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61.
Boron is an essential micronutrient for plants and animals as well as a useful component for numerous industries. It is necessary to produce low boron containing water from RO desalination plants for both human consumption and for agriculture. For plants, a small amount of boron is necessary for their growth and development, but boron becomes toxic if the amount is slightly greater than required. Desalinated seawater from RO plants often contains high boron content and, when used for irrigation, has been proven to be damaging to crops including blackberry, lemon, and grapefruit. Apart from the toxic effects of boron on plants, boron should be removed from RO desalination plants to comply with the current guideline value, 0.5 mg/L, for potable water issued by the World Health Organisation (WHO). Currently there is no simple method to remove boron from saline water. The use of multi-pass reverse osmosis membrane (RO) with pH modification and the use of ion exchange using boron selective resins (BSRs) have both been considered as effective methods for the removal of boron. A hybrid process, Adsorption Membrane Filtration (AMF), has received attention as an emerging technology for boron removal with a high efficiency and low operating costs. The purpose of this review is to give an overview on boron in general and to discuss its toxicity. The problems of boron in the MENA (Middle East and North Africa) region are discussed as well as technologies, current and future, for the removal of boron from seawater. The focus is placed on current RO and ion exchange methodologies using BSRs as well as the future for the AMF method. The fundamentals of each process, the effects of experimental parameters, and findings are discussed. 相似文献
62.
In the present study comparative electrochemical study of methanol electro-oxidation reaction, the effect of ruthenium addition and experimental parameters on methanol electro-oxidation reaction at high performance carbon supported Pt and Pt–Ru catalysts have been studied by cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) in H2SO4 (0.05–2.00 M) + CH3OH (0.01–4.00 M) at 20–70 °C. Tafel plots for the methanol oxidation reaction on Pt and Pt–Ru catalysts show reasonably well-defined linear region with the slopes of 128–174 mV dec−1(α = 0.34–0.46). The activation energies from Arrhenius plots have been found as 39.06–50.65 kJ mol−1. As a result, methanol oxidation is enhanced by the addition of ruthenium. Furthermore, Pt–Ru (25:1) catalyst shows best electro–catalytic activity, higher resistance to CO, and better long term stability compared to Pt–Ru (3:1), Pt–Ru (1:1), and Pt. Finally, the EIS measurements on Pt–Ru (25:1) catalyst reveals that methanol electro-oxidation reaction consists of two process: methanol dehydrogenation step at low potentials (<700 mV) and the oxidation removal of COads by OHads at higher potentials (>700 mV). 相似文献
63.
Aykut Caglar Tekin Sahan M. Selim Cogenli Ayse Bayrakceken Yurtcan Nahit Aktas Hilal Kivrak 《International Journal of Hydrogen Energy》2018,43(24):11002-11011
At present, carbon nanotube supported Pd catalysts are synthesized via NaBH4 reduction method to investigate their electro catalytic activity thorough formic acid electro oxidation. In order to optimize the synthesis conditions such as %Pd amount (X1), NaBH4 amount (times, X2), water amount (ml, X3), and time (min., X4), Central Composite Design (CCD) experiments are designed and determined by the Design-Expert program to determine the maximum observed current (mA/mgPd). Formic acid electro oxidation current density of the catalyst is computed by the model as 974.80 mA/mg Pd for the catalyst prepared at optimum operating conditions (41.14 for %Pd amount, 280.23 NaBH4 amount, 26.80 ml water amount, and 167.14 min time) obtained with numerical optimization method in CCD. This computed value is very close to the experimentally measured value as 920 mA/mg Pd. Finally, formic acid fuel cell measurements were performed on the Pd/CNT catalyst prepared at optimum operating conditions and compared with the commercial Pd black and Pt black catalysts. As a result, Pd/CNT exhibits better performance compared to Pd black, revealing that Pd/CNT is a promising catalyst for the direct formic acid fuel cell measurements. 相似文献
64.
Z. H. Cho Y. S. Kim S. K. Hilal Y. H. Kim 《International journal of imaging systems and technology》1989,1(2):196-206
A new spherical PET using Fresnel aperture is being designed, and construction is in progress. In the new design, the original spherical geometry is modified to accommodate a more flexible gantry construction and data processing while preserving the focused geometry of the original design. The performance of this new Fresnel aperture-SPET (F-SPET) is expected to follow closely with that of the original S-PET design. An analysis of an F-SPET designed with nine modular layers, with each modular layer being four rings, was performed in terms of the counting statistics and solid angle and compared with the original S-PET as well as the conventional cylindrical PET. According to the simulation results, the sensitivity gain of the Fresnel aperture-SPET remains a factor of 2 over the equivalent cylindrical system and has nearly the same performance as the original S-PET, while offering a simpler means in construction and data handling for the image reconstruction. 相似文献
65.
66.
Estimates of the helium requirements for superconductive magnetic energy storage, magnetically confined fusion reactors, superconducting power transmission lines, magnetohydrodynamic units, superconducting motors and generators, and particle accelerators are presented. The approach entails surveying estimates from system studies, then developing simple scaling laws to calculate helium inventories. Helium loss rates are discussed and applied to estimate annual helium makeup. 相似文献
67.
The aim of this paper was to investigate the feasibility of the removal of phosphate from aqueous solution by electro-coagulation (EC). The current density (CD) between 2.5 and 10 mA cm(-2) and duration in the limits of 5-20 min were tried for different concentrations. In order to determine optimal operating conditions, the EC process used for the phosphate removal was examined in dependence with the CD, initial concentrations and time. The results of the experimental batch processing showed high effectiveness of the EC method in removing phosphate from aqueous solutions. 相似文献
68.
Ozlem Sahin Derya Duzenli Hilal Kivrak 《Energy Sources, Part A: Recovery, Utilization, and Environmental Effects》2016,38(5):628-634
Carbon supported Pt-Ru catalysts were prepared at varying Pt:Ru ratios by polyol method. The crystallite sizes of these catalysts were determined by X-ray diffraction technique. The specific surface areas of these catalysts were also defined by Brunauer–Emmett–Teller technique. Cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy measurements were conducted on these carbon supported Pt-Ru catalysts to investigate the effect of ruthenium on the ethanol electrooxidation kinetics. Results indicated that Pt-Ru (25:1) catalyst showed the best ethanol electrooxidation activity. In conclusion, ethanol electrooxidation mechanism was proposed. 相似文献
69.
The water extract of the mountain tea was spray-dried by using different food hydrocolloids viz. β-cyclodextrin (BCD), arabic gum (AG), and maltodextrins (MD19 and MD12) as carrier materials. Powdered samples were then subjected to product yield, moisture content, water activity, bulk density, solubility, color (Lab) and SEM particle microstructure analyses. Furthermore, color (Lab), turbidity (NTU), total phenolic content (TPC), total antioxidant activity (TAA) and volatile compound (β-pinene) analyses were performed on the reconstituted mountain tea samples. The product yield increased with the addition of the carrier materials whereas decreased at higher drying temperatures. The inlet air temperature of 155 °C provided the better retention for β-pinene. Almost all physicochemical properties of the spray-dried mountain tea samples were significantly (P < 0.05) affected by the inlet air temperature, the type and concentration of the carrier materials. 相似文献
70.
Hilal Balout Pascal Boulet Marie-Christine Record 《Journal of Electronic Materials》2014,43(10):3801-3807
The purpose of this work was to investigate, by numerical simulation, the effect of isotropic and anisotropic strain on the transport properties of Mg2Si. Analysis of the effects of temperature and charge-carrier concentration on evolution of the energy gap and on the thermoelectric properties of strained Mg2Si is also reported in this paper. Gap evolution is highly dependent on the type of strain applied to the structure. The Seebeck coefficient (S) and power factor (PF) are strongly modified; a gain of up to 40% can be obtained for S and up to 100% for PF under specific conditions of strain. In most cases the temperature corresponding to the maximum value of PF was found to shift downward under the effect of strain. 相似文献