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Control Of Pyrite Surface Chemistry In Physical Coal Cleaning Technical Progress Report For The Ninth Quarter September 1 November 30 1991
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Book Synopsis Control of Pyrite Surface Chemistry in Physical Coal Cleaning. Technical Progress Report for the Ninth Quarter, September 1--November 30, 1991 by :
Download or read book Control of Pyrite Surface Chemistry in Physical Coal Cleaning. Technical Progress Report for the Ninth Quarter, September 1--November 30, 1991 written by and published by . This book was released on 1992 with total page 23 pages. Available in PDF, EPUB and Kindle. Book excerpt: The separation of pyrite from coal by flotation is based on exploiting the wettability difference between coal and pyrite. There is evidence that the wettability of coal pyrite changes upon superficial oxidation. Therefore, the oxidation of coal pyrite has been studied under carefully controlled electrochemical conditions. In order to identify the species responsible for the changes in wettability, the surface products formed during oxidation have been identified by means of various surface analysis techniques, including X-ray photoelectron spectroscopy (XPS) and ion scattering spectroscopy (ISS). It has been found that pyrite oxidation creates a sulfur-rich surface along with iron oxides/hydroxides. The ratio between these hydrophobic and hydrophilic species correlates well with the results of the wettability measurements.
Download or read book Energy Research Abstracts written by and published by . This book was released on 1993 with total page 754 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Control of Pyrite Surface Chemistry in Physical Coal Cleaning. First Quarterly Progress Report, September 1, 1989--November 30, 1989 by :
Download or read book Control of Pyrite Surface Chemistry in Physical Coal Cleaning. First Quarterly Progress Report, September 1, 1989--November 30, 1989 written by and published by . This book was released on 1990 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt: To better understand the flotation behavior of coal pyrite, studies have been initiated to characterize the floatability of coal pyrite and mineral pyrite. The hydrophobicity of coal material pyrite was examined over a range of pH and oxidation times. The results indicate that surface oxidation plays an important role in coal and mineral pyrite hydrophobicity. The hydrophobicity of mineral pyrite decreases with increasing oxidation time (20 min. to 5 hr.) and increasing pH (pH 4.6 to 9.2), with maximum depression occurring at pH 9.2. However, coal pyrite exhibited low floatability, even at the lowest oxidation time, over the entire pH range. X-ray photoelectron spectroscopy (XPS) results suggest the growth of an oxidized iron layer as being responsible for the deterioration in floatability, while a sulfur-containing species present on the sample surfaces may promote floatability. Preliminary studies of the effect of frother indicate an enhancement in the floatability of both coal and mineral pyrite over the entire pH range.
Book Synopsis Control of Pyrite Surface Chemistry in Physical Coal Cleaning. Fifth Quarterly Progress Report, September 1, 1990--November 30, 1990 by :
Download or read book Control of Pyrite Surface Chemistry in Physical Coal Cleaning. Fifth Quarterly Progress Report, September 1, 1990--November 30, 1990 written by and published by . This book was released on 1992 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt: The successful separation of pyrite from coal by flotation is dependent to a large extent upon the selectivity of the process, and the use of a pyrite depressant is one of the most important and cost-effective techniques for achieving this. This report evaluates the effects of three factors on the floatability of pyrite. These are (1) the superficial oxidation of pyrite, (2) the contamination of pyrite surfaces by carbonaceous matter, and (3) pulp redox potentials. XPS (x-ray photoelectron spectroscopy) and IR spectrometry have been used to identify surface reaction products. Microflotation, laboratory-scale conventional flotation and microbubble column flotation were used to quantify the effects of these factors. It was found that low (reducing) pulp potentials are effective depressants of pyrite (more so for fresh, unoxidized samples than for oxidized samples), whilst at the same time do not materially affect coal flotation.
Book Synopsis Control of Pyrite Surface Chemistry in Physical Coal Cleaning. Tenth Quarterly Progress Report, December 1, 1991--February 29, 1992 by :
Download or read book Control of Pyrite Surface Chemistry in Physical Coal Cleaning. Tenth Quarterly Progress Report, December 1, 1991--February 29, 1992 written by and published by . This book was released on 1992 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: One of the most difficult separations in minerals processing involves the differential flotation of pyrite and coal. Under practical flotation conditions, they are both hydrophobic and no cost-effective method has been developed to efficiently reject the pyrite. The problem arises from inherent floatability of coal and pyrite. Coal is naturally hydrophobic and remains so under practical flotation. Although pyrite is believed to be naturally hydrophilic under practical flotation conditions it undergoes a relatively rapid incipient oxidation reaction that causes ''self-induced'' flotation. The oxidation product responsible for ''self-induced'' flotation is believed to be a metal polysulfide, excess sulfur in the lattice, or in some cases elemental sulfur. It is believed that if incipient oxidation of pyrite could be prevented, good pyrite rejection could be obtained. In order to gain a better understanding of how pyrite oxidizes, a new method of preparing fresh, unoxidized pyrite surfaces and a new method of studying pyrite oxidation have been developed this reporting period.
Book Synopsis Control of Pyrite Surface Chemistry in Physical Coal Cleaning. Twelfth Quarterly Technical Progress Report, June 1, 1992--August 31, 1992 by :
Download or read book Control of Pyrite Surface Chemistry in Physical Coal Cleaning. Twelfth Quarterly Technical Progress Report, June 1, 1992--August 31, 1992 written by and published by . This book was released on 1992 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: Over the past 10 years, much research has provided convincing evidence that one major difficulty in using froth flotation to separate pyrite from coal is the ''self-induced'' flotation of pyrite. Numerous studies have attempted to identify reactions that occur under moderate oxidizing conditions, which lead to self-induced flotation, and to identify the oxidization products. During the past two report periods, it was established that: (1) freshly fractured pyrite surfaces immediately assume, at fracture, an electrode potential several hundred millivolts more negative than the usual steady state mixed potentials. Within minutes after fracture, the electrodes oxidize and reach higher steady state potentials. It was also shown, by photocurrent measurements, that a negative surface charge (upward band bending) already exists on freshly fractured pyrite, and (2) particle bed electrodes can be used to control the oxidation of pyrite and to precisely determine the electrochemical conditions where flotation occurs, or is depressed. By circulating the solution phase to an ultraviolet spectrometer, soluble products produced on pyrite by oxidation and reduction can be determined, e.g., HS− was identified as a soluble cathodic reduction product. These and other studies have provided considerable information concerning the anodic oxidation of pyrite. Much less is known about the mechanism and kinetics of oxygen reduction, the other half of the mixed potential reaction. To better understand pyrite oxidation kinetics and determine if oxygen reduction is rate determining, studies have been conducted during this report period on the oxygen reduction reaction with pyrite. In addition, to provide further support that the potential of particle bed electrodes can be controlled, the electro-adsorption and desorption of an organic surfactant was studied.
Book Synopsis Control of Pyrite Surface Chemistry in Physical Coal Cleaning. Seventh Quarterly Progress Report, March 1, 1991--May 31, 1991 by :
Download or read book Control of Pyrite Surface Chemistry in Physical Coal Cleaning. Seventh Quarterly Progress Report, March 1, 1991--May 31, 1991 written by and published by . This book was released on 1992 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt: The removal of pyrite from coal by flotation or any other surface chemistry based separation process is often hampered by the apparent hydrophobicity of the mineral. Results obtained in this project suggest that corrosion processes are responsible for the apparent hydrophobicity of pyrite in aqueous environments. Characterization of the corrosion products of pyrite in acidic and alkaline solution has been performed using electrochemical (cyclic voltammetry and single-potential-step chronoamperometry) and spectroscopic techniques (X-ray photoelectron spectroscopy -- XPS). The nature of the surface products have been correlated with hydrophobicity determined from in-situ contact angle measurements. The results show that pyrite hydrophobicity is influenced by either the oxidation or reduction conditions of the system.
Book Synopsis Control of Pyrite Surface Chemistry in Physical Coal Cleaning. Second Quarterly Progress Report, December 1, 1989--February 28, 1990 by :
Download or read book Control of Pyrite Surface Chemistry in Physical Coal Cleaning. Second Quarterly Progress Report, December 1, 1989--February 28, 1990 written by and published by . This book was released on 1992 with total page 23 pages. Available in PDF, EPUB and Kindle. Book excerpt: To better understand the surface chemical properties of coal and mineral pyrite, studies on the effect of flotation surfactants (frother and kerosene) on the degree of hydrophobicity have been conducted. The presence of either frother or kerosene enhanced the flotability of coal and mineral pyrite with a corresponding decrease in induction time over the pH range examined. Scanning electron microscopy (SEM) results indicate a correlation exists between the sample surface morphology and crystal structure and the observed hydrophobicity. As a result of the data obtained from the surface characterization studies, controlled surface oxidation was investigated as a possible pyrite rejection scheme in microbubble column flotation.
Book Synopsis Government Reports Annual Index by :
Download or read book Government Reports Annual Index written by and published by . This book was released on 1992 with total page 1400 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Control of Pyrite Surface Chemistry in Physical Coal Cleaning. Third Quarterly Progress Report, March 1, 1990--May 31, 1990 by :
Download or read book Control of Pyrite Surface Chemistry in Physical Coal Cleaning. Third Quarterly Progress Report, March 1, 1990--May 31, 1990 written by and published by . This book was released on 1992 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt: Correlation of the hydrophobicity measurements of coal and mineral pyrite with changes in the surface composition of the samples as determined by x-ray photoelectron spectroscopy (XPS) reveals that similar surface oxidation products are found on both mineral and coal pyrite samples. The surface oxidation layer of these samples is comprised of different amounts of hydrophilic species (iron hydroxy-oxides and/or iron oxides) and hydrophobic species (polysulfide or elemental sulfur). The resulting hydrophobicity of these samples may be attributed to the ratio of hydrophilic (surface oxides) to hydrophobic (sulfur-containing) species in the surface oxidation layer. Also, coal pyrite samples were found to exhibit a greater degree of superficial oxidation and a less hydrophobic character as compared to the mineral pyrite samples.
Book Synopsis Government Reports Announcements & Index by :
Download or read book Government Reports Announcements & Index written by and published by . This book was released on 1992 with total page 992 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Control of Pyrite Surface Chemistry in Physical Coal Cleaning by : G. H. Luttrell
Download or read book Control of Pyrite Surface Chemistry in Physical Coal Cleaning written by G. H. Luttrell and published by . This book was released on 1994 with total page 63 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Control of Pyrite Surface Chemistry in Physical Coal Cleaning. Final Report by :
Download or read book Control of Pyrite Surface Chemistry in Physical Coal Cleaning. Final Report written by and published by . This book was released on 1993 with total page 63 pages. Available in PDF, EPUB and Kindle. Book excerpt: In Part I, Surface Chemistry of Coal Pyrite the mechanisms responsible for the inefficient rejection of coal pyrite were investigated using a number of experimental techniques. The test results demonstrate that the hydrophobicity of coal pyrite is related to the surface products formed during oxidation in aqueous solutions. During oxidation, a sulfur-rich surface layer is produced in near neutral pH solutions. This surface layer is composed mainly of sulfur species in the form of an iron-polysulfide along with a smaller amount of iron oxide/hydroxides. The floatability coal pyrite increases dramatically in the presence of frothers and hydrocarbon collectors. These reagents are believed to absorb on the weakly hydrophobic pyrite surfaces as a result of hydrophobic interaction forces. In Part III, Developing the Best Possible Rejection Schemes, a number of pyrite depressants were evaluated in column and conventional flotation tests. These included manganese (Mn) metal, chelating agents quinone and diethylenetriamine (DETA), and several commercially-available organic depressants. Of these, the additives which serve as reducing agents were found to be most effective. Reducing agents were used to prevent pyrite oxidation and/or remove oxidation products present on previously oxidized surfaces. These data show that Mn is a significantly stronger depressant for pyrite than quinone or DETA. Important factors in determining the pyrite depression effect of Mn include the slurry solid content during conditioning, the addition of acid (HCl), and the amount of Mn. The acid helps remove the oxide layer from the surface of Mn and promotes the depression of pyrite by Mn.
Book Synopsis Oxidation of Coal and Coal Pyrite Mechanisms and Influence on Surface Characteristics. Technical Progress Report, [September--December 1991]. by :
Download or read book Oxidation of Coal and Coal Pyrite Mechanisms and Influence on Surface Characteristics. Technical Progress Report, [September--December 1991]. written by and published by . This book was released on 1992 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this research is to develop a mechanistic understanding of the oxidation of coal and coal pyrite, and to correlate the intrinsic physical and chemical properties of these minerals, along with changes resulting from oxidation, with those surface properties that influence the behavior in physical coal cleaning processes. The results will provide fundamental insight into oxidation, in terms of the bulk and surface chemistry, the microstructure, and the semiconductor properties of the pyrite. During the fifth quarter, wet chemical and dry oxidation tests were done on Upper Freeport coal from the Troutville {number_sign}2 Mine, Clearfield County, Pennsylvania.
Book Synopsis Pyrite Surface Characterization and Control for Advanced Fine Coal Desulfurization Technologies. Ninth Quarterly Technical Progress Report, September 1, 1992-- December 31, 1992 by :
Download or read book Pyrite Surface Characterization and Control for Advanced Fine Coal Desulfurization Technologies. Ninth Quarterly Technical Progress Report, September 1, 1992-- December 31, 1992 written by and published by . This book was released on 1992 with total page 29 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the 9th quarterly technical progress report for the project entitled ''Pyrite surface characterization and control for advanced fine coal desulfurization technologies'', DE-FG22-90PC90295. The work presented in this report was performed from September 1, 1992 to November 31, 1992. The objective of the project is to conduct extensive fundamental studies on the surface chemistry of pyrite oxidation and flotation and to understand how the alteration of the coal-pyrite surface affects the efficiency of pyrite rejection in coal flotation. During this reporting period, the surface oxidation of pyrite in various electrolytes was investigated. It has been demonstrated, for the first time, that borate, a pH buffer and electrolyte used by many previous investigators in studying sulfide mineral oxidation, actively participates in the surface oxidation of pyrite. In borate solutions, the surface oxidation of pyrite is tronly enhanced. The anodic oxidation potential of pyrite is lowered by more than 0.4 volts. The initial reaction of the borate enhanced pyrite oxidation can be described by:FeS2 + B(OH)4{sup =} --> [S2Fe-B(OH)4]{sub surf} + e. This reaction is irreversible and is controlled by the mass-transfer of borate species from the solution to the surface. It has been shown that the above reaction inhibits the adsorption of xanthate on pyrite. Comparative studies have been made with other sulfide minerals. The solution chemistry of the iron-borate systems have been studied to understand the electrochemical results.
Book Synopsis Control of Pyrite Surface Chemistry in Physical Coal Cleaning by :
Download or read book Control of Pyrite Surface Chemistry in Physical Coal Cleaning written by and published by . This book was released on 1992 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: Over the past 10 years, much research has provided convincing evidence that one major difficulty in using froth flotation to separate pyrite from coal is the self-induced'' flotation of pyrite. Numerous studies have attempted to identify reactions that occur under moderate oxidizing conditions, which lead to self-induced flotation, and to identify the oxidization products. During the past two report periods, it was established that: (1) freshly fractured pyrite surfaces immediately assume, at fracture, an electrode potential several hundred millivolts more negative than the usual steady state mixed potentials. Within minutes after fracture, the electrodes oxidize and reach higher steady state potentials. It was also shown, by photocurrent measurements, that a negative surface charge (upward band bending) already exists on freshly fractured pyrite, and (2) particle bed electrodes can be used to control the oxidation of pyrite and to precisely determine the electrochemical conditions where flotation occurs, or is depressed. By circulating the solution phase to an ultraviolet spectrometer, soluble products produced on pyrite by oxidation and reduction can be determined, e.g., HS[sup [minus]] was identified as a soluble cathodic reduction product. These and other studies have provided considerable information concerning the anodic oxidation of pyrite. Much less is known about the mechanism and kinetics of oxygen reduction, the other half of the mixed potential reaction. To better understand pyrite oxidation kinetics and determine if oxygen reduction is rate determining, studies have been conducted during this report period on the oxygen reduction reaction with pyrite. In addition, to provide further support that the potential of particle bed electrodes can be controlled, the electro-adsorption and desorption of an organic surfactant was studied.
Book Synopsis Pyrite Surface Characterization and Control for Advanced Fine Coal Desulfurization Technologies. Third Quarterly Technical Progress Report, March 1, 1991--May 30, 1991 by :
Download or read book Pyrite Surface Characterization and Control for Advanced Fine Coal Desulfurization Technologies. Third Quarterly Technical Progress Report, March 1, 1991--May 30, 1991 written by and published by . This book was released on 1991 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this project is to conduct extensive studies on the surface reactivity of pyrite by using electrochemical, surface analysis, potentiometric and calorimetric titration, and surface hydrophobicity characterization techniques and to correlate the alteration of the coal-pyrite surface with the efficiency of pyrite rejection in coal flotation. The products as well as their structure, the mechanisms and the kinetics of the oxidation of coal-pyrite surfaces and their interaction with various chemical reagents will be systematically studied and compared with that of mineral-pyrite and synthetic pyrite to determine the correlation between the surface reactivity of pyrite and the bulk chemical properties of pyrite and impurities. The surface chemical studies and the studies of floatability of coal-pyrite and the effect of various parameters such as grinding media and environment, aging under different atmospheres, etc. on thereof will lead to identifying the causes and possible solutions of the pyrite rejection problems in coal cleaning.
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