Oxidation of Copper Sulfides in Aqueous Ammonia. III. Kinetic Characteristics

1979 ◽  
Vol 32 (12) ◽  
pp. 2597 ◽  
Author(s):  
AO Filmer ◽  
AJ Parker ◽  
BW Clare ◽  
LGB Wadley
Keyword(s):  
Aqueous Ammonia ◽  
Sulfide Oxidation ◽  
Metal Sulfide ◽  
Diffusion Control ◽  
Sulfate Ions ◽  
Kinetics Of Oxidation ◽  
Copper Sulfides ◽  
Shrinking Core ◽  
Kinetics Of ◽  
And Diffusion

The kinetics of oxidation with oxygen of chalcocite, Cu2S, to CuS in buffered aqueous ammonia at pH 10.5 at 30� can be modeled approximately by a shrinking core of Cu2S within a thickening shell of CuxS (x ≥ 1). The Cu2S core offers partial cathodic protection to the CuxS and diffusion of Cu+ through CuxS controls the rate of reaction. The kinetics of oxidation of covellite, CuS, to Cu2+, sulfur and sulfate ions in the same solvent can be modeled by a shrinking core of CuS surrounded by a shrinking sphere of CuyS (y < 1) which is much less effectively protected cathodically by the CuS core. Oxidation of CuS is subject to mixed chemical and diffusion control. Rates of oxidation of NiS and of CuS, in the presence and absence of tetrachloroethene and ammonium sulfate, show that, whether sulfur is a major oxidation product or not, the presence of sulfur has very little, if any, influence on the rate or mechanism of oxidation. This is contrary to current ideas on metal sulfide oxidation.

Oxidation of Copper Sulfides in Aqueous Ammonia. I. Formation of Sulfur

1979 ◽  
Vol 32 (5) ◽  
pp. 961 ◽  
Author(s):  
AO Filmer ◽  
AJ Parker ◽  
LGB Wadley
Keyword(s):  
Ammonium Sulfate ◽  
Aqueous Ammonia ◽  
Copper Ions ◽  
Sulfide Oxidation ◽  
Metal Sulfide ◽  
Metal Sulfides ◽  
Copper Sulfides ◽  
Consecutive Reactions ◽  
Partial Pressures ◽  
Sulfur Containing

Elemental sulfur, rather than sulfate or thiosulfate ions, is the major sulfur-containing product when CuS or Cu2S are oxidized at temperatures below 40� with oxygen in a large excess of aqueous ammonia containing ammonium sulfate at pH 10-10.5. At temperatures above 60�, or in solutions containing low proportions of ammonia or ammonium sulfate, very little sulfur is formed. Higher partial pressures of oxygen lead to higher proportions of sulfur. These observations are explained in terms of concurrent and consecutive reactions involving copper polysulfides. The high proportion of ammonia to soluble copper ions which is required imposes some practical limitations on any potential leaching process aimed at producing sulfur. Proportions of sulfur from metal sulfide oxidation in aqueous ammonia decrease in the series of metal sulfides, Cu2S > CuS > NiS > FeS > ZnS > CoS. Some aspects of the chemistry of sulfur in aqueous ammonia are discussed.

Solid-Liquid Extraction Kinetics of Flavonoids in Ficus microcarpa

2011 ◽  
Vol 396-398 ◽  
pp. 575-581
Author(s):  
Li Sheng Wang ◽  
Li Heng Liu ◽  
Man Duan ◽  
Xiong Min Liu
Keyword(s):  
Liquid Extraction ◽  
Diffusion Control ◽  
Extraction Kinetics ◽  
Leaching Process ◽  
Shrinking Core ◽  
Higher Temperature ◽  
Ficus Microcarpa ◽  
Solid Liquid Extraction ◽  
Solid Liquid ◽  
Kinetics Of

The solid-liquid extraction kinetics of flavonoids from Ficus microcarpa with ethanol was studied. The effects of temperature and concentration of ethanol on extraction kinetics were examined. It is found that the higher temperature and concentration of ethanol, the higher leaching yields. The leaching process can be described by outer diffusion control model before 60 min and the shrinking-core model between 60 min and 150 min. The leaching process kinetics equations were established, respectively.

FISH Analysis of Bacterial Attachment to Copper Sulfides in Bioleaching Processes

2009 ◽  
Vol 71-73 ◽  
pp. 329-332
Author(s):  
J. Huergo ◽  
C. Bernardelli ◽  
M. Viera ◽  
Wolfgang Sand ◽  
Edgardo R. Donati
Keyword(s):  
Cell Attachment ◽  
Sulfide Oxidation ◽  
Metal Sulfide ◽  
Bacterial Attachment ◽  
Water Soluble ◽  
Soluble Form ◽  
Metal Sulfides ◽  
Fish Analysis ◽  
Acidithiobacillus Thiooxidans ◽  
Copper Sulfides

Bioleaching is the biological conversion of an insoluble metal compound into a water soluble form. In this process metal sulfides are oxidized to metal ions and sulfate by acidophilic microorganisms capable of oxidizing Fe2+ and/or sulfur-compounds. The metal solubilization from sulfide minerals is a chemical process which requires Fe3+ reduction. It is an environmentally friendly technique and an economical method for recovering metals that requires low investment and operation costs. In this work we studied the bioleaching of two kinds of acid-soluble copper sulfides, one easily leached by mesophilic bacteria (covellite), and the other one refractory to their activity (chalcopyrite), in acidic media with or without Fe2+ ions. We studied attached and planktonic populations of autotrophic bacteria, such as Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans and Leptospirillum ferrooxidans in pure or mixed cultures. The influence of a heterotrophic microorganism, Acidiphilium cryptum, was also studied. Attachment was evaluated with fluorescence staining and FISH using four specific probes. L. ferrooxidans showed highest initial attachment in all cases. The presence of Ap. cryptum increased the cell attachment compared with the autotrophic pure cultures. It was possible to correlate experimental data with a mechanism of bacterial-metal sulfide oxidation, the polysulfide pathway for acid- soluble metal sulfides.

Investigation of Curing Kinetics of Azo-Containing Twin Liquid Crystalline Epoxy Resins with Anhydride

2013 ◽  
Vol 702 ◽  
pp. 115-118
Author(s):  
Teng Fei Shen ◽  
Chun Feng Sun ◽  
Ying Juan Sun
Keyword(s):  
Epoxy Resins ◽  
Liquid Crystalline ◽  
Curing Kinetics ◽  
Chemical Kinetic ◽  
Diffusion Control ◽  
Kinetic Control ◽  
Control Mechanisms ◽  
Scanning Calorimetry ◽  
Kinetics Of ◽  
And Diffusion

A series of novel azo-containing twin liquid crystalline (LC) epoxy monomers were cured with anhydrides without extra catalyst and the curing kinetics was investigated by non-isothermal differential scanning calorimetry (DSC) technique. The results showed that the effect of phase behavior on activation energy (Ea) was very great. The chemical kinetic control and diffusion control mechanisms dominant the curing together, which gives a larger value of Ea. Azo group also served as a catalyst to accelerate the curing reaction.

scholarly journals Kinetics of Pb and Zn leaching from zinc plant residue by sodium hydroxide

2015 ◽  
Vol 51 (1) ◽  
pp. 89-95 ◽  
Author(s):  
M. Erdem ◽  
M. Yurten
Keyword(s):  
Plant Residue ◽  
Core Model ◽  
Diffusion Control ◽  
Shrinking Core Model ◽  
Zinc Plant ◽  
Ash Layer ◽  
Shrinking Core ◽  
Important Amount ◽  
Increasing Demand ◽  
Kinetics Of

In the hydrometallurgical zinc production processes, important amount of hazardous solid extraction residue containing unextractable Zn and Pb is generated. Due to increasing demand of metals and the depletion of high grade natural resources, these types of wastes are gaining great importance in the metallurgical industries. In this study, selective leaching and leaching kinetics of Pb and Zn from zinc extraction residue were investigated. For this purpose; the effects of NaOH concentration, contact time, stirring speed and temperature on the Pb and Zn recovery from the residue were studied. The shrinking core model was applied to the results of the experiments. Leaching results showed that 85.55% Pb and 21.3 % Zn could be leached under the optimized conditions. The leaching of Pb and Zn were found to fit well to shrinking core model with ash layer diffusion control. Activation energy values for Pb and Zn leaching were calculated to be 13.645 and 22.59 kJ/mol, respectively.

Simultaneous diffusion and chemical activation control of the kinetics of the binding of carbon monoxide to ferroprotoporphyrin IX in glycerol–water mixtures of high viscosity

1977 ◽  
Vol 55 (23) ◽  
pp. 3955-3960 ◽  
Author(s):  
Brian B. Hasinoff
Keyword(s):  
Diffusion Rate ◽  
Chemical Activation ◽  
High Viscosity ◽  
Diffusion Control ◽  
Glycerol Water ◽  
Diffusion Controlled ◽  
Kinetics Of ◽  
And Diffusion ◽  
Simultaneous Influence ◽  
Diffusion Controlled Reaction

The kinetics of the reaction of ferroprotoporphyrin IX with CO have been studied in mixed glycerol–water solvents of high viscosity in order that the simultaneous influence of chemical activation and diffusion control of the reaction might be observed. Analyses of curved Arrhenius plots indicated that in the low temperature high viscosity limits the reaction is largely diffusion controlled. The deviation of the second order diffusion rate constants, from that predicted by simple theory for reaction between uniformly reactive spheres of equal radii, is a factor of 0.3 to 0.9, depending upon the solvent composition. A couple of other models for diffusion controlled reaction, ascribing these deviations to changes of steric requirements, were also examined.

Oxidation of Copper Sulfides in Aqueous Ammonia. II. Electrochemical Aspects

1979 ◽  
Vol 32 (5) ◽  
pp. 975 ◽  
Author(s):  
AO Filmer ◽  
ID MacLeod ◽  
AJ Parker
Keyword(s):  
Aqueous Ammonia ◽  
Linear Sweep Voltammetry ◽  
Carbon Paste ◽  
Linear Sweep ◽  
Sulfate Ions ◽  
Copper Sulfides ◽  
Carbon Paste Electrodes ◽  
Controlled Potential Electrolysis ◽  
Controlled Potential ◽  
Equilibrium Thickness

The oxidation of covellite, CuS, to copper(II) and sulfur or sulfate ions in aqueous ammonia is slowed by the formation of an equilibrium thickness of a copper polysulfide Cuss (y < 1). The polysulfideis thermally and electrochemically unstable when in contact with CuS. A surface coating of sulfur, although formed, is not responsible for the semi-passivation of CuS during oxidation. Cyclic voltammetry, controlled potential electrolysis, linear sweep voltammetry, and various amperiometric and coulometric experiments with electrodes of pressed CuS, of carbon paste containing CuS and or a carbon ring with a CuS disc have been used to study the formation or decomposition of Cuss and its effect on rates of oxidation or CuS in aqueous ammonia. CuS-carbon paste electrodes offer some advantages over pressed discs of CuS for such studies.

scholarly journals Kinetic Modeling of Essential Oil Extraction by Hydrodistillation of Xylopia aethiopica (Dunal) A. Rich Fruits from Congo-Brazzaville

2021 ◽  
Vol 2 (3) ◽  
pp. 105-110
Author(s):  
Thomas Silou ◽  
Jean Bruno Bassiloua ◽  
Rosalie Kama Niamayoua
Keyword(s):  
Experimental Data ◽  
Essential Oil ◽  
Diffusion Control ◽  
First Order ◽  
Extraction Solvent ◽  
Peleg Model ◽  
Congo Brazzaville ◽  
Kinetics Of ◽  
And Diffusion ◽  
Xylopia Aethiopica

The extraction kinetics of the essential oil of Xylopia aethiopica (Dunal) A. Rich by hydrodistillation was studied for modeling its process and optimizing its yield. The oils obtained, analyzed by GC/MS, consists mainly of pinenes, sabinene, myrenal, terpinene-4-ol, limonene. Experimental data were fitted into first and second order kinetics for a 2-steps extraction, washing and diffusion, of the phenomenological model, according to the hypothesis used. The essential oil which moves inner vegetable cells by diffusion and is extracted at the surface of the particle by washing with an extraction solvent. When the washing step is instantaneous compared to that of diffusion, the mechanism, which is under diffusion control, admits first order. Considering both washing and diffusion steps, kinetic order became 2, in agreement with the Peleg model. The Monod and Langmuir models also fitted experimental data. All these models validated by the experimental data with determination coefficients R2> 0.96 can be used for optimizing the extraction of the essential oil of Xylopia aethiopica (Dunal) A. Rich.

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