Effect of chloride ions on the kinetics of nitrobenzene reduction by powdered iron

2006 ◽  
Vol 60 (5) ◽  
Author(s):  
M. Heželová ◽  
L’. Pikna ◽  
D. Kladeková ◽  
L. Lux
Keyword(s):  
Specific Surface ◽  
Reaction System ◽  
Particulate Material ◽  
Surface Reactivity ◽  
Chloride Ions ◽  
Free Medium ◽  
Iron Particles ◽  
Nitrobenzene Reduction ◽  
Powder Particles ◽  
Kinetics Of

AbstractThe effect of different chloride ions concentrations on the reactivity of iron particles was studied using chronopotentiometry. It was found that the increase of Cl− ions concentration accelerated anodic dissolution of iron, thus enhancing its surface reactivity. This fact was confirmed also by the rate of nitrobenzene reduction by iron particles. The reactivity of powder particles of various sizes, hence of different specific surface, was investigated in chloride-free and chloride-containing acetate buffer electrolytes. Experimental results indicated that the rate of nitrobenzene reduction in the presence of chloride ions in the reaction system is faster in comparison with the rate in chloride-free medium for each studied grain fraction of particulate material.

DECHLORINATION OF CARBON TETRACHLORIDE BY NANOSCALE IRON PARTICLES IN AQUEOUS SOLUTION HSING-LUNG LIEN WEI-XIAN ZHANG Department of Civil and Environmental Engineering, Lehigh University, Bethlehem, PA 18015 INTRODUCTION Recently, a method for the generation of very small (nanoscale) bimetallic particles has been reported [1,2]. These nanoscale metal particles typically have a diameter on the order of 1-100 nm and feature 0.06% by weight of palladium deposited on the surface of iron. Advantages of the nanoscale bimetallic system for treatment of chlorinated organic pollutants include: (1) High specific surface area. The nanoscale metal particles have a specific surface area around 35 m2/g. Tens to hundreds times higher than those of the commercial grade iron particles (used in conventional iron walls). (2) High surface reactivity. For example, values of surface-area-normalized rate coefficient (KSA) for the transformation of chlorinated ethylenes were about one to two-orders of magnitude higher than those reported in the literature for commercial grade iron particles [3]. Due to their small particle size and high reactivity, the nanoscale metal particles may be useful in a wide array of environmental applications. In the aqueous phase, the nanoscale iron particles remain suspended, almost like a homogenous solution. Theoretical calculations indicate that, for colloidal particles less than about 1 micrometer, gravity of the metal particles is insignificant to influence the particle movement. Brownian motion (thermal movement) tends to dominate the transport process in groundwater. Thus, we believe that the metal particles could be injected directly into contaminated soils, sediments and aquifers for in situ remediation of chlorinated hydrocarbons, offering a cost-effective alternative to such conventional technologies as pump-and-treat, air sparging or even conventional iron reactive walls. Design, construction and operation of such injectable systems should be reasonably straightforward.

2014 ◽  
pp. 69-69
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Contaminated Soils ◽  
Surface Reactivity ◽  
Metal Particles ◽  
Iron Particles ◽  
Commercial Grade ◽  
Lehigh University ◽  
Nanoscale Iron Particles

Kinetics of the catalytic hydrodesulphurization reaction system; hydrogenolysis of thiophene

1980 ◽  
Vol 45 (10) ◽  
pp. 2728-2741 ◽  
Author(s):  
Pavel Fott ◽  
Petr Schneider
Keyword(s):  
Atmospheric Pressure ◽  
Active Sites ◽  
Flow Reactor ◽  
Kinetic Equations ◽  
Reaction System ◽  
Reaction Products ◽  
Molybdenum Catalyst ◽  
Cobalt Molybdenum Catalyst ◽  
Kinetics Of ◽  
Reaction Schemes

Kinetics have been studied of the reaction system taking place during the reaction of thiophene on the cobalt-molybdenum catalyst in a gradientless circulation flow reactor at 360 °C and atmospheric pressure. Butane has been found present in a small amount in the reaction products even at very low conversion. In view of this, consecutive and parallel-consecutive (triangular) reaction schemes have been proposed. In the former scheme the appearance of butane is accounted for by rate of desorption of butene being comparable with the rate of its hydrogenation. According to the latter scheme part of the butane originates from thiophene via a different route than through hydrogenation of butene. Analysis of the kinetic data has revealed that the reaction of thiophene should be considered to take place on other active sites than that of butene. Kinetic equations derived on this assumption for the consecutive and the triangular reaction schemes correlate experimental data with acceptable accuracy.

The Reactivity of Different Active Forms of Sodium Carbonate with Respect to Sulfur Dioxide

1992 ◽  
Vol 57 (11) ◽  
pp. 2302-2308
Author(s):  
Karel Mocek ◽  
Erich Lippert ◽  
Emerich Erdös
Keyword(s):  
Thermal Decomposition ◽  
Liquid Phase ◽  
Sulfur Dioxide ◽  
Specific Surface ◽  
Surface Area ◽  
Sodium Carbonate ◽  
Room Temperature ◽  
Active Form ◽  
The Other ◽  
Kinetics Of

The kinetics of the reaction of solid sodium carbonate with sulfur dioxide depends on the microstructure of the solid, which in turn is affected by the way and conditions of its preparation. The active form, analogous to that obtained by thermal decomposition of NaHCO3, emerges from the dehydration of Na2CO3 . 10 H2O in a vacuum or its weathering in air at room temperature. The two active forms are porous and have approximately the same specific surface area. Partial hydration of the active Na2CO3 in air at room temperature followed by thermal dehydration does not bring about a significant decrease in reactivity. On the other hand, if the preparation of anhydrous Na2CO3 involves, partly or completely, the liquid phase, the reactivity of the product is substantially lower.

scholarly journals Factors affecting the permeability of isolated fat-cells from the rat to [42K]potassium and [36Cl]chloride ions

1970 ◽  
Vol 117 (3) ◽  
pp. 615-621 ◽  
Author(s):  
M. C. Perry ◽  
C. N. Hales
Keyword(s):  
Initial Phase ◽  
Chloride Ions ◽  
Fat Cells ◽  
Adrenocorticotrophic Hormone ◽  
Isolated Fat Cells ◽  
Free Medium ◽  
Fat Cell ◽  
Factors Affecting ◽  
Exchange Diffusion ◽  
High K

1. The effluxes of 42K+ and 36Cl− from isolated fat-cells from the rat were studied under a variety of conditions known to affect the metabolism of the cells. 2. 42K+ efflux from isolated fat cells was increased in a Na+-free–high-K+ medium and decreased in a K+-free medium. The existence of K+ exchange diffusion across the fat-cell membrane is suggested. 3. 36Cl− efflux from isolated fat-cells was decreased when the Cl− component of the wash medium was replaced by acetate. The basal 36Cl− efflux is suggested to be partly by Cl− exchange diffusion and partly in company with a univalent cation. 4. A variety of lipolytic stimuli, adrenaline, adrenocorticotrophic hormone, N-6,O-2′-dibutyryladenosine cyclic 3′:5′-monophosphate and theophylline, increased 42K+ efflux from isolated fat-cells. The adrenaline stimulation was biphasic; an initial, rapid and transient increase in 42K+ loss from the fat-cells was followed by a slower, more prolonged, increase in 42K+ efflux. The initial phase was inhibited by phentolamine but not by propranolol. 5. Insulin increased 42K+ efflux only after preincubation with the cells.

Study on the kinetics of process for obtaining cobalt nanopowder by hydrogen reduction under isothermal conditions

2021 ◽  
Vol 1 (1) ◽  
pp. 49-56
Author(s):  
Hieр Nguyen Tien
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Hydrogen Reduction ◽  
Average Particle Size ◽  
Chemical Deposition ◽  
Average Particle ◽  
Isothermal Conditions ◽  
Electron Microscopes ◽  
Kinetics Of

The kinetics of metallic cobalt nanopowder synthesizing by hydrogen reduction from Co(OH)2 nanopowder under isothermal conditions were studied. Co(OH)2 nanopowder was prepared in advance by chemical deposition from aqueous solutions of Co(NO3)2 cobalt nitrate (10 wt.%) and NaOH alkali (10 wt.%) at room temperature, pH = 9 under continuous stirring. The hydrogen reduction of Co(OH)2 nanopowder under isothermal conditions was carried out in a tube furnace in the temperature range from 270 to 310 °C. The crystal structure and composition of powders was studied by X-ray phase analysis. The specific surface area of samples was measured using the BET method by low-temperature nitrogen adsorption. The average particle size of powders was determined by the measured specific surface area. Particles size characteristics and morphology were investigated by transmission and scanning electron microscopes. Kinetic parameters of Co(OH)2 hydrogen reduction under isothermal conditions were calculated using the Gray–Weddington model and Arrhenius equation. It was found that the rate constant of reduction at t = 310 °C is approximately 1.93 times higher than at 270 °C, so the process accelerates by 1.58 times for 40 min of reduction. The activation energy of cobalt nanopowder synthesizing from Co(OH)2 by hydrogen reduction is ~40 kJ/mol, which indicates a mixed reaction mode. It was shown that cobalt nanoparticles obtained by the hydrogen reduction of its hydroxide at 280 °C are aggregates of equiaxed particles up to 100 nm in size where individual particles are connected to several neighboring particles by contact isthmuses.

Simultaneous photochemical generation of ozone in the gas phase and photolysis of aqueous reaction systems using one VUV light source

1997 ◽  
Vol 35 (4) ◽  
pp. 41-48 ◽  
Author(s):  
T.M. Hashem ◽  
M. Zirlewagen ◽  
A. M. Braun
Keyword(s):  
Gas Phase ◽  
Light Source ◽  
Organic Pollutants ◽  
Vacuum Ultraviolet ◽  
Oxidative Degradation ◽  
Reaction System ◽  
Photochemical Reactions ◽  
Experimental Conditions ◽  
Photochemical Generation ◽  
Kinetics Of

A more efficient use of vacuum ultraviolet (VUV) radiation produced by an immersed Xe-excimer light source (172 nm) was investigated for the oxidative degradation of organic pollutants in aqueous systems. All emitted VUV radiation from one light source was used in two simultaneous but separate photochemical reactions: (1) photochemical generation of ozone by irradiating oxygen in the gas phase and (2) photolysis of the aqueous reaction system. The gas stream containing the generated ozone is sparged into the reaction system, thus enhancing the oxidative degradation of organic pollutants. The photochemically generated ozone in the gas phase was quantitatively analyzed, and the kinetics of the degradation of 4-chlorophenol (4-CP) and of the dissolved organic carbon (DOC) were determined under different experimental conditions. The results show that the rates of degradation of the substrate and of the DOC decrease in the order of the applied processes, VUV/O3 > O3 > VUV.

Design of Nanoporous Alumina Structure and Surface Properties for Dental Composite

2007 ◽  
Vol 361-363 ◽  
pp. 809-812 ◽  
Author(s):  
C. Azevedo ◽  
B. Tavernier ◽  
Jean Louis Vignes ◽  
Pierre Cenedese ◽  
Pierre Dubot
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Porous Alumina ◽  
High Specific Surface Area ◽  
Surface Reactivity ◽  
Dental Composite ◽  
Resin Composites ◽  
Dental Resin ◽  
Adsorption Sites

Recent studies showed that the particle size of fillers, using for the reinforcement of dental resin composites, should be as small as possible to provide the maximum surface area for bonding to resin monomer, and should be kept well dispersed so as to be functionalized by a silane. In the present study, porous alumina monoliths with high specific surface area, measured by the Brunauer-Emmett-Teller (B.E.T.) method, were obtained using a novel preparation method. Structure and surface reactivity have been investigated as functions of temperature and chemical treatments. The impregnation of the as-prepared material by Triméthyletoxysilane (TMES) stabilized alumina with high specific surface area at higher temperature. A FTIR study has described the effect of TMES treatment and temperature on the structure of the material. The use of allyldimethoxysilane (ADMS) as a probe molecule for measuring the surface reactivity, has allowed us to show that the treatment of samples with TMES and their reheating at 1300°C results in adsorption sites which give stronger chemical bonds. This preliminary study has, therefore, allowed us to optimize the structural and surface treatment of experimental fillers before their use in the reinforcement of resin composites or resin-modified glass-ionomer cements.

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