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By A. O. Gapchich, T. N. Matveeva, N. K. Gromova

"Tin sulfide ores and aged man-made products obtained after their processing are distinguished by a complex material composition and uneven impregnation of sulfide minerals (chalcopyrite, galena, arsenopyrite, etc.) and tin ore (cassiterite). Enrichment of such ores is performed through sophisticated multistage schemes using not only gravitational methods, but also gravity flotation, flotation, magnetic separation techniques. Tin ores also contain rare and precious metals (indium, scandium, silver), characterized by fine dispersity and microscale to nanoscale fineness of mineral formations. During flotation concentration these metals are extracted along with the main ore minerals into concentrates (tin, copper, tungsten, etc.), however, up to 10-20 % of them are lost with final tailings. The aim of the work is an experimental study of the modification of the surface of sulfide minerals and cassiterite by stable metal-collector complexes to increase extraction of fine tin, silver, copper and other metals from complex tin ores. Triamide cyanuric acid (TCA) was studied as a thin silver flotation modifier. Thermophilic polymer with a functional group of phenylphosphine TMPPh was used as a selective flocculant. For experimental studies of the physical and chemical effects of collecting agents on the surface of minerals the following analytical techniques were used - the analytical scanning electron emission ASEM (LEO 1420VP INCA OXFORD ENERGY 350) and laser (KEYENCE VK-9700) microscopy, measurements of electrode potentials of mineral anthills by potentiometric titration, monomineral and pulp flotation. New data on formation of the adsorbed layer of DBDTC on the surface of chalcopyrite, galena and arsenopyrite were obtained, and the dimensions of the reagent films and the strength of their adsorption. The indiscriminateness of cassiterite to DBDTC ensures its selective separation into a chamber product during the flotation of sulfides. It is shown, that modification of the sulfide surface by stable complexes Me-DBDTC and Ag-TCA-TMPPh will increase the recovery of non-ferrous metals and silver into a collective sulfide concentrate and will provide a high-quality tin concentrate for flotation of tin sulfide ores.The studies were perfomed with the aid of the Russian Science Foundation (Project No. 17-17-01292).INTRODUCTIONTin sulfide ores and aged man-made products obtained after their processing are distinguished by a complex material composition and uneven impregnation of sulfide minerals (chalcopyrite, galena, arsenopyrite, etc.) and tin ore (cassiterite). Enrichment of such ores is performed through sophisticated multistage schemes using not only gravitational methods, but also gravity flotation, flotation, magnetic separation techniques. Tin ores also contain rare and precious metals (indium, scandium, silver), characterized by fine dispersity and microscale to nanoscale fineness of mineral formations. During flotation concentration these metals are extracted along with the main ore minerals into concentrates (tin, copper, tungsten, etc.), however, up to 10-20 % of them are lost with final tailings. In this regard, it seems advisable to use new varieties of flotation reagents in order to increase extraction of finely dispersed tin, silver, copper and other non-ferrous and precious metals from multi-metal tin ores (Bocharov and Ignatkina, 2007; Khanchuk etal., 2012; Wu and Zhu, 2006; Yusupov etal., 2016)."

Jan 1, 2018

By Carina Ulsen

The existing construction and demolition (C and D) waste recycling technologies and standards have been essentially focused on the production and use of coarse recycled aggregates. Very few papers focus on the production of recycled sand, although some previous results show that fine aggregates fraction represents around 40 to 60% (in mass) of the Brazilian waste and it is usually used as road sub-base or disposed in landfills. The quality of the recycled aggregate is strictly related to the content of porous and low strength phases, mainly the patches of cement remaining on recycled aggregate surface. Some technologies have already been described in the literature, even though, to the moment none of these technologies has clearly succeeded in reaching the large market available. This paper presents a summary of the main properties of the sand produced from C and D waste by tertiary crushing at vertical shaft impact crusher (VSI). Additionally mineral processing technologies were applied on the attained product, such as gravity concentration by shaking table and spirals and removal of cement paste by attrition. The main properties of recycled sand are discussed and compared to the previous C and D waste, respectively: particle size distribution, particle shape, chemical composition, cement paste content and porosity. The results demonstrates that the crushing allowed producing a VSI-sand with low porosity and water absorption due to the increasing on the content of silicates from natural rock phases and increasing liberation between these phases and porous cement paste; the particles from the attained product presented also a better shape (sphericity and aspect ratio). The attrition tests assayed on VSI recycled fine aggregates accomplished a further selective disaggregation of cement paste and other porous materials - the porosity was reduced from 10% to 7%. The concentration by shaking table at narrow sieve fractions led to a product with low porosity and reduced content of cement paste, however, concentration on spirals did not succeed since separation was performed essentially by the size of the particles. The heavy product from shaking table represented almost 75% in weight and has less than 60% recovery of CaO+LOI, and expressive reduction on porosity. The aim of producing sand from construction and demolition waste through mineral processing unit operations changes the recycling approach and contributes for up cycling the recycled sand. The exhaustion of sand deposits on Brazilian large centers, the increasing price and the construction boom encourages the development of alternative materials as construction raw material. Keywords: recycled sand, construction and demolition waste, technological characterization

Sep 1, 2012

By B. W. Zhao

Quantitative analysis of minerals composing in ore is primary in process mineralogy, a veracious quantification and analysis is very crucial to optimize or design a beneficiation process, especially for a low grade and complicated ore. This paper will discuss a SEM-EDS based quantitative analysis developed in JKtech Australia through an example from Jinchuan lean ore. For a low grade, com-plex intergrowths and texture lean ore, chemical phase analysis of value minerals and identification by optical microscope are very essential, unite the SEM-EDS based quantitative analysis, we can understand exactly the lean ore, explain and quantify the process performance.

Jan 1, 2014

By E. V. Zelinskaya, A. E. Burdonov

"In the raw aluminum production processon electrolyzers with self-baking anodes, during technological operations, flow-regulated treatment and adjustment of the electrolyte chemical composition produced by diesel and floor-rail technology, alumina and fluoride salts are spilled through the ventilation grilles of the electrolysis body aeration channels, leakage in the equipment, machinery and motorized machinery construction elements. As a result of this, a part of the bus station and the level of ± 0 (the basement room with supporting curbstones and columns, on which electrolyzers are installed) are covered with technological raw material. This leads to an increase in the conductor (bus) resistance, contact connections deterioration, cell insulation failure and raw materials loss. For example, at the enterprise ""Rusal-Bratsk"", as a result of the activity, up to 420 tons per month of alumina-containing wastes that are unfit for use in the electrolysis process are formed due to the alumina substantial contamination with salts of iron and silicon, which significantly reduces the technical and economic parameters of the electrolysis process. The main scientific problem is the processing (cleaning) of alumina-containing waste having a complex mineralogical composition of the material, its contrast and structure, from oxides of iron and silicon, using ""dry"" separation methods. In the performing the work process, qualitative indicators of the influence of external factors (air humidity, precipitation, sunlight, temperature difference) on the physicochemical processes components interaction during the raw materials storage are established. On the basis of laboratory tests, it is established that alumina-containing raw materials can be separated and photometric and gravitational separation methods used. A mathematical model of the motion of particles of primary and prepared alumina-containing raw materials in a cascade-gravity classifier was developed. The criteria and factors characterizing the alumina-containing material, as well as influencing and determining the maximum material enrichment, are established."

Jan 1, 2018

By L. X. Zeng

The low-grade nickel resource is very abundant in the western China. To make the best of the low grade nickel ore, we studied the process mineralogy and beneficiation process of nickel ore in the Yangliuping of Sichuan province. The grade of nickel is 0.45% in the nickel ore and the nickel exists in the sulfide including pyrrhotite, nickel pyrite, chalcopyrite primarily. The nickel distributes in pentlandite and magnetite over 90% and the copper does in the chalcopyrite over 95%. The carri-er minerals of useful elements tend to concentrate in space for concentration. As is shown in grain-size analysis of three major minerals, there are some more fine-grained grains with the percent of from 10% to 15% (<40 µm) and from 3.5% to 5.5% (<20 µm). So there will be some smaller size disseminated sulfide minerals difficulty to liberate in the process of concentration. The liberation degree of sulfide is not high and there are much associativity in the sulfides. Therefore, we should reclaim the sulfide aggregation dominating as pentlandite when concentrating. In addition, the sulphide minerals is so brittle that we should take care of preventing from crashing when grinding. The gangue mineral is mostly metamorphic mineral including serpentine, chlorite and amphibole which is easy to be argillization and difficult to concentrate.

Jan 1, 2014

By E. Hulthén

Cone crushers are used in the mineral, mining, and aggregate industry for fragmentation of rock materials. Control systems for cone crusher settings are widely used to compensate for wear and to protect the machines. The eccentric speed in a cone crusher affects the number of compressions the material is exposed to and thus the particle size distribution of the product. Eccentric speed also affects crusher capacity. However, the speed of the crusher is mostly fixed, because speed changes must be made by shifting pulleys, a process which is quite time-consuming. By applying a frequency converter, which has decreased in cost during recent years, it has become possible to adjust the speed continuously. By also applying mass-flow sensors to the process, the crusher can be run optimally to yield the most sellable products in a given moment. Existing systems normally only protect the machine. The sensors can be mass-flow meters, e.g., conveyor-belt scales. To analyze data from the process and calculate the appropriate value for the speed, an algorithm has been developed. The developed algorithm was tested and evolved at a crushing plant for aggregates that produces around 350 kton a year. The algorithm was implemented in a computer that could communicate with the frequency controller, retrieve data from four mass-flow meters, and also interact with the opera-tor. The computer was reachable over the Internet for the researchers at Chalmers and the algorithm was tuned and improved on-line. The result is a crushing stage that consistently and maximally produces the most desirable product. The performance (yield of required products) increased by 4%. As a bonus, the lifetime of the mantles increased 27% on the evaluated crusher.

Jan 1, 2014

By C. Hazotte, M. -O. Simonnot, V. Houzelot, B. Laubie, M. Guilpain, B. Jally

"More than 400 plants in the world are able to accumulate nickel (Ni) in their aerial parts at concentrations higher than 10 g per kg of dry biomass. Then, Ni can be recovered from the biomass of these hyperaccumulator plants. Agromining is a chain consisting in growing such plants and producing metal. It has been developed thanks to the combined know-how of agronomy and hydrometallurgy. Hydrometallurgical processes have been designed; two different pathways were developed: i) acid leaching of ashes after biomass combustion and ii) direct Ni water extraction after biomass grinding. Experiments with 2 species of Ni hyperaccumulators (A. murale from the Balkans and R. bengalensis from Malaysia) have shown that the first process is very robust and transposable. For the second one, the way Ni is stored in the plant has a strong influence on extraction. A. murale transformation was explored in more details from the lab scale to the pilot scale. Results proved that Ni is totally transferred into the aqueous phase after 2 hours at 90 °C. A life cycle assessment has clearly shown the environmental interest of this approach (especially by detoxifying agricultural soils). INTRODUCTION Agromining is an emerging phytotechnology aiming at recovering metals thanks to hyperaccumulating plants (van der Ent et al., 2018). These plants are able to accumulate very high concentrations of metal in their aerial parts. For example, for nickel, the hyperaccumulation threshold is 0.1%, i.e. 10 grams of metal per kilogram of dry biomass. There are some advantages to use this technology instead of conventional mining techniques: •,Treating unconventional metal resources: they can be (i) natural soils with low concentrations but also low fertility because of the metal presence (like serpentine soils for Ni) (Bani et al., 2015), (ii) mine tailings or (iii) industrial wastes (like surface treatment sludge) after soil construction (Rue, 2017);"

Jan 1, 2018

By S. Gerl

Since Schönert, 1980 a multiplicity of scientists have dedicated themselves intensively to the scientific investigation of wet grinding in agitated media mills. The achieved research results led to a clearly improved understanding of the comminution mechanism in wet operated agitated media mills and in consequence also to clearly more efficient machines. In contrast to this the standard of knowledge on dry grinding in agitated media mills is still very small. The practical experience from numerous plants shows however that the transferability of knowledge from wet grinding to the dry grinding regarding transport phenomena and comminution behaviour, influence of the operating parameters and also wear is very limited. In the industrial application above all the continuous mode of operation is preferred. The main problem which has to be solved in agitated media mills is minor the comminution itself, than rather the question of the trouble free material supply and material extraction as well as the cooling of the mill. The agitated media mill MaxxMill® offers an innovative concept to overcome the feeding and extraction problem with its rotating grinding chamber, the eccentrically mounted agitators as well as the eccentric flow deflector with integrated material supply. Because of the pneumatic extraction of the ground materi-al cooling of the milling chamber is not necessary. On a MaxxMill ® laboratory mill with a 5 litre grinding chamber volume extensive parameter studies were carried out to study the influence of operating parameters on the continuous dry grinding of quartz sand. The test were performed in a continuous single pass operation without classification of the final product. Apart from the influence of the throughput rate on fineness above all the influence of the agitator and grinding chamber speed as well as the grinding media size was examined.

Jan 1, 2014

By Güven Önal, Zeki Dogan, Neset Acarkan

In this study, it was aimed to produce glass sand with less than 0.15% Fe2O3 for window glass manufacture and glass ware grade with less than 0.05% Fe2O3 from Yalõköy sand dunes having 0.48% Fe2O3. In order to reduce the iron content of the Yalõköy sand dune, magnetic separation, flotation, scrubbing, H2SO4 leaching and drying were used. The optimum iron removal was achieved by H2SO4 baking at 150oC and 8 kg/t acid consumption. In this way, sand concentrate was obtained with 0.04% Fe2O3 and sand recovery 95%.

Jan 1, 2003

By C. G. Anderson

Industrially proven and applied nitrogen species catalyzed (i.e. NSC) acidic pressure leaching has been utilized to treat a number of ores, concentrates and recycled materials. This versatile technology offers many advantages including low temperatures, low pressures, low capital costs, low operating costs, faster throughput and less costly materials of construction than conventional pressure oxidation. This paper will elucidate the application of this technology for production of gold, silver, palladium, rhodium, zinc, germanium, gallium, cobalt, copper, molybdenum, rhenium and nickel. Recycled material applications will also be elucidated. In addition, details of an application for treatment of a refractory chalcopyrite copper and gold bearing ore will be presented and pertinent economics discussed.

Jan 1, 2014

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 O. V. Suvorova, V. G. Minenko, D. V. Makarov, A. L. Samusev, E. A. Selivanova

"Saponite is a valuable marketable product widely used foundry, metallurgy and construction, in the chemical, food and consumer goods industries, in medicine, and in agriculture.The feasibility of producing of high-quality construction materials with enhanced physical-chemical and decorative characteristics from saponite-containing products has been given a scientific basis and experimentally validated. The compressive strength of the samples in the sintering temperature range of 800-1000 ?? varied between 35 and 80.9 MPa; the bending strength 8 and 26.7 MPa, which is superior to the high-grade ceramic bricks of the M-300 brand. It has been established that the saponite-containing product obtained using the electrochemical separation of process water has a high sorption capacitance relatively the heavy-metal ions such as nickel and copper (40.7 and 99.8 mg/g, respectively). As a result of sintering at 750 ?? the sorption capacity of the sorbent for the nickel and copper ions increased to 194.2 and 212.8. Using the XRD and SEM with energy-dispersive spectroscopy studies, we diagnosed the metal-containing phases and validated the metal sorption mechanism.This study opens up the possibility of practical realization of the saponite-containing product as high-quality building materials and heavy-metal sorbents while addressing the issue of process water treatment. INTRODUCTION The Lomonosov deposit of the Archangelsk diamondiferous province accommodates 10 kimberlite pipes. The anticipated volume of diamond-bearing ore and dump rock to be removed before reaching the open-pit mining limit is 300 mln t (Karpenko, 2009; Bezborodov, etal. 2003). Rock in the deposit is almost completely displaced by clay minerals, predominantly saponite, amounting to 90% in the vent facies (Karpenko, 2009)."

Jan 1, 2018

By Sashnee Raja, Mehdi Nemati, Ashley Sissing, Susan T. L. Harrison

"Extreme thermophiles, operating at 65 - 90°C, are finding increasing application in biohydrometallurgy These microorganisms have the advantage of exhibiting better oxidation kinetics in terms of reaction rate and extent of mineral solubilisation. These extreme thermophiles are Archae, characterised by a different cell envelope structure perceived to provide reduced structural strength in comparison to bacterial envelopes, and customised metabolic pathways.The active tank bioleaching process, used for high rate leaching, is conducted in a slurry bioreactor. Here sufficient energy dissipation is required to ensure suspension of the mineral phase as well as to sustain high rates of gas liquid mass transfer. It is well known that subjection to hydrodynamic stress of sufficient magnitude may alter the physiological state of a range of micro-organisms through changed viability (ability of the microbes to grow), metabolic activity and integrity.In this paper, we report on studies carried out to quantify the ability of the extreme thermophile Sulfolobus to withstand the hydrodynamic stress environment generated at high pulp densities in the slurry bioreactor. Both a pyrite system (as a model system) and a chalcopyrite system (as an application) were studied. In laboratory reactor systems, the nature of biological responses to stress induced at high pulp density have been identified in terms of ability of the microbes to grow, their metabolic activity and rate of leaching and cell integrity. Critical operating conditions within the laboratory reactor are identified and the mechanism mediating reduced performance considered."

Jan 1, 2003

By S. Castro

Molybdenite flotation is strongly depressed at pH higher than 9.5 in the flotation of Cu-Mo ores in sea water. Chemically sea water contains mainly Na+ and Cl- ions, but also some secondary ions, such as SO42-, Mg2+; Ca2+, HCO3-; etc., which are not necessarily indifferent for the flotation of molybdenite. The natural floatability of molybdenite in sea water and in NaCl solutions containing different secondary ions is investigated by micro-flotation tests. The tests indicate that the floatability of molybdenite in alkaline media in 0.6 M NaCl solutions is not affected by the presence of anions, such as, SO42- and HCO3-, at concentrations similar to those occurring in sea water. However, a strong depression of molybdenite at pH ranging from 9.5-10.0, is produced by the alkaline earth metal cations (Ca2+ and Mg2+ ions), dissolved in distilled water or in 0.6M NaCl solutions. It was found that effect of Mg2+ions is significantly stronger than Ca2+ ions. Effect of both ions is attributed to hydrolysis and adsorption of MOH+ hydroxy-complexes. This is followed by subsequent precipitation of hydrophilic colloidal hydroxides at the molybdenite/solution interface, and in bulk solution.

Sep 1, 2012

By R. C. Dunne

A review of the current ?state of the art? of refractory gold treatment will be provided. This will include a global perspective of refractory processes past and present and the location of currently operating plants. Some discussion on the challenges that face the refractory gold industry will also be provided. Keywords: refractory gold treatment, flotation, roasting, pressure oxidation, bacterial oxidation, preg-robbing gold ores, fine grinding.

Sep 1, 2012

By A. V. Kurkov

The secondary action reagents (SAR) are organic diphilic compounds capable of altering ac-id-base and donor-acceptor properties of the main collector and consequently the energy of collector interaction with the mineral?s surface, its hardness and fixation forms ratio through associates formation via the hydrogen bonds. When the basic flotation conditions are being established, convergence of the electronic structure of the collector and the mineral being extracted due to minerals surface preconditioning with modifiers and the most efficient collector choice. At the next stage of the selective flotation condition establishment SAR is selected for a more precise adjustment of the energy of the collector fixation on the mineral. Such an approach makes it possible to solve efficiently various issues of flotation separation of non-sulfide minerals. In particular neutral organic substances containing groupings C==O, S==O, P==O (ethers of carboxylic and phosphonic acids, amides of carboxylic, phosphonic and sulfonic acids) were proposed as SAR. In order to enhance the flotation process selectivity in the conditions of water recycling including the selectivity of carboxylic collectors especially in the environment of high hardness water flotation, it was proposed to use SAR with long hydrocarbonic radical and groups with enhanced electronic density within the molecule: N-methylolamides of alkylphosphoric acids and ethers of methylphosphonic acid. Introduction of small amounts of these compounds alongside with the main fatty-acid collector enhance the performance of fatty-acid flotation of fluorite, beryl, columbite etc., lowers the collector consumption, and completely compensates the depressive effect of recycled water. Di-2-ethylhexyl ether of methylphosphonic acid?CH3P(O)(OC8H17-i)2 (hexarane) was more thoroughly researched as such an agent within fatty-acid flotation process. Following aspects of the flotation system were studied: interaction of oleic acid and sodium oleate with hexarane in the liquid phase (infrared spectroscopy); heat emission under the interaction of hexarane-oleic acid ? sodium oleate ? calcium salts (isoperiboric diathermic colorimeter); colloid-disperse state of the collector influenced by hexarane (nephelometric analysis); dynamics of the mineral surface hydration due to the agents (method of indicator negative adsorption); hexarane effect upon the interaction of fat-ty-acid collector with calcium salts (complexometric method with Trilon-B); floatability of pure minerals (quartz, microcline, beryl, columbite) in Hallimond tube; hexarane effect upon oleic acid (sodium oleate) adsorption (nephelometric method for identification of the residual content of oleic acid and its forms within the solution). Upon the research it can be definitely concluded that the adjusting effect of such compounds as hexarane within the non-sulfide minerals flotation process is mainly determined by their interaction with the main collector both within the pulp and at the mineral surface with associates formation due to the hydrogen bond. The consequence is calcium oleates destruction with the release of the most active collector under flotation in hard water environment which determines the efficiency of hexarane joint application with fatty-acid collector under recycled water supply. Therefore the introduction of the class of secondary action reagents is supported by their operation mechanisms and flotation process function and determines a new approach to the development of efficient conditions of selective flotation separation of non-sulfide minerals.

Jan 1, 2014

By J. Wiese, K. Corin, Z. Song

"Relating flotation performance to the electrochemical characteristics of a pulp is complex both in fundamental research and in practice. In the case of thiol collectors, different Eh values in the flotation system can result in the formation of the dimer or the metal thiolate which may or may not enhance the hydrophobicity of the mineral. Reducing or oxidizing conditions in a flotation system, viz. changing the Eh value, are usually manipulated to achieve an optimum flotation response by control of pH and dissolved oxygen levels in the system. A variation in pulp potential may also be achieved by the addition of potential modifiers such as sodium hydrosulphide (NaHS), sodium hypochlorite (NaClO) or hydrogen peroxide (H2O2). There exists anecdotal evidence which suggests that the addition of small amounts of H2O2 to the flotation process can improve sulphide mineral recovery. The objective of the present study was to investigate the effect of the addition of the potential modifier, H2O2, on sulphide mineral recoveries and grades in the flotation of sulphide minerals from two copper bearing ores from China and compare the results to those obtained for a PGM bearing ore South Africa. Batch flotation tests were conducted using the three different ores at the natural pH of the different systems, in the presence of a xanthate collector and the absence and presence of H2O2 as a potential modifier. The results indicate that the addition of carefully controlled low concentrations of H2O2 resulted in improvements in flotation performance. INTRODUCTIONElectrochemical potential as a control parameter in the flotation of sulphide minerals has been widely studied (Allison et al., 1972; Gardner and Woods, 1979; Ross and Van Deventer, 1985; Chander, 2003; Woods, 2003; Javadi, 2013). There is concensus that in order to be recovered during flotation, sulphide minerals require a suitable redox environment. During the flotation process thiol collectors and sulphide minerals are involved in electrochemical reactions which result in the formation of hydrophobic species at the mineral surface (Finkelstein and Goold, 1972; Rand and Woods, 1984). Sulphide minerals act as semiconductors and electrons are transferred during the interaction of the mineral with collector. The resultant potential difference and its magnitude are responsible for the transfer of electrons and the rate of the reaction (Bard and Faulkner, 2001; Fuerstenau et al., 2007). Reducing or oxidizing conditions in a flotation system, viz. changing the Eh value, may be manipulated to achieve an optimum flotation response by control of pH and dissolved oxygen levels in the system (Heyes and Trahar, 1979). The use of potential modifiers viz. reducing or oxidizing agents which include H2O2, NaClO, and NaHS, is an alternative method by which to control the potential of the pulp in a flotation system which may or may not promote the flotation of desired minerals (Rao, 2004). The oxidizing agent, H2O2, undergoes a cathodic reaction which can result in the enhanced flotation of valuable minerals. The potential of the system is increased which results in a shift in the mixed potential of a mineral. The magnitude of the over-potential influences the rate of the oxidation process and thus the flotation response of sulphide minerals (Kocabag and Guler, 2008). Equation 1 shows the proposed oxidation of xanthate by H2O2 (Lipkina and Streltysn, 1970)."

Jan 1, 2018

By L. E. Veki, S. M. Luukkanen, J. P. Karvonen, J. O. Leppinen

Today there is a consensus that xanthate adsorption on sulfide minerals is primarily controlled by redox reactions occurring at specific potentials on these semi-conductive minerals. Consequently, it is possible to control xanthate adsorption by controlling electrochemical conditions in the system by using oxidizing and reducing agents. The scope of this study was to investigate the possibilities to increase the selectivity of Cu-Fe-Zn ore flotation by applying electrochemical control in the conditioning of the flotation feed. In this work, mild steel grinding in a nitrogen atmosphere was used as the basis to provide a negative starting potential and minimize the amount of oxidation products on sulfide mineral surfaces. To study how different potential levels affect flotation results, a controlled conditioning procedure was utilized maintaining potential at a desired level by titrating the pulp with air. Xanthate adsorption kinetics during conditioning was examined by taking pulp samples for spectrophotometric analysis and laboratory flotation tests were conducted for samples that underwent the controlled conditioning procedure in the potential range of -200mV to +200mV vs. SHE. A clear correlation was detected between chalcopyrite recovery and the potential during controlled conditioning indicating that there was a constant increase in chalcopyrite recovery when the potential was shifted to more anodic values. It is possible that utilizing potential control in the conditioning stage, a smelter grade copper concentrate can be achieved directly in rougher flotation without cleaning stages. Conditioning in favorable conditions had significant positive effects on flotation selectivity of chalcopyrite. The improvement in copper concentrate grade being predominantly caused by the depression of pyrite. By applying the controlled conditioning procedure pyrite recovery in rougher flotation was reduced even low as under 1%, while in the tests without controlled conditioning, pyrite recovery varied between 7.5 – 65.7%. The result of this work indicate that affecting collector adsorption by electrochemical control in the conditioning stage can provide significant improvement in sulfide mineral flotation and industrial applications could lead to decreased chemical consumption, reduced equipment and maintenance costs.

Jan 1, 2018

By A. M. Amdur, A. N. Matushkina, G. I. Gazaleeva

"The article highlights results of theoretical and practical studies on the enlargement of fine gold in the process of heat treatment. The object of research is refractory gold silicate-carbonate ores of Vorontsovskoe Deposit (Northern Ural), containing fine gold. For setting up experiments and analyzing the results were used the methods of applied mathematics, mathematical statistics, mathematical and physical modeling. Modeling and calculations were performed using the software package HSC Chemistry 6.0, MatLab, setting up a full factorial experiment and other modern modeling methods. Using a scanning electron microscope, the distribution of fine-dispersed ore gold particles by size was studied. It was found that gold particles smaller than 0,4 µm smoothed the vertices and edges, i.e. they are of globules with an amorphous structure. Amorphous materials are nonequilibrium phases with high thermodynamic activity. The physicochemical properties such as melting temperature, diffusion coefficients, the content of metal impurities differ from the properties of the solid phases. In the course of the research were formulated the following scientific bases of the mechanism of enlargement of the gold particles: - the movement of dispersed droplets of gold in the process of external heat to the surface of the ore particles in the pore occurs under the action of thermocapillary pressure; - after melting of the host rock occurs flotation of molten droplets by the bubbles of gases and coagulation of fine gold; - the conditions of flotation drops of gold in oxide melts; floated drops of radius R = 1-100 µm. Analysis of the equilibrium at the perimeter of wetting a drop of gold-oxide melt-gas showed that the scheme of the tension will not significantly differ from the case of solid gold, while the radius of the gas bubbles should be at least 2 times greater than the radius of drops of gold. The proposed method of predicting the results of the enrichment of the proposed scheme, including heat treatment and gravitational centrifugal concentration of crushed ore. Experimental verification of the proposed scheme in the laboratory showed a satisfactory convergence of experiment and prediction. Gold recovery in the concentrate was 33,84 against 33,7 percent forecast. The increase in overall gold recovery to a gravity concentrate after heat treatment is more than 20 %."

Jan 1, 2018

By Luis Bergh, Iván Rojas, Juan Yianatos, Luis Vinnett

"At present, flotation rate characterization follows standard measurements to identify the overall flotation performance looking at the feed, tailings and concentrate in flotation cells or banks. This classical approach does not take into account the evolution of the true collection rate down the flotation banks explicitly. The potential for identifying the impact of the mineral characteristics (size and liberation) as well as the effect of different manipulated variables (reagents, froth depth, gas dispersion) on the true flotation process remains hindered. Top-of-froth (TOF) measurements, which consist of sampling the first layer on the froth surface, have been used to characterize the mineral collected by true flotation in rougher banks. The information provided by TOF samples allows evaluating the floatable mineral evolution (grade, particle size, liberation) down the bank. In this work, an indirect approach to estimate the flotation rate along rougher flotation banks is proposed. The new approach is based on the decreasing of collected mineral grades (on top of froth) and the feed characteristics. Flotation rates per liberation classes were used to reconstruct the TOF grades from the feed information. This approach requires a simple froth surface sampling, without constraints typically observed during mass balance surveys and uncertainties on the mineral recovery estimation. The proposed methodology was successfully applied at industrial scale using TOF measurements together with QEMSCAN information."

Jan 1, 2014