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By Alan P. Prosser

The heap leaching of gold ores by cyanide solution was simulated by computer program. The program uses only basic m1neralogical and chemical data; no process testwork data, such as column leach results, are required. The simulation can be used to forecast the consequences of various changes before and during the testwork, design and operation stages of a particular ore-process system. Also, data about the state of different parts of the heap at various times help create an understanding of what is happening. The effects of mineralogical and process variables on the overall performance of the ?heap leaching process are illustrated. Comparisons are made to column leach tests and production data. The potential of the simulation strategy is discussed for making better use of operating experience and for suggesting specific research objectives. It has become clear that more attention should be paid to other metals that dissolve in the solution.

Jan 1, 1989

By B. A. Hancock

New permit discharge standards instituted at Hecla Limited?s Lucky Friday Mine required installation of water treatment plants to manage water quality at two outfalls to the South Fork of the Coeur d?Alene River. The 002 Outfall Water Treatment Plant (WTP) is a clarification-filtration plant for treating the combined mill and underground discharge water flows. Process optimization efforts were a significant challenge until the negative impact the exploration diamond drilling products had on the clarification process was identified and resolved. The products were being wasted directly to the mine water discharge system which was pumped to the surface WTP. Anionic soluble oil and polyacrylamide based products were causing TSS particle hydrophobicity and dispersion that greatly affected coagulation and flocculation response, resulting in excessive chemical usage and treatment control issues. This paper details how problems associated with the drill products negatively impacted the 002 WTP and how system changes, alternative product usage and treatment at the source resulted in more consistent plant performance.

Jan 1, 2011

By J. F. Smith, J. E. Davison

A value for the enthalpy of formation of z2 of -3.14 i 0.21 kcal per g-atom has been measured by the technique of acid solution calorimetry. This result is in quite good agreement with two earlier determinations by tin solution calorimetry and by direct reaction caloriinetry, and averaging of values determined from the three independent calorimetric techniques gives enhanced precision and accuracy with AHh8 (CaMgZ) = - 3.15 i 0.05 kcal per g-atom. For comparison with experimental data, values for the enthalpies of formation of CaMgz, SrMgz, and BaMgz of -9.8, -7.9, and -2.8 kcal per g-atom were estimated from a calculation based on the LVigizer-Seitz approximation as modified by Raimes for polyvalent elements. While complete quantitative accord between these calculated talues and available experimental data is lacking, nonetheless numerical accord is better than might be expected and, more importantly, parallel numerical trends are observed between experimental and calculated vnlues. WITHIN the past decade the enthalpy of formation of CaMg, has been determined a) from measurement of magnesium vapor pressures over binary Ca-Mg alloys,' b) by solution calorimetry with liquid tin as the solvent,' c) from measurement of hydrogen vapor pressures over ternary alloys of calcium, magnesium, and hydrogen,3 and d) by direct reaction alorimetr. The value from tin solution calorimetry is the most precise and is probably the most reliable, and this value is within the quoted uncertainties of the other three experimental results. The overall agreement among the four independent investigations is quite good, particularly so when the diversity of techniques is noted. On the basis of this agreement, CaMgz was chosen as a test material to evaluate the operation of a newly constructed apparatus for the determination of enthalpies of formation of intermetallic phases by acid solution calorimetry. This was believed to be a severe test because of the high chemical reactivity of both calcium and magnesium which reactivity presumably accounts for the fact that an early determination5 of the enthalpies of formation of Ca-Mg alloys by acid solution calorimetry yielded values significantly more negative than the four recent determinations. EXPERIMENTAL APPARATUS AND MATERIALS Experimental Apparatus. The enthalpy of formation of CaMg, was determined by measuring the difference between the heat evolved when dissolving the metallic compound and the heat evolved when dissolving equivalent amounts of unreacted metallic elements in hydro- chloric acid. This was done differentially with an apparatus consisting of twin calorimeters which were constructed to be as nearly identical as possible. The advantage of differential calorimetry is that systematic errors arising from the individual calorimeter design tend to cancel. A schematic representation of the apparatus is shown in Fig. 1. A dead air space around both calorimeters was provided by a large, thermally insulated jacket. Each calorimeter consisted of a 2-liter Dewar flask which was completely enclosed in a copper container. Each Dewar contained 1600 g of 2.5hr HCl to act as the solvent, and thermal effects resulting from solvent evaporation were minimized by covering the acid with 50 g of mineral oil. There was no detectable reaction between the acid and the mineral oil. Equivalent amounts of mechanical energy were added to the calorimeters through twin stirring rods which were driven at the same rpm by a single motor with the intent of the stirring being to maintain thermal equilibrium throughout the solvent. To calibrate the heat capacities of the calorimeters, known amounts of electrical energy could be added by passing measured voltages and currents for known times through submerged heaters, approximately 20 ohms, which were wound noninductively from Manganin wire. A 6-v storage battery was used as a power source, and a dummy heater was used as an exercise circuit to allow the battery to stabilize at a constant electromotive force before energizing one or the other of the calorimetric heaters. A type K-2 potentiometer was used to measure the potential drop across an energized heater while the current was determined from the potential drop across an external standard resistor. Times of energization were measured with an electric timer, and the electrical energy supplied to a heater

Jan 1, 1969

By David Schlain

The galvanic corrosion properties of titanium in contact with commercially pure aluminum, copper, or type 302 stainless steel in some of the common organic acids were investigated. Acids used in these experiments were 10 percent formic, acetic, lactic, citric; 1 percent oxalic and tartaric; and 9 percent oxalic. Electrode-potential measurements and several types of galvanic couple experiments were carried out. Solutions were aerated by three methods: Flow of air, flow of helium, and natural aeration. Work was done at 35° C. with couples consisting of equal areas of the 2 metals. Titanium was resistant to corrosion in most of the organic acids studied, whether alone or in contact with a dissimilar metal. However, titanium coupled with aluminum did corrode in 1- and 9-percent oxalic acid solutions. Contact with titanium usually caused aluminum to corrode by galvanic action. Copper was subject to galvanic attack in 10-percent acetic acid with a flow of air. Contact with aluminum to some solutions in which titanium is ordinarily inert and noble with respect to aluminum caused titanium to corrode

Jan 1, 1956

By C. J. Roos

Ground-engaging tools are used to prevent damage to the main components of earth-moving equipment. These tools consist of everything from shovel teeth to replaceable drill bits to dozer wear plates. The costs of these "consumable" items are increasing with the costs of raw materials. This project developed a tool to be used by Newmont Mining Corp. to predict the consumption of excavator teeth at a particular mine site. This paper presents the results of the Montana Tech research project in which an equation was developed to predict excavator teeth consumption based on production rates and rock properties.

Jan 1, 2010

By Alexandre Monteiro

Alumina precursor powders can be precipitated from aqueous solutions, using hydrothermal decomposition of urea to deliver base homogeneously to the system. Primary particles agglomerate early in the process, generating a wide size distribution. The presence of a polymeric surfactant such as polyacrylate can suppress or delay agglomeration, reducing particle size and narrowing the size distribution. The stabilization of commercially available a-Alp03 powder with polyacrylate was studied, investigating the effects of polyacrylate molecular weight, ionic strength and temperature. The effect of aluminum concentration, polyacrylate molecular weight and urea concentration on the precipitation of alumina precursors in a sulfate- urea system in the presence of polyacrylate/polyacrylic acid was then studied. The hydrolysis kinetics were followed, and particle sizes were determined. Precipitates were further characterized using energy dispersive spectroscopy. The particle characteristics are discussed in terms of the process conditions.

Jan 1, 1994

By Jochen Petersen, Steven Bradshaw, Guven Akdogan, Ngoie Mpinga, James Mwase, Jacques Eksteen, Cornelius Snyders

"The platinum group metals (PGMs) and associated minerals are particularly refractory to most traditional direct leach processes. However, the remoteness of many new ore deposits, socio-political risks, the scarcity of skilled labor and constraints on the availability of water and electrical power makes it increasingly more difficult to implement the conventional mill-float-smelt-refine process routes to extract and refine PGMs in remote areas. This paper discusses a process to extract PGM’s from low grade ore and concentrate using a sequential stage heap leach process entailing heap bioleaching and high temperature cyanide leaching, and evaluates the feasibility of implementing a carbon-in-pulp process to recover the PGMs from the pregnant leach solution. The heap bioleaching extracts the base metals in an acidic sulfate medium using a mixed culture of thermophiles. After heap bioleaching the heap is reclaimed, rinsed, agglomerated and restacked for high temperature cyanide leaching where the cyanide liquor is directly heated via solar energy in panels. Palladium, gold and platinum are recovered during the cyanide leaching stage. The pregnant leach solution was evaluated for potential carbon-in-pulp adsorption and subsequent elution similar to gold processing. The kinetics of adsorption and elution compared well with gold adsorption and elution."

Jan 1, 2014

By J. Petersen, S. W. Robertson

Heap leaching is used extensively for the processing of low-grade copper, gold, and uranium ores. The hydrodynamics is often the most important factor that limits the rate of metal recovery. Over the past decades the author has performed physical and hydraulic testing of a large number of ore samples considered for heap leaching. The data were reviewed to investigate the effect of physical properties such as particle size distribution (PSD) and bulk density on the hydrology. The unsaturated flow through the bed is traditionally modelled with soil science models such as Brooks-Corey (BC) and Van Genuchten-Mualem (VGM), which relate the hydraulic conductivity to the degree of saturation, also known as the hydraulic conductivity function (HCF). However, most authors found a disconnect between the saturated hydraulic conductivity (KS) and the rest of the HCF, which is explained as resulting from a transition from capillary-to gravity-controlled flow. However, the author found no such transition, and found the flow to be governed by capillary flow throughout. Traditional BC or VGM fits were found to be appropriate, however it was necessary to modify the model to include a point of inflection, above which the hydraulic conductivity remains constant while the moisture content keeps on increasing. It was proposed that this is the result of unconnected or poorly connected pores, which fill with solution but do not create additional flow channels. The point of discontinuity was also found to correspond with the air entry point, measured independently from the air conductivity curves. On average, the air entry point corresponds to the experiential rule that the void saturation should remain below 65% for aerated heaps.

Dec 11, 2024

By J. A. Finch, R. R. Cunningham

The amount of foam volume generated in relation to the gas flowrate has long been used to define the foaminess of a solution and to characterize surfactants. The vessel geometry and gas flowrate range can affect the foam volume results. A fixed area column was tested alongside a variable area conical vessel with two surfactants. It was found that the fixed area vessel will cause foam volume to expand or contract which masks the effect of the surfactant. The conical vessel showed two regimes of foam volume production dependant on gas flowrate. The low gas flowrate regime revealed the physiochemical nature of the surfactant while a high gas flowrate revealed kinematic properties. Foaming properties of a surfactant is best determined with a variable area vessel at low gas flowrate.

Jan 1, 2009

By Gabriel Zarate

Mantoverde is a heap leach-SX-EW plant that was commissioned in December 1995 at a production rate of 42,130 tonnes of copper per year and 5.4 million tonnes of ore per year. Copper production was steadily increased reaching a maximum of 62,239 tonnes in 2012 for an ore throughput of 10,5 million tonnes. In order to get these production and throughput rates, a number of changes have been made in the metallurgical parameters of the plant operation since the start up, among them particle size, heap height, acid addition distribution in curing and leaching solution, leach cycles and pad type. Most of the modifications have been implemented after carrying out extensive column test work programs. The modifications implemented and the results obtained, as well as the test work programs carried out, are discussed in this paper.

By V Novoselov, R Sabirov

Flotation processing technology of water-soluble minerals has made it possible to realise, since the 1960s, the wide scale industrial processing of potash and potassium-magnesium ores (about 200 million tonnes per year) as well as to create the multi-tonnage worldwide production of sylvite (KCl) for industrial and agricultural application. In this paper the particularities of the effect of reagents (blinders, collectors and frothers) during cation flotation in saturated saline solutions are outlined. New reagent modes for activating the effects of alkylamines during the flotation of KCl and the perfecting of technological flow sheets for processing potassium ore have been developed. The results of research on the reverse flotation of carnallite ore, with the help of alkylmorpholine û a new developing technology for benefication carnallite as raw material for the production of metal magnesium and fertilisers are listed. Examples are given of the industrial applications of processed reagent modes at potash flotation factories in Russia.

Jan 1, 2005

By Vladimir Lobanov, Vladimir Skorohodov, Andrew Evdokimov, Ural State Technical University 19, Boris Radionov

"The bulk of raw materials in metallurgy of secondary platinum metals are the wastes such as multilayered ceramic-metal systems, e.g. the spent catalysts of the chemical and petrochemical industry, automobile catalysts, etc. Due high chemical resistance of a ceramic basis the extraction of platinum metals by leaching even at very fine crushing is poor. The study of sorption leaching of platinum and a palladium from the spent automobile catalysts are carried out. The average content of PGM is 0.5%. A few methods of raw materials sampling were compared: 1) direct hydrometallurgical leaching of platinum metals from the fine-grained catalyst and atomic absorption analysis of the obtained solutions; 2) fusion to a metal or sulphidic collector of precious metals with the alloy analysis by direct spectrometry; 3) fusion with dissolution of a precious metals collector and atomic absorption analysis of PGM in solutions. Leaching allows detecting out no more than 90% of a palladium and 80% of platinum. Fusion to a collector gives the best results at the chemical ending. Researches on sorption leaching are executed. Under optimum conditions the extraction of platinum metals to concentrates is comparable with similar indicators of collector fusion.The large part of raw materials in metallurgy of secondary platinum metals are the multilayered or tridimensional ceramic-metal systems, in particular the spent catalysts of the chemical and petrochemical industry, automobile catalysts, ceramic-metal condensers, etc. The content of the sum of PGMs can be from hundreds grams per ton to several percent. For processing of such materials the hydrometallurgical methods of platinum metals leaching by various reagents are used commonly. High chemical resistance of the ceramic basis covering the metal particles causes low recovery even at very fine grinding. Other fundamentally different method of catalysts opening includes dissolution of the ceramic basis in the solutions of hydrofluoric acid and the subsequent recovery of platinum metals from insoluble residue. Application of this method is associated to use of corrosive medias and appropriate equipment. Fusion of the specified materials with collecting of PGM by copper, nickel or lead at the specialized enterprises provides higher extraction in semiproduct. At the same time, complexity and duration of the subsequent extraction of platinum metals concentrates causes high total cost per unit. Thereby this method is economically acceptable only for rather poor raw materials (no more than 0,1%). Undoubtedly, that the raw materials with the high content of PGM are reasonable to process by individual technology. In the present work the processing of some kinds of ceramic-metal raw materials, particularly automobile catalysts (neutralizers) with various collectors at the conditions of a target fusion are investigated."

Jan 1, 2008

By Thomas D. Humbert, Christopher J. Ramsey

Construction of a new underground parking structure in State College, Pennsylvania, is situated on a site constrained by limited ROW and required excavations ranging in depth from 25 ft to 40 ft. Additional complications included busy surface streets, an active intersection, and numerous underground utilities that could not be disrupted by construction activities. To combat these challenges, an innovative approach for earth retention was designed that combined multiple types of retention systems. The overall system included alternating sections of soil nail walls and a hybrid system of soldier pile walls (consisting of micropiles) that were partially restrained by a soil nail wall in the lower portions of the excavation. Further, due to the limited space within the property limits that inhibited the length of the permanent nails, the wall design team collaborated with the project designers to develop a solution such that the completed wall became an integral part of the final design/construction of the underground parking structure. INTRODUCTION HERE at State College is a mixed-use, high-rise building in State College, Pennsylvania. The 12-strory building has up to 3 levels of below-grade parking, with the above-grade levels consisting of residential and commercial/retail space. The existing property was a parking lot bound by the streets Calder Way to the north, Garner Street to the east, East Beaver Avenue to the south, and Heister Street to the west. The overall property sloped approximately 20 ft in elevation from southeast to northwest. Excavation for the below-grade levels extended 21 ft to 36 ft (6.4 m to 11 m) below street level. During design-development phases of the project, it became evident that due to subsurface conditions and right-of- way limitations, conventional construction techniques would not be feasible. The full perimeter of the excavation would require earth retention including the weak shale bedrock along the bottom of the excavation. The project developer (CA Ventures) and general contractor (Brinkmann) coordinated with the specialty contractor and wall design engineer to find a solution. At this time, Coastal Drilling East (specialty contractor) and Wood Environment & Infrastructure Solutions (wall design engineer) became involved. The project developer and general contractor were aware they needed an earth retention system, but given the many variables the project faced, a single, straightforward solution would not work in this application.

Jan 1, 2019

By Yues Bertube

Molybdenite and chalcopyrite are two often-associated minerals. In Quebec, the Gaspe Copper Company, a subsidiary of the Noranda group, currently operates a molybdenite flotation circuit to recover a one percent trace of this mineral in the chalcopyrite concentrate. The low levels of molybdeni 2 preclude the use of flotation to remove molybdenum directly from the ore while scavenging of chalcopyrite concentrate for molybdenite yields a concentrate of the latter of somewhat inadequate quality. Such a situation could possibly best be solved by hydrometallurgical means, if molybdenite could be leached selectively from the chalcopyrite concentrate. Work in the field of extractive metallurgy was initiated about 22 years ago in the laboratory of the department of mining and metallurgy at Laval University, Quebec. Following a literature search, two objectives were selected. The present talk will outline some of the results obtained to-date and it is hoped the ensuing discussion of the paper can raise questions of immediate assistance to us for the future. First, as an immediate objective of-practical use, the oxidation rates for molybdenite and chalcopyrite in alkaline media would be studied under conditions of possible industrial application. Secondly, the kinetics of mass transfer of gases in pressure reactor are to be studied. Solubility data for various gases in aqueous solutions have been gathered by a few investigators, to mention the work of Pray1, Wadsworth2, Pawlek3 and Gerlach. Scattering in experimental results and discrepancies between authors are ominously present. Kinetics of mass transfer have somewhat been more neglected. A systematic investigation by the school of Berlin has greatly helped in the design of impeller most suitable for gas dispersion, without much reference however to the solid dispersing ability of the various designs. Variables affecting rates of gas transfer to the solution have not been studied. Studies on the aqueous oxidation of sulfide minerals are much more numerous. While molybdenite has been relatively less studied, work has been carried in two areas namely in alkaline oxidation of MoS2 , work performed by Dresher2 and Wadsworth, and in the hypochlorite leach of molybdenite by Bhappu4 and co-workers, These two methods showed appreciable rates of leaching for molybdenite. In general, comparisons between rates of oxidation of this sulfide with that for chalcopyrite have not been made.

Jan 1, 1972

By E. L. Tucker

PREVIOUS investigations of E. L. Tucker and R. E. Head' related in particular to the effect of cyanogen compounds on galena, sphalerite, and pyrite, and their behavior in the presence of such com- pounds. The present contribution deals with the float- ability of the copper minerals and of pyrite. All experiments were performed on minus 200-mesh material, the method of preparation being the same as that described in the previous article. Flotation tests were made in a small mechanically agitated machine of 50-g. capacity designed in this laboratory by Gates and Jacobsen." General Naval Stores pine oil No. 5 and potassium xanthate were used in constant amount in all of the experiments; these agents were selected because of their present wide use in the flotation of copper minerals. Lime additions were varied to secure four 'final hydrogen ion concentrations, namely, neutral, 0.0005 per cent CaO, 0.003 per cent CaO, and 0.02 per cent CaO. The variation in lime addition was introduced to include the range of alkalinities employed in actual flotation practice.

Jan 1, 1926

By J. W. Horne

The United States Bureau of Mines in cooperation with the State of Colorado at the University of Colorado has conducted experiments to determine the amount and composition of the noncondensable cases evolved when crude shale oil is distilled under pressure. Hydrogen sulphide is one of the components found in the complex mixture of uses produced by the distillation of shale oil under pressure. This paper deals with the apparatus and method used in determining the amount of hydrogen sulphide evolved in the laboratory experimental cracking stills.

Jan 1, 1931

By F. Mielli

Camera systems and video surveillance are usually associated with people and asset protection. However, they can be applied in a mine environment beyond conventional surveillance: For process monitoring, collision avoidance, sizing, flotation cells, conveying systems, blasting, objects and people tracking, thermal profile, and to automatically identify equipment that is missing parts,. Image and video solutions can be driven by better integration of powerful video analytics and cameras systems in automation tools such as process controllers and supervision systems.

Feb 27, 2013

By V. K. Srivastava, T. Gupta, T. Ghosh

"In recent years, the demand for rare earth elements (REEs) has grown due to increasing demand and global supply shortage. The supply deficit of these critical elements has encouraged the search for new sources, with coal and coal byproducts as possibilities. Coals from certain parts of the world can be rich in REEs and can approach a total concentration of 1,000 ppm. Two Alaskan coal samples, from Healy and Wishbone Hill, were investigated for the effects of density and particle size on REE concentrations for three selected size fractions, and flotation tests were conducted on finer fractions. Additionally, bottom ash and fly ash samples from a power plant were examined for their REE concentrations. The results show that the upgrade potential for REEs on an ash basis from a whole-coal basis ranges from 2:1 for the Wishbone Hill samples to 4:1 for the Healy coal samples. Flotations of the finer fractions of the two coal samples, conducted under similar conditions, revealed higher concentrations of REEs in the tailings. Both coal samples had comparatively higher contents of light-group rare earth elements (LREEs) than heavy-group rare earth elements (HREEs). REE content trends for the power-plant products on an ash basis indicate that fly ash has slightly higher concentrations of both LREEs and HREEs than bottom ash. IntroductionRare earth elements (REEs), also known as rare earth metals, and their compounds are vital components in industrial, automotive, petrochemical, defense and medical applications. Dysprosium in combination with other elements is used in laser materials and nuclear control applications. Neodymium is present in magnets that are used in the manufacture of wind turbines and hybrid cars. Europium, terbium and yttrium are used in devices that have visual displays such as computer screens and laptops (Haxel, Hedrick and Greta, 2002; Bunzli, 2013). REEs pose fewer environmental problems of disposal and recycling than their conventional heavy metal counterparts (Haxel, Hedrick and Greta, 2002). They are key materials for radar systems, avionics, modern national defense and satellites (Cammarata and Sieradzki, 1994; Hedrick, 2010; Martin, 2010; Szumigala and Werdon, 2011; Cordier, 2011; Bunzli, 2013). REEs are often classified into light-group rare earth elements (LREEs) and heavy-group rare earth elements (HREEs). This classification is primarily based on the electronic configuration in the outermost shell. LREEs, ranging from lanthanum to gadolinium, have a single or no spinning electron in the outermost 4f shell while HREEs, ranging from terbium to lutetium, have paired electrons in the 4f shell. This difference in electronic configuration is responsible for the differences in physical and chemical properties of REEs."

Jan 1, 2017

By M. L. Sorokin

The thermodynamic of nickel production from laterite ore and from sulfide concentrate can be analyzed using PO2 - PS2 diagram of the Ni-Fe-S-0-SiO2 system. The procedure of the diagram computation is suggested and the diagrams for various temperature and Fe/Ni ratio are calculated. Three-suffix Margules equations are used for the calculation of the thermodynamic properties of three solutions: liquid matte, liquid slag and solid Fe-Ni alloy. The diagrams are used for the considerations about direct one-stage metallic nickel production.

Jan 1, 1994

By D. Duffy, V. Papangelakis

"MgCl2 brines present a number of potential advantages for the processing of saprolite ores for nickel production. With a chloride system it is economically requisite to recover hydrochloric acid, which can be performed in a more energy efficient manner by precipitation and subsequent decomposition, as compared with conventional pyrohydrolysis. In addition, concentrated MgCl2 solutions enhance the activity of acid used, allow atmospheric leaching at elevated temperature and inhibit magnesium dissolution, which reduces acid consumption and increases metal selectivity. Leaching and iron control experiments have been conducted in concentrated MgCl2 brines, up to 4.5 m, to determine the most amenable process conditions. INTRODUCTIONChloride metallurgy has received an increasing amount of attention in recent years, especially with respect to the treatment of nickel laterites. Although the limonitic fraction can sometimes be economically treated by High Pressure Acid Leaching (HPAL), acid-consumption problems are encountered with the higher magnesium content of the saprolite fraction. As magnesium does not hydrolyze under HPAL conditions, as iron and aluminum do, any sulphuric acid used to leach magnesium is subsequently neutralized and wasted. In addition, this magnesium must later be disposed of in some fashion, further complicating the process. The most common method used to process saprolite is the Rotary Kiln-Electric Furnace (RKEF). This uses a kiln to dry and preferentially reduce nickel, before sending the calcine to an electric furnace. Although nickel recoveries are high, and the problems of acid consumption are avoided, the capital and energy costs associated with this process are high (de Bakker, 2011).The problems outlined above have led to the investigation of an atmospheric chloride process for the treatment of saprolite ores. The use of a chloride system presents a number of advantages, but also a few limitations. Metal chlorides tend to be very soluble, with a few notable exceptions (silver, mercury and lead), allowing for smaller processing equipment through more concentrated solutions. This solubility also serves to reduce the potential for scale formation. In addition, a hydrochloric acid leach is more aggressive than a comparable sulphuric acid system, and the activity of the hydrogen ion can be augmented by further chloride addition (Peek, 2011). This activity augmentation in concentrated chloride systems, first reported by Jansz, has repeatedly been referenced as a motivating factor behind chloride hydrometallurgy (Jansz, 1983; Harris and Magee, 2003; Harris et al., 2004; Demopoulos et al., 2008; McDonald and Whittington, 2008; Demopoulos, 2011; Peek, 2011; Verhulst and Lakshmanan, 2011). This activity increase allows a similar amount of acid to perform more in a concentrated solution than in a dilute solution, decreasing overall acid requirements. As such, much focus has been placed on leaching in concentrated chloride systems, or brines, using calcium, magnesium or sodium as the cation (McDonald and Whittington, 2008)."

Jan 1, 2012