塑造出不同等的执法后果。
Adsorption of two synthetic organic compounds (SOCs; phenanthrene and biphenyl) by two pristine graphene nanosheets (GNS) and one graphene oxide (GO) was examined and compared with those of a coal ...base activated carbon (HD4000), a single-walled carbon nanotube (SWCNT), and a multi-walled carbon nanotube (MWCNT) in distilled and deionized water and in the presence of natural organic matter (NOM). Graphenes exhibited comparable or better adsorption capacities than carbon nanotubes (CNTs) and granular activated carbon (GAC) in the presence of NOM. The presence of NOM reduced the SOC uptake of all adsorbents. However, the impact of NOM on the SOC adsorption was smaller on graphenes than CNTs and activated carbons. Furthermore, the SOC with its flexible molecular structure was less impacted from NOM preloading than the SOC with planar and rigid molecular structure. The results indicated that graphenes can serve as alternative adsorbents for removing SOCs from water. However, they will also, if released to environment, adsorb organic contaminants influencing their fate and impact in the environment.
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► Graphenes exhibited comparable or better adsorption capacities than CNTs and GAC. ► Graphenes had the lowest reductions in adsorption capacity in natural waters. ► Graphenes can be considered as alternative adsorbents for engineering applications. ► Graphenes, if released in environment, will adsorb and carry organic contaminants.
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•MSSBC is prepared from municipal sewage sludge by a feasible process.•Porous MSSBC contains copious active sites and magnetic property.•Multiple interactions between lead and MSSBC ...guarantee the removal efficiency.•Waste control by waste is suggestive to the treatment of both sewage sludge and wastewater.
Highly efficient magnetic sewage sludge biochar (MSSBC) discloses feasible fabrication process with lower production cost, superior adsorption capacity, usage of waste sewage sludge as resource, selected by external magnetic field and exceptional regeneration property. 2gL−1 MSSBC exhibited a high adsorption capacity of 249.00mgg−1 in 200ppmPb(II) and the lead-MSSBC equilibrium was achieved within one hour, owing to the existence of the copious active sites. The adsorption kinetics was well described by the pseudo-second-order model while the adsorption isotherm could be fitted by Langmuir model. Mechanism study demonstrated the adsorption involved electrostatic attraction, ion exchange, inner-sphere complexation and formation of co-precipitates at the surface of MSSBC. Additionally, adsorption performance maintained remarkable in a broad pH window. These outcomes demonstrated the promising waste resource utilization by a feasible approach that turns the solid waste of sewage sludge into biochar adsorbent with auspicious applications in elimination of Pb(II) from wastewater.
Nanoscale zerovalent iron (NZVI) was evaluated for the reduction of bromate that is a highly persistent and carcinogenic oxyhalid formed as an ozonation byproduct during oxidative disinfection in ...drinking water treatment. Solid-phase NZVI with different surface areas was controllably synthesized using a liquid phase reduction. Transmission electron microscopy (TEM), X-ray diffraction (XRD), and a Brunauer−Emmett−Teller (BET) surface area and porosity analyzer were utilized to characterize particle size, surface morphology, surface area, and corrosion layers formed onto NZVI before and after the reduction of bromate. Surface area of synthesized NZVI was found to be influenced strongly by ethanol contents during synthesis with a maximum surface area of 67.51 ± 0.35 m2/g in a 90% aqueous ethanol; additionally, capsule structures of NZVI with amorphous phase, in which tens of particles with diameters of 2−5 nm were packed into an iron oxide/hydroxide layer, were also synthesized using 100% ethanol as a solvent. Subsequent XRD and TEM results revealed that in a 20 min bromate reduction NZVI mostly converted to Fe2O3 and Fe3O4 corrosion products mixed with iron hydroxides. Compared to bromate reduction using microsized ZVI in a pseudo-first-order kinetic model, NZVI enhanced the reduction efficiency following a second-order kinetic model, with observed second-order rate constants (k obs) of 2.57 × 10−4 to 2.19 × 10−3 μg−1min−1L. Humic acid was found to be the most influencing factor to decrease NZVI reactivity in bromate reduction. However, the effect of sonication pretreatment showed that the bromate reduction efficiency could be enhanced by increasing the actual reactive surface area. Our results suggest that application of NZVI is a viable process for bromate reduction in water treatment.
A series of nanocrystalline mesoporous ZrO2-TiO2 binary oxide photocatalysts with different wt% of ZrO2 and TiO2 were prepared by a sol-gel method. These binary oxide photocatalysts were ...characterized by XRD, N2 adsorption-desorption, DRS, FTIR, Raman spectroscopy, photoluminescence and TEM analyses. Detailed investigations revealed that the ZrO2-TiO2 catalysts are highly micro-crystalline in nature with a larger surface area than that of the pure TiO2 or ZrO2 catalysts since the added ZrO2 plays an important role in promoting the formation of nanoparticles with an anatase structure, high surface area and acidity. The photocatalytic reactivity of the catalysts was investigated for the degradation of 4-chlorophenol in an aqueous phase in which the ZrO2-TiO2 photocatalysts were found to exhibit remarkably higher photocatalytic reactivity than that of pure TiO2 and ZrO2. The catalytic activity of the binary oxide photocatalysts for the degradation of 4-chlorophenol was observed to be gradually enhanced with an increase in the ZrO2 content and reached an optimum at 12wt% of ZrO2 while maintaining the same percentage degradation with further loading of ZrO2 until 50wt%. Such high reactivity is due to the easy transfer of the photo-formed electrons from the conduction band surface trap states of ZrO2 to the conduction band of TiO2 through strong chemical interactions, thereby, preventing the radiative recombination of the photo-formed electrons and holes. The ZrO2-TiO2 catalysts were, thus, found to be highly active for the efficient degradation of 4-chlorophenol and, in fact, exhibited just as efficient activity as the commercial P-25, Degussa TiO2 catalysts, and a new reaction mechanism has, hereby, been proposed.
In the present study, Quantitative Structure–Activity Relationship (QSAR) and Linear Solvation Energy Relationship (LSER) techniques were used to develop predictive models for adsorption of organic ...contaminants by multi-walled carbon nanotubes (MWCNTs). Adsorption data for 29 aromatic compounds from literature (i.e., the training data) including some of the experimental results obtained in our laboratory were used to develop predictive models with multiple linear regression analysis. The generated QSAR (r 2 = 0.88), and LSER (r 2 = 0.83) equations were validated externally using an independent validation data set of 30 aromatic compounds. External validation accuracies indicated the success of parameter selection, data fitting ability, and the prediction strength of the developed models. Finally, the combination of training and validation data were used to obtain a combined LSER equation (r 2 = 0.83) that would be used for predicting adsorption of a wide range of low molecular weight aromatics by MWCNTs. In addition, LSER models at different concentrations were generated, and LSER parameter coefficients were examined to gain insights to the predominant adsorption interactions of low molecular weight aromatics on MWCNTs. The molecular volume term (V) of the LSER model was the most influential descriptor controlling adsorption at all concentrations. At higher equilibrium concentrations, hydrogen bond donating (A) and hydrogen bond accepting (B) terms became significant in the models. The results demonstrate that successful predictive models can be developed for the adsorption of organic compounds by CNTs using QSAR and LSER techniques.
Flexure hinges are susceptible to fatigue damage under cyclic loading, resulting in performance degradation. This paper investigates the stiffness degradation of the right circular flexure hinges ...(RCFHs) under cyclic loading. Fatigue damage experiments are conducted to obtain the stiffness degradation curves, which can be divided into several stages by feature points. A relationship between feature lives and alternating stress amplitudes is established. A fatigue damage stiffness degradation piecewise curve model for RCFHs is proposed. The effect of notch stress concentration on fatigue damage is analyzed. Fatigue damage experiments under non-zero mean stress are conducted, and an equivalent fatigue stress equation is obtained. Finally, a generalized fatigue damage stiffness degradation model for RCFHs is developed, which establishes a relationship between residual stiffness and cycle number. On this basis, a fatigue damage performance modeling method for flexure hinge mechanisms is proposed. The fatigue damage performance of a compliant bridge mechanism was modeled and tested. The experimental results of input stiffness degradation are generally in agreement with the predicted results, which verify the validity of the method.
•Thermodynamic model of novel variable conductance loop thermosyphon was set up.•Parametric heat transfer characteristics are reported for the first time.•Technology is proven feasible for ...energy-efficient space conditioning in buildings.•Detailed thermal responses obtained are essential for precise valve regulation.
Variable conductance loop thermosyphon (VCLT) manipulates natural phase-change cycle to regulate the heat transfer. Its primary advantages include high sustainability, simple design and low cost. One of the potential applications of variable conductance loop thermosyphon is thermal control in buildings for achieving high energy efficiency. In this study, a distributed steady-state model was implemented to determine the heat transfer control characteristics of variable conductance loop thermosyphon for the first time and evaluate its effectiveness on precise air-conditioning for buildings. The internal flow resistance rises from 0.002 K/W to 0.305 K/W and the heat transfer rate decreases from 468.5 W to 71.9 W when the relative opening degree of the regulating valve reduces from 1.00 to 0.17 under normal boundary conditions. The thermodynamic analyses show that the regulating valve of the variable conductance loop thermosyphon can enable effective thermal control over a wide range of heat transfer rate to accomplish indoor thermal comfort. The study also reveals that variable conductance loop thermosyphon can be effectively adopted with various working fluids and over wide ranges of heat source and heat sink temperatures.
In this paper, diamond-based vertical p-n junction diodes with step edge termination are investigated using a Silvaco simulation (Version 5.0.10.R). Compared with the conventional p-n junction diode ...without termination, the step edge termination shows weak influences on the forward characteristics and helps to suppress the electric field crowding. However, the breakdown voltage of the diode with simple step edge termination is still lower than that of the ideal parallel-plane one. To further enhance the breakdown voltage, we combine a p-n junction-based junction termination extension on the step edge termination. After optimizing the structure parameters of the device, the depletion regions formed by the junction termination extension overlap with that of the p-n junction on the top mesa, resulting in a more uniform electric field distribution and higher device performance.
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