Diffusion deposition of aerosol nanoparticles in model granular filters

The diffusion deposition of point aerosol particles from a flow in model granular (grained) filters, i.e., separate layers composed of parallel chains of spherical granules, has been studied at small Reynolds numbers. Numerical solution of the Stokes and convective diffusion equations has been employed to determine the drag forces and granule collection efficiencies as depending on the Peclet diffusion number in a range Pe = 0.02–2 × 10⁴ and the ratio between the granule diameter and the distance between chain axes. Layers of closed chains with square and hexagonal packings have been considered. Approximation formulas have been derived for calculation of nanoparticle penetration in model granular filters.     

Inertial deposition of aerosol particles from laminar flows in fibrous filters

The deposition of aerosol particles onto filter fibers under the effect of inertial forces is studied in a wide range of Stokes numbers (St) at Reynolds numbers close to unity (Re ∼ 1). Coefficients η of the capture of inertial particles with finite sizes in model filters composed of parallel rows of identical parallel fibers located normal to the direction of a flow are determined based on the numerical solution of the Navier-Stokes and particle motion equations. It is shown that, at Re < 1 and a constant particle-to-fiber radius ratio, R = r _p/a, number St uniquely characterizes capture coefficients η for particles with different densities, while, at Re ≥ 1, the capture coefficient depends on both St and Re. At constant R and St values, the larger Re the higher the capture coefficient. The influence of the structure of the model filter on pressure drop Δp and η is investigated. A nonuniform arrangement of fibers in rows is shown to increase the Δp/U ratio at lower Re values and to make the η -St dependence more pronounced than that for systems of uniformly ordered fibers. The results of calculations agree with the experimental data.     

Dispersed phase back transport during ultrafiltration of cutting oil emulsions with a spinning membrane disc geometry

A commercial centrifugal rotary membrane module was used for the ultrafiltration of oil–water emulsions (droplet radius 50–3000 nm). This configuration can achieve high shear rates (>10⁵ s⁻¹) which are decoupled from the bulk recirculation rate. Fluxes were in the pressure controlled regime above 600 rpm with transmembrane pressures up to 345 kPa. The pressure dependent flux behaviour suggests that concentration polarization or gel formation was minimal. The dominant back transport mechanism was determined by comparing various back transport mechanisms to the permeation drag force. Back transport mechanisms included Brownian diffusion, shear induced diffusion, lateral migration, viscous drag, centrifugal and DLVO forces. The effect of the membrane surface porosity and Sherwood's correction for Stokes's law on the permeation drag were also studied. Viscous drag was the dominant force on droplet sizes between 50–1000 nm and was the only mechanism which could overcome the permeation drag force. Lateral migration was significant for droplets between 1000–3000 nm which were present in small quantities.     

Numerical Analysis of 3‐D Flow Past a Stationary Sphere with Slip Condition at Low and Moderate Reynolds Numbers

Computations are performed to determine the steady 3‐D viscous fluid flow forces acting on the stationary spherical suspended particle at low and moderate Reynolds numbers in the range of 0.1≤Re≤200. A slip is supposed on the boundary so that the slip velocity becomes proportional to the shear stress. This model possesses a single parameter to account for the slip coefficient λ (Pa.s/m), which is made dimensionless and is called Trostel number (Tr=λ a/μ). Decreasing slip, increases drag in all Reynolds limits, but slip has smaller effects on drag coefficient at lower Reynolds number regimes. Increasing slip at known Reynolds number causes to delay of flow separation and inflect point creation in velocity profiles. At full slip conditions, shear drag coefficient will be zero and radial drag coefficient reaches to its maximum values. Flow around of sphere at full‐slip condition is not equal to potential flow around a sphere. Present numerical results corresponding to full slip (Tr→0) are in complete accord with certain results of flow around of inviscid bubbles, and the results corresponding to no‐slip (Tr→∞) have excellent agreement with the results predicted by the no‐slip boundary condition.     

Viscosity and Thermodynamics of Viscous Flow for the Systems of Isomeric Pentanols with Toluene

Viscosities of the isomers of pentanol (1-pentanol, 2-pentanol and 3-pentanol) and their binary solutions with toluene in the whole range of composition have been measured at different temperatures between 303.15 and 323.15 K. Viscosities of pure components have been plotted against temperature and for binary mixtures, against the mole fraction of pentanols at different temperatures. At lower concentrations of pentanols, viscosities increase slowly, but at an increasing rate on the continued addition of pentanols in toluene. The excess viscosities and excess free energies of activation for viscous flow are in the order, 3-pentanol + > 2-pentanol + > 1-pentanol + toluene. Excess entropies are found to be negative for the systems 2-pentanol + toluene and 3-pentanol + toluene in the whole range of composition, but for 1-pentanol + toluene the values are small and they are either positive or negative at different compositions. The disruption of H-bonds in pentanols either by thermal effect or by the force of dispersion is in the order: 3-pentanol > 2-pentanol > 1-pentanol. This effect is considered to be quite significant in explaining the temperature dependence of viscosity of pure pentanols, negative excess values of viscosity, free energy and entropy for viscous flow as well as their orders for all the systems.     

The effect of gas slip on pressure drop and deposition of submicron particles in model granular filters

The Stokes flow field and aerosol particle deposition from flows in model filters, i.e., separate layers of granules with square and hexagonal structures, have been calculated taking into account the effect of gas slip at granule surface. Approximating formulas have been derived for granule drag forces to a flow. The efficiencies of diffusion collection of particles have been calculated in a wide range of Peclet numbers with allowance for a finite particle size and the existence of a Knudsen boundary layer, the layer thickness being comparable with the particle sizes. The applicability of the cell model to the calculation of granular filters has been discussed.     

Role of Vitamins B-3 and C in the Fashioning of Granules in UASB Reactor Sludge

Whereas a myriad of possible factors have been reported which effect the formation of granules in a upflow anaerobic sludge blanket (UASB) reactor and influence their properties, there is no study on the effect of vitamins on the granulation of UASB reactor sludge. The present study was undertaken to bridge this gap. It was seen that vitamins helped in better granule formation??as reflected by favorable size distribution, sludge volume index, and settling velocity??compared to controls. The vitamin-spiked reactors also achieved >85?% COD removal efficiency in half the number of days the unspiked reactors took. The vitamin supplements were effective at concentrations????1?mg/l. Hence, their use in expediting granule formation as also in developing better-quality granules appears economically viable.     

Production of carrier free <Superscript>188</Superscript>Re radioisotope generator based on aluminum tungstate matrix

Improved radionuclide generator include a substantially insoluble salt of a radioactive parent which may be directly packed in column for subsequent elution of the daughter radionuclide. An improved ¹⁸⁸Re generator was prepared by reacting a radioactive tungsten (¹⁸⁸W) as parent radionuclide incorporated with aluminum chloride to obtain an insoluble radioactive aluminum tungstate matrix. The investigated matrix was characterized on the basis of the chemical composition, IR, thermal analysis and mechanical stabilities. The factors affecting the elution performance were studied such as influence of pH, molar ratio and drying temperature. From the obtained data, the molar ratio W:Al was 1.5:1 at pH = 4, the matrix dried at 105 °C for 2 h. Chromatographic and multichannel analysis has been currently used to investigate the radiochemical and radionuclidic purity respectively on eluted ¹⁸⁸Re. An elution yield more than 80%, with radiochemical purity <98% and radionuclidic purity <99% with a ¹⁸⁸W break through >10⁻⁴% of the column. The Al⁺³ and W contents value were about 2 and 3 μg/mL eluate. The obtained data approved the stability of the prepared generator and its suitability for medical application.     

Untersuchungen an Metallkatalysatoren. XVIII. Zur Phasengestaltung,Dispersität und Oberflächenzusammensetzung von Ni?Cu?Re?Katalysatoren

Investigations on Metal Catalysts. XVIII. Phase Shaping, Dispersity, and Surface Composition of Ni? Cu? Re Catalysts Catalysts of the system Ni? Cu? Re reduced at 500°C consist of the following phases: only one f.c.c. phase in Ni? Cu samples, in Ni? Cu? Re samples with ≥10 at.-% Re there is an additional h.c.p. phase (pure Re). The greatest solubility in regard to rhenium (but never > 10 at.-%) was observed in the case of catalysts with a Ni:Cu ratio of 1:1. Ni? Cu? Re samples show considerably higher surface areas than the nickel sample. The catalyst Ni 45 Cu 45 Re 10 exhibits the maximum surface area. The surface layer of the crystallites is enriched with copper.     

A new procedure for determining copper in igneous rock and alloys

The influence of cationic surfactants, cetylpyridinium chloride (CPC), cetylpyridinium bromide (CPB), and cetyltrimethylammonium bromide (CTMAB), on the complexation of copper(II) with thenoyl-(2-oxopropyl)-N-(2-sulfo-4-nitro-5-oxyphenyl) azomethine (R) has been investigated. It has been found that monoligand compounds are formed at pH 4, while at pH 3 the formation of mixed-ligand compounds is observed. The detection limit for copper decreases and the stability constants of the complexes increase in the row Cu-R-CPC > Cu-R-CPB > Cu-R-CTMAB, with AN increase in the stability of the associates (Rh-CPC > R-CPB > R-CTMAB) in the complexation reaction. The ratio of components in monoligand (1: 1) and mixed-ligand (1: 1: 1) compounds has been determined. The limits of obedience to the Beer law have been found. A procedure has been developed for the photometric determination of copper in igneous rock and alloys.     

Cyclohexene Hydroconversion Using Monometallic and Bimetallic Catalysts Supported on γ‐Alumina

The hydroconversion of cyclohexene (CHE) using monometallic catalysts containing 0.35wt% of Pt, Pd, Ir or Re on a γ‐alumina support, as well as bimetallic catalysts containing combinations of 0.35wt% Pt with 0.35wt% of either Pd, Ir or Re on γ‐alumina, were investigated in a plug flow‐type fixed‐bed reactor. The Cyclohexene (CHE) feed was injected continuously with a rate of 8.33 × 10^?3mole h^?1 on 0.2 g of catalyst using a simultaneous hydrogen gas flow of 20 cm³ min^?1 throughout a broad reaction temperature range of 50–400 °C. The dispersion of the metals in the catalysts was determined via H₂ or CO chemisorption. The activities of the monometallic catalysts were found to be in the order: Pd > Pt > Ir > Re, whereas those of the bimetallic catalysts were in the order: PtPd > PtIr > PtRe. Cyclohexene hydrogenation and dehydrogenation reactions using the current mono‐ and bimetallic catalysts were kinetically investigated applying the absolute reaction rate theory, whereby reaction rate constant, activation energy, enthalpy and entropy of activation were computed to explain surface variations on these catalysts.     

Assembly of long carbon nanotube bridges across transparent electrodes using novel thickness-controlled dielectrophoresis

The assembly of carbon nanotubes (CNTs) across planner electrodes using dielectrophoresis (DEP) is one of the standard methods used to fabricate CNT-based devices such as sensors. The medium drag velocity caused by electrokinetic phenomena such as electrothermal and electroosmotic might drive CNTs away from the deposition area. This problem becomes critical at large-scale electrode structures due to the high attenuation of the DEP force. Herein, we simulated and experimentally validated a novel DEP setup that uses a top glass cover to minimize the medium drag velocity. The simulation results showed that the drag velocity can be reduced by 2–3 orders of magnitude compared with the basic DEP setup. The simulation also showed that the optimum channel height to result in a significant drag velocity reduction was between 100 μm and 240 μm. We experimentally report, for the first time, the assembly and alignment of CNT bridges across indium tin oxide (ITO) electrodes with spacing up to 125 μm. We also derived an equation to optimize the CNT's concentration in suspensions based on the electrode gap width and channel height. The deposition of long CNTs across ITO electrodes has potential use in transparent electronics and microfluidic systems.     

Synthesis,crystal structure,and photoelectric properties of Re(CO)(3)ClL (L = 2-(1-ethylbenzimidazol-2-yl)pyridine)

A novel Re(I) complex, Re(CO)(3)ClL (L = 2-(1-ethylbenzimidazol-2-yl)pyridine), has been synthesized and structurally characterized by single-crystal X-ray diffraction analysis. Crystal data for C(17)H(13)ClN(3)O(3)Re: space group, orthorhombic, Pbca; a = 12.713(6) A; b = 15.103(7) A; c = 18.253(8) A; Z = 8. Stable vacuum vapor deposition of the Re complex has been verified by UV-vis and infrared spectroscopy. A two-layer electroluminescent device with configuration of ITO/TPD/Re(CO)(3)ClL/Mg(0.9)Ag(0.1)/Ag has been fabricated, which gave a turn-on voltage of as low as 3 V and a maximum luminance of 113 cd/m(2) at a bias voltage of 10.5 V, and confirmed that the Re complex can function as a bright orange-red emitter and an electron transport material in an electroluminescent device.     

Improving the Photocatalytic Reduction of CO2 to CO through Immobilisation of a Molecular Re Catalyst on TiO2

The photocatalytic activity of phosphonated Re complexes, [Re(2,2′‐bipyridine‐4,4′‐bisphosphonic acid) (CO)₃(L)] (ReP; L=3‐picoline or bromide) immobilised on TiO₂ nanoparticles is reported. The heterogenised Re catalyst on the semiconductor, ReP–TiO₂ hybrid, displays an improvement in CO₂ reduction photocatalysis. A high turnover number (TON) of 48 mol_CO mol_Re^?1 is observed in DMF with the electron donor triethanolamine at λ>420 nm. ReP–TiO₂ compares favourably to previously reported homogeneous systems and is the highest TON reported to date for a CO₂‐reducing Re photocatalyst under visible light irradiation. Photocatalytic CO₂ reduction is even observed with ReP–TiO₂ at wavelengths of λ>495 nm. Infrared and X‐ray photoelectron spectroscopies confirm that an intact ReP catalyst is present on the TiO₂ surface before and during catalysis. Transient absorption spectroscopy suggests that the high activity upon heterogenisation is due to an increase in the lifetime of the immobilised anionic Re intermediate (t_{50 %}>1 s for ReP–TiO₂ compared with t_{50 %}=60 ms for ReP in solution) and immobilisation might also reduce the formation of inactive Re dimers. This study demonstrates that the activity of a homogeneous photocatalyst can be improved through immobilisation on a metal oxide surface by favourably modifying its photochemical kinetics.     

Radium desorption, manganese and iron dissolution from sand filters of a conventional ground water treatment plant under reductive conditions

Summary Sand filters are used as a filter bed in many ground water treatment plants to remove the physical contaminants and oxidation products. A build-up of radioactivity may take place on the granules, where iron and manganese oxides are deposited and form thin films on the surface of sand filter. The oxides of iron and manganese play an important role in adsorbing radium from ground water. The disposal of those granules makes a significant problem. A batch technique is used for solubilization of radium from sand filters in the presence of some organic acids, which act as reducing agents. These acids are formic acid, acetic acid, benzoic acid, succinic acid, oxalic acid, phthalic acid, and adipic acid. The data were obtained as a function of acidity, temperature, contact time and liquid/solid ratio particle size and shaking speed. It was found that oxalic acid was the best for radium removal. The effectiveness of these acids on radium removal was as follows: oxalic acid > phthalic acid > adipic acid > succinic acid > formic acid > acetic acid. The maximum removal obtained was 69.9% at 1M oxalic acid at 8 ml/g ratio. Reaction kinetics and mechanism parameters of the dissolution process were studied and compared with other published data.     

Poly (vinyl chloride) decomposition in solution

Thermal degradation of PVC in various solvents at 180° has been observed to be in the following order: benzonitrite > nitrobenzene > cyclohexanone > dioctyl phthalate > α-bromonaphthalane > decahydronaphthalene. The effect has been explained on the basis of β-eliminations of E₁-type favoured by polar solvents. An inhibition in PVC degradation has been observed in nitrobenzene containing stationary hydrogen chloride gas. The deceleration in degradation by predissolved HCl has been accounted for as a Mass Law effect.     

Cathodic electrophoretic deposition of manganese dioxide films

Cathodic electrophoretic deposition (EPD) method has been developed for the deposition of manganese dioxide films. It was shown that phosphate ester (PE) is an effective charging additive, which provides stabilization of manganese dioxide nanoparticles in suspensions. The influence of PE concentration and deposition voltage on the deposition efficiency has been studied. EPD has been utilized for the fabrication of porous nanostructured films with thickness in the range of 0.5–20 μm for application in electrochemical supercapacitors (ES). Cyclic voltammetry and chronopotentiometry data for the films tested in the 0.1 M Na₂SO₄ solutions showed capacitive behavior in the voltage window of 1 V. The highest specific capacitance (SC) of 377 F g⁻¹ was obtained at a scan rate of 2 mV s⁻¹. The SC decreased with increasing film thickness and increasing scan rate in the range of 2–100 mV s⁻¹. The deposition mechanism, kinetics of deposition and charge storage properties of the films are discussed.     

Hollow capsules formed in a single stage via interfacial hydrogen-bonded complexation of methylcellulose with poly(acrylic acid) and tannic acid

Hollow capsules can be prepared in a single stage by the interfacial complexation of methylcellulose (MC) with poly(acrylic acid) (PAA) or tannic acid (TA) via hydrogen bonding in aqueous solutions. The formation of capsules is observed when viscous solution of methylcellulose is added drop-wise to diluted solutions of polyacids under acidic conditions. The optimal parameters such as polymer concentration and solution pH for the formation of these capsules were established in this work. It was found that tannic acid forms capsules in a broader range of concentrations and pHs compared to poly(acrylic acid). The TA/MC capsules exhibited better stability compared to PAA/MC in response to increase in pH: the dissolution of TA/MC capsules observed at pH > 9.5; whereas PAA/MC capsules dissolved at pH > 3.8. The interfacial complexation can be considered as a potential single stage alternative to the formation of capsules using multistage layer-by-layer deposition method.     

不同饥饿时间下稳态好氧颗粒污泥系统的特性和动力学分析

较长的饥饿时间是好氧颗粒污泥驯化形成的关键条件. 但在稳态颗粒污泥系统中, 饥饿时间长短对颗粒污泥的影响还不清楚. 因此本实验采用四个序批式反应器(SBR), 分别在好氧饥饿时间为1、2、3和4 h(R1~R4)条件下运行, 研究了饥饿时间对稳态好氧颗粒污泥系统的运行和特性等方面的影响. 结果表明: 对于稳态的好氧颗粒污泥系统, 较长饥饿时间已不是保持污泥颗粒化的关键因素, 系统在饥饿时间缩短后依然会保持污泥颗粒化和稳定运行效果. 四种饥饿时间条件下反应器中COD去除效果没有表现出明显差异, COD平均去除率都几乎为98%以上. 但在不同饥饿时间条件下, 好氧颗粒污泥的性质有很大差别. 在 35天实验运行中, 与较长饥饿时间相比, 饥饿时间的缩短会使污泥中胞外聚合物含量降 低, 但PN/PS值会提高约6%左右, 好氧颗粒直径增大. 同时, 当饥饿时间大于2 h会使颗粒污泥中丝状菌过度生长, SVI30值升高约1.5倍, 并且导致颗粒的物理性质降低. 但是, 动力学分析指出R1~R4的有机污染物降解速率在0.25~0.29 h^-1之间, 较短饥饿时间的系统虽具有较高的qmax值, 可是并不明显. 并且R1~R4系统的饱和常数(K)和产率系数(Y)分别在5.39~8.45 mg/L和 0.391~0.746 kgMLVSS/kgCOD, 较短饥饿时间的系统会具有较高的COD出水浓度和剩余污泥产率. 综上, 好氧颗粒污泥驯化成功后, 稳态的颗粒污泥系统不再需要在较长饥饿时间条件下运行, 可以适当缩短反应时间, 这不仅仅可以节约运行成本, 降低不必要的能源消耗, 还可以使系统具有较高的稳定性能.