A Generalized Kinetic Model for Hydrometallurgical Processes

2007 ◽  
Vol 2 (1) ◽  
Author(s):  
Fathi Habashi
Keyword(s):  
Kinetic Model ◽  
Surface Area ◽  
Solid Surface ◽  
Total Surface Area ◽  
Metal Sulfides ◽  
Electric Conductor ◽  
Reduction Processes ◽  
Oxidation Reduction ◽  
Generalized Kinetic Model ◽  
Anodic Zone

In electrochemical leaching processes the solid must be an electric conductor, e.g., a metal, or a semiconductor, e.g., certain metal sulfides or oxides. Reaction takes place by the transfer of electrons at the solid surface and involves oxidation–reduction processes that take place simultaneously at two different locations not far from each other. At one location, electrons are picked up by a depolarizer, D, in solution, e.g., O2, H+, etc. (the cathodic zone) and at another location metal ions are released in solution (the anodic zone) where they react with reagent C. A single kinetic law derived theoretically is obeyed: Rate = k1k2A[D][C] / (k1[D] + k2[C]) where k1 and k2 are constants, and A is the total surface area of the dissolving solid.

scholarly journals A Facile One-Pot Approach to the Synthesis of Gd-Eu Based Metal-Organic Frameworks and Applications to Sensing of Fe3+ and Cr2O72− Ions

Sensors ◽  
2021 ◽  
Vol 21 (5) ◽  
pp. 1679
Author(s):  
Roberta Puglisi ◽  
Anna L. Pellegrino ◽  
Roberto Fiorenza ◽  
Salvatore Scirè ◽  
Graziella Malandrino
Keyword(s):  
Surface Area ◽  
Metal Organic Frameworks ◽  
3D Structure ◽  
Inorganic Ions ◽  
Total Surface Area ◽  
One Pot ◽  
Green Approach ◽  
Metal Organic ◽  
Ft Ir ◽  
Xrd Patterns

Gadolinium metal-organic frameworks (Gd-MOFs) and Eu-doped Gd-MOFs have been synthesized through a one-pot green approach using commercially available reagents. The 1,4-benzenedicarboxylic acid (H2-BDC) and 2,6-naphthalenedicarboxylic acid (H2-NDC) were chosen as ditopic organic linkers to build the 3D structure of the network. The Gd-MOFs were characterized using powder X-ray diffraction (XRD), FT-IR spectroscopy, field emission scanning electron microscopy (FE-SEM) and N2 adsorption–desorption analysis. The Gd-MOF structures were attributed comparing the XRD patterns, supported by the FT-IR spectra, with data reported in the literature for Ln-MOFs of similar lanthanide ionic radius. FE-SEM characterization points to the effect of the duration of the synthesis to a more crystalline and organized structure, with grain dimensions increasing upon increasing reaction time. The total surface area of the MOFs has been determined from the application of the Brunauer–Emmett–Teller method. The study allowed us to correlate the processing conditions and ditopic linker dimension to the network surface area. Both Gd-MOF and Eu-doped Gd-MOF have been tested for sensing of the inorganic ions such as Fe3+ and Cr2O72−.

NSAM-derived total surface area versus SMPS-derived “mobility equivalent” surface area for different environmentally relevant aerosols

2013 ◽  
Vol 66 ◽  
pp. 1-11 ◽  
Author(s):  
Megat-Azman Mokhtar ◽  
Rohan Jayaratne ◽  
Lidia Morawska ◽  
Mandana Mazaheri ◽  
Nic Surawski ◽  
...  
Keyword(s):  
Surface Area ◽  
Total Surface Area

Degradation of tetracycline antibiotics: Mechanisms and kinetic studies for advanced oxidation/reduction processes

Chemosphere ◽  
2010 ◽  
Vol 78 (5) ◽  
pp. 533-540 ◽  
Author(s):  
Joonseon Jeong ◽  
Weihua Song ◽  
William J. Cooper ◽  
Jinyoung Jung ◽  
John Greaves
Keyword(s):  
Advanced Oxidation ◽  
Kinetic Studies ◽  
Tetracycline Antibiotics ◽  
Reduction Processes ◽  
Oxidation Reduction

scholarly journals Regularities of Variation of the Red Blood Indices Characterizing the Respiratory Function of Blood in Selected Fish

2011 ◽  
Vol 56 (1-4) ◽  
pp. 35-48 ◽  
Author(s):  
Sebastian Maciak ◽  
Alina Kostelecka-Myrcha
Keyword(s):  
Surface Area ◽  
Oxygen Transport ◽  
Respiratory Function ◽  
Hemoglobin Concentration ◽  
Total Surface Area ◽  
Great Variability ◽  
Blood Indices ◽  
Erythrocyte Surface ◽  
Area Unit ◽  
Counter Current

Regularities of Variation of the Red Blood Indices Characterizing the Respiratory Function of Blood in Selected FishThere is a large diversity of red blood indices determining oxygen transport ability in vertebrates. In fish this diversity is particularly large, probably due to the great variability in water environments, which impedes the possibility of finding and understanding general patterns. It has been assumed that in mammals, the measure determining the ability of a blood unit to transport oxygen is the ratio of hemoglobin concentration (HB) and total erythrocyte surface area (TSAE). It was also shown that both in mammals and birds the amount of hemoglobin per total surface area unit (Hb/TSAE) conditions maximum use of respiratory pigment in oxygen transport, in different physiological and environmental conditions. In order to check whether this regularity occurs in fish, red blood indices were analyzed in seven species of freshwater fish, differing noticeably in their biology and body mass in two seasons of the year. Notwithstanding this marked seasonal variability to the component variables together determining the total surface area of erythrocytes, the value for TSAE was found to differ in proportion to the higher or lower concentrations of HB. In consequence, the HB/TSAE ratio indicative of the maximal use of haemoglobin in the transport of oxygen was constant in all of the fish studied between analyzed seasons. This constancy - resembling that to be noted in birds - is most probably related to the counter-current gaseous exchange ongoing in the gills of fish.

The role taken by technetium in the oxidation-reduction processes used in irradiated-fuel technology

1986 ◽  
Vol 60 (1) ◽  
pp. 43-51 ◽  
Author(s):  
V. S. Koltunov ◽  
V. I. Marchenko ◽  
A. S. Nikiforov ◽  
V. S. Smelov ◽  
V. S. Shmidt ◽  
...  
Keyword(s):  
Reduction Processes ◽  
Oxidation Reduction ◽  
Fuel Technology ◽  
Irradiated Fuel

Transport of Particle-Laden Fluids Through Fixed-Valve Micropumps

1999 ◽  
Author(s):  
Ling-Sheng Jang ◽  
Christopher J. Morris ◽  
Nigel R. Sharma ◽  
Ron L. Bardell ◽  
Fred K. Forster
Keyword(s):  
Surface Charge ◽  
Surface Area ◽  
Flow Rate ◽  
Pure Water ◽  
Maximum Flow ◽  
Total Surface Area ◽  
Maximum Flow Rate ◽  
Number Density ◽  
Polystyrene Microspheres ◽  
Negative Surface

Abstract Micropumps designed for the flow-rate range of 100–1000μl/min have been developed by a number of research groups. However, little data is available regarding the ability of various designs to directly transport liquids containing particles such as cells, microspheres utilized for bead chemistry, or contaminants. In this study the ability of pumps with no-moving-parts valves (NMPV) to transport particles was investigated. The results showed that a NMPV micropump was able to directly pump suspensions of polystyrene microspheres from 3.1 to 20.3μm in diameter. The pump functioned without clogging at microsphere number densities as high as 9000 particles/μl of suspension, which corresponded to over 90,000 particles per second passing through the pump at a flow rate of 600μl/min. Performance with polystyrene microspheres was the same as pure water up to the point of cavitation. Microspheres manufactured with negative surface charge cavitated less readily that other microspheres studied that were manufactured without surface charge. However, cavitation did not appear to be a function of microsphere size, total surface area or number density. Thus pumping polystyrene microspheres was found to be more affected by surface effects than by size, surface area or number density within the range of parameters considered. In the case of charged microspheres, the maximum flow rate was reduced by 30% compared to pure water whereas for uncharged microspheres the maximum flow rate was reduced by approximately 80%.

Comparative physiology of insect renal function

1981 ◽  
Vol 241 (5) ◽  
pp. R241-R257 ◽  
Author(s):  
J. Phillips
Keyword(s):  
Surface Area ◽  
Total Surface Area ◽  
Malpighian Tubules ◽  
Thick Ascending Limb ◽  
Small Surface ◽  
Multiplier System ◽  
Wide Range ◽  
Glomerular Filtrate ◽  
Unit Body Weight ◽  
Anion Transfer

Transport mechanisms and their control in various segments of insect excretory systems are reviewed and compared to those of vertebrate nephrons, exocrine glands, and hindguts. Formation of the primary urine in most insect Malpighian tubules (MT) is by isosmotic secretion, which is driven by an apical cation (K+) pump rather than by Na+-K+-ATPase. Unlike the glomerular filtrate of vertebrates, insect MT fluid is very different from the blood in composition, often having very high K+-to-Na+ ratios, and urine-to-plasma values much less than unity for most other solutes. The total surface area of insect MT is some 20 times that of vertebrate glomeruli per unit body weight. Secretion of MT fluid is regulated by neuropeptides over a wide range of rats, similar to glomerular filtration rate values for many vertebrate kidneys. Several secretory mechanisms for selected solutes are probably common to insect and vertebrate tubules. Unlike vertebrates, insects usually reabsorb most of the filtered water, ions, and metabolites in the rectum, which has a small surface area relative to the MT. The rectum is also where ionic and osmotic composition of the excreta is finally adjusted, under the control of neuropeptide hormones. In the rectum, insect excreta can become as hyperosmotic as mammalian urine, even though a countercurrent multiplier system is not present. Active transport of Cl- predominates in both locust rectum and the thick ascending limb of Henle's loop, but the characteristics of the anion transfer process are quite different in these two epithelia.xs

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