Chemical functionalization of diatom silica microparticles for adsorption of gold (III) ions

Diatom silica microparticles from natural diatomaceous earth (DE) silica have been functionalized with 3-mercaptopropyltrimethoxysilane (MPTMS) and their application for adsorption of gold (III) ions from aqueous solutions is demonstrated. Fourier transform infrared spectroscopy (FTIR) and X-ray Photoelectron spectroscopy (XPS) analyses of the MPTMS modified diatom microparticles revealed that the silane layer with functional group (-SH) was successfully introduced to the diatom surface. The adsorption study of Au(III) ions using MPTMS-DE indicated that the process depends on initial gold (III) concentration and pH showing maximum adsorption capacity at pH = 3. The Au(III) adsorption kinetics results showed that the adsorption was very fast and followed a pseudo-second-order reaction model. The Langmuir model was used to provide a sound mechanistic basis for the theoretical of the adsorption equilibrium data. Gold recovery from MPTMS-DE structures was also investigated by using acidified thiourea solution and found to be high (> 95%). These results show that chemically modified DE microparticles can be used as a new, cost effective and environmentally benign adsorbent suitable for adsorption of gold metal ions from aqueous solutions.     

A nanoporous interferometric micro-sensor for biomedical detection of volatile sulphur compounds

ABSTRACT: This work presents the use of nanoporous anodic aluminium oxide [AAO] for reflective interferometric sensing of volatile sulphur compounds and hydrogen sulphide [H2S] gas. Detection is based on changes of the interference signal from AAO porous layer as a result of specific adsorption of gas molecules with sulphur functional groups on a gold-coated surface. A nanoporous AAO sensing platform with optimised pore diameters (30 nm) and length (4 μm) was fabricated using a two-step anodization process in 0.3 M oxalic, followed by coating with a thin gold film (8 nm). The AAO is assembled in a specially designed microfluidic chip supported with a miniature fibre optic system that is able to measure changes of reflective interference signal (Fabry-Perrot fringes). When the sensor is exposed to a small concentration of H2S gas, the interference signal showed a concentration-dependent wavelength shifting of the Fabry-Perot interference fringe spectrum, as a result of the adsorption of H2S molecules on the Au surface and changes in the refractive index of the AAO. A practical biomedical application of reflectometric interference spectroscopy [RIfS] Au-AAO sensor for malodour measurement was successfully shown. The RIfS method based on a nanoporous AAO platform is simple, easy to miniaturise, inexpensive and has great potential for development of gas sensing devices for a range of medical and environmental applications.     

Effect of preparation route on the microstructure and electrical conductivity of co-doped ceria

Dense Ce_0.8Sm_0.1Gd_0.1O_2?δ electrolytes were fabricated by sintering of CeO₂ solid solutions which were prepared from metal nitrates and NaOH using self propagating room temperature synthesis (SPRT). Three different routes were employed to obtain CeO₂ solid solution powders: (I) hand mixing of reactants, (II) ball milling of reactants and (III) ball milling of Ce_0.8Sm_0.2O_2?δ and Ce_0.8Gd_0.2O_2?δ solid solutions previously prepared by ball milling of corresponding nitrates and NaOH. Density measurements showed that ball milling, which is more convenient than hand mixing, is an effective way to obtain almost full dense samples after presureless sintering at 1550 °C for 1 h. These samples had larger grain size and consequently higher conductivity than the samples obtained by hand mixing. The highest conductivity of 2.704×10^?2 (Ω cm)^?1was measured at 700 °C in a sample prepared by route II. It was found that reduced grain size in samples obtained by hand mixing leads to a decrease in grain boundary conductivity and therefore decrease in the total conductivity. The results showed that mixing of single doped ceria solid solutions improved densification and inhibited grain growth.     

Outage analysis of selection diversity over Rayleigh fading channels with multiple co-channel interferers

In this paper an approach to the performance analysis of signal-to-interference (SIR) based selection combining (SC) operating over the Rayleigh fading channels experiencing an arbitrary number of multiple, Rayleigh co-channel interferers is presented. We have presented a general analysis of multibranch SC where each branch experiences an arbitrary number of multiple equal power co-channel interferers. Useful closed form expressions are derived for the probability density function (PDF) and cumulative distribution function (CDF) at the output of the combiner. Also an outage analysis is performed in order to show the effects of the number of multiple interferers, diversity order and input SIR unbalance to the system performances.     

Heating Cable Application in Solving Paraffin Deposition Problem in Tubing

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Effects of copper and Al2O3 particles on characteristics of Cu–Al2O3 composites

High-energy milling was used for production of Cu–Al₂O₃ composites. The inert gas-atomized prealloyed copper powder containing 2 wt.%Al and the mixture of the different sized electrolytic copper powders with 4 wt.% commercial Al₂O₃ powders served as starting materials. Milling of prealloyed copper powders promotes formation of nano-sized Al₂O₃ particles by internal oxidation with oxygen from air. Hot-pressed compacts of composites obtained from 5 and 20 h milled powders were additionally subjected to the high-temperature exposure in argon at 800 °C for 1 and 5 h. Characterization of processed material was performed by optical and scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), microhardness, as well as density and electrical conductivity measurements. Due to nano-sized Al₂O₃ particles microhardness and thermal stability of composite processed from milled prealloyed powders are higher than corresponding properties of composites processed from the milled powder mixtures. The results were discussed in terms of the effects of different size of starting copper powders and Al₂O₃ particles on the structure, strengthening of copper matrix, thermal stability and electrical conductivity of Cu–Al₂O₃ composites.     

Occlusion and ion exchange in the molten (lithium chloride-potassium chloride-alkali metal chloride) salt + zeolite 4A system with alkali metal chlorides of sodium, rubidium, and cesium

Interaction between molten salts of the type LiCl-KCl-MeCl (Me = Na, Rb, Cs, x _MeCl = 0 to 0.5, x _KCl/x _LiCl = 0.69) and zeolite 4A have been studied at 823 K. The main interactions between these salts and zeolite are molten salt occlusion to form salt-loaded zeolite and ion exchange between the molten salt and salt-loaded zeolite. No chemical reaction has been observed. The extent of occlusion is a function of the concentration of MeCl in the zeolite and is equal to 11±1 Cl⁻ per zeolite unit cell, (AlSiO₄)₁₂, at infinite MeCl dilution. The ion-exchange mole fraction equilibrium constants (separation factors) with respect to Li are decreasing functions of concentration of MeCl in the zeolite. At infinite MeCl dilution, they are equal to 0.84, 0.87, and 2.31 for NaCl, RbCl, and CsCl, respectively, and increase in the order Na<Rb<Cs at identical MeCl concentrations. The standard ion-exchange chemical potentials are equal to −(0.0±0.5) kJ·mol⁻¹, −(0.4±0.3) kJ·mol⁻¹, and −(6.5±0.5) kJ·mol⁻¹ for Na⁻, Rb⁻¹, and Cs⁺, respectively.     

An entropy generation metric for non-energy systems assessments

Processes in non-energy systems have not been as frequent a subject of sustainability studies based on Thermodynamics as have processes in energy systems. This paper offers insight into thermodynamic thinking devoted to selection of a sustainability energy-related metric based on entropy balancing of a non-energy system. An underlying objective in this sustainability oriented study is product quality involving thermal processing during manufacturing vs. resource utilization (say, energy). The product quality for the considered family of materials processing for manufacturing is postulated as inherently controlled by the imposed temperature non-uniformity margins. These temperature non-uniformities can be converted into a thermodynamic metric which can be related to either destruction of exergy of the available resource or, on a more fundamental level of process quality, to entropy generation inherent to the considered manufacturing system. Hence, a manufacturing system can be considered as if it were an energy system, although in the later case the system objective would be quite different. In a non-energy process, a metric may indicate the level of perfection of the process (not necessarily energy efficiency) and may be related to the sustainability footprint or, as advocated in this paper, it may be related to product quality. Controlled atmosphere brazing (CAB) of aluminum, a state-of-the-art manufacturing process involving mass production of compact heat exchangers for automotive, aerospace and process industries, has been used as an example.     

cis-1,3,4,6-Tetranitrooctahydroimidazo-[4,5-d]imidazole (BCHMX), its properties and initiation reactivity

Pre-treatment of simulated industrial wastewaters (SIM1, SIM2 and SIM3) containing organic and inorganic compounds (1,2-dichloroethane, sodium formate, sodium hydrogen carbonate, sodium carbonate and sodium chloride) by oxidative degradation using homogeneous Fenton type processes (Fe²⁺/H₂O₂ and Fe³⁺/H₂O₂) has been evaluated. The effects of initial Fe²⁺ and Fe³⁺ concentrations, [Fe^2+/3+], type of iron salt (ferrous sulfate vs. ferric chloride), initial hydrogen peroxide concentration, [H₂O₂], on mineralization extent, i.e., total organic content (TOC) removal, were studied. Response surface methodology (RSM), particularly Box–Behnken design (BBD) was used as modelling tool, and obtained predictive function was used to optimize the overall process by the means of desirability function approach (DFA). Up to 94% of initial TOC was removed after 120 min. Ferrous sulfate was found to be the most appropriate reagent, and the optimal doses of Fe²⁺ and H₂O₂ for reducing the pollutant content, in terms of final TOC and sludge production were assessed.     

Transverse bulk solid behaviour during discharge from troughed belt conveyors

Guidelines for the calculation of bulk solid material cross sectional dimensions and the influence of the belt conveyor transition length on the inclination of the trajectory at discharge are well established. However, not a great deal of research has been conducted on the influence of bulk solid material properties and conveyor belt transition geometry on the bulk solid material cross section at discharge. As such, assessment of cross section break-up associated with cohesive materials and transverse spreading of free flowing materials is missing. Conversely, the majority of discharge trajectory analysis techniques focus on analysis in a single vertical plane along the length of the belt.This paper presents an analysis of high speed conveyor discharge trajectories in three dimensions, taking into account transverse spreading of free flowing materials and shearing, or cross section discontinuity, exhibited by cohesive materials. Transverse bulk solid material behaviour and trajectory discharge is evaluated using a combination of experimental laboratory tests, a continuum mechanics approach incorporating CAD and Discrete Element Modelling (DEM). The work presented shows that bulk solid material behaviour at discharge is directly influenced by material characteristics and interactions resulting from the geometry of the belt conveyor transition zone.