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By X. Zhu, L. Chen, R. Guru, M. Peiravi, M. Mohanty, L. Ackah, B. Xu

"The overall goal of this study was to develop a suitable flowsheet to extract rare earth elements (REEs) from coal ash. Only the findings from the first part of this study is being reported at this time. A total of fourteen coal samples of different ranks were examined for REEs concentration. An anthracite coal sample, originating from Pennsylvania having more than 700 ppm (in the coal ash) was selected for the REE extraction tests. The experimental program completed so far included high temperature leaching using nitric acid, followed by the solvent extraction tests. A 4x2x2 experimental design was used to conduct a total of thirty two high temperature leaching tests by varying acid molarity (at 4 levels), solid content (at 2 level) and leaching time (at 2 level). The highest LREE (light REE) recovery of 90% and HREE (heavy REE) recovery of 94% were obtained from the most optimum leaching test condition while maintaining the impurity recovery to the leachate at less than 40%. Solvent extraction experiments were conducted to recover the REE’s from the above leachate solution using a variety of organic extractants including, TBP, Cyanex, D2EHPA and their combinations. D2EHPA was found to be the best extractant during this SX text series providing nearly 99% recovery of REEs. INTRODUCTION The demand for rare earth element and other strategic metals (REM) in the world is rapidly increasing due to their use in a variety of high technology applications. More than 100,000 tons of rare earth oxides (REO) are being used worldwide on an annual basis. However, we have less than 10% of the world reserve of rare earth element (REE) mineral deposits in the US. More than 60% of rare earth oxide (REO) was imported to the US from outside (mostly from China) in the year of 2013. However, China’s institution of export quota has significantly reduced the supply of REMs to the U.S. Hence, new ways of producing REM and/or finding substitutes for those metals for the high-tech applications need to be invented/discovered in a timely manner. Coal Combustion Byproducts (CCBs), which are discarded as waste materials in most cases, are known to contain REEs (in low concentration) that could be extracted using a suitable process flowsheet. This may be a worthwhile route to pursue considering the short supply of REMs and the abundance of coal ash in thousands of ash ponds in the US. On an annual basis, more than 110 million tons of Coal Combustion Byproducts (CCBs) are being produced while satisfying our nation’s need for electricity (ACAA, 2014). However, less than 50% of these CCBs are being successfully used in various applications and the remainder is being dumped as waste materials in the landfills and ash ponds."

Jan 1, 2017

By X. Zhu, Chen. L., R. Guru, M. Peiravi, M. Mohanty, L. Ackah, B. Xu

"The overall goal of this study is to develop a suitable flow sheet to extract rare earth elements (REEs) from coal ash. A total of 14 coal samples of different ranks were examined for REE concentration, and an anthracite coal sample with the highest REE concentration of more than 700 ppm in the coal ash was selected for REE extraction tests. This paper reports on the results of the experimental program completed in the first part of the study, which included hightemperature leaching with nitric acid followed by solvent extraction tests using various organic extractants, namely, tributyl phosphate, Cyanex 572, di-(2-ethylhexyl)phosphoric acid (D2EHPA) and their combinations. A 4×2×2 experimental design was used to conduct a total of 32 high-temperature leaching tests by varying acid molarity at four levels, solids content at two levels and leaching time at two levels. The highest recovery rates of 90 percent for light rare earth elements (LREEs) and 94 percent for heavy rare earth elements (HREEs) were obtained from the optimum leaching test conditions while maintaining impurity recovery to the leachate at less than 40 percent. D2EHPA was found to be the best extractant in this solvent extraction test series, providing an REE recovery rate of nearly 99 percent.IntroductionGlobal demand for rare earth elements (REEs) and other strategic metals is increasing rapidly due to their use in a variety of advanced technological applications, with more than 100 kt of rare earth oxides used worldwide on an annual basis. The United States has less than 10 percent of the world reserves of REE mineral deposits, and in 2013 imported more than 60 percent of its rare earth oxides from other countries, mainly China (United States Geological Survey, 2017). China’s institution of export quotas has significantly reduced supply to the United States, raising the urgency of finding new ways of producing REEs and/ or substitutes. Coal combustion byproducts, which are usually discarded as waste materials, are known to contain REEs in low concentrations that could be extracted with a suitable process flow sheet. This may be a worthwhile route to pursue, considering the short supply of rare earth minerals and the abundance of coal ash in thousands of ash ponds in the United States. More than 110 Mt of coal combustion byproducts are produced annually in the process of satisfying the country’s need for electricity (American Coal Ash Association, 2016), and less than 50 percent of these byproducts are being successfully used in various applications, with the remainder dumped as waste materials in landfills and ash ponds."

Jan 1, 2017

By D. R. Nagaraj, Raymond Farinato

Water constitutes one of the most valuable resources employed in mineral recovery and processing. Identifying potential problems encountered in mineral processing in waters unusable for drinking or agriculture (including seawater and even hypersaline waters), understanding chemical factor interactions, and optimization of flotation reagents will greatly expand our ability to create more sustainable beneficiation technologies. The current paucity of our knowledgebase regarding high salinity effects on flotation clearly signals a need for a significant research effort. We report here results of a study designed to probe effects of pulp chemistry on metallurgical performance in the flotation of Cu and Cu-Mo ores in saline waters. The results clearly demonstrate that pH (more correctly dosage of pH modifier to target a pH set point) has the most significant effect on Mo recovery when using seawater. This is linked to the formation/precipitation of Mg(OH)2 when pH = 10.3 (in seawater). The type of pH modifier used, NaOH or Ca(OH)2, had no impact on Cu or Mo recovery, indicating that Ca2+ ions were not involved in any reduction in Mo recovery in the pH range of 9-11. Our results in tap water spiked with either Ca2+ or Mg2+ ions in the same pH range (controlled by NaOH), confirmed that Ca2+ ions had no effect on Cu or Mo recovery, but that addition of Mg2+ ions had a severe adverse effect on Mo recovery at pH = 9.5, and to a lesser extent on Cu recovery. The onset of Mg(OH)2 precipitation occurred at a higher pH, and the adverse impact of Mg(OH)2 on Cu recovery (and perhaps Mo recovery as well) was less, in sea water than in tap water spiked with Mg2+. These effects are attributed to the mitigating role of the high electrolyte concentration, notably NaCl.

Jan 1, 2014

By D. R. Gibbons

This morning I would like to speak to you about an area of chemistry that is enjoying a revival-organometallic compounds. This renewed interest, principally stimulated by defense needs, has already created new markets for the products of the mineral industry. Although the consumption of metals in these new products is modest at oresent, several hold promise of importance. Because this is a new and growing market, I am sure the Council of Economics is aware of many of its facets and is interested in new developments. Of course, the chemical industry has been a significant consumer of minerals for many years. I estimate that in 1957 the chemical-industry purchased a total of $1175 million worth of minerals as raw materials (not including fuels). This estimate can be broken down as follows: [Metals and metallic minerals $375 million Nonmetallic minerals (excluding hydrocarbons ) 330 million Hydrocarbons 470 million $1175 million]

Jan 1, 1958

By Richard Klimpel

1. Introduction Laboratory and industrial grinding tests have shown that the process of size reduction can be significantly influenced by chemicals added to the powder or slurry being ground. The terms grinding aid or grinding additive refers to a substance which when mixed into the mill contents causes an increase in the rate of size reduction. The increased rate can be used to grind a higher feed rate to the desired product size or it can be used to produce a finer product size at a fixed feed rate. Whether the use of a grinding aid is justified in any given situation depends on the cost of the substance versus the improvement of output or product quality obtained with its use. Obviously, an expensive chemical must be effective in very small concentrations if it is to be economically justifiable; the cost criteria is calculated on the basis of the cost of the grinding additive per ton of material ground. Although there is direct experimental verification of the advantageous effect of grinding additives, no sound scientific explanation has yet been offered which explains or predicts the general behavior of additives. Rose and Sullivan have summarized most of the work undertaken prior to 1950 and Hartley, Prisbrey, and Wick have recently prepared an updated synopsis of the grinding additive literature. Many of the studies reported consist of subjecting materials with simple geometric shapes to some type of hardness or controlled single fracture test. On the other hand, a number of the studies were carried out on operating industrial scale mills, with little control or precise monitoring of the effect of the additives.

Jan 1, 1977

By S. R. Wardwell, M. J. Robison

INTRODUCTION The first phase of the Los Angeles Metro Rail Project consists of 7.1 km of subway and stations running through downtown Los Angeles from Union Station to MacArthur Park. Contract A146, Tunnels from 5th/HILL Station to 7th/Flower Station, involves tunnel construction through the heart of downtown Los Angeles. The alignment of the tunnels passes beneath twelve buildings, ranging from a 3-story below grade parking structure to numerous 12 to 14 story buildings. The soil along the alignment is alluvium, consisting of silts and clays, clean sands and gravels located above the ground water table. Because of unstable ground conditions, which led to excessive ground losses in several instances, and because of the potential for excessive building settlements, it became necessary to design and perform a program of chemical grouting. The chemical grouting program was designed such that tunneling could proceed on a one shift per day basis, with chemical grounting being performed on the remaining two shifts. Each day 21,000 to 31,000 liters of sodium silicate grout were injected through sleeveport grout pipes installed 18 m deep through the tunnel face. Tunnel advance rates of 12 m per day, 60 m per week, under full chemical grout cover were achieved. The chemical grouting program virtually eliminated both ground loss and settlement and permitted successful excavation of the tunnels. The purpose of this paper is to describe the chemical grouting program used to control ground losses and settlement on Los Angeles Metro Rail Contract A146. The paper begins with a description of

Jan 1, 1991

By K. Soucek

Extraction of hard coal reserves, but also of mineral resources in general in the underground coal mines includes in itself many anthropogenic interventions in the earth crust. These interventions are closely associated with the solution of stability problems in the mine and with occupational safety. One of potential applications of such geo-technical interventions in rock mass is the chemical grouting technology. The chemical grouts are very suitable to affect the physical and chemical properties of rock mass. With the present development of chemical grouts, primarily based on polymers, there come into existence new composite materials during the grouting process (the so called geo-composites), which properties significantly differ from the original rock. An important factor, which affects a choice of chemical grouts and at the same time the effectiveness of grouting technology is the resulting properties of geo-composites. The properties of a coal geo-composite differ from the ones of the unmodified coal seam. On the basis of the laboratory geo-mechanical tests, the differences of properties of both material types were found. While the pure coal samples were destroyed very brittle and explosive, the geo-composite samples were making higher level of tenacity and load bearing ability after overstep of material strength. The presented paper discusses the different behaviour of these original and modified coal samples. The X-ray CT scans were used for observation and demonstration of failure evolution in these samples of pure coal and coal geo-composites after compressive loading.

Jan 1, 2006

By Davis. B. R.

There are a number of hydrogen storage systems proposed for automotive applications. However, all of the current suggestions fall short of the DOE targets for storage density and volumetric density. The DOE has suggested that only through radically new ideas will a practical solution to hydrogen storage for automotive applications be realized. This paper provides some background in chemical hydrogen storage and discusses roadblocks to the implementation of some proposed technologies.

Jan 1, 2005

By Girolamo Belardi, Silvia Serranti, Giuseppe Bonifazi, Roberta Palmieri

Ore textural and structural characterizations play a fundamental role in any preliminary study (i.e. comminution, classification, separation) addressed to the design and set up of beneficiation flow sheets. The possibility to utilise automatic tools able to perform a classification, and a quantitative description, of the mineralogical and petrographical characteristics of raw ore samples thus represents an important step to define, to control and to verify the entire set of parameters, ore-texture-related, that can affect the final beneficiation results. The procedure usually adopted is based on the analysis of polished sections and more in details the recognition of the different mineralogical species and associations and the measurements of some quantitative parameters estimating both the geometrical characteristics of each species and the possible spatial relationships between them. This approach, originally carried out by experts, utilising optical and/or electronic microscopy, was ‚replaced? during the years by more and more sophisticated devices integrating analytical facilities and acquired data processing. Such integrated analytical devices formed the breakthrough platforms into what is now known as modern Process Mineralogy. In this paper the possibilities offered by chemical imaging based devices and techniques, to perform ore minerals recognition/classification, and to perform their topological assessment, are presented. Tests have been carried out and are discussed in order to analyze the problems related to the development of suitable and low cost strategies addressed: i) to realize a full mapping of ore minerals/gangue inside selected samples, ii) to define the optimal data-flow handling to optimize the speed of processing versus the quality of the results and iii) to start to define logics and procedures finalized to implement innovative smart detection engines, chemical imaging based, for mineral processing addressed to perform both a preliminary characterization of the ore, at laboratory scale, and a further possible control of the different processed minerals flow streams.

Jan 1, 2014

By H. Matsuda, T. Iwashita, H. Awata, H. Liwei, D. Hirabayashi, Y. Saito, S. Ozawa, Y. Goto

"The present study is concerned with investigating the effect of chemical treatment on enhancing the HCl absorption capacities of coal burnt ash and slag. It was found that the HCl absorption capacity of coal burnt ash discharged from fluidized bed combustor was improved by hydration with water and 5% polyethylene glycol solution. This phenomenon was based on an increase of the specific surface area of treated coal burnt ash. The HCl absorption capacity of hydrated ash with polyethylene glycol solution was almost equivalent to that of standard CaO and Ca(OH)2. In particular, the specific surface area of hydrated ash with polyethylene glycol solution was found to be 19 m2/g, which was more than over eight times larger than that of raw sample. Hydrated slag treated with lON sodium hydroxide solution also showed high HCl absorption capacity, with highly improved surface area. It was found that the absorption capacity of slag for HCl depended on the treatment time, showing the maximum absorption capacity for 12 hours of hydration treatment.IntroductionA large amount of coal burnt ash, slag and dust are discharged from such industrial processes as coal combustion and metal refinery etc., and it becomes an serious problem to recover and diminish these solid wastes because of the shortage of dump sites and subsequent metal elution to the environment. Figure 1 shows the present situation of reutilization of coal burnt ash and slag in Japan [1,2]. It is shown in this figure that these solid wastes are recycled as materials in the fields of earthwork, agriculture and forestry etc. A part of these solid wastes, however, is still dumped to landfill. To decrease this dumped amount, the development of environmentally friendly reutilization technique for these solid wastes is of great importance."

Jan 1, 2000

By Robert B. Fulton

The use of industrial minerals by the chemical industry as raw materials for manufacturing and in processing spans a wide assortment of minerals. This chapter aims to supplement rather than duplicate the commodity chapters. Its objective, to describe the uses of industrial minerals in the manufacture of chemicals, is attained by considering minerals used by the chemical industry in terms of the chemical element required and by giving particular emphasis to market factors. The mineral aspect, which is covered in the commodity chapters, is subordinated and attention is focused on the chemical and market aspects. Condensing this broad subject into a few pages permits treating only the most important elements derived from industrial minerals. The elements derived from petroleum, hydrogen and carbon, which quantitatively dominate as raw materials for the chemical industry, are omitted, as are the metallic elements and the minerals covered in other "use" chapters such as phosphorous, potash, and nitrogen for fertilizers and titanium dioxide for pigments. After eliminating on this basis, our definition leaves six elements of major importance: boron, bromine, chlorine, fluorine, sodium, and sulfur. These elements are treated individually under separate headings. Salt brines have particular importance as raw material sources for the chemical industry as shown in Table 1 "Salt Brine Derivatives" (Anon., 1967), which charts the chemical compounds derived from four types of brines: (1) Owens Lake type brines which are sources of boron and sodium compounds; (2) Midland type brines from which bromine, iodine, and chlorides of calcium, magnesium, potassium, and sodium are derived; (3) Searles Lake type yielding boron, bromine, lithium, magnesium, potassium, and sodium compounds; and (4) Silver Peak type produced mainly for lithium. Table 2 (Jones, 1973) affords an overview of the chief industrial minerals, the chemical products derived from them, and end uses of the products.

Jan 1, 1975

By Robert B. Fulton

The objective of this chapter is to discuss the interrelationship between industrial minerals and chemical manufacturing. It is intended to supplement rather than duplicate the commodity chapters. Particular emphasis is given to the pertinent chemical element and to market factors. Condensing this broad subject into a few pages of this handbook permits treating only the most important elements derived from industrial minerals. Hydrocarbons, which quantitatively dominate as raw materials for the chemical industry, are omitted, as are the metallic elements and the minerals covered in other "use" chapters such as phosphorous, potassium and nitrogen for fertilizers, and titanium dioxide for pigments. The remaining six elements of major importance are: boron, bromine, chlorine, fluorine, sodium, and sulfur. These elements are treated individually under separate headings. Table I (Jones, 1973) affords an overview of the main industrial minerals, the chemical products derived from them, and end uses of the products. Salt brines have particular importance as raw material sources for the chemical industry. Table 2 (Anon., 1967) is a chart of the chemical compounds derived from four types of brines: (1) Owens Lake-type brines, which are sources of boron and sodium compounds; (2) Midland-type brines, from which bromine, iodine, and chlorides of calcium, magnesium, potassium and sodium are derived; (3) Searles Lake-type brines, yielding boron, bromine, lithium, magnesium, potassium, and sodium compounds; and (4) Silver Peak-type brines, produced mainly for lithium. Market Attributes Some of the important market traits common to industrial minerals used by the chemical industry are listed below. 1. They are international commodities, such as fluorspar and sulfur, which largely move to foreign consumers. 2. Grade, and freedom from deleterious elements are important factors affecting their usability in chemical processes. An example is salt (NaCl) used in electrolysis where ultrapure evaporated salt is required to meet rigid specifications. 3. Purified products take on the characteristics of specialty items and command a distinctly higher price than the basic commodity from which they are derived. 4. In practically all cases, chemical users require some sort of cleaning or beneficiation of the naturally-occurring mineral to bring it to specification, and individual specifications may vary from user to user for essentially the same use. 5. In some instances it is necessary to strike a balance between what the vendor can supply and what the buyer requires, with the result that specifications have to be eased to afford the needed materials in marginal cases. 6. Because they tend to be bulk commodities, low cost for handling and transportation are important and such costs may limit the area from which a chemical user can draw his supply. For example, fluorspar from China and Thailand normally goes to Japan, while South African fluorspar can go either to Japan or to the US. 7. Shipments are usually in bulk and frequently in multiple-car, full-trainload or full-shipload lots to reduce transport costs, which in turn may require large terminal investment facilities.

Jan 1, 1983

By George W. Maynard

IN the biographical notice of Thomas F. Witherbee, published in Bulletin No. 32, August, 1909 (p. xxv), it is said that ". he is believed to have been the first manager in America to use the chemical laboratory for the purpose of controlling the regular running of the blast-furnace." Since the year is not given, I cannot decide as. to Mr. Witherbee's priority; but the statement leads me to contribute a bit of history, showing an early departure from the "rule-of-thumb " blast-furnace work to the employment of a chemist. In the autumn of 1868 the department of mining and metallurgy was established at the Rensselaer Polytechnic Institute. In connection with the assay-department a laboratory was equipped for making general commercial analyses. In January, 1869, Alexander L. Holley, the manager and builder of the Bessemer plant at the Rensselaer Works of John A. Griswold & Co., the first plant erected in the United¬States under the Bessemer patents, began to send me samples of ore, pig-iron, and steel for analysis. Early in 1869 I was regularly retained as chemist for the Rensselaer Works; and while the laboratory was not located at the works, for all practical purposes it was the works-laboratory. The increase in work soon made it necessary for me to secure an assistant. I applied to Prof. Charles F. Chandler, who recommended Dr. August Wendel, who had been an assistant of Rammelsberg and had lately landed in New York. Dr. Wendel remained with me until 1873, when I left Troy. My leaving made necessary the erection of a laboratory at the Rensselaer Works, which, was done under my supervision, and Dr. Wendel was employed as chemist. During the period from 1868 to 1873 my work as consulting mining engineer frequently called me to the Lake Champlain

Nov 1, 1909

By Vladimir Vigdergauz, Elena Belogub, Dmitriy Makarov

The influence of supergene oxidation on physicochemical and technological properties of polysulfide ores was studied. Modeling and analysis of oxidation pyrite copper-zinc ore samples from the Valentorskoye deposit show that sulfide floatability is decreased by the longer-term oxidation. The treatment of oxidized samples by sulfuric acid in oxidative conditions and its impact on the elemental sulfur composition on the surface of sulfides was discussed. It is shown that an enhancement of the floatability of sulfides of oxidized polysulfide ores after leaching by sulfuric acid could be perspective for the developing of combining floatation-hydrometallurgical technology of the nonferrous metals recovery.

Jan 1, 2014

By Falbo A, Barbaro M, Esposito MA, Passariello B

Acidic reductive leaching is one of the best known and most widely employed chemical processes for beneficiating minerals of industrial interest. Conventional acidic leaching with sodium dithionite (Na2S2O4), employed to bleach industrial minerals used in the production of ceramics, glassware, paper etc, does not always allow products of high quality to be obtained. In the work reported here two reducing agents, ascorbic acid and oxalic acid, have been employed in a medium acidified by means of sulphuric acid. Continuous systematic tests have been performed on a kaolin sample containing 0.8 per cent Fe2O3, adopting various operating parameters such as, leaching time, temperature and reagent concentration. In each case the total quantity of bi- and trivalent iron dissolved was ascertained. Removal of 80 per cent and 100 per cent of iron with ascorbic and oxalic acid respectively was obtained, while less than one per cent of iron was dissolved in the presence of sulphuric acid only. Products having a very good degree of whiteness (92 - 94 per cent) were obtained, whereas with sodium dithionite the degree of whiteness was in the 85 to 88 per cent range. The best conditions identified were applied to a sample of quartz for the removal of ferric impurities.

Jan 1, 1993

By Wescomb R. Jones

The United States is the world's largest producer of hydrofluoric acid (HF), with its 1971 output of 317,000 short tons representing about 40 percent of the estimated Free World production. U. S. production has increased over five fold in the past 20 years, with a growth rate of about 7 percent per year between 1960 and 1970. However, the growth rate to 1977 is expected to be less than 5 percent per year, due primarily to a reduced rate of growth in requirements by the aluminum industry and an expected increase in imports from Canada and Mexico. This discussion will include our analyses of the consumption pattern for HF in 1972 and the factors influencing the demand forecast for 1977.

Jan 1, 1973

By C R. Crook

A brief outline of production methods and processes is given to show how maintenance fits into the picture at this plant. The work force, and the tools needed to carry out this function, are then described. Preventive maintenance practices, scheduled annual shutdowns and routine check-downs are explained, especially as related to planning and to the materials and labour involved for a mini-mum downtime. A brief explanation of the materials, sup-plies and spare parts program, as well as the part played by the Stores Department in conjunction with the Maintenance Department, is given. Cost control and equipment expenditure indicators are explained. Some specific examples of maintenance jobs are described in order to show the flexibility of the program. S HERRITT GORDON Mines Limited has been in continuous production, except for the planned downtimes needed for expansion tie-ins, or the annual shutdown check-over periods, since the first shipment of nickel on a commercial basis in July of 1954.

Jan 1, 1964

By Magnus Troilius

INTRODUCTION BY C. P. SANDBERG. SINCE the discussion On steel rails in America has forcibly drawn attention to the value of chemical analysis, if not as a necessary stipulation, at least as a guide to control the usual mechanical tests, some doubt has been thrown upon the accuracy of the analytical results Obtained by different chemists. To any One having the least acquaintance with chemistry., it is quite clear that if exactly similar results are to be obtained from the same borings of steel, exactly the same methods must be used by the different analysts. Hence the necessity (if complications are to be avoided) of establishing what I may call standard or normal methods, to be used both by the inspectors and by the chemists at the works. Remembering that the application' of chemistry to steel-rail inspection is yet in its infancy, it is of great importance to possess a perfect acquaintance with the best methods in use. Being myself a grateful pupil of Professor Eggertz, of the School of Mines in Sweden, it Occurred to me, two. years ago, that I could not do better than start a laboratory of my. own, and engage One of his pupils, Mr. Troilius, for the purpose of analyzing the steel borings from mechanically-tested rails, so that I might thus Obtain without delay thoroughly accurate determinations. Moreover, in Order to carry on the, operations in perfect accordance with the methods used at the steel works in England and Germany, where I had to control the manufacture, I deemed it desirable to allow Mr. Troilius to go through a course of training at these works; and I gladly seize this opportunity of expressing my grateful acknowledgments to several works in England and in Germany for affording every facility for such an exchange of information as was found necessary in arriving at the best analytical methods to be used.

Jan 1, 1882

By Paul W. Johnson

Chemical mining is the in situ extraction of metals from ores located within the confines of a mine (broken or fractured ore, stope fill, caved material, ores in permeable zones) or in dumps, prepared ore heaps, slag heaps, and tailing ponds on the surface. These materials represent an enormous, untapped, potential source of all types of metals. The field of chemical mining, now in its infancy, encompasses the preparation of ore for subsequent in-place leaching, the flow of solutions and ionic species through rock masses and within rock pores, the leaching of minerals with inexpensive and regenerable lixiviants under prevailing conditions of the in-place environment, the generation and regeneration of such solutions, and the recovery of metals or metal compounds from the metal-bearing liquors. It is not inconceivable that eventually our ore reserves will consist largely of low-grade, refractory, and inaccessible new deposits and low-grade zones near previously worked deposits, caved and gob-filled stopes, waste dumps, tailing ponds, and slag-heaps. Chemical mining promises economic recovery from these types of deposits. Before it can come of age, however, a much better understanding is needed concerning its chemical and physical aspects.

Jan 1, 1967

By A. Anderko, V. G. Papangelakis, G. Moldoveanu, G. Azimi, M. Carlos

"OLI Analyzer is a software package that uses the powerful Mixed Solvent Electrolyte (MSE) model to simulate the behavior of multicomponent electrolyte solutions from infinite dilution to the limit of fused salt, and from temperatures below the freezing point up to near critical temperature of the mixture. The software also allows the creation of thermodynamic parameters for new chemical systems unavailable yet in public-domain or commercial software databanks. This communication reviews the basics of the model and provides some examples of modeling hydrometallurgical applications with emphasis on high temperature applications, including calcium sulfate scale formation in autoclaves, high temperature pH inference and iron control. INTRODUCTIONModeling of electrolyte systems has been of particular interest to various industrial processes, such as separation processes (e.g., solution crystallization, extractive distillation, seawater desalination or bio-separations), environmental applications (e.g., gas treatment, wastewater treatment or chemical waste disposal) and hydrometallurgy (e.g., pH control and neutralization, iron control, scaling and fouling of equipment). Using a chemical model, time-effective predictions of various properties of electrolytes can be obtained, which is beneficial not only during process monitoring, but also during process optimization and process scale up. As a result, pilot scale studies can sometimes be eliminated where budgetary constraints exist. Development of such a powerful model requires the use of a speciation-based model, in which solution chemistry is explicitly addressed (as compared with some models that treat electrolytes either as undissociated or fully dissociated systems), despite being computationally challenging. In addition, as a feature of electrolyte systems, speciation equilibria inherently influence the phase equilibria due to complex formation, ion pairing, and acid-base reactions. Therefore, how the electrolyte solutions behave at various conditions may differ significantly due to the non-ideality, which must be carefully addressed to obtain a model that is applicable to a wide range of conditions such as concentration, temperature, pressure and solvent system."

Jan 1, 2012