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By Pragna N. H. Bhakta

The minerals industry is under political and economic pressure to reduce its processing wastes and minimize their impact on the environment: Recycling is one of the means by which the minerals Industry can reduce the quantities of effluents and residues that are discharged to the environment. The wise use of available resources is not only an environmental necessity but also an economic benefit as natural mineral resources are depleted and/or become more complex. The purpose of this paper is to review the technical and regulatory issues that will help shape the future of minerals recycling over the next ten years. Research and development to address technical issues will be discussed with emphasis on the Bureau of Mines recycling research program.

Jan 1, 1992

By K. S. Han, M. Yoshimuura, H. Fujita, Y. Sato, S. W. Song

"Film of LlCoO2 as cathode material for rechargeable lithium microbatteries has been fabricated on the platinum metal substrate by electrochemical-hydrothermal method in concentrated LiOH solution at 200 °C as Soft Solution-Processing. The film fabrication has been understood in terms of dissolution of cobalt metal powders and subsequent oxidative deposition on the substrate. The film structure was characterized using scanning electron microscope, X-ray diffraction analysis; X-ray photoelectron spectroscopy and micro-Raman spectroscopy.IntroductionRapid growth of wireless communications and emerging integrated optoelectronic circuits caused the miniaturization· cif electronic devices, thus the demand for high energy density microbatteries as a power source for the microelectronics increases. In this regard, all solid-state lithium microbatteries including LiCoO2 and LlMn2O 4 [l-4], the most promising intercalation cathode material, have been developed. However, major difficulty of .fabrication of a lithium microbattery arose from the preparation of cathode film, according to a· recent report on Rare Metal News [5]. Although many attempts have been made to deposit the cathode films, all those methods are mostly chemical vapor deposiiton (CVD), various evaporation, sputtering techniques and spray pyrolysis. These methods require preparation of bulk cathode materials cir its precursor, then deposition with complicated instruments including high· vacuum system, and even postsynthesis annealing to obtain desire electrochemical 'properties. It is clear that all of these techniques are neither economic nor environmentally friendly. Compared to those methods, film form.ation from an aqueous solution is thought to be simpler and more economical, and requires much· less energy consumption. Our .group has demonstrated the utility of Soft SolutionProcessing [6,7], which is defined as environmentally friendly processing using (aqueous) solutions, to produce films of a variety of functional solid materials. According to the Pourvaix's diagram [8], some metal can be dissolved in an alkaline solution and consequently combined with hydroxyl group or oxygen anion forming metalate or metalite. Cobalt also seemed to form cobaltite, HCoOi in strong alkaline solution in the Pourvaix's pH-potential diagram. Based on this information, it was expected that LiCoO2 could be prepared using the cobalt metal in Li OH solution by Soft Solution-Processing. Recently, we reported the successful single step fabrication of electrochemically active LlCoO2 films on the cobalt metal substrate by hydrothermal methods without any post-synthesis annealing as Soft SolutionProcessing [9,10]. Film formation mechanism could be elucidated by the following evidences. . As expected from Pourvaix's diagram, cobalt metal was dissolved in concentrated LiOH solution forming dissolved cobalt species which was detected by an observation of absorption band in UV-VIS absorption spectrum [10]. Thus the reaction was assumed to be started from dissolution. Time dependent potential of Co electrode exhibited only one-step evolution with 0.6 eV from Co metal to LiCoO2 [10]. Another strong evidence was the finding of LiCoO2 powder precipitates at the bottom of tetlon beaker after the reaction [11]. Based on those experimental findings, it was understood that film is formed by dissolution-precipitation mechanism [9-11]."

Jan 1, 2000

By J. M. Floyd

Technology in use commercially and available for commercialisation for injection processing of base and precious metals in bath reactors is surveyed and compared. Differences between bath smelting and suspension smelting systems are highlighted in relation to important smelting criteria. The factors affecting the results achievable with various tuyere and lance injection bath smelting systems are discussed in relation to the various smelting, converting and refining operations involved in copper, nickel and precious metal processing steps. Process chemistry, process dynamics and heat and mass transfer rates are discussed for the different systems.

Jan 1, 1993

By Saskia Duyvesteyn

For many applications in hydrometallurgy and water treatment it would be advantageous to use ion-exchange resins in stirred reactors. However, attrition of the resin may lead to significant losses of both resin and metal values and prevent water quality goals from being reached. We have studied the recovery of fine resin particles by froth flotation, using the model copper - Dow XFS4195 chelating resin system. As the functional group on the resin is a bis-picolylamine, the resin should be amenable to flotation by anionic collectors, such as sodium dodecylsulfate and sodium dodecylsulfonate. The kinetics of copper loading from dilute aqueous solutions in an agitated vessel were studied as a function of copper concentration, pH and resin bead size. The flotation of unloaded resin was investigated for different types of collector, collector concentration, conditioning time, and resin bead size. Potential applications are discussed.

Jan 1, 1995

By John Wallace

"Monitoring compound semiconductor crystal growth using multifrequency eddy currents for sensing illustrates some of the extreme problems of measurement and interpretation that are not often seen in metallic systems. Using sensor arrays and scanning sensors have produced a qualitative and quantitative understanding of some of the high temperature electrical conductivity mechanisms in several compound systems. A detailed review of the CdTe/CdZnTe data is presented showing some of the complexity in the data as opposed to what is found in elemental semiconductors.HistoryThe most common goal in the use of eddy current measurement in crystal growth is to deter-mine the curvature of the liquid solid interface during growth to test if the heat transfer estimates of the thermal design were adequate for single crystal growth[l]. This aim could be met but represented only a small fraction of the data that was produced observing a growth cycle. A secondary consideration was what could be discovered in the recorded data about the growth and subsequent heat treatment as the boule cooled. This is usually a more difficult task because a crystal growth process is not a controlled experiment so much as a process that continually sees modification. Using a sensor arrays or a scanning loop has produced a qualitative and quantitative basis for understanding some of the high temperature electrical conductivity mechanisms. The implication of the these measurements of electrical conductivity variations are important in that they reflect the complex defect states that will occur on cooling and heat treatment following crystal growth. In contrast to the complex behavior of the conductivity of these compound semiconductors in the solid and liquid state we have the very well characterized system silicon to compare. Initially the interest on using eddy currents to monitor compound semiconductors came from G. Westphal at the Texas; Instruments Company in 1987 to monitor aspects of growth and compounding of GaAs. This was followed by work on solution growth of HgCdTe with D. Witter. The initial interest in the use of eddy cur-rents for monitoring CdTe crystal growth came from Prof. Wilcox at Clarkson University in the practical interest to determine and control the crystal interface curvature during vertical brigdeman growth. The first actual work was done by one of his former students. G. Neuge-bauer at the II-VI Corporation which was carried on by G. Rosen at Clarkson and R. Shetty at II-VI Corporation and with A. Socha at Johnson-Matthey Electronics. The work on CdTe extends over four years and yielded sufficient data to allow one to evaluate the utility of the information produced as compared to what could be obtained from monitoring an elemental semiconductor such as silicon."

Jan 1, 1997

By S LeClair

Intelligent manufacturing involves intelligent, product-directed systems that facilitate the on-line, real-time generation of an improving product process cycle. A first step in the journey relates to self-directed systems which have the ability to reason and create their own processing paths in response to varying product and process conditions encountered during the process. This paper discusses an application of self-directed process control in the manufacture of graphite-epoxy laminated composites. An Air Force team involving researchers and production personnel have caused the development of a system now in use at the Air Force Logistic Center at McClellan Air Force Base in Sacramento CA. The paper discusses results and lessons learned in the process of trying to speed the implementation of research efforts which show significant potential of improving the product quality in less time and at less cost

Jan 1, 1992

By René Winand

The paper gives a synthesis of research work performed in the department during the last ten years and dealing with cobalt , copper and manganese electrodeposition in chloride aqueous solutions. Special emphasis is given to electrocrystallization. For copper, properties of the electrolyte such as solubility limits, electrical conductivity and complex ions stability are discussed in connection with leaching, purification of the electrolyte, and metal recovery. When possible, kinetic parameters and probable electrode mechanisms are given. Problems that are still to be solved are also listed.

Jan 1, 1985

By B. Mishra

Calcium and lithium gallides have been synthesized by powder metallurgy techniques in the stoichiometries that can be used as reduction alloys for the Rocky Flats Plant Salt-Scrub (SS) process. The SS process is performed to recover valuable metals from salts generated in the electrorefining and the molten salt extraction processes. Combustion synthesis has been optimized for variable heating rates up to the reaction ignition temperature and for green densities of the powder compacts in terms of the ignition temperature and the exothermic heating of the product in an effort to develop LiGa and CaGaz alloys. The problems arising from the melting point and density differences of calcium, lithium and gallium have also been studied. The SS alloy compositions were produced by mixing, pressing and sintering the metal-powders. The efficiency of the intermetallic alloy, Ca-17 wt. pct. Ga, as a reductant and the effect of gallium on salt clean- up has been discussed. Measurement of actinide recovery has been studied with cerium as the surrogate for the actinide metal. The development of an alloy for SS reduces a major contaminated waste disposal problem besides recovering the valuable reactive metal.

Jan 1, 1993

By C. R. Palmer

The Bureau of Mines investigated the use of ion-exchange technology for the recovery of precious metals from cyanide leach and spent electrolytic solutions. This research included adsorption of gold and silver on both weak-and strong-base anion-exchange resins. The effects of nickel, mercury. and iron on precious metal loading of strong-base resins were also determined. Due to the nonselectlvity of strong-base resins, selective elution also was investigated. Both commercially available and experimental weak-base anion-exchange resins were tested. None of the commercial weak-base resins tested were suitable for a caustic-cyanide system owing to their low recovery of precious metals at pH 10 or above; however, three experimental resins have possible application. Continuous tests conducted with mill cyanide solution in a multicompartmented ion-exchange column using strong-base anion-exchange resins adsorbed nearly 100 pct of the precious metals as well as the iron and nickel. During the elution of this loaded resin the iron was first removed with NaCI plus NaOH; then nickel with dilute H2S04 or HCl; finally gold and silver with thiourea in dilute HCl.

Jan 1, 1988

By F. W. Warnaars

Chanarcillo is a historically well-known silver deposit which produced over 100 million ounces. High grade vein-type mineralization is confined to a prominent set of nearly vertical, NNW to NE fractures that intersected limestones, andesites and tuffs of Early Cretaceous age. A significant amount of disseminated silver mineralization extends laterally outward from the fractures for considerable distances in pyritic carbonaceous limestones, whereas more competent volcanic beds rarely contain lateral mineralization. Local exposures of skarns are mostly barren. Silver and minor base metal mineralization was probably formed peripheral to a granodioritic intrusion inferred to exist at shallow depth. Part of this intrusion is exposed nearby where it contains significant hydrothermal mineralization and alteration. This intrusion was dated at 83.8 m.y.

Jan 1, 1987

By Yan Beygelzimer, Alexander Spuskanyuk, Victor Varyukhin

"The main idea of the report is that the yield surface can be presented as thick, ""foamed surface"" with dimensionality exceeding two. By other words, perhaps, the yield surface is fractal, i.e. it belongs to the class of geometric objects with fractional dimensionality. Apparently, fractal structure of the yield surface is determined by the fractal structure of natural materials. ""Cloud of internal stresses"" term is introduced to describe the stress distribution in representative volume element. Its plastic flow is determined by the interaction of this cloud with the thick yield surface. Thick yield surface and internal stress cloud concepts allow to determine an additional correlation between micro mechanical models of polycrystals and phenomenological theory of plasticity.1. IntroductionClassical plastic flow models are not satisfying the modem requirements. There are two main directions in their development. The first, mathematical, is connected with the development of the general theory of rheological relationships; the second, physical, is connected with the development of the representative volume element (RVE) models which are based on specific ideas about deformation mechanisms. Within the framework of the first direction, the macroscopic experimental data is formalized; the second approach deals with the generalization of physical research results for the different scale levels that are involved in plastic deformation.These approaches have advantages and disadvantages. In phenomenological theories, the advantages are the mathematical simplicity and laconic formulation of constitutive relations, which allows using them in practical calculations. However, the mathematical models of this class can not be considered as general, they are useful only for the description of limited range of deforming processes. On the other hand, physical theories that are based on the description of real plastic deformation mechanisms are very explanatory and predictive, but they lack mathematical simplicity. The above circumstances lead us to the necessity of compromise that can be found in determining the constitutive relations for RVE, which structure and parameters would bear the information about rnicrolevel and mesolevel phenomena. In this synthesis direction, the fundamental role belongs to [1,2], etc."

Jan 1, 2001

By J. Fogarty, J. Sofra

The mobile telecommunications sector is one of the fastest growing industries worldwide. However, increasingly stringent environmental regulations are placing pressure on manufacturers to accept responsibility for end of life products. The companies are therefore exploring avenues to recover the valuable components contained within the mobile telecommunications devices thus reducing the quantities of toxic components going to landfill. Batteries used to power the devices, are typically based on either nickel-cadmium, nickel metal hydride, or lithium ion cells. They contain toxic metals including nickel, cadmium, lithium, potassium, lead, and cobalt in a complicated arrangement of battery cells surrounded by a metals then plastic casing. The Ausmelt Catalytic Waste Converter (CWC) for waste treatment and recycling is well suited to processing all three mobile phone battery types for the recovery of valuable metals in marketable products that can be recycled to industry without turning out harmful levels of toxic emissions. Ausmelt recently demonstrated the capabilities of its CWC by continuously processing 4.5 tonnes of nickel-cadmium batteries. Using Ausmelt's pilot plant facility in Australia, the nickel-cadmium batteries were processed to produce a nickel iron sulphide (matte), a cadmium fume and a final slag which satisfied CS toxicity leach test criteria and was safe f<~r disposal to landfill. This paper explores the commercial development of the Ausmelt CWC for treating each of the three battery types in light of (a) the outcomes of the recent demonstration, and (b) the current and expected future availability of batteries for processing.

Jan 1, 2000

By Jose Luis Lopez Mendez

In May 1992, MEXICANA DE CANANEA, S.A. DE C.V. finalized the life of its Reverberatory Furnace which lasted 16 years. This created the need to prepare the Smelter for the next campaign.

Jan 1, 1994

By Michael Sheedy

Sulfuric acid is widely used as an electrolyte for the electrorefming and electrowinning or metals. Impurities in this electrolyte are controlled by continuously bleeding solution from the tank house. In addition to the contaminant these bleed streams contain high levels of sulfuric acid and the metal being recovered. Subsequent treatment of these bleed streams often requires neutralization which generates large volumes of solid waste. Absorption resin technology employing a novel ion exchange technique known as Recoflo® allows the separation of the mineral acid from dissolved metal salts. The recovered acid is suitable for recycle back to the electrolyte circuit. The metal salt and other contaminants leave the process free .of the sulfuric acid. In this process, known commercially as the APU®, ion exchange resin is used to sorb sulfuric acid while excluding the metal salts. The purified acid is then removed by washing the resin with water. The process has been extensively used for the recovery of waste pickling acids in the steel industry and anodizing solutions in the aluminum industry. In the mining and metallurgical industries the process has been successfully evaluated for the separation of excess sulfuric acid from copper electrolytes, the removal of magnesium and manganese contaminants from zinc electrolytes, and nickel and copper from copper electrolytes. A full scale installation on a copper refinery bleed stream at Palconbridge's Kidd Creek plant in Timmins, Ontario has now been operating successfully for more than 1 year while pilot field trials have been successfully completed on other applications.

Jan 1, 1997

By R. M. G. S. Berezowsky

Treatment of Hudson Bay Mining and Smelting Co. Ltd. (HBM&S) zinc concentrate in the Sherritt zinc pressure leach process produces a residue containing elemental sulphur, residual sulphides, precipitated iron species, si1ver and gold. Flotation of the residue recovers most of the elemental sulphur and residual sulphides to the concentrate, leaving iron oxides and bask sulphates in the tailings. The tailings also contain most of the sflver and some gold. Direct cyantde leaching of the oxide tailings (220 g/t Ag, 1.4 g/t Au) was capable of leaching most of the gold, but only a minor portion of the silver. This paper reports testwork, conducted by Sherritt on behalf of HBM&S, to define a process for a high recovery of the precious metals from the oxide tailings. A si1ver enhancement treatment, consisting basically of digestion of the residue with lime at 90°C to render the silver amenable to enhanced recovery by subsequent cyanidation, was selected as the most promising approach. Batch silver enhancement and cyanidation tests showed that treatment of the oxide residue with 80 kg/t CaO at 90°C for 1 to 2 h increased the silver extractability in subsequent cyanidation from <20% to 96%. A 96 h continuous miniplant test (1 kg/h solids feed rate), of a circuit including a silver enhancement treatment step followed by conventional cyanidation and carbon in pulp silver and gold recovery, confirmed metal recoveries to the carbon of 90% Au and 96% Ag. Reagent consumption rates were 1ess than 100 ?kg/t CaO and 5 kg/t NaCN.

Jan 1, 1990

By N. A. Warner

To filly secure the environmental and social acceptability benefits of making a sulphide smelting facility and its ancillary sulphuric acid plant or other means for fixing sulphur, a virtually zero gas emission operation, it will be necessary to utilise exclusively technically pure oxygen. The strategy proposed for preventing the smelter from overheating involves highly efficient energy transfer by promoting sulphur trioxide formation at a relatively higher temperature than normal. A closed-loop gas circuit uses an eductor system actuated by the process oxygen to recirculate sulphur trioxide and unconverted sulphur dioxide back to the smelter, the endothermic dissociation of sulphur trioxide becoming a major contributor to the removal of excess heat. The only gases leaving the system relate to the bleed of nitrogen impurity introduced in the tonnage oxygen.

Jan 1, 1998

By Frank M. Kimmerle

Spent Potlining (SPL) contains recoverable chemical elements (C, F, Na and Al) which are lost in stabilization or immobilization processes primarily aimed at eliminating cyanides and reducing leach rates of soluble fluorides prior to landfiling. They can be recovered in a variety of mineral forms for recycling in the aluminum industry and elsewhere. Alcan has developed a cost-effective hydrometallurgical route, combining a number of proven unit processes to destroy cyanides, recycle the chemical values and provide a zero-discharge process. Pilot plant studies of this Low Caustic Leach and Liming (LCL&L) Process prove that the fluoride scan be converted to acid grade fluorspar, while the sodium and aluminum are recovered as a sodium aluminate and caustic feed to the Bayer Plant operations. The remaining brick and carbon fraction constitutes a high ash solid fuel which meets TCLP leach criteria and whose reduced sodium content enhances its value as a chemical reducing agent.

Jan 1, 1994

By Karen Tempel

Newmont&apos;s Lone Tree Mine is located 30, miles east of Winnemucca in Humboldt County, Nevada. Starting in February 1994 a pressure oxidation circuit was commissioned to treat refractory gold ores. Gold is leached and recovered from the oxidized slurry in a six-stage carbon-in-leach (CIL) circuit. Lone Tree has been able to maintain tighter control&apos; of cyanide addition and reduce cyanide consumption its CIL circuit through the installation of Degussa&apos;s Cyplus® CCS Cyanide Control System in the spring of 2000. &apos;The Cyplus® CCS, along with additional inputs&apos; from plant sensors, has allowed tor a more efficient and effective control strategy over the manual control method used ,in the past. This paper documents the key aspects of the Cyplus® CCS installation; the development of the control strategy, and the benefits achieved from enhanced control.

Jan 1, 1998

By Batric Pesic

Adsorption of gold on activated carbon from gold bromide solutions was examined as a function of pH, particle size, carbon amount, initial gold bromide concentration, bromine concentration, temperature, and various cations and anions. pH did not have any effect below pH=6. Above pH=6, pH had dramatically negative effect. The adsorption results satisfied a first reaction order model. The reaction rate constant was proportional to the inverse of carbon particle radius. It was also proportional to the amount of carbon, and independent of initial gold concentration. Temperature had a very little effect at pH=l. At pH=8, the activation energy was a function of the extent of a reaction, increasing with the extent of a reaction. Cu, Fe, Ca, Mg, and Na cations and sulfate, chloride and bromide anions did not have any effect on gold adsorption. Bromine had a very negative effect on gold uptake.

Jan 1, 1991

By Robert E. (Bob) Brown

Magnesium was discovered by Davy in 1808. The production processes as they exist are not economically competitive with aluminum The electrolytic magnesium process is divided into two steps; one to make the MgCh feed and the other to apply large amounts of electric current to dissociate the feed into magnesium (450 g) and chlorine (1200 g). The production of fuJIy anhydrous, pure cell feed is a major problem Recently, there has been a growth of thermal processes, mainly the Pidgeon silicothermic production process using FeSi to reduce dolomite in horizontal retorts. Pechiney has a large vertical electrical furnace process that also uses FeSi to reduce calcined dolomite in a molten bath containing alumina. Work is proceeding to develop new or modified processes that will greatly improve magnesium production. The present methods and the research and R&D will be reviewed in this paper.

Jan 1, 2001