Search Documents

By Bernard P, Lhoumaud E, Gunzburger Y, Conin M, De Santis F, Kinscher J

Seismic repeaters are commonly observed in natural fault zones dominated by slow aseismic motion. The corresponding seismic signal, characterized by highly similar wave forms, is usually interpreted as the repeating ruptures of locked asperities on fault planes (“patches of higher roughness”), loaded by a-seismically slipping areas (“creeping areas”) (Chen & Lapusta 2009; Bourouis & Bernard 2007). Only very few occurrences of seismic repeaters have been reported in underground mines, where these phenomena are rather unexpected since the stress state and the seismic wave propagation continuously evolve with the advancing excavation front (Kinscher et al., 2020). A recent study based on a local seismic network installed in the underground mine of Garpenberg, Sweden, has shown that seismic repeaters and multiplets represent the main part of the total released seismic energy (magnitude of seismic events: -2 < M <1, on moment magnitude scale), with some seismic families being active during several months to years. It is suggested that repeaters are linked to aseismic slip on pre-existing talc-filled fractures, induced by the excavation, and loading of asperities. These results imply that part of redistribution of stresses in the mine is due to aseismic slip, which might explain the observed distant and delayed seismicity.

Apr 26, 2022

By D. Meadows, P. Carrato, E. Wingate, K. Churchill

Extracting lunar ice, to be processed into pure water or hydrolyzed into oxygen and hydrogen, faces many challenges. On the Moon icy-regolith deposits that contain up to 10% water are found within Permanently Shadowed Regions (PSR) at both lunar poles, where temperatures approach -220 ⁰C. NASA has identified several technology gaps that exist in developing these resources including: • Excavating large quantities of icy-regolith • Delivering large quantities of acquired resources • Hardware that is lightweight and energy efficient • Hardware that is reliable and durable. NASA uses public challenges to incentivize innovative approaches to closing these gaps. The Break the Ice Lunar Challenge provides over three million dollars in prize money to teams that compete in developing solution to mining the Moon. This paper describes the rules for this challenge and presents some of the proposed solution.

Feb 1, 2023

By Ritayan Chatterjee, P. K. Mukhopadhyay, Surajit Biswas, Dinabandhu Ghosh, Sandeep Agarwal

An Indian magnetite ore from the Nagaland region was characterized by powder X-ray diffraction, spectroscopies (ultraviolet-visible and Raman), high temperature magnetization and thermal analysis. A Rietveld refinement of the diffraction data revealed that the principal phase present in the sample is magnetite with partial substitution of Fe with Mg (mainly) and Cr, leading to the chemical formula of MgCr0.2Fe1.8O4. The UV-visible spectra of the sample in MeCN solution showed three distinct peaks. The lower region bands are due to metal-oxygen charge transitions and the other band is for d-d transition of iron. Raman spectral study at room temperature gave four characteristics bands of magnetite. The sample underwent a magnetic transition at high temperature and the thermomagnetization curve shows hysteresis during cooling cycle which indicates the possibility of first order structural transition at high temperature. The thermal property of the concentrate was studied by differential scanning calorimetric technique.

Mar 1, 2018

By Ying Qin, Shujing Zhu

The characterization of adsorption of natural and composite bentonite in lead aqueous solution has been studied. The results showed that adsorption of both natural and composite bentonites strongly depended on the pH values of the solution. At lower pH values, the mechanisms that govern the adsorption of bentonites were dissolution of crystal structure and competition between the metal ions and the H+. To composite bentonite, the lead ion removal capacity was close to 250 mg/g. At higher pH values, formation of lead hydroxyl species might lead to either participation to the adsorption or precipitation onto the bentonites. Hence, a rapid increase in the equilibrium removal capacity of lead was obtained when pH > 7.0. An increase in the initial lead ion concentration led to the increase in the equilibrium adsorption capacity increased to a certain degree; and then, a plateau was obtained at higher concentrations. As a result, the adsorption performance of composite bentonite was better than the natural bentonite in both physical and chemical changes. The data fitted well with both Langmuir and Freundlich isotherms.

Mar 1, 2017

By Timothy W. Ellis, John A. Howes

The production of lead-acid batteries is defined by a closed-loop product life-cycle. Active material and grid alloys converge on an adaptable specification that improves both performance and recyclability. This mapping of product requirements for lead-acid batteries has taken over 80 years to develop. But, as the use of batteries made with other chemistries continues to grow, the need for a comparable life-cycle management process becomes increasingly apparent given societal needs to manage raw materials, e.g. the European Union Battery Directive recycling targets. What has taken more than 80 years for lead-acid to evolve in a closed-loop paradigm must now be accomplished in less time for batteries using other chemistries and technologies. End-of-life costs are embedded in the product cost of lead-acid batteries. However, end-of-life costs are not reflected in the product cost of batteries made with other chemistries. Those costs are borne by other constituencies with often inefficient and environmentally damaging results. Lead-acid is a materials technology management model for other products.

Mar 1, 2017

By Georges Houlachi, Akram Alfantazi, Michael Mahon, Maysam Mohammadi

Corrosion resistance of the lead-based anodes directly influences the purity of the final product in the zinc electrowinning process. The anodic MnO2 layer that is electrodeposited on the anodes during this process can protect the anodes against corrosion. Sand-blasted anodes generate a uniform, adherent and shiny MnO2 layer, which gradually blisters and eventually sloughs off after several weeks. In this study, we attempted to develop a new method to stabilize the MnO2 protective layer on the anodes during the electrowinning process by providing suitable nucleation sites for electrodeposition of this layer. MnO2 particles (P80=40µm) were used as seed material for this purpose. Different techniques of galvanostatic and cyclic voltammetry polarizations, scanning electron microscopy (SEM) and atomic absorption spectroscopy (AAS) were employed to investigate the performances of the MnO2-seeded lead anodes. The experimental results showed that growth of the MnO2 layer is influenced by the MnO2 seed particles on the anode surface. The MnO2 layers electrodeposited on the MnO2-seeded lead anodes were uniform and strongly adherent to the substrate. This layer was more stable than those formed on the PbAg anode without MnO2 seeding. This could provide the anode with a higher level of corrosion protection. Moreover, formation of undesirable MnO2 mud in the electrolyte and the rate of manganese consumption were decreased when the MnO2-seeded lead anodes were polarized. These observations could be attributed to the different properties of the electrodeposited MnO2 layer on this anode in comparison with that formed on the PbAg anode.

Jan 1, 2016

By Alain E. Holeyman

After scoping out the objectives of this general report, the report reviews the three assigned main themes addressed by the papers submitted to the session: pile monitoring, testing, and data processing. It focuses on later developments and on issues requiring clarification, thereby identifying topics for potential discussion. Pile Monitoring does not bring much novelty, except for the integration of IT on construction sites. As far as testing, new developments focus on internal pile loading procedures while more confidence is being gained with dynamic and kinematic load tests. Significant advances are noted in the interpretation of data, where variability of results are coped with, loading rate effects are being better addressed, and more routine use of Finite element analyses are observed. Several many older problems remain while new issues emerge from more recent technologies and approaches.

Jan 1, 2006

By Richard G. Geyer

One aspect of a program to improve the chances of survival following coal mine disasters is the development of a communications sys tem which will allow surviving miners to make their circumstances known to rescue teams. At present, it appears that an electromagnetic system may be most practical. The development and design of an effective electromagnetic communications link for signalling between mine workings and the surface requires knowledge of pertinent physical properties of the rocks overlying the mine workings and the characteristics of the ambient noise against which a communications signal must be recognized. Knowledge of the overburden electrical transmission properties is useful not only for determining a practical operating transmitter frequency at a given mine, but also for ensuring the best possible electromagnetic coupling for routine or emergency communication purposes. Field studies of the electrical transmission properties of the overburden of coal mines in Colorado, Illinois, and Pennsylvania generally show that a relatively uniform and unimodal electrical conductivity distribution exists provided that the region has not been subject to considerable structural or metamorphic deformation such as that observed in the Gary District of West Virginia. Measurement s of ambient surf ace electromagnetic noise levels at several mines in Colorado, Illinois, and West Virginia were taken and analyzed and are presented in the form of amplitude histogram plots both as a function of frequency and time of day. These amplitude histograms may be used in conjunction with overburden resistivity data in implementing an uplink communications beacon system which will yield a specified signal- to-noise ratio at the surf ace. Numerous C .W. field transmission tests were made in various coal mining environments with use made of either a buried vertical-axis transmitting loop or a short insulated grounded current line. These transmission tests were made from 20 Hz to 20,000 Hz in frequency and at several geographic surface receiving sites. The results of these field measurements show, in general, good agreement with theoretically calculated results. Since the produced surf ace magnetic field from a buried vertical-axis loop source or the produced surface horizontal electric field from a buried horizontal current line show better agreement with theoretical results, they could be used for beacon location system. One criterion would be in detecting the equatorial and polar null lines of the horizontal electric field component which is normal to the direction of emplacement of a buried transmitting line current source. A second criterion would be in the surface mapping of the maximum in the vertical magnetic field directly over a vertical-axis loop transmitter and the associated null is the vertical magnetic field at a horizontal offset distance which is about 1.4 times the depth of burial of the transmitter. Finally, a third criterion would lie in the surface mapping of the null in the horizontal magnetic field directly over the vertical-axis beacon and the associated maximum in the horizontal magnetic field at an offset distance from the transmitter axis of half the depth of burial of the loop transmitter. In mapping the vertical magnetic field over a buried vertical-axis loop transmitter, the size effect of the transmitter loop must be taken Into account when the separation distances between the transmitter and receiving sensor are less than ten times the effective radius of the source loop; increasing the size of the transmitting source relative to the source-receiver separation distance shifts the null in the vertical magnetic field to greater offsets. In mapping either the vertical or horizontal magnetic field over a buried vertical-axis loop transmitter, care should be exercised in ascertaining that measured nulls and maxima are along radials through the axis of the buried source loop. For the main part, coupling experiments show that ambient electromagnetic noise in coal mining districts is less of a problem above 1000 Hertz. But secondary and perhaps undesirable maxima and null phenomena (as well as penetration problems) would occur in many coal mine provinces in the behavior of the surface horizontal magnetic field (over a buried vertical-axis loop transmitter) if transmission frequencies as high as 10 kHertz were used.

Jan 1, 1974

By MARK J. VANARELLI

Estimating groundwater inflows in rock deep tunnels is critical to the safety of personnel constructing the tunnel and the cost of construction. This paper presents two case studies for estimating steady-state groundwater inflows into deep rock tunnels. The case studies included the Chattahoochee and Nancy Creek tunnels. In this paper, statistical methods were applied to packer test data obtained from exploratory borings during geotechnical site investigations. A semi-empirical procedure was utilized for estimating groundwater inflows into these deep rock tunnels. The Chattahoochee and Nancy Creek tunnels are deep rock tunnels which exhibit radial flow conditions. For the radial flow condition, a statistical analysis presented in this paper indicates that the semi-empirical procedure works well; however, variations in the procedure and/or an insufficient amount of testing could lead to underestimations of the inflow quantities. Packer test data plotted in histograms were observed in all cases to be log-normally distributed for the radial flow condition. Modeling using Monte Carlo simulations was observed to be an effective tool for removing irregularities in the distribution of the data and incorporating high-end permeability data to derive reasonable groundwater inflow estimates.

Jun 13, 2021

By Mario A. Terceros Herrera, Mario Terceros Arce, Antonio Marinucci

A Smart Cell is a closed-type tip post-grouting device that is attached to the bottom of the steel reinforcement cage of a drilled shaft and is used to enhance performance and to reduce uncertainty thereof. Control of the grout is maintained within the device during injection and a uniform stress is imparted across entire base area simultaneously, inducing a pre-mobilization load into the shaft as well as the soil. This paper describes the construction and tip post-grouting of drilled shafts from two bridge projects in the Santa Cruz, Bolivia region along the Paraí River. During the grouting process at each project site, there were noticeable differences in the grouting pressures achieved and responses observed, even within short distances between shafts. For this project, the greater benefit of using the Smart Cells was the reduction of risk and uncertainty of performance due to the highly variable soil conditions. Ultimately, since the response of each shaft was observed during grouting and because a “minimum” value of shaft resistance (i.e., pre-mobilization of load) was measured, there is a greater reliability with the anticipated performance of the shafts when axial loading is eventually applied.

One of the most important factors leading to the success of a cement plant is its location. A multicriteria decision-making method is used to rank alternative plant locations. The set of criteria is established and corresponding criteria should be established for each case study, although this multicriteria decision-making approach has broader applicability. In this paper, the analytic hierarchy process (AHP) with 5 criteria is used to develop a location evaluation hierarchy for an alumina?cement plant in East Azerbaijan province of Iran. Five alternatives for the plant location are evaluated. The main criteria are transportation, water supply, power supply, fuel supply and land. Other criteria have the same importance as these five alternatives. The alternatives are ranked by a multicriteria method and the best site is proposed. Keywords: plant location; multicriteria decision-making

Jan 1, 2005

By G. K. Nimal Subasinghe

The establishment of grind size that optimally liberates the valuable mineral for efficient down-stream processing is of great importance for most mineral processing operations. Reasonably accurate comminution models as well as models of downstream separation processes may be found in the literature but their use in optimizing grind size is limited without an associated liberation model. In this work, an attempt has been made to address the above shortcoming by demonstrating how the effective parameters of the downstream flotation process may be predicted from the liberation characteristics based on the ore texture data for a disseminated nickel ore. In this regard, the liberation model based on linear intercept distributions of mineral and gangue proposed by King (1979) and its application to predict the flotation performance of an industrial plant demonstrated by Schaap (1979) may be considered useful contributions. However, while the model proposed by Schaap is simplistic enough, it is based on several assumptions due to the non-availability of intercept length measurements on the parent rock, in particular, on the extent of mineral exposure on the surface of comminuted particles. In this work, the linear mineral and gangue intercepts on polished specimens of a binary ore, comprising darker pentlandite as the valuable mineral and lighter barren host rock were measured using an image analyser. The resulting intercept distributions followed negative exponential distributions. Using the mean sizes of mineral and gangue intercepts, the proportion of liberated, compo-site and mineral occluded particles of a given size, the extent of mineral exposure on the surface of particles and their mean mineral contents were calculated using principles of renewal theory. The rock was then crushed and ground and different size fractions were floated. It has been shown that the parameters of observed recovery data based on 1st order kinetics such as the associated rate constant and ultimate recovery agrees well with those predicted from the quantities calculated above. This work has important practical implications since it can indicate variations in flotation performance arising from changes in mineralization within a large ore body.

Jan 1, 2014

By L. M. Demers, D. C. Kuhn, N. El-Ayouby, C. F. Stanley

"Oxygenated metabolites of arachidonic acid (MJ are produced by the alveolar macrophage (AM) and have been shown to mediate inflammatory reactions. We therefore assessed the production of eicosanoids by AM harvested from the lungs of rats ex· posed to a bituminous coal dust for 2 wk in an inhalation chamber in order to determine if AA metabolism was altered in a manner that may promote an inflammatory response in the lung. Exposure to coal dust resulted in a 66% increase in the number of AM harvested, an increase in thromboxane A2 (TxA;i) and leukotriene 84 (LTB,j) production to 222% and 181% of control values, respectively, and a decrease in prostaglandin E2 (PGE:i) production to '62% of control values. In AM harvested from rats allowed to breath clean air for 2 wk following coal dust exposure, PGE2 production returned to control levels but TxA2 and LTB4 production remained elevated. The TxA2 synthesis inhibitor UK 38,485 reduced TxA2 production in dust-exposed AM both immediately and 2 wk following exposure. Thus, exposure of rats to coal dust significantly alters the metabolism of AA in AM, with potentially important aspects of AA metabolism remaining altered even after a 2-wk recovery period. Based on the established role of eicosanoids in inflammatory and fibrotic processes, these results suggest that the alteration of AM eicosanoid production as a result of the inhalation of coal mine dust may be an important factor in the pathophysiology of coal workers' pneumoconiosis.The authors are grateful to Joan Greenwood and Barbara Scheetz for their excellent technical assistance and to Brenda Pavone for the preparation of the manuscript. This research was supported by the U.S. Department of The Interior's Mineral Institute Program administered through the Generic Mineral Technology Center for Respirable Dust under grant 1135142.Request for reprints should be sent to Douglas C. Kuhn, Ph.D., Department of Pathology, The M.S. Hershey Medical Center, Hershey, PA 17033.INTRODUCTIONPulmonary alveolar macrophages (AM) are activated by foreign particles and microorganisms that enter the small airways (Kass et al., 1966; Herscowitz, 1985). This defensive reaction involves phagocytosis, lysosomal enzyme release, and the generation of reactive oxygen species by the AM (Snella, 1986; Rich et al., 1987). A number of agents, including phorbol esters, zymosan, adenosine diphosphate, organic hydroperoxides, and calcium ionophore, have been shown to activate the AM in vitro (Badger, 1986; Marshall and Lands, 1986; Snella, 1986). The AM response to these activators appears to be mediated in part by the oxygenated metabolites of arachidonic acid (AA) (Bertram et al., 1988; Demers et al., 1987; Mcleish et al., 1987).The AM may metabolize AA through cyclooxygenase- and lipoxygenase- catalyzed pathways to produce a variety of eicosanoids including prostaglandin (PG) E2, thromboxane (Tx) A2, leukotriene (LT) B4, LTC4, LTD4, and several hydroxyeicosatetraenoic acid derivatives (HETEs) (Willis, 1970; Camp et al., 1983; Poubelle et al., 1986). The production of these eicosanoids may enhance the. defensive ability of the challenged lung since they stimulate chemotactic cell recruitment to the site of invasion, enhance extravasation of circulating immune cells, and promote local vasodilatation. However, continued stimulation of the AM population, with the consequent production of proinflammatory eicosanoids, may ultimately enhance the disease process by contributing to chronic bronchoconstriction, fibrosis, and the persistent release of toxic oxygen species."

Jan 1, 1990

By J. J. Crowder, A. L. Coulson

Ground support is a significant component of underground mining costs. The rehabilitation of failed support, however, is often much more expensive than the initial installation. This paper investigates whether the right type and length of support can be designed correctly the first time, through forward modelling of the support and the mining process. Back analyses demonstrate how high-quality instrumentation and monitoring can help with the estimation of the post-peak (post-failure) rock mass parameters required for a comprehensive analysis. A hybrid modelling approach combines a three-dimensional mine-wide boundary element model with a non-linear finite element model to allow for the failure process in the rock mass. The back analyses demonstrate that, for the case study site, the post-peak Generalized Hoek-Brown value of mr must be reduced significantly in order to properly simulate displacements observed in instrumentation data. High-quality instrumentation data is the key to post-peak rock mass parameter calibration. The procedures outlined in the paper highlight the need for a new hybrid numerical modelling package that can use the influence of three-dimensional mining-induced stresses to predict displacements in, and potential failure of, rock masses surrounding mining infrastructure in order to radically alter strategic and tactical mine design.

Jan 1, 2007

By S. B. V. Stewart, W. W. Forsyth

"Since the Mathew&apos;s method for open stope design was first proposed by Golder Associates in 1980 it has been applied at a number of mine sites in Canada. The initial hypothesis was based on a relatively small amount of data and the intervening period has allowed the collection of a significant amount of new data to test the validity of the method.This paper examines a brief history of the evolution of rock mass classification systems to provide background and emphasize their empirical and non-rigorous approach. It also presents the new data which appear to indicate that the initial hypothesis was reasonably good. The modification to the original graph proposed by Potvin is discussed as well as the applicability of the method to predicting the onset of caving. The original graph has been updated and has been subdivided into four zones described as ""stable""; ""potentially unstable""; ""potential major failure""; and ""potential caving"". The method is recommended as a useful open stoping design tool provided it is recognized that it is not a rigorous design method.Finally the paper proposes a recommended approach for application of the method by would-be users and addresses some typical pitfalls that may be encountered."

Jan 1, 1995

By Rakesh Sehgal, Pushkar Verma, Mohit Sharma

"SJVN Limited successfully commissioned its Rampur HEP (412 MW) in 2014. The project has been planned to operate in tandem by directly utilizing the Tail Water of SJVN’s prestigious Nathpa Jhakri Hydro Power Station 1500 MW located upstream. The initial filling of voluminous water conductor system of RHEP with 10.50 m diameter, 15 Kilometer long Head Race Tunnel, involved more than 1.5 million m3 of water. The filling operation of such a large diameter tunnel constructed in young folded Himalayas which always offer less ideal sites for tunnelling and their subsequent operations under pressurized conditions is worth sharing with tunnelling fraternity. The paper covers meticulous planning, execution, precautions taken, and performance monitoring during filling process keeping in view the fragile geology, low rock cover zones, shear zones in close vicinity of thickly inhabited areas, squeezing zones, hot water zones encountered during excavation.1.0 RAMPUR HYDRO POWER STATION IN BRIEFRampur Hydroelectric Project (412 MW), is located in Himachal Pradesh (India). This project is a downstream development of Nathpa Jhakri Hydro Power Station (1500 MW) constructed on river Satluj and commissioned during 2003. Both the projects today are now successfully working in tandem. The upstream NJHPS has been constructed on the left bank of the river while the downstream Rampur HPS is located on right bank of the river (Figure-1).The major length of HRT of Rampur project lies on right bank of river before it crosses under the river in its initial reach (Figure-2). The main features of the project are as below:• 10.50 m diameter 15 km long HRT ending in a 155.75 m deep, 38.00 m diameter surge shaft.• 3 steel lined pressure shafts, 5.4 m dia, 211-220m long.• Surface valve house 69 m long x 10.50 m wide x 23 m high housing 3 No. butterfly valves• 3 No. surface penstocks 5.4m dia 368-382m long, bifurcating into six penstocks, each of 3.80 mdia. to feed six generating units of surface power house 158 m long x 24.50 m wide x 48 m high, with Francis turbines each of 68.67 MW capacity."

Jan 1, 2016

By S. Fitzel

The Betts process for electrorefining of lead has been in operation since 1902 in the Trail Operations Metallurgical complex. The Betts process allows production of high purity lead in a single electrochemical step. Process improvements and plant expansions have taken place over the many decades of operation of this process which has proven to be robust, flexible, and capable of successfully treating a large range of anode bullion compositions. This paper reviews the history of the Betts lead electrorefining process, the innovations and quick industrial adoption of new discoveries that took place at the end of the nineteenth century. The process was first implemented in Trail Operations and integrated very well with metallurgical needs then and now.

By David S. Graham, Joseph D. Bailey, Paul J. Axtell, Michael K. Muchard

"Two instrumented test piles were simultaneously subjected to a static lateral load test by jacking the piles apart. One of the piles was loaded in axial compression via kentledge during the lateral load test. Both piles were constructed in an identical manner. These piles were constructed and tested as part of a construction-phase load test program for a floodwall improvement project along the Missouri River in Kansas City, Kansas. Details of the subsurface conditions, drilled pile construction, instrumentation, and load testing procedures are described. Data collected during testing of the piles are presented and compared. Potential effects of the axial compressive load related to observed differences in pile lateral response are discussed.INTRODUCTIONTwo instrumented test piles were simultaneously subjected to a static lateral load with one of the piles also subject to a combined axial load during testing. The load test program was part of a floodwall improvement project in Kansas City, Kansas. Known as the BPU floodwall, the floodwall runs along the south bank of the Missouri River at a Kansas City Board of Public Utilities power generation and water treatment facility. The project location is shown in Fig. 1.Drilled, 2-ft (610-mm) diameter piles were designated by the designer, the U.S. Army Corps of Engineers (COE), as the foundation type for supporting extended floodwall footings. The drilled piles are fully cased, cast-in-place concrete, reinforced with a steel 12x74 (310x110) H-pile. In order to test soil lateral response and pile structural response under combined loading, the COE required that both a lateral test and combined lateral and axial test pile be constructed and tested. In order to most efficiently test both piles and to allow for simpler comparison, the two piles were simultaneously laterally loaded by jacking the piles apart, applying a maximum lateral load of 195 kips (867 kN). A constant axial load was applied to the combined test pile by kentledge prior to lateral loading and was maintained for the duration of the lateral load test. The total weight of the kentledge was 61.5 kips (274 kN). Fig. 2 shows the test setup."

Jan 1, 2017

By Alan Jessop

A small group has been set up at the Dominion Observatory, Ottawa, to make a survey of terrestrial heat flow throughout Canada. Terrestrial heat flow is the heat rising from the interior of the earth and escaping at the surface, and is calculated from a knowledge of under-ground temperature distribution and the thermal conductivity of rocks. A small number of diamond drill holes are being sunk for the purpose of measuring temperatures below the surface, but the program is inadequate for a thorough survey. Mines and holes drilled for other purposes are being sought by the Dominion Observatory group to supplement their own drilling program. F ROM January, 1.962, to December, 1964, geo-physicists of many nations will be cooperating in the "International Upper Mantle Project." Unlike tl1e International Geophysical Year, which was mainly concerned with the fluid layers surrounding the earth, the Upper Mantle Project is an intensive study of the solid earth. Canada, with its large land area and extensive Precambrian Shield, is an active participant in the project.

Jan 1, 1964

By S. M. Bradshaw, C. Dorfling, F. Ngandu

"Selenium removal and platinum group metal (PGM) recovery from copper sulfate leach solutions form an integral part of platinum producers’ base metal refinery operations. Recent studies found that substantially higher PGM recoveries can be achieved if excess thiourea instead of sulfurous acid is used as precipitation reagent; however, the impact of the proposed process on downstream processes was unknown. The objective of the current study was therefore to investigate the effects that excess thiourea and residual selenium present in the rich copper sulfate electrolyte have on copper electrowinning. This was achieved by performing cyclic voltammetry tests using a platinum rotating disk as working electrode, a graphite auxiliary electrode and a saturated calomel reference electrode. A synthetic copper sulfate electrolyte containing 0.01 M Cu2+, 1 M H2SO4 and varying amounts of selenium (20 – 150 mg/L) and thiourea (10 mg/L and 100 – 300 % excess) was used. The results obtained have shown that both thiourea and selenium interact with the cupric ion cathodic reduction reaction. Thiourea polarized the working electrode and lowered the efficiency of the cupric reduction reaction. Tests on the solutions with high selenium concentration showed simultaneous reduction of copper and selenium, which led to copper selenide formation. Nodule formation on the deposit surface also became significant at higher selenium concentrations. Based on these results, it was concluded that precipitation of PGMs from the copper sulfate solution with excess thiourea is not feasible due to the detrimental effect on downstream electrowinning operations.INTRODUCTION During the high pressure oxidative leaching stage in a typical base metal refinery (BMR) circuit, selenium, tellurium and some platinum group metals (PGMs) are dissolved along with the desired copper ions. The impurities (selenium and tellurium) may pass to the copper electrowinning circuit where it can result in the formation of nodular copper electrodeposits or reduced current efficiency. The presence of PGMs in solution, on the other hand, increases the precious metal inventory and potential losses of the operation. Currently, sulfurous acid is widely used for selenium and tellurium precipitation from copper sulfate leach solutions. Sulfurous acid is capable of reducing cupric ions to cuprous ions; the generated cuprous ions then react with Se4+ and Se6+ to precipitate selenium as a copper selenide (Bello, Dorfling, 2014). Recent studies have, however, proposed the use of excess thiourea as a precipitating agent for the removal of selenium and tellurium; it has the advantage of improved PGM recovery in the Se/Te precipitation step (Lottering, Eksteen et al., 2012; Mulwanda, Dorfling, 2015)."

Jan 1, 2018