Search Documents

Much has been published in recent years on the challenges facing the engineer of the 21st century and the consequent challenges facing the education providers and industry. The world is changing rapidly on the social, economic, political, technical and environmental fronts and our metallurgists/mineral processing engineers of the future will arguably need to have a different set of skills than those which were traditionally regarded as adequate during the latter half of the 20th century. This paper attempts to explore some of these issues and their ramifications.

Jan 1, 2014

By Peter Ay, Vincenz Mehlstaubl, Satyanarayana Narra

"This study gives an insight into non-destructive testing methods suitable for porosity analysis at a small scale, firstly summarizing relevant state-of-the-art technology and pending patents, secondly realizing and documenting the start-up of the VHX-2000 digital microscope by the manufacturer Keyence and thirdly demonstrating practical application with the extended analysis of three fundamentally different agglomerates for which important application-related parameters are determined. Various analysis procedures on the different agglomerates the efficient and timesaving operational features of the digital microscope are outlined. Firstly an analysis of flax fibre agglomerates determines the process conditions best suited to produce agglomerates with specific properties by determining sphericity, cubicity, density and porosity as well as fibre damage and alteration. Secondly the production of iron-hydroxide - hemp-fibre agglomerates serves to obtain information on porosity values as a result of a cauterization of the fibres. The third analysis provides estimations of porosity values for acid-treated lignin agglomerates. Measurements were carried out with compact dry agglomerates and with soaked, expanded agglomerates, determining factors for total water carrying capacity. Practicability of non-destructive testing by digital microscopy is demonstrated and explained concerning the applications in this study by obtaining definite structural findings about the analysed agglomerates. Information on its operation is made available by a practice-oriented manual for the VHX-2000 digital microscope. Further suggestions for more in-detail analysis results with different instruments are given."

Jan 1, 2014

By M. Marinov

The Bulgarian deposits of quartz-kaolin raw materials are localized in the NE Bulgaria. For many years, the quartz-kaolin sand separation has been performing by water washing technology. After wet separation the raw material yields two products ? washed kaolin (different grades) and quartz sand (different grades). Research and development program has started to improve the quartz-kaolin sand separation. The program has undertaken an increasing of processing capacity, to decrease the losses in the tailings and to provide production of new quartz sand grades. The kaolin-silica raw materials from Vetovo open mine and the technological tailings from Vetovo processing plant were characterized. It was established that there are a lot of losses of quartz in final tailings. New approach on kaolin-silica raw material separation was tested in laboratory scale. The test work was performed on Derrick Stacksizer screening machines. The results of laboratory experiment show that there are possibilities to increase the quartz sand recovery and to start the production new grade sand. The full-scale pilot test was performed including the following units: two Derrick Stacksizer screening machines equipped with 0.430 mm and 0.150 mm opening Derrick Urethane Panel, respectively; Flat bottom DN 500 Hydrocyclone and DN 100 Hydrocyclon. The pilot test data clearly demonstrate that the Derrick Stacksizer screening machines are suitable for Bulgarian silica-kaolin raw material. Based on the test data a new quartz-kaolin separation technology was developed. The new technology was introduced in Vetovo processing plant increasing processing capacity and decreasing the losses of quartz in final tailings. Additionally the production of silica sand grade PK 0.16 is increased and starts the production a new grade PK 0.10.

Sep 1, 2012

By Jing Zhou

2-hydroxy-3-naphthoy hydroxamic acid code name F203 is a good collector of cassiterite, 1-hydroxy-2-naphthoy hydroxamic acid code name ZJ-3. F203 and ZJ-3 are similar series of isomers. They have similar naphthye, and similar series of functional OH and ?CONHOH, but the seat of OH and ?CONHOH group are different, on the F203 is 2.3; on the ZJ-3 is 1.2, ortho position too. According to Isomeric principle ZJ-3 is a good collector of cassiterite slime too. Using ZJ-3 as collector flotation -10µm occupies 90%, grade 1.16% Sn cassiterite slime of Da Chang Chehe concentration plant, pass one coursing flotation, two cleaning and one scarenging flotation, and obtains grand 18.26% Sn, recovery 92.68% cassiterite concentrate. The result proves the Isomeric principle of flotation reagents is correct again. This principle may supply to synthetize new flotation reagents reference. Keywords: F2O3, ZJ-3, cassiterite flotation, Isomeric principle, Isomeric principle of flotation reagents

Sep 1, 2012

By Jyotirmoy Sarma

The surface-active agent, like sodium humate, in the present systems produces a very stable suspension. Saline water up to 15% is used as a flocculating agent for recovery of water from the dispersed phase containing 1% solid. The recovered water in the presence of humate at different concentrations (0.05-0.2%) and at pH 8 also produces a stable dispersed phase of iron ore fines and tailings. The beneficiation techniques adopted in the present systems can increase ~ 2-3% iron value in the concentrate of iron ore fine, however, for tailings the increase in iron value is not observed. Keywords: beneficiation, flocculation, iron ore fines, tailings, saline water, surface-active agent

Sep 1, 2012

By S. J. Neethling

"This paper examines the impact of several key variables on the performance of flotation cells. The study makes use of a simulator for the froth phase of the flotation vessel, as the main purpose of this study is to separate the impact of different variables from one another. In experiments it is very difficult to separate the effect of variables from one another as a change in a singe input parameter, such as air rate, invariably also affects many of the other key variables, such as bubble size and bubble bursting rates.In order to achieve this a base case simulation that is typical of many of the rougher cells found in sulphide flotation circuits was carried out. Four key variables, air rate, incoming bubble size, surface bubble size and the fraction of the bubbles flowing out of the cell unburst, were varied in order to obtain the system.s response.The most significant results were obtained when the bubble size was varied. An increase in the incoming bubble size has the effect of reducing the pulp zone recovery, but increases the froth zone recovery. If it were possible to vary the incoming bubble size without influencing the overflowing bubble size, the impact of the change would be unclear because of these two competing effects. The effect of a change in the overflowing bubble size has an opposite effect on the froth recovery, with larger bubbles resulting in lower froth recoveries.A final interesting result is that all the effects examined affect the process to a similar degree, which implies that none of these variables can be disregarded, either in industry or in further research."

Jan 1, 2003

By Ari Kokko

Metso has a long history supplying boilers for high ash coal firing. These boilers are based on circulating fluidized bed (CFB) technology. CFB?s biggest benefit is fuel flexibility ? it can burn fuels from high moisture content to high ash content. Metso has delivered tens of CFB boilers burning waste or high ash coal starting on 80?s. Some of the boilers have been in operation twenty years meaning that there is a long term experience from these plants available. This feedback includes boiler performance and maintenance issues of the boiler. Metso is also delivering coal washing plants to improve coal quality, i.e. reducing ash content of the coal. The idea to combine coal washing plant and CFB boiler was made up two years ago in Metso. Up-coming legislation of coal washing and restrictions for washery reject land-filling in India are good drivers for this kind of concept. Pre-study of this kind of concept led to the conclusion that coal washing process can be fine-tuned so that reject?s calorific value is only 1100 kcal/kg and that was set as a target for boiler design. Metso shipped 200 tons of washery reject to its own research center located in Tampere Finland. First a wide range of fuel characterization tests were done in lab-scale and after that one week test run in 4 MW CFB pilot boiler was done. Test run proved that 1100 kcal/kg can be fired without any support fuel with special boiler design. Test run results gave a good set of data regarding combustion efficiency, emission performance and boiler dynamic behaviour when burning this kind of fuel. These results are introduced in this paper. This paper introduces also the CFB boiler concept for washery reject firing including boiler plant, fuel and ash handling systems and flue gas cleaning system. Power plant can be integrated with coal washing plant so that boiler size matches with washing plants c

Sep 1, 2012

By Graeme Lamson, Rene Dobbe, Merle Kalstrom, Janice Baron, Robert Thorpe, Chris Martin, Snezana Bajic, Amanda Palko

"This paper presents early results from a case study at the Mount Polley porphyry copper mine in British Columbia, Canada. Daily mineralogical data was acquired and reconciled with daily plant assay and recovery balances to interrogate the mineralogical controls on plant performance. After commissioning, the Minesite machine operated smoothly and reliably, creating daily data to generate mineralogical balances around the circuit for a period of several weeks. The key data, on final products were produced within 13 hours of the end of the respective operating period. The resulting information allowed for a greater understanding of the opportunities and limitations of the Mount Polley metallurgy. In this paper, how this information can be used to help long term strategic planning for the operation, as well as mine planning and production forecasting and the fine tuning of day to day mill operations is described. Early data available at the time of preparing this paper indicated that roughly 40% of the sulphide losses, or 32% of total copper losses existed as low grade inclusions in +75 micron tails. This represented the dominant form of long term copper losses, demonstrated repeatedly in the routine analytical data. However, on a day-to-day basis, the amount of copper present as chrysocolla is the major driver behind variations in total copper recovery. The degree to which this influences mill recovery is valuable to the geologist or mine planner. As they are armed with mineral speciation information for future ores, this will allow for improved mine planning, prediction of copper recoveries and production forecasting. The data was also started to find value in the mill by showing what caused sulphide losses. In the roughers, for example, the data showed poor recovery was the result of poor flotation performance and not any changes the speciation of copper sulphides or their liberation characteristics."

Jan 1, 2014

By J. Masinja

The mining industry is known to be a potential major contributor to the industrial development of any economy. Large-scale mining has been going on in Zambia for the last 100 years. The impact of mining in Zambia has been to create a development corridor along the line of rail to the Copperbelt Province, where hitherto, mining was concentrated, and then to develop a large consolidated high-density economic zone covering an area of about 72 km by 60km. This area is home to a number of very large integrated copper/cobalt mining complexes. The mining zone has expanded to the Northwestern Province in the last 10 years, where the largest copper mine in Africa now exists, having produced about 300 000 tonnes of copper in 2011. The total output of the Zambian mining industry is now about 820 000 tonnes per annum with projections of reaching 1.5 million by 2015, due to new Greenfield investments expected to come online by then. These new mining industry developments have come on the back of strong and sustained high base metal prices, in the last 10 years or so, due to demand mainly from China and India. This new lease of life has increased the contribution of the sector to the national treasury. The mining industry in Zambia has undergone a very important ownership restructuring with the sale of the previously Government owned parastatal, Zambia Consolidated Copper Mines (ZCCM) which dominated the sector, to allow for private sector participation. The privatization process lasted from about 1995 to about 2002. The recent growth of the mining sector has unfortunately not been matched by an adequate supply of skilled manpower for various reasons. These include: (i) A lack of strong in-house training strategies by the new mine owners (ii) Decrease in industry support to the training institutions (iii) The demise of and restructuring of ZCCM which has consequently limited the Government human resources planning tools for the mining sector (iv) The cyclic nature for the fortunes of the sector has lead to fluctuating interest of student recruitment into training institutions (v) Limitations, both staff and equipment, in the training institutions (vi) A re-structuring of the training institutions This paper examines the current status, and student output from tertiary training institutions for the mining sector in Zambia. This is then compared to the skilled labour demands of the sector. The various cause and effect issues are considered and a proposal on how this skills gap could be addressed sustainably is proposed. Keywords: skills gap, graduate training, quality of graduates

Sep 1, 2012

By Chenyang Zhang, Zhigang Yin, Wei Sun, Jingxiang Zou, Jianyong He, Yuehua Hu, Zhijie Xu

"In this work, a novel compound 4-Amino-5-mercapto-1,2,4-triazole was first synthesized and its selective adsorption mechanism on the surface of chalcopyrite was comprehensively investigated using UV-vis spectra, zeta potential, Fourier Transform Infrared Spectroscopy(FTIR), X-ray Photoelectron Spectrscpy Measurements(XPS), and Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and first principle calculations. The experimental and computational results consistently demonstrated that AMT would chemisorb onto the chalcopyrite surface by the formation of a five-membered chelate ring. The first principle periodic calculations further indicated that AMT would prefer to adsorb onto Cu rather than Fe due to the more negative adsorption energy of AMT on Cu on the chalcopyrite (001) surface, which was further confirmed by the coordination bonding energies of AMT-Cu and AMT-Fe based on the simplified cluster models at a higher accuracy level (UB3LYP/Def2TZVP). The bench scale results indicated that the selective index improved significantly when using AMT as a potential chalcopyrite depressant in Cu-Mo flotation separation.INTRODUCTIONFroth flotation is one of the most important processes to separate valuable minerals from gangue by taking advantage of differences in the physical chemistry of their surface properties(Laitinen et al., 2014), particularly in their surface hydrophobicity. Hydrophobicity differences between valuable and gangue minerals could be regulated by adding different chemical additives (surfactants)(Kor, Korczyk, Addai-Mensah, Krasowska, & Beattie, 2014), such as collector and depressant. It could be conducted economically to selectively separate and enrich the complicated and/or poor ores, by adopting appropriate surfactants. For example, the beneficiation of molybdenite usually relies on a two-stage process to realize flotation separation of molybdenite from other unwanted sulphide ores(Wie & Fuerstenau, 1974). In the first step, a bulk molybdenite concentrate is produced by utilizing kerosene/ diesel oil and pine oil/alcohols as collector and frother, respectively. Second, sodium hydrosulphide, sodium cyanide, ammonium sulphide, or Nokes reagent are adopted as depressants in the separation stage. However, these depressants are usually toxicant and cannot meet the requirements of environmental protection. A large number of efforts have been taken to develop alternative environmentally-friendly depressants (Ansari & Pawlik, 2007; J. H. Chen, Lan, & Liao, 2013; Li et al., 2015; Yin, Sun, Hu, Zhai, & Guan, 2017; Yin, Sun, Hu, Zhang, Guan, Liu, et al., 2017; Yin et al., 2016). Although some novel and environmental-friendly depressants have been reported to achieve good performance in Cu-Mo flotation separation at a laboratory scale, there are still some challenging problems, including toxicity, high price or poor performance in practice, which severely limit their practical applications in Cu-Mo flotation separation on a commercial scale."

Jan 1, 2018

By S. Banisi, A. R. Hasankhoei, A. R. Ghasemi, E. Razi, G. A. Parsapour

At the pelletizing plant of the Gol-E-Gohar mining and industrial company two parallel dry closed grinding circuits, each with the average throughput of 300 t/h, are used. Each grinding circuit consists of a burner, a dry ball mill (6.2 m×13 m) and an air separator. The ball mill consists of a 2 m-long drying and an 11 m-long grinding chambers. The iron ore concentrate is fed to the drying chamber by a feed chute. The first 1.35 m of the drying chamber consists of 56 flights in two rows to decrease the feed moisture from 5% to below 0.2% and the rest of dryer chamber consists of deflectors to pass the material to the grinding chamber. It was found that when the feed moisture content increased from 1.3% to 3.5%, the throughput decreased by 12% (35 t/h) indicating a low performance of the dryer. Monitoring the wear rate of flights for a period of 12 months showed that the first 0.8 m length of the flights length did not experience any wear. This means that about 59% of flights do not contribute in material distribution and drying. A DEM simulation of feed chute and the drying chamber demonstrated that due to the inappropriate design of feed chute most of materials do not get in touch with the first 0.8 m length of the drying chamber. To overcome this problem, various feed chute designs with different geometries were simulated by the KMPCDEM© software. With the aim of arriving at a proper material trajectory, where the total length of the flights are used, a new feed chute was selected. The simulation results indicated that if the height of the flights is increased from 1.60 to 2.26 m and the slope is increased from 45 to 48 degrees the material arrive at the first 0.48 m of drying chamber. In this manner, the unused part of the drying chamber decreases from 59% to 36% of the length. After installation of the new feed chute, during a period of three months the throughput increased by 36 t/h.

Jan 1, 2018

Flinders Power, formerly NRG Flinders, is considering the possible use of low rank coal from Lake Phillipson, South Australia (SA) in its power stations at Port Augusta, SA. Typically, this coal contains about 35% moisture and 10% ash. Unfortunately, it also contains high levels of sodium (1% Na) and chloride (0.95% Cl) with a Na2O level in ash of 18.9%. Such levels cause serious problems during coal combustion, making the use of as-mined coal impractical for power generation. This paper describes the development of an aqueous leaching technique to remove 90% of the sodium and chloride and to yield a product with a Na2 O level in ash of less than 3%. Small-scale agitation leaching tests with good quality tap water at ambient temperatures showed that the coal needed to be crushed to minus 5.6 mm to obtain maximum removal of water-soluble sodium and chloride in 30 min. Leaching kinetics, but not the ultimate removal of salt, were enhanced by the use of higher temperatures (up to 150°C), but this was deemed uneconomic. Varying the pulp density between 20% and 50% had little effect on extractions and there was no benefit in multiple stage water washing. The best results by water leaching were 69%~74% extraction for sodium and 95%~97% for chloride, meaning that the sodium removal was well below the target level. From SEM examinations of the leached product it was concluded that the remaining sodium was organically bound to the carbon atoms in the coal. Further tests using aqueous solutions containing cation exchange additives such as calcium chloride (CaCl2) or ammonium chloride (NH4Cl) or sulphuric acid (H2SO4) showed that significantly enhanced sodium extractions were possible and target specifications were met. Two options, namely a single-stage and a two-stage leach, were then investigated. In a single-stage leach with additive, minus 5.6 mm coal was leached at 33%~50% solids for 30 min at ambient temperature and then filtered and washed with fresh water. This gave a sodium removal level of about 81% and a Na2O level in ash of about 5%. These levels do not quite meet tar-get specifications. In a two-stage leach, the coal was first leached with water alone without an additive as in the single stage leach, and the washed residue re-leached under similar conditions for about 5 min with an additive (CaCl2), and then filtered and washed. This gave a cumulative sodium removal of 96% and a Na2O level in ash of 1.4%~2.4%. These levels are well within target specifications.

Jan 1, 2014

By Claudio L. Schneider, Peter R. King, Reiner Neumann

"Predicting the liberation spectra that are produced from breakage of two-phase ores under the random fracture assumption can be accomplished by measuring the conditional, on length, linear grade distribution directly from images obtained from a representative sample of the unbroken texture. The technique tremendously simplifies the prediction problem by avoiding the multiple convolutions that arise from the traditional method based on a description of texture from a measurement of the chord length distributions associated with each phase in the unbroken texture. For a 3-phase system, the phase transition probabilities associated with the textural information make the traditional calculation an almost insurmountable mathematical problem. The direct measurement procedure on the other hand can be expanded to three phases comparatively easily.A coal sample is used here to demonstrate the procedure. It is concluded that the conditional, on length, linear grade distribution can be predicted in the same fashion for multi-phase systems. Accurate stereological conversion is the practical hurdle to be overcome for multi-phase systems, but it is already a reality for 3- phase systems."

Jan 1, 2003

By E. Szelag

The adsorption and stabilization of mineral dispersed systems by using Pluronic copolymers with different molecular weights and EO content has been studied. The role of sequential adsorption of EO-PO copolymers and cationic surfactant (CTAB) on the carbonate particle properties and in determining the stability of their suspension was studied with particular attention to the conformation of the polymer at the solid-liquid interface. The purpose of this work was to investigate the flocculation phenomena, influence of polymer molecular size on stability of suspensions of magnesite and dolomite and the effect of addition mode of polymer and surfactant. The suspension stability measurements and the determination of sedimentation speed were carried out using an optical analyser (Turbiscan). In most of investigated cases, the biggest floccs and the fastest sedimentation were found for low concentrations of copolymers.

Jan 1, 2014

By D. Tao

A novel rotary triboelectrostatic separator has been developed and patented recently at the University of Kentucky with unique features, including a high efficiency rotary charger, charger electrification, laminar air flow, etc. A parametric study has been performed with a coal combustion fly ash sample to investigate the effects of major operating parameters on the process performance. Most significant operating variables and optimum conditions were identified. Separation tests performed with four fly ash samples indicated that the rotary triboelectrostatic separator showed effective fly ash separation.

Jan 1, 2014

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

By Aidan Giblett, Karen McCaffery, Robert Dunne

"A worldwide decline in competency levels of practicing metallurgists over recent decades has become clearly evident and is a common topic of discussion among senior practitioners and professional associations. The associated impacts on the industry are material and include operational inefficiencies, missed optimisation opportunities and suboptimal new plant designs. There are many contributing factors to this condition. Decrease in competency is particularly evident both in regions where imbalance between supply and demand has led to a general reduction in experience levels for comparable roles over time and in emerging regions where a rapid rise in demand for practitioners has occurred in conjunction with rapid economic development and industrialization. The context, depth and breadth of education curricula and levels vary with location such that solutions to the technical competency dilemma may need to be developed specifically for each region with these influences in mind. Delivering, demonstrating and maintaining competencies are a critical requirement of undergraduate training and ongoing professional development. Other factors such as generational and cultural characteristics and expectations, political influences, role requirements and employment reward and recognition systems all play a critical role in determining if core competencies can be effectively developed, applied and subsequently maintained. This paper reviews factors impacting and some common approaches to competency development. The authors’ experiences in the management of professional development efforts within the global industry are reviewed and a blueprint proposed to address industry requirements in this area."

Jan 1, 2014

By J. Menuge, G. Barker

"Liberation (QEM-SCAN) and surface chemical (time of flight secondary ion mass spectrometry -ToF-SIMS) analyses have been undertaken on plant Pb circuit flotation samples with the aim of defining the factors resulting in sub-optimal recovery. Lead flotation circuit feed, cleaner concentrate and tails samples were examined on a size-by-size basis using QEM-SCAN. Sulfide minerals accounted for approximately one third of the flotation feed with pyrite making up 16 wt.%, followed by sphalerite (13 wt.%) and galena (3 wt.%). Non-sulfide gangue minerals comprised calcium carbonates calcite (26 wt.%), dolomite (14 wt.%) with quartz, feldspars and barite all contributing > 5 wt.%. QEM-SCAN analysis indicated that liberation was not the primary cause of the poor flotation response. Principal component analysis was applied to the ToF-SIMS data derived from five samples (as for QEM-SCAN plus rougher concentrate and tails) to enable identification of correlated surface chemical components. Although a significant range of correlations were observed we focus here on those that show a discernible pattern throughout the float circuit. It was found that for the flotation feed the surface of galena were largely obscured but where Pb was observed there was a strong correlation to surface Fe. For the rougher and cleaner concentrates the galena surfaces were relatively clean with no correlation to Fe for the rougher concentrate and minor correlation in the cleaner concentrate. However, in the rougher and cleaner tails the clear correlation of galena with Fe was again apparent. These results suggest, in combination with prior studies of pyrite morphology, that the principal factor effecting grade is the rapid oxidation of the framboidal pyrite resulting in the contamination of the galena surface with a high loading of hydrophilic oxidised Fe species, thus depressing flotation."

Jan 1, 2014

By E. P. Olberg, A. Yu. Chikin, S. V. Petrov, M. P. Belykh, N. L. Belkova

"Bacteria that grow in autochtonous communities of gold heap leaching (HL) wastes are adapted to high concentrations of contaminants and environmental conditions. An example of a mine in the Sakha (Yakutia) Republic showed that the bacterial factor had a significant influence on cyanide breakdown and copper and nickel removal in the conditions of HL ore pile zoning compared to chemical oxidation. The diversity of bacterial communities growing in natural and simulated conditions of a HL ore pile was determined for the purpose of the study. The identified bacterial communities included genus Achromobacter and Serratia, which were found to be adapted to a wide range of temperature and can be considered as potential microorganisms for detoxification of gold HL wastes. INTRODUCTION Technologies and systems of passive treatment are of a special interest in relation to solving environmental problems of gold HL wastes detoxification, when neutralization time is not considered as a limitation (Alvarez et al. 2005). Passive treatment methods are based on reagentless spontaneous breakdown of cyanide caused by natural factors, including activity of autochthonous bacterial communities. Implementation of a reagentless biodetoxification technology for mature HL operations provides reduction of environmental impact on industrial site locations and substantial economic benefits compared to conventional chemical processes of neutralization that prevail in the Russian Federation territory. Passive treatment of cyanide-containing wastes was investigated by M. Botz, T. Mudder, S.V. Petrov, L. Simovic, A. Smith, C.A. Young etc. However, the bacterial factor (autochtonous bacterial communities) role in this process is practically unexplored. Thus, the aims of the study included the investigation of a bacterial factor influence on passive treatment of gold HL wastes and the identification of functional groups of bacteria involved in passive treatment."

Jan 1, 2018

This investigation addressed two products from Samarco?s desliming circuit, namely underflow of cleaning cyclones and underflow of desliming cyclones. The roughing cyclones receive the product of the grinding circuit. The underflow of the roughing cyclones feeds the cleaning cyclones and the overflow feeds the desliming cyclones. The underflows of cleaning and roughing cyclones are combined to constitute the feed of the flotation circuit. These fractions were characterized and a new process route was proposed. The size distributions of the two fractions are quite different. The desliming cyclones underflow presents higher amount of material passing 37 µm and of ultrafines as compared with the cleaning cyclones underflow. Laboratory scale flotation tests were performed in a mechanical machine aiming at comparing the performances of these products in the presence of the reagents employed in the concentrator. Pi-lot scale column flotation yielded enhanced iron recoveries for both products in comparison with those achieved in laboratory mechanical cells, without impairing the concentrate quality. The in-crease in recovery was more significant in the case of the cleaning cyclones underflow. These results suggest the use of columns in the flotation of this product aiming at increasing the overall iron recovery. Nevertheless the results also showed that the use of columns to float the cleaning cyclones underflow should also be taken into consideration. Despite the fact that this product requires a longer residence time in order that the required silica content in the concentrate is achieved, the indication is that higher levels of iron recoveries might be reached. The conclusion is that, due to the different behaviors of the two products, they should be processed in distinct circuits to maximize the iron recovery.

Jan 1, 2014