Frank Lloyd Wright Ballroom AB

Chair: Mike Moats, Missouri University of Science and Technology, Rolla, MO

Sponsored by: 

1:30 PM

Atmospheric Tank Leaching of Chalcopyrite Concentrate in Ferric Sulfate Media

R. Kurniawan, W. Liu, and D. B. Dreisinger, Department of Materials Engineering, University of British Columbia, Vancouver, BC

Chalcopyrite leaching at atmospheric conditions exhibits slow kinetics and poor leaching efficiency. This has been attributed to the formation of passivating layers on chalcopyrite surface hindering further oxidation of the mineral. Various strategies have been developed to overcome passivation, such as increasing leaching temperature and pressure, use of chloride media, increasing mineral surface area by fine grinding, use of microorganisms, and the addition of additives or catalysts. This research aims to develop a catalyzed atmospheric tank leaching process to leach chalcopyrite concentrate in ferric sulfate media. A series of stirred reactor tests was carried out to determine the effects of different parameters on the effectiveness of this process. The experimental results show that the kinetics of copper dissolution could be greatly enhanced in the presence of the catalyst.

2:00 PM

Evaluating the Use of a Dynamic Model to Predict Direct Copper Electrowinning Tankhouse Performance

Suné Grobbelaar, Department of Chemical Engineering, Stellenbosch University; Christie Dorfling, Department of Chemical Engineering, Stellenbosch University; Margreth Tadie, Department of Chemical Engineering, Stellenbosch University

A dynamic model can be coupled with advanced control strategies to improve the efficiency of tankhouses employing resource-intensive direct copper electrowinning. Consequently, a high-fidelity, dynamic model that captures the complex fundamental chemistry associated with the variable electrolyte composition present in direct copper electrowinning was developed. A self-updating parameter-fitting approach was incorporated to calibrate the model for use on tankhouse-specific data. Validation of the model was performed using industrial electrowinning data. This paper presents the findings, challenges, and opportunities associated with the application of the model to industrial case-study data obtained from a direct copper electrowinning tankhouse.

2:30 PM

Precious Metals Refinery Transformation – Piloting as a Basis for Success

Christoph Ziegler, Aurubis AG, Hamburg, Germany; Leslie Bryson, Aurubis AG, Hamburg, Germany

Aurubis is considering upgrading its precious metals refinery. Developed internally, the current process is based on a Möbius type silver electrolysis and a combined nitric/chloride gold refining and platinum group metals (PGM) solution production. A future refinery shall be based on a direct chloride leach of the silver anode slimes and a subsequent treatment of the resulting gold/PGM solution and silver chloride residue. For this purpose we developed a full flowsheet based on lab scale results. In this paper we present how we planned, built and operated a pilot plant for this flowsheet. Furthermore, we will discuss the importance of an early definition of scope and success criteria. Finally, the results of the piloting were transformed into process design criteria that are the basis of a feasibility engineering.

3:00 PM

Optimization of Silver Electrorefining at Aurubis

Leslie Bryson, Aurubis AG, Hamburg, Germany; Christoph Ziegler, Aurubis AG, Hamburg, Germany

Aurubis is considering the upgrade of its precious metal refinery. Developed and optimized over the years, input to the current process is based on cast silver anodes feeding a Möbius type silver electrolysis section. It has been envisaged that the future refinery shall continue to incorporate a Möbius based silver electrorefinery, however at unprecedented higher PGM contents and operating current densities. These modifications aim at the development of a silver-based Precious Metals refinery with a higher degree of flexibility and lower CAPEX and working capital. In this paper we will discuss these new developments along with the design and operation of a pilot plant used to validate design criteria. These design criteria have been considered in the basis of a feasibility engineering study.

4:00 PM

Improving the Rate of Recovery from Copper Leach Residue with the Addition of a Wetting Aid: A Metallurgical and Geophysical Study

M.L. Catling, BASF Corporation, Tucson, AZ; R.G. Copp, BASF Corporation, Tucson, AZ; JJ Taute, BASF Corporation, Tucson, AZ; D.F. Rucker, HydroGEOPHYSICS, Inc. Tucson, AZ; B.D. Cubbage, HydroGEOPHYSICS, Inc. Tucson, AZ

Ore grades have been shown to be decreasing globally, forcing more mining operations to increase the annual throughput of ore to maintain metal production targets. A leaching aid has been developed with the goal of increasing the kinetic rate and overall metal recovery in heap-leaching processes. This investigation utilizes electrical resistivity testing to investigate the conductivity of an active leach pad before and after the addition of a leaching aid and discusses the changes observed in the geophysical and metallurgical data following its addition, as well as the implications of those results.

4:30 PM

Performance Evaluation of Modified Biopolymers as Acid Suppressants in Copper Electrowinning

Marcio Ribeiro, W Tech Technologies Ltd; Peter So, W-Tech Technologies Ltd; Patrick Wong, W-Tech Technologies Ltd

Sulfuric acid mist is released during the electrowinning of copper. Among several techniques applied to suppress acid mist formation, fluoroalkyl based products have been the most chemistry type used worldwide. In this paper, modified biopolymers were tested as alternative surfactants to reduce acid mist in copper electrowinning. Two products, Biopolymer NCB and Biopolymer LB, were tested in laboratory to determine their effects on acid mist suppression. Both products lead to over 90% reduction of sulfuric acid mist with no significant impact on current efficiency. The two products were recommended for a commercial field test.

5:00 PM

Leaching Metals from Phyllosilicate Ores

Isabel Barton, University of Arizona Department of Mining & Geological Engineering; Maxwell Drexler, Rio Tinto Inc.; Molly Radwany, Freeport-McMoRan Inc.; Pierre Marie Zanetta, Univ Jean Monnet, Saint Etienne, France

Phyllosilicate minerals are important ores of V, Zn, Ni, and sometimes Cu. This paper uses phyllosilicate crystal chemistry, leaching experiments, and transmission electron microscopy to examine metals’ three distinct modes of occurrence and leachability in these ores. (1) Adsorbed metals can be liberated via exchange with solution cations, depending on chemical conditions and phyllosilicate type. (2) Crystallographically contained metals are partially leachable, typically at elevated temperatures, if they are in octahedral or higher coordination. (3) V, Ni, Cu, and possibly other metals, form discrete nanometer-scale inclusions within phyllosilicates whose leachability is mostly controlled by their mineralogy, not the phyllosilicate host’s.

 Frank Lloyd Wright Ballroom CD

Chair: Jaeheon Lee, Colorado School of Mines

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1:30 PM

Extraction and Possible Seperation of Tungsten and Vanadium form Spent SCR Catalyst by Hydrometallurgical Approaches

Rajesh Kumar Jyothi, Korea Institute of Geoscience and Mineral Resources, Daejeon, Korea; Jong Hyuk Jeon, Korea Institute of Geoscience and Mineral Resources, Daejeon, Korea; Jin-Young Lee, Korea Institute of Geoscience and Mineral Resources, Daejeon, Korea

2:00 PM

Temperature Dependence of Biooxidation of Coal-Based Pyrite

Kitsel Lusted, University of Utah; Prasenjit Podder, University of Utah; Joel Ilunga, University of Utah; Kara Sorenson, University of Utah; Prashant Sarswat, University of Michael Free, University of Utah

Rare earth elements have properties that make them useful in advanced electronics, magnets, and batteries. However, they are difficult to isolate from their constituent elements, which results in an environmentally costly operation to refine them. An environmentally friendly alternative extraction method involves biooxidation which uses bacteria to generate acid and ferric ions from pyrite to free the REEs from chemically bonded constituents. Because bacteria are living creatures, one of the most important factors to consider when running a bioreactor is the operating temperature. This study involved testing and analysis of the temperature dependence of biooxidation using pyrite concentrated from coal waste. The temperature was varied from 25°C to 40°C. Acid production in the bioreactor was monitored with pH measurements and bacterial oxidation was measured using the oxidation-reduction potential (ORP) of the system. Bacterial vitality was monitored by periodic ferrous oxidation tests which quantitatively assessed the biooxidation rate. The ferrous biooxidation rate (BOR) was evaluated using the Michaelis-Menten or Monod kinetic equations. Elemental and volumetric mass balances were done after each parameter. Pyrite recoveries were analyzed using energy-dispersive x-ray spectroscopy (EDS), scanning electron microscope (SEM) analysis, and x-ray diffraction (XRD). Additionally, bacteria species analysis showed that Leptospirillum ferriphilum was the dominant bacteria species, showing divergence from the original Acidithiobacillus ferrooxidaans culture. Analysis showed that 35°C had the lowest pH, highest ORP, and highest BOR, while 40°C caused bacterial death.

2:30 PM

Hydrometallurgical Treatment of Copper Flash Smelter Dusts via Ammoniacal Leaching

Joseph Trouba, Colorado School of Mines, Kroll Institute of Extractive Metallurgy; Corby Anderson, Colorado School of Mines, Kroll Institute of Extractive Metallurgy

Copper smelter flue dusts contain appreciable quantities of Cu, which would represent a substantial financial loss if not recovered. The presence of deleterious elements including Bi, As, and Pb limits the ability to recycle dusts back into the smelter as it inhibits downstream operations. Disposal of dusts also presents a challenge, due to the toxic elements As and Cd. A hydrometallurgical method involving ammoniacal leaching for treatment of dusts addressing these challenges is presented. This method also provides improved potential for recovery of minerals critical to thin film photovoltaic applications including Cd and In.

3:00 PM

Sequential Leaching of Nevada Sedimentary Claystones for Subsequent Selective Lithium Extraction

Angela Tita, Department of Mining and Metallurgical Engineering, University of Nevada, Reno; Pengbo Chu, Department of Mining and Metallurgical Engineering, University of Nevada, Reno

To meet the current high demand for lithium, new sources of lithium are needed. A Nevada sedimentary claystone containing lithium was analyzed for its composition, phase transformation, and leaching efficiency for lithium extraction through a 5-step sequential (step-by-step) leaching. Methods such as XRD, SEM, AAS, and ICP-MS were used to characterize the clay and its resulting products. The study found that the clay consisted mainly of compounds of Ca, Al, Mg, Fe, K, and Na, as well as Li having 1188 ppm. In the first step trace element extraction was performed using MgCl2, which positively impacted the second step for calcite removal. In the second step, about 50% of Ca was removed in 5 hours at room temperature with 1M sodium acetate, which was an indication that some of the Ca was associated with the carbonate-bound fraction. In the third step, the temperature was applied at 96oC with hydroxylamine hydrochloride in acetic acid. Under these conditions, less than 20% of the Fe was removed, which suggested that the Fe is barely associated with the Fe-oxide bound fraction. The last step (residual step) made use of aqua regia, aiming at attacking the silicate matrix. At this step, most of the metal ions were released. The results showed that most of the metal ions were situated in the crystalline matrix (residual fraction).

4:00 PM

Intra-Lanthanide Separation Processes Using Neutral Diglycolamide Extractants

Kevin L. Lyon, Idaho National Laboratory, Idaho Falls ID, USA; Santa Jansone Popova, Oak Ridge National Laboratory, Oak Ridge TN, USA; Derek M. Brigham, Oak Ridge National Laboratory, Oak Ridge TN, USA; Mitchell R. Greenhalgh, Idaho National Laboratory, Idaho Falls ID, USA; Amy K. Welty, Idaho National Laboratory, Idaho Falls ID, USA; Melissa M. Warner, Idaho National Laboratory, Idaho Falls ID, USA; Bruce A. Moyer, Oak Ridge National Laboratory, Oak Ridge TN, USA

Separation of individual rare earth elements (REE) is often regarded as the most difficult processing step in the production of high-purity rare earth oxides for end-use technology applications due to their inherent chemical similarities. Current industrial REE separation practices utilize solvent extraction with organophosphorus extractants, a complex process plagued by poor adjacent-lanthanide selectivity, excessive chemical reagent consumption, and adverse environmental impacts. Consequently, research efforts within the Critical Materials Institute (CMI) are aimed at the development of alternative REE separation technologies that improve economic viability and environmental sustainability to enable domestic supply diversification. Recent efforts have focused on electroneutral solvating diglycolamide (DGA) extractants as an alternative method for the separation and purification of critical rare earth elements. DGAs offer distinct advantages over traditional phosphonic acid extractants used in separations including elimination of saponification to achieve high recovery in a solvent extraction cascade and improved adjacent-lanthanide separation factors, ultimately requiring fewer solvent extraction stages to facilitate the required separations. Novel DGA extractants have been synthesized and tested to maintain high intra-lanthanide selectivity, high organic-phase loading capacity, and proper phase dispersion behavior for high throughput separations. In this paper, solvent extraction cascade design principles have been tested using the well-known DGA N,N,N’,N’-tetraoctyldiglycolamide as the first test case to validate separation performance in counter-current solvent extraction equipment to obtain high degrees of REE recovery and purity. Finally, challenges and ongoing research associated with this family of neutral extractants are evaluated within the context of domestic rare earth oxide production from bastnäsite ore.

4:30 PM

Enhancing the Recovery of Rare Earths and Phosphate Enriched By-Product from Monazite Ore via Sulfuric Acid Baking with Additives

Tarek Mohammed, College of Science, Technology, Engineering and Mathematics, Murdoch University; Andro Tomas, College of Science, Technology, Engineering and Mathematics, Murdoch University; Gamini Senanayake, College of Science, Technology, Engineering and Mathematics, Murdoch University; Wensheng Zhang, Hydrometallurgy Innovation, CSIRO Mineral Resources

Monazite, a rare earth phosphate mineral, is the second most important primary source of REEs for increasing demand in modern technologies. Current technologies for processing monazite ore using sulfuric acid are primarily focused on REE recovery. However, these technologies result in the loss of phosphorus in waste streams, which impedes downstream REE recovery processes. Therefore, there is a need for efficient processing methods that could recover both REEs and phosphorus from monazite ore. This study presents a method for recovering both REEs and phosphorus as iron phosphate battery precursor from monazite ore by sulfuric acid baking with the addition of sulfate salts. The leaching efficiency of REEs and P varied depending on the additives used, with the highest efficiencies observed for the ferric sulfate system. As the temperature increased, the leaching efficiency of REEs and P decreased when baking with no additive. However, the addition of ferric sulfate salt to the baking reactants improved leaching efficiency of REEs and favourably enriched P in the residue for subsequent processing as battery precursor (FePO4). The XRD confirmed the successful constraining of P and Fe in the residue while more than 95% REEs were selectively leached. The results suggest that this method can be a promising alternative to conventional methods for processing monazite ore. An integrated flowsheet was proposed to produce a marketable REO product of over 99% purity.

5:00 PM

The Use of Hydrogen Peroxide to Inhibit Silicon Co-Extraction with Iron during Slag Leaching-M2-6

Michael Caplan, Kroll Institute for Extractive Metallurgy, Colorado School of Mines; Corby Anderson, Kroll Institute for Extractive Metallurgy, Colorado School of Mines; Erik Spiller, Kroll Institute for Extractive Metallurgy, Colorado School of Mines; Roberto Huamani, Universidad Nacional de San Agustin de Arequipa

The extraction of silicon and iron commonly pose problems during hydrometallurgical leaching. These problems generally arise during downstream processing where iron can co-extract with target elements and silicon-based gels can hinder processing. This work presents a mechanism by which hydrogen peroxide can be used to suppress iron and silicon extraction during leaching of pyrometallurgical slags with sulfuric acid. Ferro-silicates are common in slags, therefore the extraction of iron and silicon by leaching in slags is linked. By increasing the oxidizing environment during leaching, the thermodynamically favored iron bearing species becomes solid. This reduces the degradation of the ferro-silicates in slag, which reduced the silicon available for extraction. This work supports this mechanism by leaching a mixture of copper reverberatory slag and lead blast furnace slag with sulfuric acid and hydrogen peroxide. The presence of hydrogen peroxide suppressed the extraction of both iron and silicon.