Many advanced technological applications require ceramic materials with specific mechanical, ther... more Many advanced technological applications require ceramic materials with specific mechanical, thermal, electrical or magnetic properties. The chemical composition and microstructure of these materials must be conwolled precisely, by using appropriate processing techniques. Chemical routes generally give much better control than can be achieved using the more traditional physical and mechanical ceramics processing methods. One of the most versatile chemical processing routes is tile hydrolysis of metal-organic complexes, such as alkoxides (loosely described as sol-gel methods). Under different conditions, sub-micron, monosized powders, monolithic components, aerogels, films and coatings can be prepared by hydrolyzing metal alkoxides dissolved in alcohols. However, these methods are relatively costly, and give rather low product yields. The solvent extraction systems used routinely in hydrometallurgy, particularly cation-exchangers, are somewhat similar to alkoxide solutions, and provide a technically promising, economically competitive route for synthesizing oxide ceramics. A wide range of oxide powders, including magnetic ferrites and zirconia, have been precipitated by direct hydrolysis of carboxylate solutions at elevated temperatures. This behavior is discussed in terms of thermodynamics, kinetics, the structure and composition of the metal carboxylate complexes and other factors influencing precipitate nucleation, growth and agglomeration. Rare-earth oxalate powders, which can be calcined to oxides, have been precipitated from carboxylate and D2EHPA extractants, using emulsions to control the size and morphology of the powders. Metal-loaded solvent extractants might also be used to prepare oxide thinfilms, or to coat whiskers with thick layers of oxides to facilitate the fabrication of composite materials. In some cases these materials preparation routes could be integrated with primary solvent extraction circuits. For other applications, the initial solvent extraction stage could be used to prepare high-purity materials from cheaper feedstocks.
OBJECTIVES xtive of this research is to develop a mechanistic understanding of the ox-Jation of c... more OBJECTIVES xtive of this research is to develop a mechanistic understanding of the ox-Jation 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 cleaning processes. Work during the nineteenth quarter has concluded studies of the surface functional groups produced on coal by severe thermal and chemical oxidation, and on investigating the partition of metal ions between such strongly oxidized coal samples and aqueous solutions. This partitioning behavior was being followed to obtain further information on the chemistry of the coal surfaces after different oxidation treatments. Adsorption isotherms for the uptake of Cd2+ on coal oxidized by different methods were obtained, and these and the Cu2+ adsorption isotherms reported in the last report have been scrutinized, and interpreted more exhaustively. The apparent discrepancies noted in the last report for the analysis of surface functional groups have been investigated further. The adsorption behavior has been related to the surface chemistry of Upper Freeport coal oxidized by different methods. EXPERIMENTAL METHODS AND RESULTS a. Coal Sample Upper Freeport coal from the Troutville #2 Mine, Clearfield County, Pennsylvania was used in this study. Table I shows the composition of this sample. The coal was stored under argon after mining to prevent oxidation, and was ground in a ball mill and sieved. The +250-200 mesh (63-75 pm) size fmction was stored under argon for use in this work. b. Oxidation Treatments Thermal oxidation: Upper Freeport bituminous coal from the Troutville #2 Mine, Clearfield County, Pennsylvania was oxidized thermally in air by heating the coal in a Precision mechanical convection oven at 230°C for 28 hours.
The objective of this research is to develop a mechanistic understanding of the oxidation of coal... more 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 cleaning processes.
at 13erkeley Dept. Materials Science and Mineral Engineering DE93 00746"/ TECHNICAL PROGRESS REPO... more at 13erkeley Dept. Materials Science and Mineral Engineering DE93 00746"/ TECHNICAL PROGRESS REPORT (9/30/92) RESEARCH OBJECTIVES 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 infl1_ence the behavior in physical 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.
Doyle, F.M., 1988. The physical chemistry of the precipitation process for removing iron (III) fr... more Doyle, F.M., 1988. The physical chemistry of the precipitation process for removing iron (III) from carboxylate solutions with dilute sulphuric acid. Hydrometallurgy, 20: 65-85. Precipitation stripping is a single-stage process for stripping a metal from a loaded liquid cation exchanger with dilute mineral acid while simultaneously precipitating a hydrolyzed phase. The process has potential applications for removing iron from hydrometallurgical process streams; iron(III) can be stripped from carboxylate solutions with dilute H2SO4 (10-40 g/l), at 100°C under atmospheric pressure, to give goethite or basic sulphates. Experimental results for precipitation stripping are summarized. The thermodynamics of the process are examined and equilibrium constants for the precipitation stripping process are estimated at 25 °C and 100 ° C. For the formation of goethite and hematite, these constants are very high at both temperatures. This indicates that iron (III) can only be extracted in reasonable concentrations by carboxylic acids before precipitates have nucleated, or when the metastable phase Fe (OH)3 is present. The sluggish kinetics of Fe (III) hydrolysis and precipitation favour extraction at 25 ° C. At 100 ° C, however, goethite and hematite precipitate more rapidly, which drives the precipitation stripping process to near completion. The structure of the iron carboxylate complexes within the organic phase is discussed, along with the influence of these structures on the kinetics of stripping and the nature of the hydrolysis products.
The ability of oxidized Upper Freeport bituminous coal to adsorb Cu{sup 2+}, Cd{sup 2+} and MN(VI... more The ability of oxidized Upper Freeport bituminous coal to adsorb Cu{sup 2+}, Cd{sup 2+} and MN(VII) from very dilute aqueous solutions has been studied. Low-rank coal is known to adsorb heavy metal ions from dilute, aqueous solutions, probably by ion exchange and/or chelation by acidic functional groups on the coal surface. However, it would be advantageous to use higher rank coals for water treatment. Coal samples were oxidized thermally or by 30% H{sub 2}O{sub 2} to increase the surface concentration of phenolic and carboxylic groups, then portions were shaken with Cu{sup 2+} and Cd{sup 2+} solutions. Acidic KMnO{sub 4} was also used to oxidize coal, with concurrent sorption of the resulting MN(IV) and Mn(II). The effect of oxidation treatment, metal ion concentration, and solution pH on metal uptake kinetics was investigated. Potential applications for treating effluents, especially those containing oxidizing ions, are discussed, along with possible flowsheet options.
The solubilities of metal-surfactant salts in aqueous systems influence foam separation processes... more The solubilities of metal-surfactant salts in aqueous systems influence foam separation processes. The solubility products of selected salts of metal ions with anionic C,, surfactants were determined. Lead dodecylsulfate, lead dodecylsulfonate, lead dodecanoate and chromium dodecylsulfate have solubility products of 1.9 x 1 O-lo, 5.0 x IO-", 4.4 x IO-l6 (mol dm-3)3, and 6.9 x lo-l4 (mol dm-3)4, respectively, as determined from turbidity measurements. Copper and cadmium dodecylsulfates have significantly higher solubility products of 3.79 x 1O-3 and 3.18 x lo-' (mol dm-3)3, respectively, determined by chemical analysis of supernatants produced after precipitation of the salts.
CV Diniz, PM Doyle, AH Martins Minerals and Metallurgical Processing(USA) 17:44, 217-222, 11/2000... more CV Diniz, PM Doyle, AH Martins Minerals and Metallurgical Processing(USA) 17:44, 217-222, 11/2000. ... ion-exchange tests demonstrated the ability of this resin to produce pure manganese chloride solution from an acidic manganese chloride leach solution contaminated by Cu ...
International Journal of Mineral Processing, Mar 1, 1989
... Science and Mineral Engineering, Hearst Mining Building, Berkeley, CA 94720 (USA) (Received S... more ... Science and Mineral Engineering, Hearst Mining Building, Berkeley, CA 94720 (USA) (Received September 4, 1987; accepted after revision June 9, 1988) ABSTRACT Doyle, FM, Arauco, H. and Feng, LM, 1989. Iron removal during oxidative, acid pressure leach ing of a zinc ...
Acid mine drainage is generally regarded as the principal environmental problem caused by the min... more Acid mine drainage is generally regarded as the principal environmental problem caused by the mining of sulphide ore deposits. Acid mine drainage results from the reaction of pyritic material with oxygen and water: $$Fe{{S}_{2}} + 15/4{{O}_{2}} + 7/2{{H}_{2}}O = Fe{{(OH)}_{3}} + 2{{H}_{2}}S{{O}_{4}}$$ In general, oxidation proceeds by electrochemical mechanisms, with the cathodic reduction of oxygen being sufficiently strongly polarized that dissolution is slow. However, the solubility of Fe(III) increases with decreasing pH. This introduces an alternative, less strongly polarized cathodic reaction, which accelerates the oxidation of pyrite and release of acid. Oxidation may also be accelerated by naturally occurring bacteria, such as Thiobacillus ferrooxidans, which metabolize sulphide, sulphur and Fe(III) species. These bacteria are generally most active in acidic waters. Hence both the electrochemical and biological oxidation mechanisms are autocatalytic; once acid mine drainage develops, the problem tends to worsen and is extremely difficult to halt. Appreciable work has been done on acid mine drainage from coal mines. However sulphide ore deposits present an additional environmental threat; many sulphides are oxidized by acidic waters containing Fe(III), and release alarming amounts of heavy metals into affected drainage. Unfortunately, there is evidence that coal and ore pyrite exhibit different oxidation behaviour, thus existing preventive and mitigative technology addressing acid mine drainage from coal mines is not necessarily appropriate for sulphide ore deposits.
Abstract Magnetic nickel ferrite particles were precipitated from a tertiary C10 monocarboxylic a... more Abstract Magnetic nickel ferrite particles were precipitated from a tertiary C10 monocarboxylic acid solvent extractant loaded with Fe(III) and Ni(II), in an aliphatic hydrocarbon diluent, by treating with water at 140–180 °C. The reaction, an example of hydrolytic stripping, can be represented as: x Ni(RCOO) 2 + (8−2x) 3 Fe(RCOO) 3 + 4H 2 O = Ni x Fe (8−2x) 3 O 4 +8 RCOOH x⩽1 Homogeneous precipitation occurred in the absence of any seed. Active alumina, colloidal graphite and magnetite had no effect on the precipitation kinetics, whereas activated carbon, silica and sintered nickel ferrite slowed precipitation. Hematite and nickel hydroxide were ineffective as seeds for nickel ferrite, hematite or nickel hydroxide. Heterogeneous precipitation occurred only in the presence of precipitated ferrite; the rate was linearly proportional to the seed area and independent of stirring speed, or water concentration above the stoichiometric requirement. At Fe:Ni concentration ratios of 2:1, the rate was inversely proportional to the concentration of free carboxylic acid, and independent of the iron and nickel concentrations. The rate increased for Fe:Ni ratios of 4:1, which gave an iron-rich ferrite, and decreased at ratios of 1:1. The apparent activation energy for the process was 124 kJmol−1. The behavior is discussed in terms of the species present in the metal-loaded carboxylate solutions, particularly the dominant mixed complex, thought to be NiFe2(OH)4(RCOO)4(RCOOH)2.
Many advanced technological applications require ceramic materials with specific mechanical, ther... more Many advanced technological applications require ceramic materials with specific mechanical, thermal, electrical or magnetic properties. The chemical composition and microstructure of these materials must be conwolled precisely, by using appropriate processing techniques. Chemical routes generally give much better control than can be achieved using the more traditional physical and mechanical ceramics processing methods. One of the most versatile chemical processing routes is tile hydrolysis of metal-organic complexes, such as alkoxides (loosely described as sol-gel methods). Under different conditions, sub-micron, monosized powders, monolithic components, aerogels, films and coatings can be prepared by hydrolyzing metal alkoxides dissolved in alcohols. However, these methods are relatively costly, and give rather low product yields. The solvent extraction systems used routinely in hydrometallurgy, particularly cation-exchangers, are somewhat similar to alkoxide solutions, and provide a technically promising, economically competitive route for synthesizing oxide ceramics. A wide range of oxide powders, including magnetic ferrites and zirconia, have been precipitated by direct hydrolysis of carboxylate solutions at elevated temperatures. This behavior is discussed in terms of thermodynamics, kinetics, the structure and composition of the metal carboxylate complexes and other factors influencing precipitate nucleation, growth and agglomeration. Rare-earth oxalate powders, which can be calcined to oxides, have been precipitated from carboxylate and D2EHPA extractants, using emulsions to control the size and morphology of the powders. Metal-loaded solvent extractants might also be used to prepare oxide thinfilms, or to coat whiskers with thick layers of oxides to facilitate the fabrication of composite materials. In some cases these materials preparation routes could be integrated with primary solvent extraction circuits. For other applications, the initial solvent extraction stage could be used to prepare high-purity materials from cheaper feedstocks.
OBJECTIVES xtive of this research is to develop a mechanistic understanding of the ox-Jation of c... more OBJECTIVES xtive of this research is to develop a mechanistic understanding of the ox-Jation 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 cleaning processes. Work during the nineteenth quarter has concluded studies of the surface functional groups produced on coal by severe thermal and chemical oxidation, and on investigating the partition of metal ions between such strongly oxidized coal samples and aqueous solutions. This partitioning behavior was being followed to obtain further information on the chemistry of the coal surfaces after different oxidation treatments. Adsorption isotherms for the uptake of Cd2+ on coal oxidized by different methods were obtained, and these and the Cu2+ adsorption isotherms reported in the last report have been scrutinized, and interpreted more exhaustively. The apparent discrepancies noted in the last report for the analysis of surface functional groups have been investigated further. The adsorption behavior has been related to the surface chemistry of Upper Freeport coal oxidized by different methods. EXPERIMENTAL METHODS AND RESULTS a. Coal Sample Upper Freeport coal from the Troutville #2 Mine, Clearfield County, Pennsylvania was used in this study. Table I shows the composition of this sample. The coal was stored under argon after mining to prevent oxidation, and was ground in a ball mill and sieved. The +250-200 mesh (63-75 pm) size fmction was stored under argon for use in this work. b. Oxidation Treatments Thermal oxidation: Upper Freeport bituminous coal from the Troutville #2 Mine, Clearfield County, Pennsylvania was oxidized thermally in air by heating the coal in a Precision mechanical convection oven at 230°C for 28 hours.
The objective of this research is to develop a mechanistic understanding of the oxidation of coal... more 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 cleaning processes.
at 13erkeley Dept. Materials Science and Mineral Engineering DE93 00746"/ TECHNICAL PROGRESS REPO... more at 13erkeley Dept. Materials Science and Mineral Engineering DE93 00746"/ TECHNICAL PROGRESS REPORT (9/30/92) RESEARCH OBJECTIVES 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 infl1_ence the behavior in physical 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.
Doyle, F.M., 1988. The physical chemistry of the precipitation process for removing iron (III) fr... more Doyle, F.M., 1988. The physical chemistry of the precipitation process for removing iron (III) from carboxylate solutions with dilute sulphuric acid. Hydrometallurgy, 20: 65-85. Precipitation stripping is a single-stage process for stripping a metal from a loaded liquid cation exchanger with dilute mineral acid while simultaneously precipitating a hydrolyzed phase. The process has potential applications for removing iron from hydrometallurgical process streams; iron(III) can be stripped from carboxylate solutions with dilute H2SO4 (10-40 g/l), at 100°C under atmospheric pressure, to give goethite or basic sulphates. Experimental results for precipitation stripping are summarized. The thermodynamics of the process are examined and equilibrium constants for the precipitation stripping process are estimated at 25 °C and 100 ° C. For the formation of goethite and hematite, these constants are very high at both temperatures. This indicates that iron (III) can only be extracted in reasonable concentrations by carboxylic acids before precipitates have nucleated, or when the metastable phase Fe (OH)3 is present. The sluggish kinetics of Fe (III) hydrolysis and precipitation favour extraction at 25 ° C. At 100 ° C, however, goethite and hematite precipitate more rapidly, which drives the precipitation stripping process to near completion. The structure of the iron carboxylate complexes within the organic phase is discussed, along with the influence of these structures on the kinetics of stripping and the nature of the hydrolysis products.
The ability of oxidized Upper Freeport bituminous coal to adsorb Cu{sup 2+}, Cd{sup 2+} and MN(VI... more The ability of oxidized Upper Freeport bituminous coal to adsorb Cu{sup 2+}, Cd{sup 2+} and MN(VII) from very dilute aqueous solutions has been studied. Low-rank coal is known to adsorb heavy metal ions from dilute, aqueous solutions, probably by ion exchange and/or chelation by acidic functional groups on the coal surface. However, it would be advantageous to use higher rank coals for water treatment. Coal samples were oxidized thermally or by 30% H{sub 2}O{sub 2} to increase the surface concentration of phenolic and carboxylic groups, then portions were shaken with Cu{sup 2+} and Cd{sup 2+} solutions. Acidic KMnO{sub 4} was also used to oxidize coal, with concurrent sorption of the resulting MN(IV) and Mn(II). The effect of oxidation treatment, metal ion concentration, and solution pH on metal uptake kinetics was investigated. Potential applications for treating effluents, especially those containing oxidizing ions, are discussed, along with possible flowsheet options.
The solubilities of metal-surfactant salts in aqueous systems influence foam separation processes... more The solubilities of metal-surfactant salts in aqueous systems influence foam separation processes. The solubility products of selected salts of metal ions with anionic C,, surfactants were determined. Lead dodecylsulfate, lead dodecylsulfonate, lead dodecanoate and chromium dodecylsulfate have solubility products of 1.9 x 1 O-lo, 5.0 x IO-", 4.4 x IO-l6 (mol dm-3)3, and 6.9 x lo-l4 (mol dm-3)4, respectively, as determined from turbidity measurements. Copper and cadmium dodecylsulfates have significantly higher solubility products of 3.79 x 1O-3 and 3.18 x lo-' (mol dm-3)3, respectively, determined by chemical analysis of supernatants produced after precipitation of the salts.
CV Diniz, PM Doyle, AH Martins Minerals and Metallurgical Processing(USA) 17:44, 217-222, 11/2000... more CV Diniz, PM Doyle, AH Martins Minerals and Metallurgical Processing(USA) 17:44, 217-222, 11/2000. ... ion-exchange tests demonstrated the ability of this resin to produce pure manganese chloride solution from an acidic manganese chloride leach solution contaminated by Cu ...
International Journal of Mineral Processing, Mar 1, 1989
... Science and Mineral Engineering, Hearst Mining Building, Berkeley, CA 94720 (USA) (Received S... more ... Science and Mineral Engineering, Hearst Mining Building, Berkeley, CA 94720 (USA) (Received September 4, 1987; accepted after revision June 9, 1988) ABSTRACT Doyle, FM, Arauco, H. and Feng, LM, 1989. Iron removal during oxidative, acid pressure leach ing of a zinc ...
Acid mine drainage is generally regarded as the principal environmental problem caused by the min... more Acid mine drainage is generally regarded as the principal environmental problem caused by the mining of sulphide ore deposits. Acid mine drainage results from the reaction of pyritic material with oxygen and water: $$Fe{{S}_{2}} + 15/4{{O}_{2}} + 7/2{{H}_{2}}O = Fe{{(OH)}_{3}} + 2{{H}_{2}}S{{O}_{4}}$$ In general, oxidation proceeds by electrochemical mechanisms, with the cathodic reduction of oxygen being sufficiently strongly polarized that dissolution is slow. However, the solubility of Fe(III) increases with decreasing pH. This introduces an alternative, less strongly polarized cathodic reaction, which accelerates the oxidation of pyrite and release of acid. Oxidation may also be accelerated by naturally occurring bacteria, such as Thiobacillus ferrooxidans, which metabolize sulphide, sulphur and Fe(III) species. These bacteria are generally most active in acidic waters. Hence both the electrochemical and biological oxidation mechanisms are autocatalytic; once acid mine drainage develops, the problem tends to worsen and is extremely difficult to halt. Appreciable work has been done on acid mine drainage from coal mines. However sulphide ore deposits present an additional environmental threat; many sulphides are oxidized by acidic waters containing Fe(III), and release alarming amounts of heavy metals into affected drainage. Unfortunately, there is evidence that coal and ore pyrite exhibit different oxidation behaviour, thus existing preventive and mitigative technology addressing acid mine drainage from coal mines is not necessarily appropriate for sulphide ore deposits.
Abstract Magnetic nickel ferrite particles were precipitated from a tertiary C10 monocarboxylic a... more Abstract Magnetic nickel ferrite particles were precipitated from a tertiary C10 monocarboxylic acid solvent extractant loaded with Fe(III) and Ni(II), in an aliphatic hydrocarbon diluent, by treating with water at 140–180 °C. The reaction, an example of hydrolytic stripping, can be represented as: x Ni(RCOO) 2 + (8−2x) 3 Fe(RCOO) 3 + 4H 2 O = Ni x Fe (8−2x) 3 O 4 +8 RCOOH x⩽1 Homogeneous precipitation occurred in the absence of any seed. Active alumina, colloidal graphite and magnetite had no effect on the precipitation kinetics, whereas activated carbon, silica and sintered nickel ferrite slowed precipitation. Hematite and nickel hydroxide were ineffective as seeds for nickel ferrite, hematite or nickel hydroxide. Heterogeneous precipitation occurred only in the presence of precipitated ferrite; the rate was linearly proportional to the seed area and independent of stirring speed, or water concentration above the stoichiometric requirement. At Fe:Ni concentration ratios of 2:1, the rate was inversely proportional to the concentration of free carboxylic acid, and independent of the iron and nickel concentrations. The rate increased for Fe:Ni ratios of 4:1, which gave an iron-rich ferrite, and decreased at ratios of 1:1. The apparent activation energy for the process was 124 kJmol−1. The behavior is discussed in terms of the species present in the metal-loaded carboxylate solutions, particularly the dominant mixed complex, thought to be NiFe2(OH)4(RCOO)4(RCOOH)2.
Uploads
Papers by Fiona Doyle