高比表面积介孔网状氧化镁的制备、表征及对废水中Pb(Ⅱ)的吸附性能和机理

以天然水菱镁矿为原料，通过"煅烧-水化-煅烧"的简单方法制备了高比表面积介孔网状MgO，且实验过程中无须加入任何试剂。系统性研究了氧化镁用量、吸附时间、吸附温度及pH对氧化镁吸附模拟废水中铅离子吸附性能的影响，揭示了吸附机理，并考察了氧化镁对多种离子的吸附效果。结果表明：该氧化镁吸附剂具有188 m²·g^-1的高比表面积和0.85 cm³·g^-1的高孔体积，平均孔径为12.33 nm，其吸附动力学和等温线数据与伪二级模型和Langmuir模型高度吻合，表明重金属离子在氧化镁上为单层化学吸附。MgO介孔网状结构表现出对Pb（Ⅱ）的高吸附性能，最大吸附量为7 431.5 mg·g^-1，该数值远高于其他报道的基于MgO吸附剂的数值，铅去除率高达99.8%以上。介孔网状MgO的吸附机理主要是羟基官能团以及Mg（Ⅱ）与MgO表面重金属离子之间的离子交换所致。另外，该氧化镁可同时吸附多种离子，对Cd、Cr、Ni、As、Co、P、Se、Be、Bi、Cu、Fe、Mn、V、Zn、Al离子均具有优异的吸附性能。     

Surface area of papermaking woodpulps used by the British paper industry

The surface area was determined for various papermaking woodpulps: bleached eucalyptus globulus sulphate pulp; bleached eucalyptus grandis sulphate pulp; bleached betula verrucosa sulphate pulp; bleached pine/spruce sulphate pulp; bleached pine/spruce sulphate pulp fines. The method of negative adsorption was used which gives an effective wet surface area. By looking at negative adsorption data more closely, some inference can be made about the morphology of the substrate.Glossary of symbols B (e²/2kT)^1/2 - ¯C concentration of fibre per unit volume of pulp - 1 - ¯¯c - h angle between pore and the axis of the bed in a permeable material - K permeability coefficient - k Boltzmann constant - k ₀ shape factor for pores in a permeable material - n _i concentration of co-ion in the bulk solution - n _i experimentally observed increase in concentration of co-ion in the bulk solution - S surface area - S _t wS - S ₀ surface area per unit volume of permeable material - V _t total volume of solution - V excluded volume - V _s excluded volume accessible to water but not to ions - V _obs experimentally observed excluded volume - w weight of dry fibre - ¯ effective volume of fibres in a permeable pad - surface potential at outer Helmholtz plane     

Singular perturbed Markov chains and exact behaviors of simulated annealing processes

We study asymptotic properties of discrete and continuous time generalized simulated annealing processesX(·) by considering a class of singular perturbed Markov chains which are closely related to the large deviation of perturbed diffusion processes. Convergence ofX(t) in probability to a setS ₀ of desired states, e.g., the set of global minima, and in distribution to a probability concentrated onS ₀ are studied. The corresponding two critical constants denoted byd and withd are given explicitly. When the cooling schedule is of the formc/logt, X(t) converges weakly forc>0. Whether the weak limit depends onX(0) or concentrates onS ₀ is determined by the relation betweenc, d, and . Whenc>, the expression for the rate of convergence for each state is also derived.     

Efficient synthesis of magnetic nanoparticle-Musa acuminata peel composite for the adsorption of anionic dye

The impregnation of magnetite (Mt) nanoparticle (NPs) onto Musa acuminata peel (MApe), to form a novel magnetic combo (MApe-Mt) for the adsorption of anionic bromophenol blue (BPB) was studied. The SEM, EDX, BET, XRD, FTIR and TGA were used to characterize the adsorbents. The FTIR showed that the OH and CO groups were the major sites for BPB uptake onto the adsorbent materials. The average Mt crystalline size on MApe-Mt was 21.13 nm. SEM analysis revealed that Mt NPs were agglomerated on the surface of the MApe biosorbent, with an average Mt diameter of 25.97 nm. After Mt impregnation, a decrease in BET surface area (14.89 to 3.80 m²/g) and an increase in pore diameter (2.25–3.11 nm), pore volume (0.0052–0.01418 cm³/g) and pH point of zero charge (6.4–7.2) was obtained. The presence of Pb(II) ions in solution significantly decreased the uptake of BPB onto both MApe (66.1–43.8%) and MApe-Mt (80.3–59.1%), compared to other competing ions (Zn(II), Cd(II), Ni(II)) in the solution. Isotherm modeling showed that the Freundlich model best fitted the adsorption data (R² > 0.994 and SSE < 0.0013). In addition, maximum monolayer uptake was enhanced from 6.04 to 8.12 mg/g after Mt impregnation. Kinetics were well described by the pseudo-first order and liquid film diffusion models. Thermodynamics revealed a physical, endothermic adsorption of BPB onto the adsorbents, with ΔH^o values of 15.87–16.49 kJ/mol, corroborated by high desorption (over 90%) of BPB from the loaded materials. The viability of the prepared adsorbents was also revealed in its reusability for BPB uptake.     

神光-Ⅱ装置三倍频实验中靶场单元技术的改进

 主要介绍为了满足神光-Ⅱ高功率激光装置三倍频光（351nm，3ω）的物理实验要求，靶场三倍频模拟光源和瞄准监视系统两个主要单元技术的改进，即三倍频模拟光源由基频光（1 053nm，3ω）通过腔外的KTP+BBO晶体倍频获得，再经八路分光系统和主激光耦合；瞄准监视系统由透射式光学系统改进为反射式光学系统，避免原系统存在较大的色差，提高瞄准精度。     

Using symbolic computation software packages in production of multidimensional finite volume‐based large eddy simulation codes

The numerical simulation of turbulence is one of the most challenging tasks in the field of the modern computational science. At present, the most advanced approach is the large eddy simulation (LES) technique wherein a formal separation between resolved (large) and unresolved (small) scales of the motion is in effect by means of a filtering operation applied onto the governing equations. However, LES requires very sophisticated numerical discretizations in terms of both accuracy and efficiency. Often, the modelling of the unresolved subgrid scale terms adds further computational complexities. This paper illustrates the suitability in using software packages for symbolic computation (in the present case, Maple© for helping in the production of subroutines for a new multidimensional, high‐order accurate finite volume‐based LES code. Specifically, it will be detailed how producing, rapidly and efficiently, the routines for computing convective, diffusive as well as subgrid scale modelling fluxes. It is particularly detailed how exploiting the package for differential calculus and linear algebra for the analytical integration of the flux polynomials over the finite volume faces. The structure of the LES code is illustrated, and an accuracy analysis of the local truncation errors is performed comparing the third‐order accurate multidimensional upwind and the classical second‐order centred reconstruction in the wavenumbers space. Then, some numerical results for the turbulent plane channel and some brief points concerning the parallelization issue are addressed. Copyright © 2012 John Wiley & Sons, Ltd.     

Toward low‐noise synthetic turbulent inflow conditions for aeroacoustic calculations

The accuracy of boundary conditions for computational aeroacoustics is a well‐known challenge, due in part to the necessity of truncating the flow domain and replacing the analytical boundary conditions at infinity with numerical boundary conditions. In particular, the inflow boundary condition involving turbulent velocity or scalar fields is likely to introduce spurious waves into the domain, therefore degrading the flow behavior and deteriorating the physical acoustic waves. In this work, a method to generate low‐noise, divergence‐free, synthetic turbulence for inflow boundary conditions is proposed. It relies on the classical view of turbulence as a superposition of random eddies convected with the mean flow. Within the proposed model, the vector potential and the requirement that the individual eddies must satisfy the linearized momentum equations about the mean flow are used. The model is tested using isolated eddies convected through the inflow boundary and an experimental benchmark data for spatially decaying isotropic turbulence. Copyright © 2013 John Wiley & Sons, Ltd.     

Redox switchable ligands suitable for transition metal ions: Protonation,complexation and electrochemical properties of a ferrocene-modified tetraamine diketone and its saturated analogue

Abstract

The new ferrocene-containing water-soluble ligands 1 and 2 were synthesized and their protonation and complexation properties toward Ni^II and Cu^II studied as a function of pH, by means of potentiometric titration experiments. Electrochemical measurements were performed in aqueous solution on pure 1 and 2 and in the presence of Ni^II and Cu^II cations, in the pH range 2–12, allowing us to determine the redox potential values relative to the ferrocene oxidation in the free ligands and in their Ni^II and Cu^II complexes. 1 and 2 behave as redox switchable ligands, the former enhancing, the latter decreasing its binding ability upon oxidation of the appended ferrocene function. Besides, the Cu^II complex of ligand 1 and the Ni^II complex of ligand 2 behave as two-centre two-electron redox systems, the complexed metal cation being subject to further oxidation to M^III.     

Effect of bovine serum albumin on the surface properties of ionic liquid-type Gemini surfactant

The effect of bovine serum albumin on the surface properties of IL-type gemini surfactant ([C₁₀-4-C₁₀im]Br₂), have been investigated by surface tension method. The critical micelle concentration (CMC) as a function of BSA concentrations at various temperatures was investigated. The CMC of [C₁₀-4-C₁₀im]Br₂ increases with increasing the concentration of BSA as well as the temperature of the system. The interfacial parameters viz; maximum surface excess concentration (Γ_max), the minimum area per molecule (A_min), and surface pressure at CMC (Π_cmc) were calculated. In addition, thermodynamic parameters of adsorption and micellization were evaluated by using surface tension data. The results indicated that the binding of [C₁₀-4-C₁₀im]Br₂ to BSA is spontaneous and exothermic in nature. The process is entropy driven and hydrophobic interactions are the major driving forces.     

Strategic measures in optimal control problems for stochastic sequences

Controlled discrete–time stochastic processes axe studied using the convex–analytic approach. Some new properties of strategic measures spaces are established, particular Markov models are considered. The meaningful example is presented.