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By V. Panayotov, M. Panayotova

"Wastewater from ores processing is often polluted by molybdate and sulfate (SO42-) ions. Sorption is one of suitable methods for removing those pollutants when presenting in low concentrations. This work reports results on adsorption of sulfate and molybdate ions on metal modified (with barium - Ba and lead - Pb) and organic reagent modified (with Hexadecyl-trimethyl-ammonium bromide - HDTMA) clinoptilolite. Zeolite’s modification with Pb, Ba and HDTMA increases its uptake capacity with respect to Mo(VI) at pH 3, with the uptake capacity decreasing in the order CL-Pb > CL-HDTMA > CL-Ba. Lead-modified clinoptilolite shows high uptake with respect to Mo(VI) in acidic, neutral and slightly alkaline conditions. The presence of SO42- in concentrations twice higher than the amount of Mo(VI) do not interfere with the Mo(VI) removal by CL-Pb. Zeolite’s modification with Ba and Pb renders it able to immobilize SO42- from water in the pH range 3-9. Kinetics of the uptake process is best described by the pseudo-first order kinetic equation. Increasing the initial concentrations of Mo(VI) and SO42- increases the removed amount of pollutants. INTRODUCTION Wastewater from copper-molybdenum ores processing is often polluted by molybdate and sulfate ions. Molybdenum (Mo) migrates easily in water and consequently the Mo polluted areas could extend for hundreds and thousands of meters (Ryzhenko, 2010). Molybdate anion is the only Mo(VI) species in natural water, i.e. at pH > 6.0. Its median freshwater hazardous concentration affecting 5% of the species (HC 5.50%) is 38.2 mg Mo/L (De-Schamphelaere et al., 2010). The marine water chronic toxicity (HC 5.50%) is assessed at 5.74 mg Mo/L (Heijerick et al., 2012). The predicted no-effect concentrations (PNEC) are 12.7 mg Mo/L and 1.92 mg Mo/L correspondingly for freshwater and marine water (Heijerick et al., 2012a). When sulfates present in drinking water in excess of 250 mg/L they cause a cathartic action (especially in children) in the presence of sodium and magnesium, and when the concentration exceeds 600 mg/L, diarrhea. When sulfate-rich effluents are discharged into the environment, they may increase the acidity of water bodies and soils (Guimarães and Leão, 2014). Because of the adverse effects to human health and the environment, limits are set for SO42- concentrations in waters and wastewaters in the range of 250 / 500 mg/L."

Jan 1, 2018

By Brian Hart, Rong Fan, Roger Smart, Andrea Gerson, Ning Xu

A complete strategy has been developed for identification of the reasons for losses in recovery and/or grade, due to changes or complications in mineralogy and in mineral surface conditioning, and their subsequent correction. The sequence of methods starts with comparison of mineral phases between QEMSCAN/MLA (compositional) and Rietveld XRD (crystalline diffraction) with bulk assay reconciliation. This methodology has recently led to identification of unrecognised amorphous content (12-40 wt.%), previously attributed to crystalline phases, in the fine fraction (<35 µm) of some problematic flotation feeds. Attached amorphous silica, talc- and chlorite-like fines have direct influence on the hydrophobic/ hydrophilic ratio on value mineral surfaces adversely affecting flotation. SEM/EDS is used in the backscattered imaging mode to determine possible problems with liberation (e.g. remnant local locking), not detected in standard liberation analysis, resulting in gangue flotation. EDTA extraction is used to assess bulk feed pre-oxidation and sequential oxidation product loading through the circuit. Changes in circuit solutions are assayed with speciation modelling of precipitates and potentially adsorbing species. ToF-SIMS with principal component analysis is then used to correlate surface species with specific minerals and can be used to assess the effectiveness of specific reagents particularly collectors. This approach identifies unwanted activating species and interference with value surfaces by adsorbed hydrophilic ions, precipitates and fine particles. When the interference or ineffective reagents are specifically identified, remedial action can be targeted. This method has identified residual talc-like layers (<10 nm thick) inducing gangue flotation of pyroxene and chromite in PGM flotation. Recent case studies of application of the full methodology to losses of molybdenite at KUCC and to sphalerite activation in the Cu/Pb circuit at Brunswick Mines with remedial action are discussed.

Jan 1, 2014

By I Brum

Brazil and Colombia have large reserves of coal, those reserves in Brazil are located predominantly in the south and Colombia the main reserves are located in the north. Despite the relative ease of exploitation, these resources have been underestimated as a source of energy. Currently, these countries are developing projects and partnerships aiming to qualify this mineral resource, adding quality to the final product of the processing plants. In this scenario the processing of Brazilian and Colombian coal in flotation columns appears as a promising alternative, having been successful in mineral systems containing fine particles This paper aims to study the overall process of column flotation for a specific Brazilian coal and a specific Colombian coal. The material used in this study consists of fine coal from Brazil (Copelmi) and Colombia (Cerrejon). The objective is to recover carbonaceous matter and reduce the ash and contaminants grade. The two coals were floated using a negative bias in a 5 cm diameter conventional flotation column of 5 m high. Flotation parameter investigated included air velocity in the range 0.6 to 1.5 cm/s. For all runs, a constant negative bias of -0.25 cm/s and a pulp concentration of 8% w/w were used. For Cerrejón coal, 300 g/ton of frother and 907 g/ton of collector was used, whereas for Copelmi coal, 600 g/ton of frother and 1815 g/ton of collector was employed. The frother was a commercial Aerofroth 65 (AF65), whereas the collector was Kerosene. For the Colombian coal, in general, yield, organic recovery, ash recovery and water recovery decreased with the increasing air rate. However, for Brazilian coal the air rate had no significant effect. For Colombian coal, the highest yield (60% w/w) and organic recovery (69% w/w) were obtained at the lowest air rate (0,6 cm/s). Keywords: negative bias, column flotation, coal

Sep 1, 2012

By A. V. Rasskazova

"The oxidized and mixed ores are processed by heap leaching. Primary ores with high gold content are floated. In recent years mining of primary ores with the low gold content (up to 4 ppm) has increased. Extraction of gold from these ores by floatation is technologically ineffective. Gravity concentration is ineffective for fine gold particles because of their floatability. The research objective was assessment of the viability of processing gold-bearing ore with combined gravitational and hydrometallurgical methods and testing of recovery of metals from a gold-copper oxidized ore chloride-hypochlorite leaching solution. The advantage of chloride-hypochlorite lixiviant is the low cost of reagents which is produced by the electrochemical synthesis of NaCl solution with the addition of HCl. The adsorption of chlorine compounds by a mineral matrix and its ability to oxidize the refractory ore components and allows for the application of chloride-hypochlorite systems for gold recovery for both oxidized and primary ores. The complexity and problem in using a gold–chloride system is the strong adsorption of gold–chloride complexes onto mineral surfaces, such as goethite, quartz, and alumina. In preliminary testing, gold recovery from gravity circuit gold bearing concentrates processed by agitation leaching in chloride-hypochlorite solution, gold recovery has reached up 82% after 4 hours of leaching. Chloride-hypochlorite leaching of copper-gold oxidized ore with preliminary processing by sulfuric acid provided for 94 % gold recovery to solution. Understanding of ecological hazard of cyanides is the motive power of researches in the field of search non-cyanic chemistries to provide for technologically and economically effective solvents of gold. Soluble compounds of chlorine with a suitable oxidizer are one of the alternatives to cyanides. Basic researches of gold extraction by chloride-hypochlorite solution have shown high rates of gold recovery.INTRODUCTION Because of the continued and growing environmental concern for the use of cyanide for gold processing, interest for the use of non-cyanide lixiviants, especially with halides has renewed recently (Tran et al., 2001; Ferron et al., 2003; Bhaghalha, 2007). Leaching solutions based on halides (chloride, bromide and iodide) are viable alternative to cyanide (Kwang et al., 2008). The major disadvantage of the chlorine–chloride system is the high reactivity of chlorine in reaction with sulfide and gangue carbonate minerals. It is believed that only high grade materials may be treated by chlorine–chloride systems economically (Baghalha, 2007). Another important problem of the application of gold–chloride complex is that it tends to be rather unstable and may re-precipitate upon contact with a reductant, such as sulfidic minerals of ore. It is well known that Au(III)–chloride hydrolysis species are strongly adsorbed by goethite, quartz, and alumina (Machfsky et al., 1991). To minimize adsorption of gold–chloro complexes, it works best to minimize the adsorption time."

Jan 1, 2018

By Zhong Hong

A novel ilmenite collector, tert-butyl benzoic hydroxamic acid (TBHA), was investigated in this paper. The flotation performance and adsorption mechanism of TBHA to ilmenite were evaluated through pure mineral flotation tests, ?-potential measurement and IR spectrum analysis. The experiment results indicated that TBHA exhibited strong collecting capability to ilmenite under pH 6.0-8.5. At pH 7.0-10.0, TBHA existed in the form of anionic species in aqueous solution, and the ?-potential measurement results showed the surface of ilmenite maintained negative and more negative after the adsorption TBHA on it, which inferred that TBHA might adsorb on the surface of ilmenite through chemical interaction. The IR spectrum analysis further confirmed the chemical interaction between TBHA and ilmenite surface. Keywords: Tert-butyl benzoic hydroxamic acid, Ilmenite, Flotation, Chemical adsorption mechanism

Sep 1, 2012

By M. McClintock

"High Pressure Grinding Rolls (HPGR) is increasingly being chosen for comminution circuits for its energy-efficiency for hard rock mining operations. Despite HPGR’s growing popularity, geo-metallurgy programs are still prohibitively expensive because of large sample requirements. Traditionally, sizing HPGR application requires a significant amount of sample, in the order of 1 to 10 tonnes, depending on the level of study and complexity of the resource. Therefore, engineering and design of HPGR circuits typically are reliant on few composites that are required to be representative of the resource and mine plan. Three bench scale HPGR test methodologies were developed in 2015 at NBK Institute of Mining Engineering at the University of British Columbia (UBC) capable of defining the energy size breakage relationship of pilot HPGR. These methodologies were developed to allow bench scale testing for different levels of study from PEA (Preliminary Economic Assessment) to detailed design and operations. The Piston Press test defines the energy size reduction relationship by measuring specific energy consumption and corresponding feed and product size distributions. The advantage of Piston Press testing is the small sample requirement of 5 to 10 kg. Small sample requirements allow multiple samples to be tested across a deposit. Piston Press testing allows extensive geo-metallurgy programs that can determine ore variability and inform in optimization and production planning. To date, the Piston Press methodologies have been validated on a pilot-scale HPGR unit located at UBC. Recently, testing was conducted to calibrate and validate the Piston Press test against full-scale HPGR on a gold sulphide ore deposit. The program included the collection of operational data with the respective HPGR feed and recycle sample. Sample collected was used both for Piston Press testing and HPGR piloting. This paper discusses the test-work and results as carried out during this program, using the aforementioned methodologies."

Jan 1, 2018

By Jerzy A. Mielczarski

The separation of albites from quartz by flotation applying the conventional HF-methods is no longer acceptable from an environmental and health point of view. Therefore, the search for a new reagent scheme without using HF depressor for separation of albite from quartz is under consideration. The flotation behaviour of ore mineral components depends on the produced hydrophobic or hydrophilic surface coverage (chemical functionalization). Currently we have excellent possibility of monitoring surface composition and structure at molecular and atomic levels at surfaces of natural minerals contacted with aqueous solutions of collectors, activators, depressants which is vitally important for the understanding of the surface chemistry that govern selective and efficient flotation. Detailed surface characterization of minerals before and after their exposition to different solution conditions was performed by the most modern spectroscopic techniques such as developed by us the infrared external reflection technique combined with spectral simulation and X-ray photoelectron spectroscopy (XPS). It is possible to monitor surface reactions which facilitate the separation process and those which bring disadvantage to selective flotation. At first we found that a small amount of ?mineral impurity? presented in natural ore could play important role in selective hydrophobization process. It was found that the pH of solution (parameter possible to control) and natural mineral impurities present in mineral samples (parameter related to ore origin) play a very important role in the separation process. Another important parameter is interaction between minerals, quartz and albite, present in aqueous solution. The limitation of flotation separation resulting from chemistry will be discussed. Moreover, the most promising scheme for separation of albites from quartz will be examined.

Jan 1, 2014

By Fedotov Pavel

One of the efficient means of ore disintegration during the processing is its volume breakage in such machines as roller-presses. Up to date neither the ore disintegration mechanism in roller-presses nor the reasons of their high efficiency are thoroughly investigated. In this work, the mathematical model of Finite Element Method of bad material disintegration in roller-press is discussed. The mechanism of the interparticle ore disintegration is traced.

Sep 1, 2012

By L. S. Zhou

HermesTM metal magnetic liner (MML) has been invented and manufactured by China Metallurgy and Mining General Co. (CMMC). This paper describes its mechanism, structure, magnetic field distribution, application, economic benefit and safety performance. The 10 years? service life in Benxi Steel?s Waitoushan Mine, along with 6 years? technological analysis on its application in 5500mm×8800mm (diameter × length) ball mill in Anshan Steel?s Diaojuntai mineral processing plant, has proved its advantages such as super reliability, long service life, light weight, thin thickness, low noise and short payback period. It has also demonstrated its positive effects on the grinding process such as high productivity, energy-effective performance and low consumption of grinding media. It reduces labour intensity and improves working conditions, due to its easy installation, free maintenance and the fact that it doesn?t require fastening bolts or cause slurry leakage. It is de-signed scientifically in accordance with the varieties of processing lines, mill specification, ore type and grinding media, and has been applied in different grinding processes for magnetite, hematite, gold ores, nonferrous ores and other materials. HermesTM MML has three types of products: General, Composite and Heavy-duty. They are designed to meet the requirements from customers in China and abroad. So far, more than 400 sets of MML have been applied in ball mills with diameter rang-ing from 1500mm to 5500mm. It has become highly popular in American market recently due to its safe and effective performance.

Jan 1, 2014

By Markus A. Reuter, Bernardete Castro, Antoinette van Schaik, Han Remmerswaal

This paper describes the inseparable relation between product design, liberation, and metallurgical recovery in the optimisation of the recycling of passenger vehicles. This is illustrated by the use of an optimisation model that uses among others a material combination matrix based on metallurgical process data, which depicts the consequences of the quality of intermediate recycling products on the metallurgical material recovery and final alloy metal quality. Various simulations will illustrate the effect of changes in product design and hence liberation on the recycling of end-of-life vehicles. Although this paper focuses on cars, the discussion is equally valid for any end-of-life product. Calibration of the model will be discussed with reference to experiments carried out in order to study the optimal recovery of aluminium applications used in passenger vehicles.

Jan 1, 2003

By A. Vidyadhar

Using pure quartz and hematite minerals, the adsorption mechanism of mixed cationic/anionic reagent schemes was investigated through Hallimond flotation studies. The flotation response of quartz and hematite independently with cationic and anionic collectors as well as with mixed cationic/anionic collector systems is assessed. The flotation response as a function of pH and collector concentration was investigated. The single mineral flotation tests in the presence of anionic collectors, quartz does not respond to flotation, but the C12 amine flotation of quartz was observed to be pH and concentration dependent. It was observed that hematite flotation recovery is maximum at acidic pH with sodium dodecyl sulphate (SDS), neutral pH with oleate, and at basic pH about 9.5 with C12 amine. Flotation results with both quartz and hematite indicate an increased adsorption of cationic collector in the presence of anionic collector apart from its own co-adsorption. The incorporation of oleate in between C12 amine molecules decreases the electrostatic head-head repulsion and thereby increasing the adsorption of C12 amine due to attractive tail-tail hydrophobic bonds, besides forming a closely packed adsorbed layer enhancing the hydrophobicity. The increase in oleate concentration beyond C12 amine concentration leads to the formation of soluble C12 amine-oleate complex / precipitate and the adsorption of these species decreased the flotation since the alkyl chains are in chaotical orientation with a conceivable number of head groups directing towards the solution phase. Keywords: quartz, hematite, adsorption, mixed collector system, flotation, zeta-potential

Sep 1, 2012

Mineral processing is an energy and water intensive activity. Mill comminution equipment usually has high energy requirements which necessitate extensive cooling to remove heat. Cooling requirements are typically 10% to 20% of the comminution energy. If there is an adequate supply of suitable water, open water-based cooling systems are the simplest, cheapest and most energy efficient cooling method available. This paper describes a method to determine the water demand for open water-based cooling systems at a plant and to determine whether the mine has sufficient water to meet that demand.

Jan 1, 2014

By T. C. Alex

Mechanical activation of gibbsite [?-Al(OH)3] is the theme of this paper. Industrially prepared gibbsite used in the study has a mono modal size distribution with a median size, d50=110 µm. Mechanical activation of this gibbsite has been carried out in a planetary mill at ambient conditions. Mechanical activated gibbsite samples are characterised in terms of particulate characteristics, structural characteristics and reactivity. As a result, of milling, mono modal size distribution of the unmilled gibbsite changes to a broad multimodal distribution. Size reduction has been sharp in the initial stages of milling; median size reduces to ~7 µm during 15 min of milling. Thereafter no decrease in median size is observed; rather it is found to increase gradually with further increase in milling time, indicating particle aggregation. Morphological studies of milled gibbsite have shown that the platelets forming the agglomerate are separated first; the separated platelets then undergo breakage. Aggregation of particles sets in the later stages of milling as a result of increased surface area and surface energy. X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies have clearly revealed the changes in gibbsite structure during milling. Analyses of XRD data show that the crystallite size of gibbsite decreases as the milling time progresses whereas its microstrain is found to increase. Accumulation of energy in the structure is the result in both cases. TEM micrographs with signs of defects leading to disordering of gibbsite structure complement the XRD results. Reactivity of milled gibbsite, decrease in its deydroxylation temperature and increase in alkali dissolution, is found to increase with mechanical activation. Increased reactivity of milled gibbsite is found to have a strong correlation with the BET specific surface area. Keywords: mechanical activation, gibbsite, alkali dissolution, thermal dehydroxylation, reactivity

Sep 1, 2012

By M. Kalicinski, M. Lyssyy

"Access to information is a key component for making improvements to any process. This is particularly true for all aspects of the iron mining and steelmaking process. The ability to make rapid control decisions can significantly influence process outcomes, including ensuring product specification, mining quality, transportation limits, upgrade factors, waste bypass and direct shipping, among many others. While traditional laboratory methods provide feedback for such processes, having access to analysis results in real-time can lead to positive reactive and predictive control decisions to be made rapidly, leading to significant improvements throughout the process. Scantech has been designing, manufacturing and supplying technological products to the minerals industry since 2002 to enable the availability of such real-time information to a mine or plant, with the benefits being enjoyed by a wide range of operators. This paper provides a summary of the available technologies used in the iron ore and steel industries, as well as providing case studies of their use in African and Australian iron ore and European steel, as well as a description of the potential benefits of a range of analysis equipment.INTRODUCTION Access to information is critical for any process, and is a fundamental component for making process control decisions. In order to yield effective processing outcomes, it is important for that information to be readily available, preferably as quickly as possible, and to be as accurate as possible. While speed and accuracy are often traded off against each other, there are numerous technologies available in a processing environment that allow for both rapid flow of information and a high level of accuracy. The use of on-belt analysis equipment has a long trusted history of use in a number of mining and processing environments and industries, providing information such as elemental composition and grade of conveyed materials, moisture content, waste proportion and energy information. Australian company Scantech has been a provider of such equipment since 1981, and has become an industry leader in both the supply and development of on-belt analysers across a range of industries."

Jan 1, 2018

By H. J. Schulze

From a colloidal science point of view (Schulze 1984, Nguyen & Schulze, 2004) five micro-processes are responsible for successful particle-bubble formation: the approaching of the particle to the liquid-air interface, the thinning and rupture of the intervening liquid film, the expansion of the three phase contact perimeter, the generation of sufficient large capillary force to stabilise the aggregates and the transport process of particles into and within the froth layer. Flotation reagents influence mainly the thinning and rupture of the intervening liquid film between particles and air bubbles, the expansion of the three phase contact after the rupture of the liquid film and the stability of the aggregates against external destruction forces in the flow field. But it exist also a non-negligible influence on the approaching of particles to the bubble surface during the encounter process and on their passing over into the froth layer and the froth stability.

Jan 1, 2003

By Hui Zhang, Fei Yang, Tong Guan, Guangqin Fu, Lihong Deng, Yuanlin Chen, Xiaotong Zhou

"For a copper-sulfur polymetallic mine in south China, the main valuable minerals were chalcopyrite, pyrite and pyrrhotite. The flotability of pyrrhotite was similar with chalcopyrite and pyrite and it was easy to be oxidized. As a result, the indexes of copper concentrate and sulfur concentrate were unsatisfactory. Furthermore, the recycling of tailings water ulteriorly deteriorated the technical indexes of copper-sulfur ore beneficiation. After a large amount of experimental studies, under the condition that the tailings water recycling rate was 100%, the copper concentrate with a grade of 22.25%Cu and a recovery of 82.46% on average was obtained for the raw ore containing 0.517%Cu, 15.94%S, 25.46%Fe on average, through using new technology “magnetic separation-flotation” and effective adjustment of parameters in the industrial test which was continuously conducted for 14 shifts in 5 days with a scale of about 75t/d. Comparing with the production indexes (the copper concentrate with a grade of 17.49%Cu, the recovery was 62.27%) during the corresponding period, the grade of copper concentrate increased 4.76%Cu, and the recovery increased 20 percentage points. Besides, the indexes of sulfur concentrate gained a considerable improvement. Currently, the new technology was adopted in the design of the new-built plant with a scale of 7000t/d of this mine. The new technology provided powerful support for the tailings water recycling and indexes improvement of copper-sulfur ore beneficiation.INTRODUCTION Chalcopyrite was usually associated with pyrite and pyrrhotite in copper-sulfur ore. Due to the similar flotability, it was difficult to obtain copper concentrate and sulfur concentrate with high grade. Furthermore, sulfide ore was easy to be oxidized and a large amount of ions formed in the pulp by the dissolution of minerals, which made the pulp become acidic. As a result, pyrite and pyrrhotite were easy to be activated in acidic solution and their flotabilities became stronger. Meanwhile, hydrophilic film formed on the surface of chalcopyrite in raw ore. The flotability of chalcopyrite became weaker and it made the separation of chalcopyrite from pyrite and pyrrhotite more difficult. So it was more difficult for copper and sulfur recovering with the recycling of tailings water containing high content of heavy metal ions and reagents."

Jan 1, 2018

The status quo of ecological rehabilitation in metal mine in China and progress in the technology for ecological rehabilitation are presented, including soil reconstruction, soil improvement, plant selection. The present and future research fields are suggested: basic theory of ecological rehabilitation, operative technology of ecological rehabilitation, new technology application research and ecological rehabilitation plan, management and policy.

Jan 1, 2014

By A. D. Ramirez, L. E. Gutierrez, M. A. Garces

"Scarcity of freshwater in mining operations in arid zones in different parts of the world has led to the mining companies to think about using seawater as an alternative source in mineral processing operations. Examples of this situation are Minera Centinela (AMSA) and Minera Sierra Gorda (KGHM), both plants located in northern Chile. Previous studies showed that molybdenite flotation is depressed at high pH values in seawater as a result of the action of hydroxy-complexes of magnesium and calcium that attach to the faces of the molybdenite particles, reducing its hydrophobicity and as a result flotation recovery. In this work, a study of the interactions between molybdenite and kaolinite is presented. The effect of sodium hexametaphosphate (SHMP) dispersant on the recovery of molybdenite in the presence of kaolinite is studied in different aqueous media and it is correlated with induction time data. The results allow to conclude that kaolinite has a stronger depressing effect on molybdenite in seawater compared to its effect in freshwater. Magnesium and calcium are the cations that have the strongest effect in enhancing the interactions between molybdenite and kaolinite. SHMP reduces the negative effect of kaolinite on the floatability of molybdenite both in seawater and freshwater. The induction time data correlate well with the micro-flotation results.INTRODUCTION The need for water in mining processes in arid and semi-arid zones has led to the search for new alternatives for this resource, among which seawater has gained an important space. In Chile, most of the mining operations are located in the northern part of the country, an area that has limited availability of freshwater for the processing of copper and molybdenum sulfides (Castro and Laskowski, 2011, Castro et al., 2012 a). Seawater is an aqueous solution with high concentrations of ions such as Na+, K+, Mg2+, Ca2+, So42-, Cl-, and other less concentrated species which generate important effects in the flotation process as they modify the properties of the solid/liquid, and liquid/gas interfaces, and also increase the consumption of some important reagents used to depress pyrite such as lime. It has also been proposed that flotation of copper sulfides is negatively affected in seawater because of the reduction of oxygen solubility compared to freshwater (Millero et al., 2002; Duan and Sun, 2003). In contrast, it has been shown that the presence of ions in solution in the process of flotation of natural hydrophobic resources improve recovery as result of the compression of the electric double layer (Laskowski, 1974; Klassen and Mokrousov, 1963, Laskowski and Castro, 2008."

Jan 1, 2018

By A. V. Yevdokimov, Ye. V. Bogorodsky

The paper presents the results of the research on the development of gravity concentrates processing technology (gold grade is from 50 g/t to 1 kg/t and over) using intensive cyanidation with gold recovery to pregnant solutions followed by precipitation of metals from them using various methods. Test work and pilot plant results confirm that a new developed hydrodynamic regime provides an efficient treatment of gravity concentrates of polydisperse composition without their grinding and preliminary desliming. The resulting pregnant and washing solutions are amenable to metals recovery using electrowinning, cementation onto zinc dust and CIS. Cone plants with a lower ball valve for cyanidation of unground gravity concentrates developed by IRGIREDMET JSC have been successfully tested at a number of Russian operations. Currently, a modular plant equipped with gold electric precipitation from pregnant solution unit is successfully operated at a Russian gold processing plant. Cyanidation of the resulting high-grade gravity concentrate is carried out at the concentration of 8-10 g/L NaCN and 10 g/L NaOH. Gold recovery to the solution is 97-98%. Electrowinning is carried out in flow cell GNC-40M. In this case, the residual gold concentration yield is 0.3-0.5 mg/L. Also, a modular plant for relatively low-grade middlings (50-100 g/t Au) of gravity concentration has been introduced. The concentration of NaCN and NaOH is 2-3 g/L and 1.5-2 g/L, respectively, during leaching. This plant is equipped with a unit for gold cementation from pregnant solution with zinc dust. This cementation unit is of original design. It is made in the form of a filtering device and is composed of several layers of carbon fiber which contacts with zinc powder. The residual gold concentration yield from a cementation unit is less than 0.1 mg/L. Gold recovery is 93-97%. In 2017-2018, the introduction of intensive cyanidation modular plants to gravity concentrates will be planned at new projects of Russia and the CIS.

Jan 1, 2018

By Verónica Fernández, Jaime Solari

"The Chilean Environmental Impact Assessment System (EIAS) of investment projects was created in 1994, date in which the General Environmental Law was enacted. The compulsory environmental approval of projects began in 1997 when the Regulation (S.D. 30/97) was officially issued. By beginning late to regulate the environmental effect of investment projects, Chile could take advantage of the international experience in the matter and therefore, the EIAS has many of the attributes of successful environmental assessment systems elsewhere. Thus, the main characteristics of the Chilean EIAS are: preventive, single-window, specific to certain projects, multi-agency assessment at the regional scale, 3 kind of applications, deadlines, citizen and native communities participation, link to relevant permits, definite conditions of approval/rejection, review of applications by an ad hoc institution. The Chilean EIAS has allowed during the period 1997-2013, the review of 21,110 projects for a total investment value of US$ 408 billion, of which a 76% have been approved. In the case of the mining projects, the corresponding figures for the similar period are 1,257 projects for a total investment value of US$ 119 billion, of which 78% projects were approved. The experience derived from the environmental impact assessment of mining projects indicates that Chile has been successful in linking together mining development with environmental protection. There is still little prejudice against mining and this is a still a largely welcome economic activity at all levels in the relevant regions of the country. The challenge that mining companies face today in Chile is to improve the sustainability of projects and operations, by learning to share scarce and valuable resources (water, glaciers, renewable energy) with the local and native communities, through a process of dialogue whereby mining development also generates benefits for these communities."

Jan 1, 2014