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By M. V. Sowmya

Batch biosorption experiments were carried out for the bio-remediation of Cr (VI) ions from aqueous solutions using Serratia marcescens, a Gram negative, heterotroph and Gram positive bacterial isolates from a chromite mine. The influence of various experimental parameters such as contact time, pH, concentration of Cr (VI) ions and amount of biomass was evaluated with respect to the uptake of Cr (VI). The bio-sorption of Cr (VI) was found to be quite rapid and the percentage biosortion was found to increase with increase in the equilibrium chromium concentration. The free energy of biosorption of Cr (VI) was estimated to be in the range of -23 to -25 kJ/mol for the chosen bacteria. The uptake of chromium by the bacteria was confirmed by EDX and FTIR spectroscopy. As a follow up of this study, bacterial strains resistant to hexavalent chromium were isolated from a chromite mine in Karnataka, India and identified as Arthrobacter sp., Micrococcus sp. and Exiguobacterium sp. using 16s rRNA sequencing. The efficacy of the bacterial isolates for Cr (VI) uptake was assessed and over 90% bioremoval could be achieved for Serratia marcescens and Micrococcus sp. isolate. Possible mechanisms of chromium uptake by the microorganism are discussed. Keywords: bioremediation, hexavalent chromium, biosorption, bioreduction

Sep 1, 2012

By Z. S. Abisheva

Results of the study targeted to development of universal acidic-extraction-precipitation technology for gallium recovery from the sublimates are presented in the paper. This will let to utilize a new non-traditional source for gallium production. Phase composition of gallium containing dust was studied. Forms of gallium in the sublimates were determined. The main form is Ga2O3, however, GaP form is also present in the cottrel dust and Na5Ga3F14 form is present in the dust of aluminum electrolysis. The possibility of gallium concentration was established via secondary pyro-selection of the dust. Kinetics of interaction of dust components with sulfuric acid was studied. The products of the interaction subsequently were leached with water. Optimum conditions for direct leaching with HCl and H2SO4 were determined providing gallium recovery from the cottrel dust and the ash carry outs up to 95 %. Gallium recovery from the primary dust and the secondary dust of aluminum electrolysis was at 52; 64 % and 63; 83 % respectively. Effect of Fe, P, K, Na and Al admixtures for gallium extraction from hydrochloric acid solutions was studied. It was shown that gallium chloride complex (GaCl4-) is extracted into the organic phase from the following acid mixtures: HCl + H2SO4, HCl + H3PO4, HCl + H2SO4 + H3PO4, HCl + HF. Kinetic regularities of gallium extraction in the system (tri butyl phosphate) TBP ? HCl - Ga were studied using diffusion cell method with agitation. Optimum conditions for gallium extraction from complex hydrochloric acid solutions with TBP were found providing 99.9 % recovery and separation coefficient for gallium and iron (III) of more than 25 in one stage. Sodium hydroxide and water were selected as reagents for re-extraction of gallium from the organic phase. Different options for disposal of by-products that are formed in the processing of cottrel dust, ash sublimates and dust of aluminum electrolysis were proposed and tested. Keywords: gallium, kinetic, sulfatization, leaching, extraction, technology

Sep 1, 2012

By R. T. Dec

Current industrial compacting and briquetting practices are largely based on trial-and-error techniques. This paper introduces a two-dimensional finite element model of briquetting process in the roller press. Compared with other modeling techniques used in the past, finite element method offers the most versatile approach because it incorporates adequate information about powder behavior, geometry and frictional conditions and offers predictions for the density distribution, the velocity field, the stress distribution, roll force and torque. More over, when the model includes elasticity, it offers predictions on the internal stress state in the briquette after its exit from the roll. This enables to perform realistic computer experiments which are helpful for establishing the forming cavity geometry and process conditions necessary to produce briquettes with the desired properties. Three forming cavity profiles are analyzed. Results from model are verified on experimental roller press and best cavity profile is recommended for briquetting of sub bituminous coal fines.

Jan 1, 2014

By V. Sheikhzadeh, M. Saghaeian, R. Hejazi, A. Abazarpoor

Green pellet strength including drop number and green compression is highly depended on particles size and shape. The used grinding method, ball mill or high pressure grinding roll (HPGR), directly vary the particle size and shape. Considering mode of pellet crack, green pellet is composed of particle-binder-moisture system. Different type of forces existed in such a system to create a stable green pellet: solid particle interaction, magnetic, binding and cohesive forces in the interface of particle-moisture. The pellet failure can occur at solid-liquid interface and/or through liquid phase. Pellet crack occurs when crack passed through entirely the plane failure. In this research, the effect of particle size and shape of pellet feed on green pellet strength has been investigated. It was deduced that green pellet strength highly improved by increase of specific surface area. The drop number and green compression strength of pellets prepared by HPGR was higher than ball mill. It was found that the main reason responsible for this difference was the particle shape. Capillary force is responsible for part of pellet force and improves by decrease of particle size. Also more elongated shape of HPGR particles resulted in higher capillary force due to thinner interface layer between particles. The less circular shape of particles lead to improvement of capillary force as can be occurred for HPGR particles. The rougher shape of HPGR particles resulted in higher wettability of particles and better diffusion of water among particles. In fact the rougher particles means lower connection angle. Aspect ratio of particles was of great importance of crack growth because the required energy of pellet failure increases directly. The required energy for pellet failure increases by increment of particle aspect ratio. The relationship among crack failure force, roughness and aspect ratio has been modeled considering 3 shape descriptors.

Jan 1, 2018

"The JKMRC researchers have been redeveloping the suite of breakage testing techniques to more realistically align with the breakage environment in comminution equipment. Computational modelling, especially with the DEM, has highlighted the modes of impact and contact, along with the energies of these interactions in a wide range of equipment. This has driven the need to match these modes in laboratory ore characterisation tests. The objective has been to build a continuum of breakage tests and associated models that span the required range of breakage forces and environments. The ore sample is subjected to a sequence of tests covering: abrasion (surface breakage) of angular through to smoothed particles; single particle impact from high energy single impact breakage down to low energy; incremental breakage covering 60 mm down to 50 µm particles; particle strength distribution; and bed breakage over a range of compression and energy input. These tests are suited to multi-component ores with a distribution of strengths. A modelling technique is also being developed to utilise primary breakage for modelling breakage under different types of confinement. This paper draws together these techniques, previously published by the authors, into a coherent whole. The suite of tests is approaching the point where a fixed set of tests can be used to model the performance of a full range of equipment, removing the need to conduct repeat ore characterisation tests for each different piece of equipment incorporated in a circuit design. This path should open up the application of different circuit configurations and novel equipment in comminution circuit design.1 INTRODUCTION Comminution modelling utilizes a wide range of ore characterisation techniques and methods to deal with the range of comminution equipment available for production use. In general, the tests have been designed to correlate with specific pieces of equipment, using calibration factors to provide the link between the small-scale test and industrial-scale performance. The majority of tests focus on estimating the power requirement of process equipment to achieve a desired throughput and grind size. Overall, this approach has achieved acceptable outcomes in the past, but the reality is that equipment sizing suffers from considerable uncertainty, in excess of ±20% is not uncommon. This uncertainty is covered by safety margins and automatic scaling factors in equipment selection. In striving to improve reliability, the industry tends to add more adjustment factors to the tests, and design margin rather than question the basic validity of the testing process. As the tests are often correlated to production equipment via carefully guarded databases, they are also locked into historic operating inefficiency, not providing direction or revealing opportunities to improve production efficiency in comminution equipment or circuits. Safe in the knowledge that they are achieving the expected production based on test work predictions, a site is unlikely to set their sights on reducing specific energy consumption by 10%."

Jan 1, 2018

By A. A. Lavrinenko, N. I. Gluhova, L. M. Sarkisova, D. V. Makarov

"The purpose of the study is to study the feasibility of using sodium diisobutyl dithiophosphinate (DDP) to enhance the recovery of platinum group elements from low-grade refractory copper-nickel ores characterized by a portion of nickel and platinum group elements (PGEs) locked in the dominant sulfide mineral — pyrrhotite. These ore characteristics dictate the need to produce a bulk PGE-containing sulfide concentrate due to the difficulties of producing selective concentrates without a significant loss of the metals.New data on the adsorption and flotation performance of DDP-containing collectors were obtained by measuring the electrode potential, hydrophobicity of the sulfide mineral surfaces and by means of extraction spectrophotometry and flotation studies. The interaction between DDP, pyrrhotite, and pentlandite leads to the formation of surface hydrophobic layers consisting mainly of disulfide and a small amount of metal compounds. These adsorption layers are formed by the reaction with butyl xanthate. In the case of cooperite, DDP reacts with the surface, forming not only disulfide, as in the case of butyl xanthate, but also a complex platinum compound. DDP-containing agents demonstrate stronger collecting properties with respect to sulfide minerals of copper-nickel ores compared to butyl xanthate, which is explained by a stronger hydrophobizing effect and foaming properties.The addition of a combination of DDP-containing agents and butyl xanthate at a ratio of 3:1 for the recovery of sulfides and PGEs in the bulk flotation of copper-nickel ore made it possible to improve the recovery of Ni, Pt, and Pd by 13.6, 9.2, and 9.4%, respectively, relative to the recovery achieved in flotation with butyl xanthate.Bulk flotation with the addition of a composition of DDP-containing agents and butyl xanthate allows the most complete recovery of all valuable elements and is the only technologically feasible method for processing of lowgrade ores, when it is impossible to produce without loss high-grade selective concentrates suitable for smelting."

Jan 1, 2018

By G. B. Abaka-Wood

"The versatility of froth flotation has made it vital in the beneficiation of rare earth elements (REE) minerals from either high or low grade ores of complex mineralogy. There has been a significant increase in the tonnage of rich iron oxide tailings obtained from extraction of primary commodities such as copper and gold in Australia, which have been identified to have very low grade rare earth oxides (REO) (= 1%). There is a vast knowledge gap in the upgrade of REO from such tailings. The aim of this research is to investigate the feasibility of the use of fatty acids for the upgrading of REO from selected iron-oxide rich tailings. Two forms of fatty acid collectors (oleic acid and sodium oleate) were employed in this investigation. Bench scale flotation tests were carried out using a Denver D-12 cell.The effects of pulp pH, fatty acid dosage, particle size distribution (-150 +75 µm, -75 +38 µm and -38 µm) and conventional depressants (sodium silicate and starch) dosage on flotation recovery of REO were investigated. A comparison of the flotation results indicated that sodium oleate was the more efficient fatty acid for REO flotation at all the pulp pH investigated. The flotation performance is demonstrated to be particle size-dependent. The results on the effect of depressants dosage indicated that both sodium silicate and starch were unselective in reducing the recovery of hematite (Fe2O3) and quartz (SiO2) with corresponding decrease in REO recovery. Generally, Fe2O3 and SiO2 formed substantial contents of the flotation concentrates obtained, both in the absence and presence of depressants, which indicates liberation is a major challenge in achieving selective REO upgrade and recovery.The flotation tests carried out on the iron-oxide rich tailings suggest the possibility of REO upgrade using fatty acids, although particle size distribution and minerals liberation are key limiting factors in achieving selective REO upgrade and recovery."

Jan 1, 2018

By T. Fraszczak, U. A. Peuker, T. Mütze, T. Leißner, A. Wikedzi

The present paper highlights on the comminution and liberation properties of two greisen-type lithium bearing-mica ore blends (L1, L2) subjected to different breakage devices; cone crusher (CC), roller crusher (RC), rotor beater mill (RBM) and a screen mill (SM). The particle size distribution (PSD) of the products from each device were evaluated to search for an appropriate PSD model using Gates-Gaudin-Schuhmann (GGS) and Rosin-Rammler (RR) functions. In order to determine an appropriate function that could better describe the PSDs from the devices used, the coefficient of determination (R2) was used as a criterion. In terms of mineral liberation studies, due to costs, only products from rotor beater mill (RBM) were examined through an automated scanning electron microscope (SEM) technique. It was found that RBM, RC and SM products were better described by the RR model than the GGS model with higher R2 values (0.97-1.0). However, cone crusher products for L1 were better described by GSS model, while that for L2 were better described by RR model. In terms of the spread of size distribution as indicated by RR model parameters, RC products were more uniformly distributed compared to products from other devices, for both ore blends. Also the RBM products were more scattered than products from other devices. The results indicate that the composition of individual ore blends affected the comminution products PSDs since different PSD model parameters were obtained for samples comminuted by same devices. The modal mineralogy of the two ore blends indicate both to be rich in quartz, topaz, zinnwaldite and muscovite. Further, the result indicate that, for both ore blends, zinnwaldite phase is more enriched in the fraction < 250 µm. Moreover, better liberation of zinnwaldite is observed for L1 compared to L2. This could be explained by differences of the two ore blends in three aspects; the nature of mineral association, reduction ratio of the fractions analysed and the nature of spread of the size distribution.

Jan 1, 2018

By T. V. Vijaya Kumar

Most of the iron ore washing plants set up in India consist of sizing of the ore by dry / wet screening, washing and classification by screw classifiers followed by multi-stage hydrocycloning of screw classifiers? overflow. The underflow of the hydrocyclones forms the concentrate which is used for pellets making. As the cut-point of hydrocyclones is generally at 20 microns, relatively lower diameter cyclones in a cluster with parallel feeding are used. This is found to, often, result in choking of the spigots, at times, by extraneous material as well reporting along with the slurry. It is observed to lead to sub-optimum performance of the cyclones with loss of iron values into cyclone overflow and thereafter into tailings. Analysis of data of an operating beneficiation plant (Beneficiation Plant - 1, BP - 1) of M/s Jindal South West (JSW) Steel Limited, Karnataka, India over a period of one year indicated that weight recovery of the concentrate from two-stage hydrocycloning was 45% (with respect to feed to the cyclones) and assaying 63.43% Fe, 4.43% SiO2 and 2.32% Al2O3. CSIR - National Metallurgical Laboratory - Madras Centre (NML - MC), India developed flotation process for processing screw classifier overflow with a view to improve the recovery of ultrafine iron values from it. Detailed investigations at laboratory scale flotation column and on-site pilot plant trials proved that the production of the concentrate and productivity of the plant could be enhanced by adopting reverse cationic column flotation technology. It was established that a typical screw classifier overflow analyzing 60.54% Fe, 5.95% SiO2 and 3.67% Al2O3 could be upgraded to 64.21% Fe, 2.64% SiO2 and 2.20% Al2O3 with 82.7% weight and 84.7% Fe recovery. This translates into an increase of 80% in weight recovery of the concentrate compared to what is being obtained, at present, by two-stage cycloning. It had an added advantage of reduced SiO2 in the concentrate. Thus, SiO2 in the final concentrate could be reduced to 2.64% from 4.43% by adopting column flotation. The concentrate so generated meets the stringent specifications, especially in terms of alumina in it(should be less than 2.50%) for pellets making. Later, JSW Steel Limited set up the flotation plant in BP - 1 based on the process developed by NML - MC and was commissioned in 2010. Keywords: iron ore, washing, ultra fines, alumina reduction, column flotation

Sep 1, 2012

By Lilong Huang, Xiang Zhao, Yuan Long, Li Shi, Guowang Zhang, Xiao Xiao

"Vertical stirred mill is expected to upgrade the iron concentrate by further size reduced efficiently. The tests for fine grinding of iron ores from Baiyun Boyu iron ore, Baogang Goup, iron contained tails of Cu-Pb-Zn ore in Wanguo ore, Xiaoshalong iron ore in Qinghai were conducted in this paper. The data of appropriate grinding fineness, optimum grinding conditions and energy consumptions obtained from the test were used to select appropriate scale of the vertical stirred mill, optimize the parameters of the grinding process and upgrade the iron concentrate of the iron ore dressing plant or design the new ore dressing plant. Based on the laboratory tests, industrial system of regrinding and magnetic separation with vertical stirred mill as the regrinding mill in micro-fine grained iron concentrate upgrading has worked out very well. The grade of Fe in iron concentrates has increased to about 65.0% (by 4.0~6.5 point percent) when the iron concentrates were reground to designed fineness and the specific energy is 5.0~7.1kWh/t. The system of regrinding and magnetic separation is proven to be eco-efficient in iron concentrate upgrading."

Jan 1, 2014

By H. R. Manouchehri

The importance of the grinding environment and its effect on sulphide minerals flotation behavior has been known for many years. The grinding environment may play a role in controlling fine and coarse particle flotation along with dissociation of different chemical species in grinding environment. Dissociation of different chemical species and ions within the process water may result from changing the grinding environment. The mining and mineral processing industry undertakes activities that may impact on water resources. These include use and storage of chemical storm-water management, process water management, mine dewatering and management of tailings. In mineral flotation understanding and controlling water quality is paramount important not only because of its effect on flotation but also with respect to control the quality of the water which is released to the environment. Releasing of different anionic and/or cationic chemical species in the process water results from the interactions among different mineral within the ore, process water, and the milling environment. In fact grinding mill acts as an electrochemical reactor which affects the flotation performances of different value minerals as well as the quality of the tailing products. An increasing in antimony content in process/discharge water at Boliden?s Tara processing plant in Ireland to above limitation level was reported in April 2010 which needed to be controlled. An increase up to 6 times of the permitted level was reported which needed an immediate action to control due to environmental considerations. Therefore attempts were made to detect why this higher amount of Sb is released and how to control and minimize its release to the process/reclaim water. This paper discusses how/why Sb content in process/reclaim water was increased by changing the mill electrochemistry and the strategies were taken into considerations to control it. Different strategies, including electrochemical controlling of the milling section, Fenton process, using Bauxsol in treating the process water, etc., have been considered and tested which are described herein. All strategies taken into consideration for solving the problem were successful which indicated good understanding of the issue and good decision making. Furthermore, for each solution the capital and operational costs were roughly estimated. Accordingly, the Sb content in process/discharge water was controlled to a value lower than allowed limitation, i.e., 1 ppm. Keywords: antimony, water contamination, mill electrochemistry, ag milling, grinding media, eh-ph, sulfide minerals, fenton process, bauxsol, lime addition

Sep 1, 2012

By I. Yelkin, Erico Tabosa, Alex Jankovic, R. Hayashida, R. Faveere

"The mining industry faces growing challenges from more complex and lower grade deposits, rising costs, limited energy and water availability, and increasing societal pressure to operate more sustainably. Mining operations need to be more efficient, not just to reduce environmental impact, but also to remain economically viable.To maximize profitability and sustainability, existing operations and new projects must consider integration and optimization of all stages of production. A mining operation is essentially a series of inter-connected processes, with the performance and outputs of each stage affecting the subsequent ones. Optimizing stages in isolation can result in sub-optimal overall performance.The industry has long recognized the benefits of holistic optimization using the Mine-to-Mill concept, and there are many well documented successes. However, it is increasingly common to observe operations simply increasing explosive consumption in the mine and expecting optimization of the entire value chain (mining and processing). For true holistic optimization, blast intensity is not necessarily increased, but rather adjusted to best suit the requirements of the different types of ores treated, the circuit configuration and equipment, installed comminution power and the downstream beneficiation processes. It is a fully integrated effort with optimization of many aspects in the mine, comminution and separation processes.To be successful, optimization of the production chain from mine to process requires a site-specific, structured methodology supported by extensive ore characterization, auditing, surveys, data analysis, mathematical modelling simulations and a cost / benefit analysis. Following this methodology, optimization strategies are rapidly identified and implemented considering mine and plant constraints. Management needs to set up appropriate KPIs and site personnel need to be trained for the new operating strategies to be successfully incorporated into site practices and procedures in the production environment. This will ensure the benefits are achieved and maintained. This paper describes the methodology employed by Hatch to improve overall efficiency and profitability from mine to process. Two case study examples at Russian gold operations and benefits achieved are presented."

Jan 1, 2018

By S. Liu

With the development of global economy, the demand of mineral?s quantity and quality are in-creased, valuable minerals are more and more finer and poorer, and the capacity of concentration plant are more and more high. Using large-scale flotation cells can obviously enhance the capacity of treating the mineral, reduce the cost, and increase the economic benefit and competitive ability for the enterprise. BGRIMM advanced advisable technical scheme with optimally parameter and route for the feature of dynamic in large scale flotation machine, and developed the KYF Large Scale Flotation Cells, which have used more than 400. The paper advanced the history, the design principle, the operating principle, the structure feature and the application of KYF flotation ma-chine.

Jan 1, 2014

By Jingzhong Kuang, Zheyu Huang, Chuanzhou Guo, Pengfei Liu

"In this paper, scheelite and scheelite coated with Pb2+ (SC) were synthesized by chemical precipitation with the help of ultrasonic. The role of the Pb2+ on scheelite was evaluated. Additionally, the dissolution behavior of minerals and the adsorption mechanism of collectors were investigated systematically via SEM, XRD, EDS. The results indicate that the ultrasonic cavitation can promote the formation of scheelite with large particle size and high crystallinity. Due to the exchange of WO4 2- and OH-, the dissolution of scheelite are not in a 1:1 equivalent amount by chemical formula and the concentration of WO4 2- is higher than that of Ca2+ in the solution because Pb2+ promotes the transfer of WO4 2- from scheelite surface into the solution. The dissolution of scheelite is an endothermic reaction and its enthalpy reaches the maximum value of 692.59J·mol-1 at pH=8~10. But the coating of Pb2+ changes the thermal effect of scheelite in the solution and the dissolution of SC is an exothermic reaction with the dissolution enthalpy of -262.30 J·mol-1. At pH=8~10, the adsorption capacity of sodium oleate and salicylhydroxamic acid on the surface of SC is higher than that of scheelite which delivers that Pb2+ contributes to the scheelite surface dissolution and enhances the adsorption of collectors on the mineral surface, thus achieving activation.INTRODUCTIONIn modern society, tungsten is a type of quite important rare metal and also a strategic resource. Because of its low vapor pressure, high melting point, good electrical and thermal conductivity properties, it is widely applied in high-temperature technology, lighting, machine and engine construction (Zhao,Z.W, 2013; Yan, W, 2017; Ilhan, S, 2013). Both scheelite and wolframite are the major tungsten deposits. With the depletion of easily-processed wolframite, scheelite has drawn a great deal of scientific and industrial attention. Scheelite can be recovered by flotation due to the metathesis of polarity and chargeability on minerals surface via adding regulators and collectors."

Jan 1, 2018

By E. T. Tuzcu

In this manuscript, a new approach for modeling the rate of grinding process is explained. A review about grinding rate definitions so far is given and the possible ultimate way for grinding modeling is given as modeling the rate based on energy spectra. The traditional/phenomenological approaches for modeling size distribution of grinding mills give their place to a new generation modeling technique. Developments in the computational methods and necessity to model product size distribution of large mills, larger than ball mill size, paved the way for this novel technique. The traditional grinding rate models are mostly based on the back calculated breakage parameters from the experimental data. However, direct modeling of breakage parameters and hence the prediction of size distribution of the grinding mills may become possible with this approach. The material breakage data and discrete element method (DEM) energy spectra are the main components of this approach. Albeit the focus in this study is on modeling of breakage rate under impact mode of breakage, the abrasion mode of breakage was also tested by carrying out abrasion tests. Impact mode of breakage was analyzed using ultra-fast load cell device (UFLC) and drop weight tester. Dry tumbling test was carried out for abrasion experiments. Obtained material breakage versus energy data are combined with the collision energy spectra to obtain the breakage rate function. In addition, the material breakage versus energy information from the tests is converted into breakage distribution function. The model was verified in a lab scale mill (90 cm diameter-15 cm length). 10 to 15 kg of limestone was ground using 50 mm steel ball at varying conditions, i.e., rpm, volume loading. It is shown that the proposed model predicts all (1, 2, 4 min.) grinding intervals for all experiments highly accurate.

Sep 1, 2012

By V. A. Chanturiya

The results study the minerals oxidation were obtained by us during the methods of microscopic, FT-IR spectroscopic, XRD and chemical analyses of sulphides in tailings of copper-nickel wastes in Kola peninsula. Sulphide minerals begin to oxidize already at the stage of stockpiling and initial stages of storing. The proportion of non-ferrous metals and magnesium oxide increases with time, calcium partially precipitating in the form of gypsum. Comparison of heavy metal contents in pore solutions in cur-rent and stale copper-nickel ore concentration tailings has revealed a significant difference in practically all the parameters. The lower metal contents in current tailing pore solutions (by 5~30 times) are probably due to the presence of float reagent residues blocking oxidation. Much lower concentrations of magnesium and calcium can be accounted for by the difference in kinetics: the rate of sulphide oxidation at this stage is much higher than that of solution interaction with non-metallic minerals as the result of which the solid phase ? solution equilibrium is not achieved. It is generally believed worldwide that it the mining wastes with acidic pore solutions that pose the greatest hazard for the environment. Our findings suggest that although the solution pH in all the samples is higher than 7.8, the contain heavy metal concentrations by far exceeding permissible values. The direct determination of the total and silicate Ni contents in the tailings from current production and in storage tailings has shown that both sulphide and silicate Ni forms occur in tailings. However, the role of silicate Ni is much larger in the storage tailings. The average silicate Ni content accounts for 10% of the bulk Ni content in the current tailings and it increases to 40% in the storage tailings. Thus, the storage tailings are marked not only by sulphide oxidation and the removal of water-soluble sulfates, but also by the interaction of sulfates with the silicate matrix. Although complete equilibrium is not achieved even within 30 yr under polar-region conditions, the major part of the Ni in fine-grained fractions passes into silicate form. The probability of Ni transition to the silicate form directly correlates with the dispersion of the material and the amount of chemically reactive serpentine and hydrochlorite. The migration of Ni as sulfates and its precipitation by chemically active silicates distorts the distribution of this component in the coarse- and fine-grained fractions that are typical of tailings from the current production of copper-nickel ores. On the one hand, the variation of the mode of Ni occurrence in storage tailings lowers the value of technogenic raw materials as a source of this metal.

Jan 1, 2014

By Abhilash

Different methods of utilizing refractory bauxite and disposing red mud are practiced throughout the world, but none of them are known to be environmentally innocuous due to the complexity and /or high cost, and none has been found to be feasible on an industrial scale. Under these conditions, the use of bioleaching process seems promising. The present study emphasizes on the isolation of native extremophiles from the source Indian bauxite and red mud, with their detailed cellular and physio-chemical, and biochemical characterization. These organisms were tested for their ability to thrive in physically or geochemically extreme conditions. The gram positive capsule rich mesophiles and thermophiles were tested for removal of gangue minerals from the bauxite and red mud samples. Keywords: refractory bauxite, red mud, extremophiles, bio-beneficiation, gangue

Sep 1, 2012

By Venugopal Tammishetti

One of the important technological challenges facing the iron ore industry in India is to find commercially viable technologies to process alumina rich iron ore fines and slimes. The key to solving this problem lies in developing selective reagents for the separation of iron oxide minerals from associated gangue minerals like quartz, gibbsite, kaolinite and montmorillonite. We present in this paper our successful results on the dispersion-flocculation of three different natural iron ore slime samples from mines in India using the reagent combination of PVP dispersant and corn starch flocculent. All the three samples contained hematite, goethite, kaolinite and gibbsite minerals as confirmed by X-Ray Diffraction (XRD) analysis. The effect of various process parameters such as pH, dosage of reagents, settling time and pulp density was studied. We were able to produce a concentrate assaying 66.2% Fe and <2% Al with a yield of 67.4% by weight (with a recovery of 77% of iron values) using PVP (1 ppm dosage) and corn starch (20 ppm) for one of the slime sample (Sample I) assaying 58.2% iron (Fe) and 3.8% aluminium (Al). The XRD analysis of settled and dispersed fractions revealed that alumina-containing minerals like clay and gibbsite mostly remain in the dispersed phase while iron-bearing minerals tend to concentrate in the flocculated fraction. Keywords: iron ore, slime, flocculation, dispersion, beneficiation, starch, polyvinylpyrrolidone

Sep 1, 2012

By A. S. Chekmarev, T. Z. Lygina, K. G. Egorova, A. V. Skvorcov

"We have conducted analytical and technological evaluation of sepiolite containing clay. The possible areas of application of the sepiolite have been investigated and complex methods of enrichment of natural sepiolite have been identified. It was determined that for preserving the structure of minerals after processing the most effective method of the natural agglomerates disintegration was the soft abrasion of the clay fraction up to 0,5 mm. Disintegration of sepiolite clay along with using high energy-stressed effects on the matrix can deteriorate the rheological properties of clay suspensions and reduce the yield of drilling mud and sorption properties. To improve the quality of clay powders we used combined gravity-modifying method of wet enrichment. After the wet enrichment the yield of drilling mud increased up to 12.7 m3/t, with the addition of MgO up to 20,3 m3/t. It was noted that drilling muds contenting more than 50% of sepiolite are stable in mineralized (salt) waters. Based on the studied activated sepiolite rocks we obtained the effective heat-insulating materials with relatively low thermal conductivity – 0,165 W/m·K, average strength – 7,29 MPa and water absorption-49,0%.INTRODUCTION The modern development of the Russian economy requires the implementation of scientific and technical tasks. The solutions of it involves a radical reduction in energy, heat losses and material consumption of products, rational and efficient using of all types of resources, as well as the using of new types of mineral raw materials and materials based on it. An example of a new type of mineral raw materials for Russia is sepiolite containing rocks, due to unconventional conditions for their soils accumulation in the climate of the Far North. Sepiolite is a unique type of nonmetallic mineral. It is formed in soils, marine and saline basins, occurs in carbonate and carbonate-clay rocks in the form of lenses and lens – shaped layers, rarely nodules, loose powdery masses, shell-like concretions. Sepiolite may have a soft porous macroscopic appearance or less often the structure of the fibrous mass. Color of sepiolite is from white to cream with gray, green, pink and even crimson shade depending on the degree of pollution. Sepiolite can be in two forms - a-sepiolite (parasepiolite), which occurs in the form of large packets of crystalline fibers and ß-sepiolite, which occurs in the form of amorphous aggregates or small flat rounded particles. The sepiolite fibers have a length of from 0.2 to 2 Å, width from 100 to 300 Å, the thickness from 50 to 100 Å (Geological dictionary, 1973)."

Jan 1, 2018

By Jianjun Tian, Changjiu Zhang, Chunmin Wang

Two lines of single stage autogenous milling circuits have been installed and commissioned as the primary grinding process for the Sino Iron project where magnetite ore is treated to produce iron concentrate via magnetic separation. Various challenges were encountered during the commissioning and ramp up stages which are discussed in the paper and include treating a highly competent ore in a closed circuit AG mill, operating the largest mills in the world and dealing with a number of engineering issues related to plant operability. Details of how these challenges were overcome are described as well as the observed operating characteristics of the mills and their optimisation through rigorous study, simulation and successful solution implementation. Further potential improvement opportunities are also discussed as part of the ongoing technical program at site.

Jan 1, 2014