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By J. Bigu, M. G. Grenier

"Dust size distribution and aerosol size distribution measurements have been carried out in several Canadian underground uranium mines. In addition, dust samples have been analyzed for long-lived radioactive products of the U-238 and Th-232 natural decay chains using ex-spectroscopy and -y-spectroscopy techniques.From the data collected one may summarize: (a) most airborne particulates are of size below I u-m and 50% by mass are found above 1 u-m; (b) dust clouds are bimodal; (c) preferential deposition of radon (thoron) daughters takes place on airborne particulates in the sub -micron range at about 0.1 u-m; (d) deposition of radon (thoron) daughters is proportional to particle surface area; and (e) ex-spectroscopy and -y-spectroscopy of dust samples reveals the presence of U-238, Ra-226 and some of their short-lived and long-lived decay products.IntroductionExtended inhalation of airborne radioisotopes poses a potential health problem to occupational workers. Because of this, monitoring of radiation and dust levels for dose exposure calculation purposes is not only recommended but in most cases mandatory.CANMET (Energy, Mines a nd Resources Canada) has long since been engaged in a comprehensive monitoring program aimed at determining dust concentrations in the respirable size range, aerosol concentration in the sub-micron range, and in the radioactivity associated with these particulates in underground uranium mines. Measurements have been carried-out with gravimetric dust samplers, dust size selectors (including a horizontal elutriator , a fineparticle spectrometer and Nuclepore* filters of different pore sizes) and a condensation nucleus counter(1 – 6). Inactive and active working sites have been monitored according to some typical mining operations. A summary of these data has been given elsewhere(3- 5)."

Jan 1, 1984

By Shuan-cheng Gu

Roof bed separation often occurred due to the deformation incoordination of surrounding rock following the excavation of mine roadway. Bed separation has effect on the bolts, and the estimation of the influence will directly affect the safety of support systems. In this paper, the hyperbolic function model to analyze the load transfer mechanism on the bolts was simplified as the exponential function form for easy calculation. An elastic-plastic analysis model of the bolt loading occurred by the bed separation was established. And the development low that the bed separation affected to the bolt loading was discussed. According to the parameters analysis of different separation values and locations, the influence law of the bolt loading caused by roof bed separation was summarized. Finally, the effects of bed separation were considered for the bolting design, it was able to provide a reference to the anchorage design of stratified rock.

Aug 1, 2013

By J. A. Drozdiak, W. Tse, P. P. Rosario

"In a recent publication (SAG 2015), we presented a non-conventional high pressure grinding roll (HPGR)-ball mill circuit as a lower capital cost alternative to the “standard” HPGR circuit. The circuit was designed for the treatment of a hard ore and relatively high tonnage (50,000 t/d). That paper provided details such as flowsheets, layouts, and equipment lists for the two options and compared their calculated capital costs demonstrating significant savings for the proposed circuit. This paper extends the analysis to a third option, a traditional semi-autogenous ball crushing circuit, giving the same level of details and now including the operating cost estimates for all three options for a more comprehensive analysis. Moreover, this work also provides information about the strengths and weaknesses of the non-conventional HPGR circuit when compared to the “standard” HPGR option.This study demonstrates that the proposed non-conventional HPGR-based circuit not only provides a lower overall capital costs for the project if compared to a “standard” HPGR circuit but also brings the capital cost to the level of the traditional semi-autogenous grinding (SAG)-ball mill circuits. In addition, the innovative HPGR circuit provides similar operational cost savings of the “standard” HPGR and thus a significant advantage when compared to the SAG option. With the current capital cost sensitivity for most greenfield projects, the proposed alternative circuit should help make HPGR-based circuits more competitive and thus promote the utilization of a technology that enables higher energy efficiency and reduced greenhouse gas emissions. INTRODUCTIONThe application of high pressure grinding roll (HPGR) technology in comminution circuits is well established for the processing of cement, diamonds and iron ore (Broeckmann & Gardula, 2005), and over the past 10–15 years, this technology has slowly been applied to hard ores in high-tonnage precious and base metal operations. Unfortunately, under the current economic climate, the ability to finance large capital projects has become very difficult and companies tend to have an easier time securing funding if the capital expenditures (CAPEX) are low with a proven process method. The traditional semi-autogenous grinding (SAG) mill / ball mill circuits easily fit into this mould, having been installed in countless plants around the world over the past 30 years with relatively low capital requirements. In contrast, it has been well-documented that HPGR-based circuits are capital intensive with complex material handling systems (Seidel, Logan, LeVier, & Veillette, 2006). Although these circuits benefit from reduced operating costs with the increase in energy efficiency and the elimination of steel grinding media (Rosario, Boyd, & Grundy, 2009), if the company is unable to secure financing to build the plant, these advantages remain out of reach. With the current trend to retrofit existing SAG circuits with a secondary crushing circuit to achieve design throughput, the opportunity to circumvent this gross inefficiency by making HPGR-based circuits more capital friendly would greatly benefit the industry."

Jan 1, 2016

Presentation Topics ? Low and Intermediate Level Waste ? Project Location and Site ? Geological Setting ? Key Features ? Project Overview ? Licensing and EIS ? Next Steps DGR Waste Package Inventory Approximately 50,000 packages over 35 years: ? ~40,000 packages or 80% of inventory are LLW Bins ? ~7,000 ILW Shields (concrete boxes) ? ~2,000 resin liner packages

Oct 1, 2010

By D. C. Fraser, W. J. Scott

"Airborne electromagnetic surveys were flown during 1965 in the Moose River area of Ontario. The systems used were INPUT Mark II and the Canadian Aero Otter. Anomalies indicated by both systems were located on the ground with vertical-loop EM. Two such anomalies were drilled, with no explanation being found in the bedrock geology. Subsequent seismic, resistivity and gravity surveys indicated that the sources of these anomalies lay in the overburden. Current work in the similar geological environment of the Winisk River area has shown that comparable AEM anomalies can still be misleading. The lesson to be, learned from these experiences is that additional geophysical work can help to resolve doubtful cases before drilling decisions are made."

Jan 1, 1973

By K. D. Genn, A. Mucha

This paper deals with Hilton Mines' approach to the maintenance of wear items such as truck boxes, shovel buckets, tractor pads, crawler sprocket idlers and the drop-ball. Each will be given a brief. description as to application, design, kind of materials involved and type of wear. The maintenance procedure is then outlined in terms of materials used, preliminary preparation, and welding and machining practices. The service history of new and re-paired items and the relative economics of repair vs replacement will then be presented.

Jan 1, 1969

By K. Horikawa, S. Kitahata, H. Kobayashi

"It has been clarified that the Al-5%Mg alloys containing 200 mass ppm of sodium showed grain boundary (GB) fracture, even when tested at room temperature, as well as at high temperatures (~500°C). SEM/EDX study revealed that the GB fracture was associated with the segregation of sodium on grain boundaries of the Al-Mg base alloys. Differential scanning calorimetry (DSC) revealed that the GB fracture at room temperature of Al-Mg alloys was caused by sodium segregation in the solid state. It was also shown that the tendency of the GB fracture strongly depended on the heat treatment; the alloys after the solution heat treatment showed severe GB fracture compared with the alloys after the homogenizing treatment. Moreover, it was shown that the GB fracture at room temperature by sodium segregation was suppressed by the addition of bismuth or indium. The suppression of the GB fracture by the additional elements was believed to be the scavenging effects by forming the sodium bearing compounds in grains.INTRODUCTIONIt is widely known that Al-Mg base alloys containing high amount of magnesium(~5 mass%)show better workability at room temperature, while that the alloys show grain boundary (GB) embrittlement at higher temperatures ranging from 200 to 500°C, depending on grain size(Otsuka, 1984), sodium impurity level(Ransley, 1959, Okada, 1997, Horikawa, 2001)and testing strain rate(Yamada, 2012). In the case of coarse-grained Al-5%Mg alloys (~300 ?m), 2 mass ppm of sodium causes severe GB fracture around 300°C, however, the Al-5%Mg-2ppm alloy does not show GB fracture at room temperature. It has also been shown that the GB embrittlement caused by 2ppm of sodium was suppressed by the additional elements, such as bismuth (Talbot, 1995), antimony (Ueda, 1997) and indium (Horikawa, 2012). Basedon these facts, we have concluded that the GB embrittlement at higher temperatures of Al-Mg alloys is attributed to the synergy effects of GB segregation of atomic sodium and GB sliding. For the GB embrittlement mechanism of Al-Mg alloys, involvement of low melting point metallic phases has been pointed out (Lynch, 2002),since the GB embrittlement appeared only at high temperatures. Up to date, the effects of high amount of sodium addition more than 2 ppm on GB fracture were not fully investigated in Al-Mg alloys. In the present study, the effect of 100 ppm ordered sodium impurity on GB fracture of Al-5%Mg alloys was examined, together with the effect of another additional elements."

Jan 1, 2017

By Zhiqing Zhang, Changyun Chen, Qing Liu, Lin Lin, Zhihong Jia, Guangjie Huang, Lipeng Ding

The effect of interrupted quenching (IQ) treatments on natural aging and bake hardening response of Al-Mg-Si alloy was investigated by hardness measurements, tensile test, differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). The results show that interrupted quenching at 100oC could effectively suppress natural aging and improve bake hardening response. The optimized interrupted quenching treatment is 100oC for 45min, which gives the alloy a relatively low T4 temper strength and higher bake hardening response. The formation of highly dense cluster(2) during the interrupted quenching could be the reason for suppressing the natural aging and accelerating the precipitation of ß? phase during the paint bake treatment. In addition, interrupted quenching at higher temperature (170oC) results in unfavorable properties in both T4 temper and paint bake treatment. The formation of large precipitates is responsible for these undesired effects.

Jan 1, 2015

By Z. Y. Liu

A local additional potential model (LAPM) was developed to illustrate the role of strain rate in stress corrosion cracking (SCC) of pipelines. According to LAPM, both density and mobility of the local active spots on the steel surface, i.e., dislocation emergence points, increase linearly with strain rate. Generation of such active spots introduces an additional negative potential locally, affecting the electrochemical reaction and, consequently, the susceptibility of the steel to SCC. Electrochemical corrosion measurements, slow strain rate tests and electrochemical hydrogen permeation test were combined to demonstrate the validity of LAPM to illustrate pipeline SCC in an acidic soil solution. It is found that a maximum of the SCC susceptibility occurs at strain rate of 10-6 s1, which is associated with an enhanced hydrogen evolution due to the local additional potential (LAP) effect.

Jan 1, 2010

By Karl Dufresne

Blasting in geothermally high temperature ground and/or extremely reactive ground is an increasing common challenge for surface and underground mines. Many current PETN based non-electric and electronic detonators have manufacturer published in-hole temperature limits ranging from 55°C to 65°C (131°F to 150°F). When confronting blasthole temperatures above the manufacturer published limits, operations may request site-specific guidance and qualification for use. The advised safe loading window for in-hole PETN based detonators is often too short to be practicable for production blasting. To overcome limitations of PETN based initiation systems, surface mines with high temperature ground and/or reactive ground are known to load blastholes with a qualified high temperature bulk emulsion that are top primed with a cartridge of temperature qualified detonator sensitive emulsion plus an RDX detonating cord downline. As there is no in-hole delay detonator in this system, blasthole timing is accomplished with surface delays. Although this system is safe, top priming and surface delaying does influence floor quality and top size fragmentation, and safe loading windows times reduce blast block size and increase blasting frequency. A mining company with a site characterized by geothermally high temperature ground plus highly reactive ground employed a blasting system like the one described above. The site desires to improve blasting performance by moving to an in-hole delay initiation system that can withstand the site ground conditions. At the request of the mining house, DynaEnergetics developed an electronic initiation system for application in geothermally high temperature ground and/or extremely reactive ground conditions. The DynaEnergetics IGNEO high temperature electronic initiation system is rated for in-hole use in ground up to 150C (302°F) for 48 hours. The detonator consists of a high strength detonator with an HMX base charge and thermally resistant downline. To make up a primer, the detonator is inserted into a booster charge assembly that is fitted with a small HMX shape charge. This high energy primer is designed to be compatible and reliable for firing bulk emulsions, including those with high percentages of urea inhibition to combat reactive ground. Up to 1000 detonators may be programmed in 1ms increments up to 1500ms. The system is controlled by a digital firing panel that can be used with either a wired or wireless trigger.  The system enables high temperature and/or reactive ground sites to utilize in-hole delay initiation and realize the associated performance benefits. Conclusions and Future Work 1] The HMX based electronic initiation system permits bottom in-hole delaying in ground temperatures above 80°C (175°F). As compared to top priming and surface delaying, in-hole bottom delaying is known to improve floor quality, muckpile fragmentation uniformity and reduce oversize. 2] Field evaluation of the HMX initiation system at the Lihir Mine is continuing. 3] Work on the next generation of the HMX initiation system is underway and will bring with it expanded application range and flexibility. 

Oct 1, 2024

By S. Khallouk, J. Zollinger, J. R. Kennedy, E. Bouzy, B. Rouat, D. Daloz

Titanium aluminides recently replaced Ni-based superalloys as turbine blades in the last LP stage of aircraft engines. To extend their range of use at higher temperature their properties need to be improved, either by alloying or processing. An efficient solution is to reduce the grain size during the solidification process. In the first part of the paper, an overview is given on the possibilities for grain refinement of such alloys, based on literature data and new results. The most efficient grain refinement is obtained with boron addition which leads to boride formations that are detrimental for in-use properties of turbine blades. In this work, the use of the high grain refinement potency of inoculation with non-brittle particles has been used by developing new refractory-based inoculants. The effect of one of these inoculants on grain refinement of an as-cast structure in a Ti-46Al is presented; resulting in a reduction of the grain size by a factor of 3.While less efficient compared to the potency of boron containing alloys, the grain refinement is effective and does not introduce any embrittling particles.

Jan 1, 2015

By R. Heikkilä

A large research and development program called RYM PRE (Process Re-Engineering) has been active in Finland since 2010. As a part of the program, a work packet Infra FINBIM is focused on the development of new national process model, specifications and requirements for the whole Finnish Infra Industry. In the Infra FINBIM, total 15 companies and main owners and 3 research organisations are included. The work is further continuing. The main achieved results up today have been the first specifications and requirements of the BIM based total process for infra sector, about 30 different pilot projects for testing of the new design and construction process models producing a lot of results and observations, a new open information transfer format Inframodel3 based on LandXML standard, the achieved acceptance of the Building SMART organization for support of international development, utilization and extension of the format within the whole infra industry, processes, software and other technical equipment. An evaluation of the results and this work will be drawn.

Aug 1, 2013

By A. S. H. Kabir, I-H. Jung, J. Su, Yue. S., M. Sanjari

One of the major problems associated with conventional wrought magnesium alloys is the unwanted basal texture that forms during plastic deformation which generally does not change markedly after post-deformation annealing. Formation of precipitates on the recrystallized grain boundaries during annealing may affect the usual rotation of grains towards preferred basal direction resulting in texture weakening. In this study, Mg-Al-Sn alloy was hot compressed at 250°C and annealed at 350°C for various times. The initial as-deformed microstructure was partially dynamic recrystallized with dynamic precipitates on the grain boundaries. After annealing at 350°C, static recrystallization of the bimodal microstructure took place where at this temperature no static precipitates formed. The goal of this work was to study the effect of dynamic precipitation on the texture evolution during the annealing process. Texture evolution was studied during annealing by electron backscattered diffraction (EBSD) technique through a microstructure tracking process. It was found that precipitates on the recrystallized grain boundaries have significant effect on the usual rotation of the grains towards the basal direction, meaning significant texture weakening, which is beneficial for final mechanical properties.

Jan 1, 2015

By J. R. del Castillo, J. Ruiz, N. Kuyucak, J. Chavez

Environmental Impact Assessment (EIA) and Feasibility Studies (FS) were carried out to evaluate the potential use of treated acid mine drainage (AMD) occurring at the Kingsmill Tunnel in the Central Andes of Peru. The 11-km long tunnel drains the underground works of the Morococha Mining District and discharges about 1.25 m3/sec of AMD directly into the Yauli River, which is located within the Amazon Basin. The communities living downstream cannot use the Yauli River water due to its low pH and elevated concentrations of metals (e.g., Cu, Zn, Fe, Mn, As, Cd) and sulfate. Studies carried out for this project included technical feasibility, EIA, economic viability and social impact assessment phases. During the "Technical Feasibility" phase, the treated AMD was produced by simulating a high density sludge (HDS) lime neutralization/precipitation process and was evaluated for various potential uses. Mining companies located in Morococha, in particular Centromin Peru S.A., and the Water Works Company of the City of Lima (Sedapal) collaborated with Golder Associates during the studies. The Canadian International Development Agency (CIDA) provided the financial assistance. The results of the physical, chemical, biological and toxicological analyses demonstrated that the treated AMD could be used for supplementing the drinking water supply of Lima and for agricultural (e.g., irrigation and livestock) and recreational purposes. Process design and scale-up parameters were also determined for the implementation of the full-scale treatment facility to the site. The use of the treated AMD as a drinking water supplement would be economically feasible.

Jan 1, 2004

By P. J. Le Roux

"Mining worldwide and definitely in South Africa, is constantly under pressure to reduce its cost structure so as to sustain profitability. In underground gold mines where an open stope mining method is employed, dilution often has a significant effect on the viability of sustaining profits. Target Mine practices Open Stope mining Method and it was found that in some open stopes dilution was in excess of 10%, which has a significant impact on the sustainability of the mine.Dilution in excess of 10% can result in the reduction of the recovered grade from 5,5 to 4,5 grams per ton (g/t). The reduction of 1 g/t in recovered grade results in a potential loss of about ZAR21 Million per month bases on a gold price of ZAR240 000 per kilogram. Based on Life of Mine projections the potential loss of income could be as much as ZAR3,3 Billion. A reduction in dilution would have the opposite effect. There are a number of factors which affect dilution of which falls of ground in open stopes is a major contributor. The falls of ground can be attributed to a number of factors such as beam failure as a result of a larger than normal expected roof area (hydraulic radius too large), poor ground conditions, and poor blasting. The cost of damage to or loss of trackless equipment as a direct result of the falls of ground in open stopes, is very significant. The review of financial figures has indicated that this could be as high as ZAR491 million. This combined with the added cost of transport, hoisting, secondary blasting, milling and plant treatment costs of ZAR293 results in an estimated opportunity loss of ZAR784 million.Currently there is a significant amount of data available in the mining industry which could be effectively used to develop suitable back analysis techniques but to date this has not been used effectively. If dilution can have such an impact on current and future mining ventures then the optimization of back analyses for the prediction of dilution in open stoping could assist significantly in the reduction of dilution in massive open stopes. Rockmass classifications, geotechnical information, blast techniques, blast design, the stress strain environment and hydraulic radius all have an effect on, or play a role in the evaluation of dilution. Each of these factors will be taken into consideration to ultimately determine a measurable or calculated percentage of dilution in massive open stopes.The amount of overbreak in an open stope can be determined by subtracting the planned stope volume in m3 from the actual measured final stope volume in m3, which is obtained from the CMS (cavity monitoring system). This is in turn divided by the planned stope volume in m3 to determine the percentage overbreak. The CMS wireframe is imported into the geological model and its grade re-evaluated. From this the actual percentage dilution for this open stope can be determined. The dilution obtained can result in a major reduction of recovered grade for the open stope, but can also increase the recovered grade. The latter is normally the exception rather than the rule.When analysing data from Target mine the following was achieved:• Using 11 years of data a method of measuring and predicting the percentage dilution in open stoping was developed. This took into account rock mass quality, stress-strain state, and the hangingwall hydraulic radius (size of stope hangingwall exposed).• Implementation of this prediction method resulted in a reduction in falls of ground in open stopes. The benefit of this was a reduction in the damage to mechanised equipment resulting from less falls of ground which had a positive effect on the profit margins of the mine. As a direct result the recovered grade from the open stopes increased due to the reduction in the amount of dilution.• A design criterion, Dilution Stress-Strain Index (DSSI), was developed which allows the user to calculate, with certainty, the stability of the open stope and determine if m"

Jan 1, 2015

By A. G. Pathan

Rock and soil mechanics investigations were carried out in block VIII at Thar Coalfield, Pakistan. Most of the strata were mainly composed of sand, with an average content of 67.68 %. Laboratory studies of rock and soil samples from drill hole GT-01 revealed that the strata in block VIII are very weak with an average uniaxial compressive strength of 3.59 MPa, an average tensile strength of 0.68 MPa, an average Young?s Modulus value of 0.234 GPa, an average cohesion of 129.19 KPa, and an average friction angle of 55.47°. Slope stability analysis, based on a probabilistic approach, was carried out using Slide-V software. Monte Carlo simulations have been applied to investigate the probability of failure in the slopes of an open pit lignite mine in block-VIII. From the slope stability investigation, it was found that the probability of failure is 0 % at a slope angle of 16°.

Aug 1, 2013

By M. Mbonimpa

Field experimental cells were constructed in 2007 to assess the performance of different cover scenarios for the reclamation of the Parc 1 tailings disposal facility at the Westwood-Doyon Mine site (Abitibi, Quebec). Three configurations of cover with capillary barrier effects (CCBEs) with different thicknesses and material types for the moisture retention layer (MRL) were studied. MRL with 80 cm till, 40 cm till, and 40 cm clayey silt were used for cell nos. 2, 3, and 5, respectively. The capillary barrier layer (CBL) and drainage and protection layer (DPL) of the CCBE consisted of 30 cm gravel. A reference cell without cover was also constructed to compare the geochemical performance of the CCBEs. Due to an unexpected flooding in the leachate exit area of the cells in spring 2008, the cell instrumentation for hydrogeotechnical monitoring was postponed to spring 2009. Changes with time in volumetric water content, suction, soil oxygen concentration, and temperature were measured at different depths. This paper presents and discusses preliminary results obtained from spring 2009 to autumn 2010. In all cases, the degree of saturation Sr is lower in the CBL than in the MRL, indicating the presence of capillary barrier effects at the interface of these layers. Cell nos. 2 and 5 showed hydrogeotechnical behavior typical of an effective CCBE, with Sr maintained above 85% in the MRL and lower than 30?50% in the DPL and CBL. Based on the obtained results, and as expected, MRL thickness and the type of construction material used appear to affect the hydrogeotechnical behavior of the CCBE. Oxygen concentration profiles through the CCBEs were used to estimate the oxygen flux, and results indicate that cell nos. 2 and 3 performed better than cell no. 3. CCBE performance is currently being investigated using the geochemical monitoring data.

Aug 1, 2013

By S. Amira

The corrosion behavior of high pressure die-cast and thixocast AXJ530 magnesium alloys has been investigated in 0.05M NaC1 solution at pH 6.0 using potentiodynamic polarization tests, electrochemical noise (EN) technique, electro-chemical impedance spectroscopy (EIS) and scanning reference electrode technique (SRET). The behavior of die-cast and thixocast specimens were compared using each of these techniques and the results discussed. Further tests have been carried out with die-cast AZ91D alloy to better compare and interpret the results. Experiments indicate that the thixocast specimens of AXJ530 alloy have a better corrosion resistance than those of die cast alloy in neutral solution.

Jan 1, 2006

By G. Granata, C. Tokoro, M. Matsuoka, K. Horiuchi

"Given the high demand of copper and the lack of new high-grade deposits, low grade copper ores containing copper oxides and refractory sulfides need to be processed as well. However, in order to recover copper from refractory copper ores, the leaching performances should be improved. In this study, we investigated the effect of the mechanical activation in the leaching of copper from covellite. The influence of a mechanical treatment by planetary ball milling on leaching rate in sulfuric leaching media was evaluated by using X-ray diffraction (XRD), mineral liberation analysis (MLA) and X-ray absorption fine structure (XAFS). Results showed a significant increase in copper leaching from around 50%up to 100% along with an improvement of the leaching kinetics when using planetary ball milling. XRD spectra showed the disappearance of the covellite peak from (101) face, thus suggesting the amorphization of covellite associated with the use of planetary ball milling. XAFS results showed that the coordination number of Cu changed from 6 to 3, thereby confirming the effectiveness of the mechanochemical effect.INTRODUCTIONDuring the last decades, while the copper grade in copper ores has been decreasing, the concentration of impurities such as arsenic tends to increase, thus requiring for the processing of low grade copper ores. For a suitable processing of copper minerals, hydrometallurgical processes are preferable due to the lower costs, the lower environmental impact and the easier implementation (Watling, 2006). However, for an economical recovery of copper, the leaching performances must be improved.Among the recent advancements in leaching technologies, the mechanochemical activation allows for an improvement of the leaching performances by means of high-intensity grinding(Mohammadabad et al., 2016). In the first place, the improvement is the result of the dramatic decrease of particle size, which results in an increase of the mineral surface area and the consequent enhancement of leaching kinetics. Furthermore, the intense mechanical stress due to the high-intensity grinding could induce the rupture of the crystal structure producing a decrease of crystallinity. Such changes of the mineralogical structure, also known as mechanochemical effect, can lead to more leachable mineral, thereby resulting in a greater dissolution of copper. Last but not least, whereas the mineral surface might undergo passivation during leaching, the high-intensity grinding can continuously refresh the surface of the mineral, thus exposing portions of unleached bulk mineral."

Jan 1, 2017

By P. A. Riveros

This paper describes the leaching of the common copper minerals tennantite (Cu12As4S13), tetrahedrite (Cu12Sb4S13) and enargite (Cu3AsS4) in acidic media using Fe(SO4)1.5, FeC13 or 02 as oxidizing agents. At temperatures <100°C, tennantite dissolves slowly in Fe(SO4)1.5-H2SO4 media, and the rate is directly proportional to the area of the sized tennantite. The rate increases sharply with increasing temperature and the apparent activation energy is 69 kJ/mol. Increasing Fe(SO4)1.5 concentrations slightly increase the tennantite leaching rate. The kinetics of dissolution of disks of synthetic iron-bearing tetrahedrite in Fe(SO4)1.5-H2SO4 media are linear; the leaching rates are slow but increase significantly with increasing temperature, with an apparent activation energy of 120 kJ/mol. The dissolution of sized particles of natural Ag-bearing tetrahedrite in FeC13- HC1 solutions proceeds according to the shrinking core model, and both Cu and Ag dissolve at about the same rate, provided that the total chloride concentration of the solution is sufficiently high to solubilize the AgC1 reaction product. The leaching rates are slow, and the apparent activation energy is 116 kJ/mol. The addition of sulphate ions to the FeC13-HC1 system reduces the tetrahedrite leaching rate to values similar to those realized in the Fe(SO4)1.5-H2SO4 system. At <100°C, enargite dissolves slowly in either Fe(SO4)1.5 or FeC13 media, and the dissolution rate obeys the shrinking core model. The rate increases with increasing temperature and the apparent activation energies are 50-64 kJ/mol. The rate increases slightly with increasing FeC13 concentrations in 0.3 M HC1 media. The leaching of enargite at elevated temperatures and pressures was also investigated. Potentially useful leaching rates are achieved above 170°C, at which temperature sulphate, rather than sulphur, is produced. Lower temperatures (130-160°C) lead to fast initial leaching rates, but the dissolution of the enargite is incomplete because of the coating of the enargite particles by elemental sulphur.

Jan 1, 2007