碰撞能量对反应Sr＋HF转动取向的影响

在推广LEPS势能面上,用经典轨线方法,研究了反应碰撞能量对反应Sr＋HF的转动取向的影响.计算结果与产物轨道角动量模型进行比较.计算结果表明,随着碰撞能量的增加,产物转动取向越强烈.     

中东常压渣油热反应样品Zeta电位的研究

长期以来,有诸多研究者认识到了渣油的胶体性质,并且利用各种实验手段对其进行了研究。渣油的胶体稳定性对其热反应性能有重要影响作用。前人的研究认为,渣油胶体体系中的分散相主要是由沥青质构成,分散介质由芳香分和饱和分共同构成,吸附层由胶质构成。胶体的一个重要性质是电性质,渣油分子中含有大量的杂原子,使渣油极性分子的存在和渣油胶粒具有一定的电性。     

MgO脱除HCN的动力学研究

研究了MgO在不同温度下对HCN的脱除作用,并用XRD对反应后固相产物进行分析。研究了温度、MgO质量分数、HCN初始体积分数和停留时间等因素对HCN脱除效率的影响,并求出MgO与HCN反应的动力学参数。结果表明,673 K时,MgO已经开始与HCN发生反应,当温度高于873 K时,HCN中气态"N"已转化到固相产物MgCN₂中;HCN脱除效率随温度、MgO质量分数和停留时间的增加呈线性增加,但随HCN初始体积分数增加呈负幂函数的规律下降;MgO与HCN的反应级数α为0.72,表观活化能E为32.2 kJ/mol。     

物理法COD减排理论极限能耗的热力学分析

首先针对系统的可持续性发展提出了三点本质要求,在此基础上提出了基于减排过程节能机制的热力学框架,并根据热力学第一、第二定律建立了计算物理法脱除有机污染物理论极限能耗的热力学分析方法.此外,以典型有机污染物的脱除为例,分别计算了封闭体系中298.15K和1.01325×105Pa下不同初始浓度、不同种类以及不同COD减排量的有机污染物脱除的理论极限能耗.本文的计算结果表明,废水中有机污染物的减排需要很高的能耗,脱除相同量有机污染物所需的理论极限能耗随着初始浓度的减小而显著增加,且不同种类污染物处理的难易程度和能耗高低相差很大,这充分说明减排与节能有着密不可分的联系,充分考虑污染物的种类、物理化学性质、毒性和浓度将有助于减排政策的科学制定.     

Thermodynamic analysis of the theoretical energy consumption in the removal of organic contaminants by physical methods

The essential requirements for evaluating the sustainable development of a system and the thermodynamic framework of the energy conservation mechanism in the waste-removal process are proposed.A thermodynamic method of analysis based on the first and second laws of thermodynamics is suggested as a means to analyze the theoretical energy consumption for the removal of organic contaminants by physical methods.Moreover,the theoretical energy consumption for the removal by physical methods of different kinds of...     

Zeta电位法选择农药悬浮剂所需润湿分散剂

采用Zeta电位法对质量分数为20%的吡氟草胺悬浮剂所需润湿分散剂进行筛选,以激光粒度分布仪对实验体系的平均粒径(Dav)进行了验证。研究结果表明,除木质素磺酸钠以外,阴离子型润湿分散剂均可使体系的Zeta电位绝对值(│ζ│)达到40mV以上,体系较为稳定;阴离子型润湿分散剂NNO和MorwetD425复配后,相同使用量下体系的│ζ│较单一使用NNO和MorwetD425的大;当m(NNO):m(MorwetD425)=1:4,复配润湿分散剂的总质量分数为1%时,│ζ│达到最大值,颗粒平均粒径最小,热贮前后变化很小,体系达到最佳分散效果。因此,Zeta电位表征润湿分散剂在农药悬浮剂中的润湿分散性能与体系颗粒平均粒径的变化规律有良好的对应关系,故Zeta电位可作为表征润湿分散剂分散性能优劣的指标。     

Zeta potentials of PDMS surfaces modified with poly(ethylene glycol) by physisorption

Controlling zeta potential of PDMS surface coated with a layer of PEG is important for electroosmosis and electrophoresis in PDMS made microfluidic chips. Here, zeta potentials of PDMS surfaces modified by simple physisorption of PEG of different concentrations in phosphate buffer solutions, pure water, and PEG solution were reported. Coating PEG on PDMS surfaces was achieved by immersing a PDMS layer into the PEG solution for 10 min and then taking it out and placing it in an oven at 80℃ for 10 h. To avoid damaging the PEG layer on the PDMS surface, an induction current method was employed for zeta potential measurement. Zeta potentials of PEG modified PDMS in electrolyte solutions were measured. The results show that 2.5% PEG can effectively modify PDMS surface with positive zeta potential value in phosphate buffer solutions, pure water and 10% PEG solution. Further increase in PEG solution beyond 5% for surface modification has no obvious effect on zeta potential change.     

Interaction of Na2B12H11SH with liposomes: Influence on zeta potential and particle size

The interaction of Na₂B₁₂H₁₁SH (BSH) with liposomes has been studied. BSH is a compound used clinically in boron neutron capture therapy of glioblastoma, and is known to enter tumor cells. Liposomes were used as a model for studying the interaction of BSH with cell membranes. BSH led to changes in the zeta potential of liposomes consisting of DODAB (dioctadecyldimethylammonium bromide) alone or with DOPC (dioleylphosphatidylcholine) or DOPE (dioleylphosphatidylethanolamine). It also led to changes of the size of DODAB liposomes, with a maximum size at small zeta potentials. A firm binding of BSH with the head groups of the lipid must be assumed.     

Reaction of propionitrile with methylidyne: A theoretical study

The results of a CCSD(T)-F12/cc-pVTZ-f12//ωB97XD/cc-pVTZ quantum-chemical study of the potential energy surface (PES) for the reaction of propionitrile with methylidyne are combined with Rice-Ramsperger-Kassel-Marcus (RRKM) calculations of the reaction rate constants and product branching ratios in the deep space conditions corresponding to the zero-pressure limit at various collision energies. The most energetically favorable reaction pathways have been identified. The reaction outcome has been shown to strongly depend on the branching in the entrance reaction channel, between CH additions and insertions into various C-H and C-C bonds. For instance, CH addition to the N atom predominantly leads to 3H-pyrrole + H (p9), with CH₂NC + C₂H₄ (p2) also being a significant product. CH addition to the triple C≡N bond mostly results in 2-methylene-2H-azirine + CH₃ (p13), whereas CH insertions into C-H bonds in the CH₃ and CH₂ groups of propionitrile form CH₂CN + C₂H₄ (p1) and CH₂CHCN + CH₃ (p7) respectively. Less likely CH insertions into single C-C bonds yield CH₃CHCHCN + H (p5) and CH₂CHCH₂CN + H (p8). The results indicate that the methylidyne + propionitrile reaction may represent a critical step toward the formation of heterocyclic N-containing molecules in the interstellar medium and in planetary atmospheres.     

Transitional properties of starch colloid with particle size reduction from micro- to nanometer

High-pressure homogenization was used to disperse starch particles in water and reduce the size from micro- to nanometer. The resultant starch colloids were characterized by particle morphology, mean size, size distribution, and zeta potential. Starch slurries were transformed from a mixture containing sediment, dispersion, and sol, to gel as a result of reduction of the particle size from 3–6 μm to 10–20 nm under a pressure of 207 MPa. Furthermore, this process led to the transition of fluid properties without affecting the crystal structure and thermal stability of starch granules. Viscosity of the colloids increased with an increased number of homogenization passes, accompanied by a decreased particle size, narrower particle size distribution (PSD), and an increased absolute zeta potential, indicating the formation of a suspension or stable gel composed of nanoparticles. Lognormal and two other mathematical functions were established to describe the PSDs and their relationship to the homogenization passes. Hence, an environmentally friendly means of producing starch-based nanoparticles or nanogels with high yields, and predictable size and viscosity properties was presented.     

Study on the difference in adsorption thermodynamics for water on swelling and non-swelling clays with implications for prevention and treatment of pneumoconiosis

Excessive inhalation of mineral dust can cause irreversible damage such as diffuse fibrosis of lung tissue. Water-based dust reduction technology can effectively control the dust concentration. The study of the interaction of water-clay mineral dust is helpful to the prevention and treatment of pneumoconiosis by water-based dust removal technology. To better understand the underlying adsorption mechanisms of water molecules on clay mineral dust, the detailed adsorption thermodynamics analysis is necessary. In this paper, we research the thermodynamics of adsorption of water molecules on swelling clay of montmorillonite and non-swelling clay of illite. First, the adsorption isotherms of water molecules on montmorillonite and illite at 293–313 K were measured by gravimetric method. Then, the key thermodynamic variables, including entropy change (ΔS), surface potential (Ω), isosteric heat of adsorption (Q_st) and variation of Gibbs free energy (ΔG), were analyzed. Results illustrate that the adsorption amount for water molecules on illite is one order of magnitude smaller than that on montmorillonite, suggesting that swelling clay plays a dominant role in water molecules adsorption process. For water molecules adsorption on montmorillonite, the contribution of secondary adsorption to total adsorption (a₂/a) is always less than 30%. For water molecules adsorption on illite, the contribution of primary adsorption to total adsorption (a₁/a) is greater than a₂/a at the low pressure region, while a₂/a can exceed 60% at the high pressure region. The difference in the uptakes of water molecules adsorption on non-swelling and swelling clays is mainly resulted from the difference in primary adsorption on two clays. The Henry’s constant (K_AA) for montmorillonite is in the range of 21.37–75.08 mmol/g/kPa, which is evidently larger than the K_AA values of 0.34–0.98 mmol/g/kPa for illite. Compared with non-swelling clay, the adsorption spontaneity degree for water molecules on swelling clay is higher, and the interaction of swelling clay-water molecules is stronger. Meanwhile, the movement of adsorbed water molecules in swelling clay is more confined than that in non-swelling clay. These findings can offer meaningful guidelines for the prevention and treatment of pneumoconiosis.     

CE characterization of semiconductor nanocrystals encapsulated with amorphous silicium dioxide

The electrophoretic mobility of silica-encapsulated semiconductor nanocrystals (quantum dots) dependent on the pH and the ionic strength of the separation electrolyte has been determined by CE. Having shown the viability of the approach, the electrophoretic mobility mu of the nanoparticles investigated is calculated for varied zeta potential zeta, particle radius r, and ionic strength I employing an approximate analytical expression presented by Ohshima (J. Colloid Interface Sci. 2001, 239, 587-590). The comparison of calculated with measured data shows that the experimental observations exactly follow what would be expected from theory. Within the parameter range investigated at fixed zeta and I there is an increase in mu with r which is a nonlinear function. This dependence of mu on size parameters can be used for the size-dependent separation of particles. Modeling of mu as function of I and zeta makes it possible to calculate the size distribution of nanoparticles from electrophoretic data (using the peak shape of the particle zone in the electropherogram) without the need for calibration provided that zeta is known with adequate accuracy. Comparison of size distributions calculated via the presented method with size histograms determined from transmission electron microscopy (TEM) micrographs reveals that there is an excellent matching of the size distribution curves obtained with the two independent methods. A comparison of calculated with measured distributions of the electrophoretic mobility showed that the observed broad bands in CE studies of colloidal nanoparticles are mainly due to electrophoretic heterogeneity resulting from the particle size distribution.     

锰改性活性焦脱除合成气中单质汞的影响因素

采用等体积浸渍法制备了Mn改性活性焦吸附剂(Mn-AC),研究了模拟合成气(0.04%H2S、20%CO、30%H2、N2为平衡气体)下Mn-AC对单质汞的吸附特性,并利用BET、XPS、XRD等手段对吸附剂进行表征,分析了还原性气体对吸附剂脱汞性能的影响。结果表明,在模拟合成气气氛下,Mn-AC具有优异的汞脱除能力,200℃下2 h内平均汞脱除率达到84.3%。合成气中,H2S提供了具有脱汞能力的活性硫吸附位(Sad),显著地提高了Mn-AC的高温脱汞能力;H2消耗了吸附剂表面的活性氧,不利于活性硫的生成,CO消耗了生成的活性硫吸附位,两者对汞脱除均有抑制作用。高温下由于活性硫和汞的反应减弱,同时H2的抑制作用加强,吸附剂对单质汞的脱除能力下降。     

Optimization of the polyelectrolyte dosage for dewatering sewage sludge suspensions by means of a new centrifugation analyser with an optoelectronic sensor

The flocculation of sewage sludge with poly(diallyldimethylammonium chloride) (PDADMAC) as well as cationic, poly[acrylamide-co-(N,N,N-trimethylammoniumethylacrylate chloride)] (PTAC), and anionic acrylamide copolymers, poly(acrylamide-co-acrylate) (PAAM/AA), was investigated by using a new method to evaluate the velocity of centrifugal separation and the packing behaviour of the sediments. By means of a centrifugation analyser with an optoelectronic measuring system the position of the centrate/sediment interface of the conditioned suspensions can be determined as a function of the separation time, which allows the polyelectrolyte dosage to be optimized for various rotational speeds. At high centrifugal accelerations it was found that using the anionic polyelectrolyte PAAM/AA does not result in better dewatering performance, whereas both polycations recorded high degrees of separation. Furthermore, the measurements with the high-molar-mass PTAC indicate a high resistance to centrifugation which correlates with floc stability. In contrast, addition of the low-molar-mass PDADMAC gives more fragile flocs, leading to faster collapse of the sludge cake in the compression zone of the centrifuge at lower gravitational forces. These experimental findings agree well with the much higher filtration capacity of sludges conditioned with PTAC which was measured by means of a pressure filtration device. Comparisons of the optimum polyelectrolyte concentrations obtained by pressure filtration or centrifugation at low gravitational forces with the zeta potential of the flocculated particles appear to be consistent with bridge formation for PTAC and with the charge patch mechanism for PDADMAC. The centrifugation experiments at high centrifugal accelerations show an optimum separation efficiency at relatively low degrees of coverage and a high level of agreement with the large-scale process. Received: 24 November 1998 Accepted in revised form: 12 February 1999     

Bioaccumulation of arsenic by freshwater algae (Nostoc sp.) and the application to the removal of inorganic arsenic from an aqueous phase

An arsenic-resistant blue-green alga, Nostoc sp., was screened from an arsenic-polluted environment. The effects of the culture conditions on the growth and the arsenic bioaccumulation were investigated. In five culture media tested, Microcystis aeruginosa medium was found to be optimum for the growth. The effects of the concentration of five nutrients (P, Co, Fe, Mo and N) in the MA medium on arsenic bioaccumulation by the Nostoc sp. were also investigated. From the experimental results, the authors proposed a new culture medium which was designed for effective arsenic bioaccumulation by the Nostoc sp. The new medium was named the Modified MA medium (abbreviated as MMA). Removal of arsenic from an aqueous phase by means of arsenic bioaccumulation by the Nostoc sp. was investigated. When arsenic-polluted water was enriched with the nutrients of MMA, the arsenic level was found to be effectively lowered by the Nostoc sp. to 0.05 ppm.     

Dielectric relaxation spectroscopy of aqueous micellar electrolyte solutions: A novel application to infer Dukhin number and zeta potential of a micelle

The complex permittivities of aqueous SDS solutions, with and without the addition of sodium chloride (NaCl), are measured in the frequency range from 200 MHz to 14 GHz. The SDS concentrations are chosen such that the SDS molecules aggregate to micelles. In this frequency range, the measured spectra allow for the identification of two different relaxation processes. That is, the relaxation of the water molecules at frequencies above 1 GHz and the micellar relaxation at frequencies lower than 1 GHz. It is found that the addition of NaCl to the system mostly affects the micellar relaxation process. In detail, the time constant as well as the amplitude of the relaxation decrease by adding NaCl. These effects are attributed to the change in the solution conductivity that changes the properties of the micelle's electrical double layer. We also extract the Dukhin number of the micelles as a function of surfactant and electrolyte content from the measurements. The Dukhin number is a dimensionless group that describes the influence of the surface conductivity on a phenomena. A regression between Dukhin numbers and free sodium ions is found so that all data collapses on a single curve independent of the surfactant concentration. The surface conductivity is a manifestation of the electrical double layer and we use the Bikerman equation to infer the zeta potential of the micelles. Comparison to literature data shows very good agreement and proves that dielectric relaxation spectroscopy can be engaged to infer the zeta potential of micelles. Abbreviations: CMC critical micelle concentration, DRS dielectric relaxation spectroscopy, EDL electrical double layer     

The molecular structure and conformation of trichloronitromethane as determined by gas-phase electron diffraction and theoretical calculations

The molecular structure of trichloronitromethane has been studied in the gas phase using electron diffraction data. The molecules are found to undergo low barrier rotation about the CN bond with a planar CNO₂ moiety in agreement with HF/MP2/B3LYP/6-311G(d,p) calculations. The experimental data are consistent with a dynamic model using a potential function for the torsion of V = (V₆/2)(1 − cos 6τ). The major geometrical parameters (r_g and ) for the eclipsed form, obtained from least squares analysis of the data are as follows: r(NO₃) = r(NO₄) = 1.213(2) Å, r(CN) = 1.592(6) Å, r(CCl)_av = 1.749(1) Å, Cl₅CN/Cl₆CN = 109. 6°/106.3°(2), O₃NC/O₄NC = 117. 6°/114.1°(4), τCl₅C₁N₂O₃ = 0.0°, and V₆ = 0.20(25) kcal/mol.     

Influence of surface properties of particles on their adhesion and removal

The effect of surface properties of particles on their adhesion and removal was investigated using an immersed system consisting of nylon particles and a quartz plate. The nylon particles were dyed with a reactive dye in order to change their properties and were used for the adhesion and removal experiments in comparison with undyed particles. The electrokinetic potentials of the particles were measured by micro-electrophoresis and the Hamaker constants were independently evaluated using experimental values of dispersive component of surface free energy determined by the Wilhelmy technique. The experimental results were used for the discussion of particle adhesion and removal on the basis of the heterocoagulation theory. The differences in adhesion and removal efficiencies between dyed and undyed particles were explained in terms of the electrostatic and dispersive van der Waals interaction by considering the differences in thier properties, the electrokinetic potential and the Hamaker constant, due to dyeing.