Water pollution by various toxic substances remains a serious environmental problem, especially the occurrence of organic micropollutants including endocrine disruptors, pharmaceutical pollutants and naphthol pollutants. Adsorption process has been an effective method for pollutant removal in wastewater treatment. However, the thermal regeneration process for the most widely used activated carbon is costly and energy-consuming. Therefore, there has been an increasing need to develop alternative low-cost and effective adsorption materials for pollutant removal. Herein, β-cyclodextrin (β-CD), a cheap and versatile material, was modified with methacrylate groups by reacting with methacryloyl chloride, giving an average degree of substitution of 3 per β-CD molecule. β-CD-methacrylate, which could function as a crosslinker, was then copolymerized with acrylamide monomer via free-radical copolymerization to form β-CD-polyacrylamide (β-CD-PAAm) hydrogel. Interestingly, in the structure of the β-CD-PAAm hydrogel, β-CD is not only a functional unit binding pollutant molecules through inclusion complexation, but also a structural unit crosslinking PAAm leading to the formation of the hydrogel 3D networks. Morphological studies showed that β-CD-PAAm gel had larger pore size than the control PAAm gel, which was synthesized using conventional crosslinker instead of β-CD-methacrylate. This was consistent with the higher swelling ratio of β-CD-PAAm gel than that of PAAm gel (29.4 vs. 12.7). In the kinetic adsorption studies, phenolphthalein, a model dye, and bisphenol A, propranolol hydrochloride, and 2-naphthol were used as model pollutants from different classes. The adsorption data for β-CD-PAAm gel fitted well into the pseudo-second-order model. In addition, the thermodynamic studies revealed that β-CD-PAAm gel was able to effectively adsorb the different dye and pollutants at various concentrations, while the control PAAm gel had very low adsorption, confirming that the pollutant removal was due to the inclusion complexation between β-CD units and pollutant molecules. The adsorption isotherms of the different dye and pollutants by the β-CD-PAAm gel fitted well into the Langmuir model. Furthermore, the β-CD-PAAm gel could be easily recycled by soaking in methanol and reused without compromising its performance for five consecutive adsorption/desorption cycles. Therefore, the β-CD-PAAm gel, which combines the advantage of an easy-to-handle hydrogel platform and the effectiveness of adsorption by β-CD units, could be a promising pollutant removal system for wastewater treatment applications. 相似文献
The differential structure on the κ-Minkowski spacetime from Jordanian twist of Weyl algebra is constructed, and it is shown to be closed in 4-dimensions in contrast to the conventional formulation. Based on this differential structure, we have formulated a scalar field theory in this κ-Minkowski spacetime. 相似文献
We consider a simple extension to the previously found gravity solution corresponding to a boost invariant Bjorken plasma, by allowing components that are asymmetric under parity flipping of the spacetime rapidity. Besides the question whether this may have a realization in collisions of different species of projectiles, such as lead-gold collision, our new time-dependent gravity background can serve as a test ground for the recently proposed second order conformal viscous hydrodynamics. We find that non-trivial parity-asymmetric effects start to appear at second order in late time expansion, and we map the corresponding energy–momentum tensor to the second order conformal hydrodynamics to find certain second order transport coefficients. Our results are in agreement with the previous results in literature, giving one more corroborative evidence for the validity of the framework. 相似文献
1. IntroductionIn recent y6ars, some progress has been made towards increaJsing the flexibility of linearregression models. One of the obvious extensions in this direction is the sthcalled varyingcoefficient regression models in which the regressiOn funtions are llnear in the regressors,but their coefficients are allowed to change with the value of another factor. Specificallysuppose that we have a response variable Y and regressors X1 t X2,' t Xv as well as anothervariable V. A varyingco… 相似文献
Photocatalytic activity of titanium(IV) oxide (TiO2) can be enhanced through modification of its surface‐active sites. Here, iron(III) carboxylate [MIL‐53[Fe]]‐incorporated TiO2 (as MIL‐53(Fe)/TiO2) was prepared using a hydrothermal method. This material was then calcined at 500°C to obtain a MIL‐53(Fe)‐derived γ‐Fe2O3/TiO2 photocatalyst. A photocatalytic study of MIL‐53(Fe)/TiO2 and MIL‐53(Fe)‐derived γ‐Fe2O3/TiO2 toward cationic methylene blue (MB) and anionic methyl orange (MO) showed that MIL‐53(Fe)/TiO2 (0.25 wt%) and MIL‐53(Fe)‐derived γ‐Fe2O3/TiO2 (0.75 wt%) resulted the best degree of dye degradation. The MIL‐53(Fe)‐derived γ‐Fe2O3/TiO2 (0.75 wt%) composite for instance is capable of degrading almost 100% of 20‐ppm MB and MO, respectively, within 6 hr. Photocatalytic degradation of MB and MO was well fitted to the Langmuir‐Hinshelwood pseudo‐first order kinetics model, which indicates physisorption as the key partway that facilitates dye decomposition on the surface of a photocatalyst under UV‐A irradiation. This study provides new insights into the exploration of MILs/TiO2 materials for the environmental remediation and pollution control. 相似文献
Structural and electronic properties of ternary clusters AlkTilNim, where k, l, and m are integers and k + l + m = 4 , are investigated. These clusters are generated and studied by performing a two-stage density functional theory (DFT) calculations using the Slater, Vosko, Wilks, and Nusair (SVWN) and Becke three-parameter, Lee-Yang-Parr (B3LYP) functional exchange correlations. In the first stage, an unbiased global search algorithm coupled with a DFT code with a light exchange-correlation and smaller basis sets are used to generate the lowest energy cluster structures. It is then followed by further optimization using another round of DFT calculation with heavy exchanged correlations and large basis set. Electronic properties of the structures obtained via the two-stage procedure are then studied via DFT calculations. The results are illustrated in the form of ternary diagram. Our DFT calculations find that the stability of the cluster increases with the increase in the number of nickel atoms inside the clusters. Our findings provide new insight into the ternary metallic cluster through the structure, stability, chemical order, and electronic properties studies. 相似文献
Bamboo-/kenaf-reinforced epoxy hybrid composites were prepared by hand layup method. The aim of this study is to look into the hybridization effect of bamboo and kenaf fibers at different ratios on thermal and thermo-oxidative (TOD) stabilities of hybrid composites. Three types of hybrid composites were fabricated with different mass ratios of bamboo fiber mat (B) to kenaf fiber mat (K), namely B/K 70:30, B/K 50:50 and B/K 70:30 while maintaining total fiber loading of 40% by mass. The thermal stability and thermo-oxidative (TOD) stability were analyzed by thermogravimetric analyzer. Differential scanning calorimetry (DSC) was used to investigate the oxidation onset temperature (OOT) of all the composites. The results reveal that bamboo composite shows higher thermal stability than kenaf composite in both inert and oxidative atmospheres. An increase in bamboo fibers mass ratio in the hybrid composite improved the thermal and TOD stability. The thermal and TOD stabilities of the hybrid composites follow the sequence of B/K 70: 30?>?B/K 50:50?>?B/K 30:70. Pure epoxy composite recorded the highest OOT at 197.50 °C. The results show that the addition of natural fiber in the epoxy matrix has significantly reduced the OOT compared to the pure epoxy. Data obtained from this work will help us to fabricate a sustainable and biodegradable component for automotive or building materials.
Satisfying the boundary conditions at the free surface may impose severe difficulties to the computation of turbulent open-channel flows with finite-volume or finite-element methods, in particular, when the flow conditions are nearly critical. It is proposed to apply an iteration procedure that is based on an asymptotic expansion for large Reynolds numbers and Froude numbers close to the critical value 1.The iteration procedure starts by prescribing a first approximation for the free surface as it is obtained from solving an ODE that has been derived previously by means of an asymptotic expansion (Grillhofer and Schneider, 2003). The numerical solution of the full equations of motion then gives a surface pressure distribution that differs from the constant value required by the dynamic boundary condition. To determine a correction to the elevation of the free surface we next solve an ODE that is obtained from the asymptotic analysis of the flow with a prescribed pressure disturbance at the free surface. The full equations of motion are then solved for the corrected surface, and the procedure is repeated until criteria of accuracy for surface elevation and surface pressure, respectively, are satisfied.The method is applied to an undular hydraulic jump as a test case. 相似文献
In this work, the stress relaxation behavior of PMMA/PS blends, with or without random copolymer addition, submitted to step
shear strain experiments in the linear and nonlinear regime was studied. The effect of blend composition (ranging from 10
to 30 wt.% of dispersed phase), viscosity ratio (ranging from 0.1 to 7.5), and random copolymer addition (for concentrations
up to 8 wt.% with respect to the dispersed phase) was evaluated and correlated to the evolution of the morphology of the blends.
All blends presented three relaxation stages: a first fast relaxation which was attributed to the relaxation of the pure phases,
a second one which was characterized by the presence of a plateau, and a third fast one. The relaxation was shown to be faster
for less extended and smaller droplets and to be influenced by coalescence for blends with a dispersed phase concentration
larger than 20 wt.%. The relaxation of the blend was strongly influenced by the matrix viscosity. The addition of random copolymer
resulted in a slower relaxation of the droplets. 相似文献