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By T. Wajima

"A novel carbonaceous immobilizing agent for heavy metal contaminated soil was prepared from rice straw using sulfur immersion and pyrolysis, and the lead immobilization in artificial contaminated soils using sulfur-impregnated carbonaceous material was estimated. The rice straws were cut to 1 cm pieces, and then immersed in 0.1 - 1 M K2S solution for 0 - 24 h to prepare sulfur-immersed materials. The immersed-materials were heated at 400 oC for 1 h in nitrogen gas to produce the sulfur-impregnated carbonaceous material by pyrolysis. The abilities of the product to immobilize lead from aqueous solution were examined to obtain the product with high lead immobilization ability. With increasing K2S concentration, the immobilization ability of the product for lead gradually increases and then above 0.5 M K2S those are almost constant, while 15 min is sufficient for the immersed time to obtain the product with high lead immobilization ability. The product prepared from material immersed in more than 0.5 M K2S solution for less than 15 min has a maximum immobilization ability for lead ion. The lead immobilization using the sulfur-impregnated product is sustainable due to the formation of leadhillite [Pb4SO4(CO3)2(OH)2] and anglesite [PbSO4]. The product can immobilize lead ion in various artificial lead contaminated soils. By mixing artificial lead contaminated soil with the sulfur-impregnated product, the eluted solution became neutral, and the eluted concentrations of lead ion dropped below the Japanese elution standard for soil.INTRODUCTION Soil contamination with heavy metals is a worldwide problem. Accumulation of heavy metals in soils affect soil ecology, agricultural productivity, quality of agricultural products, water resources, and serious health problems for human and animal (Raicevic, et al., 2005). In the United States, for example, approximately 63 % of the sites on the National Priority List (NPL) for the treatment of contaminated soils are contaminated by metals, and lead is the most common metal, found at 15 % of the sites. In Japan, according to a report by the Ministry of Environment, 43 % of the contaminated sites that exceed the environmental quality standards are contaminated by lead compounds. Soil contamination by lead compounds is also prevalent in other developed and developing countries where lead compounds are used extensively in industrial activities without careful contamination management. Lead is a ubiquitous heavy metal pollutant in soils due to their use widely. The primary sources of Pb contamination include industrial activities such as mining, smelting of metals, and the use of Pb-containing products such as paints, lead-acid batteries, bullets, gasoline and pesticides (Cao, et al., 2009). It can damage human nervous (especially children) and reproductive systems (ATSDR, 2007). The high concentration of Pb in the soil poses risks to human and animal health by the leaching of metals from the soil into water and the consumption of edible plants growth in the contaminated soil. Therefore, proper remediation is necessary to reduce metal availability in soil for protecting human health."

Jan 1, 2018

"The research aimed at solving the problem of measuring instantaneous local physical quantities for multiphase flows in mineral processing, which are common in minerals industry and with significant challenges. Due to the lack of proper measurement tools currently in minerals industry, multiphase flows (such as in flotation cell) are treated as in a “black-box”. It is crucial to develop measurement technique by which the acquired processing data can be used for process optimization and control. By measuring the conductivity distribution across a measurement area, Electrical Resistance Tomography (ERT) has been adopted by many researchers to monitor and investigate many processes involving multiphase flows in other industry sectors. A compact ERT probe was built and then used to measure the conductivity distribution within a few flotation machines. In a flowing foam flotation column, the results showed that ERT can accurately measure the change of liquid content (high conductivity fluid distribution). In another part of work, based on the Green-Kubo relations, ERT can measure turbulence via the fluctuation of conductivity caused by bubbles moving through the measurement area, changing the density of the fluid. The tests with the Metso 3 m3 RCS flotation cell were also carried out for turbulence measurement under different air rates and impeller speeds. The results of flotation cell from ERT measurement showed that varying impeller speed had more pronounced influence than changing air rate. When impeller speed is increased, the size of the high turbulent zone increases. ERT is a powerful technique that has the potential to be used for a wider range of applications. The future work will be carried out with more case studies and expanded to more processes such as leaching process, high temperature flows in further downstream production chain (steel making process and alloy manufacturing process).INTRODUCTIONMultiphase flows constitute a majority of the naturally-occurring and industrially-relevant flows, especially in mineral processing. Some of the measurement techniques have been used for the study of fluid characteristics. Optical techniques such as Laser Doppler Anemometry (Kyselaa et al., 2013) and Particle Image Velocimetry (Nobach and Bodenschatz, 2009) can produce accurate measurement results with high spatial and temporal resolution, but their applications are limited to transparent flows. Hot wire probes (Amini et al., 2013) have high spatial and temporal resolution in turbulence quantification, but they are susceptible to environmental factors."

Jan 1, 2018

By Kremena Dedelyanova, Tsvetan Damyanov, Nikolay Hristov, Evgeni Kostadinov, Lubomir Kuzev

"Spherical grinding media (balls) are the most widely used media for comminution of ores by grinding. One way to optimize the grinding process in a tumbling mill is associated with the development and testing of a new media shape. By modelling simulation study of the behaviour of two types of grinding media (balls and tetraballpebs) in the grinding process was conducted to determine the possible advantages of the new media shape. Tetraballpebs are in the shape of tetrahedrons with spherical convex walls. D305 mm and L305 mm Bond ball mill sizes were used in the experiment. They are modelled milling tetraballpebs bodies corresponding by weight to five ball sizes, namely ¾, 7/8, 1, 1¼ and 1½ inches which form the grinding media used in a Bond ball mill. They are cast steel grinding bodies. Studies carried out with both types of grinding media include equal number of milling bodies of the same weight and volume. Having thus ensured a uniform mass of the grinding media and the same number of milling bodies, all other conditions and process parameters being identical, conclusions can be drawn about the influence of the grinding media shape on the grinding process. Compared to steel balls, the tetraballpebs used in laboratory tests carried out in closed cycle by Bond ball mill and the study of the rate of grinding gave five to six per cent higher yield of a control size of minus 0.1 mm. Measurements of the Bond ball mill power consumption demonstrated that tetraballpebs grinding media achieved energy saving of 4.7 per cent for the production of one gram of the control size of minus 0.1 mm."

Jan 1, 2014

By A. V. Zimin

It is a well-known fact that usage of reverse cationic flotation in magnetite ores processing enables to improve the quality of magnetite concentrates. We designed an iron ore concentrate technology (with 70 -71 % of iron) including reverse cationic flotation in pneumo-mechanical flotators RIF (developed by RIVS Corporation, Russia) with good biodegradable etheramines as collectors for flotation of quartz. Practical application of high biodegradable flotation reagents decreases environmental impact risk of objects and enterprises of mining industrial complex. This work presents results of development of flotation technology for production of high quality ferruginous concentrates from magnetite ores of Russia and Ukraine deposits. Keywords: magnetite ores, reverse cationic flotation, ferruginous concentrates, pneumatic-mechanical flotation machines, environmental impact

Sep 1, 2012

By Rong Fan, Roger Smart, Ning Xu

As part of an Australian Research Council project with Newmont and Newcrest mining companies studying the influence of clay minerals on rheology, hydrodynamics and flotation response, the cryo-SEM technique has been used to capture and image the clay (low crystallinity kaolinite Q38) aggregate structures in the flotation pulp immediately after collector and before frother addition. Samples were also collected from the earliest froth phase and the froth overflow corresponding to early and later concentrates. In this technique, a copper tube is filled with the sample during operation of the cell. The tube is immediately plunged into liquid nitrogen vitrifying the water phase before it can crystallise as ice thereby retaining the structures without volume or other physical change. After sublimation of the vitrified water surface, the aggregate structures are revealed and can be compared between pulp and froth phases from clays in different feeds and flotation conditions. The images from both low-clay ore and ore with clay content reveal various levels of aggregation as predominantly edge-edge connected aggregates similar to those found in our previous studies of high-clay tailings. For the samples from the ore with clay content, more extensive edge-edge clay strings are found in the early froth phase as compared to exiting froth overflow and the pulp phase with short edge-edge connected strings. It is suggested that the strings of clay particles result from edge-edge aggregation in the Plateau borders of the bubbles before breakage during sampling and the more extensive edge-edge aggregation in early froth phase is induced by crowding in the bubble borders. The clay strings collected into the overflow concentrate are almost all broken up compared with the Froth before drop-back. The implications for entrainment and entrapment mechanisms of gangue capture in froth will be discussed.

Jan 1, 2014

By Silvia Serranti, Giuseppe Bonifazi, Roberta Palmieri

The possibility to develop an efficient recovery and reuse of concrete materials from Demolition Waste (DW) represents one of the main targets applied to end-of-life constructions dismantling/recycling. The need to recycle end-of life concrete materials is strongly increasing in these last years for several reasons: i) the decrease of steady supplies of good quality natural aggregates, ii) the need to secure ample supplies of concrete aggregates to the construction industry and, finally, iii) the environmental constraints limiting the DW wastes disposal. The fulfilment of these goals produces several benefits, that is: i) a reduction of new resources consumption, ii) a strong reduction of the costs linked to transport and energy production, iii) the possibility to utilize materials, otherwise lost (e.g. land filled), iv) land preservation and, finally, v) the reduction of the environmental impact of new exploitation activities. A lot of efforts have been addressed to develop, set-up and apply innovative technologies to maximize DW conversion into useful secondary raw materials. The possibility to utilize efficient, reliable and low cost analytical tools to perform detection/control actions: i) to assess concrete characteristics, before demolition, and ii) to detect the presence of contaminants in coarse aggregates (e.g. bricks, gypsum, steel, glass, plastics, wood, etc.) represent the key issues to fulfil in order to develop innovative process/control actions/procedures inside the DW sector. In this paper a new technology, based on HyperSpectral Imaging (HSI) sensors is investigated to develop suitable and low cost strategies finalised to define and implement innovative smart detection engines for sorting and/or DW flow stream quality control, addressed to perform recovered materials and/or products certification. The proposed sensing architecture is fast, accurate, affordable and it can strongly contribute to bring down the economic threshold above which recycling is cost efficient.

Jan 1, 2014

By A. Akcil, O. Celep, C. Erust, E. Y. Yazici1, H. Deveci1

"Recycling of WEEE has already gain prime importance from both environmental and economic point of view. For the recovery of metals from e-waste, many conventional physical, bio/hydrometallurgical and pyrometallurgical processes are proposed. Economic potential of e-waste is mainly driven by its precious metal content. Physical separation methods (e.g. electrostatic, magnetic, eddy current and gravity separation) exploit the differences in the physical properties of metals and non-metals. Physical separation methods are simple and economically sound but they suffer from metal losses and ineffectiveness at fine sizes. Hydrometallurgical processes are promising owing to their relatively low cost, reduced environmental impact, potential for high metal recoveries and suitability for small scale applications. Hydrometallurgical processes can be developed for selective extraction of base/precious metals using suitable reagent systems. Sulphate-based leaching with a suitable oxidant (e.g. H2O2, O2, Fe3+) is effective for copper and other base metals. After removal/recovery of base metals, precious metals can be easily extracted using various lixiviants including thiosulphate, thiourea, cyanide and chloride. However, further research is required to develop new, cost effective and environmentally friendly processes and/or refine existing ones for leaching and, in particular, downstream processes. INTRODUCTION Electrical and electronic equipments are indispensable to modern societies with numerous applications in the field of medicine, transport, communication, education, security and environmental protection. With technological developments and innovations, the replacement of old equipment leads to ever fast accumulation of waste materials such as waste electrical and electronic equipment (WEEE or e-waste). People are upgrading their mobile phones, computers, televisions, audio equipment and printers more frequently than ever before (Babu et al., 2007; Lee et al., 2007). With the rapid growth in technology today, the life span and utilisation period of most electronic and electrical equipment has been reduced considerably with concomitant generation of huge amounts of WEEE over the past several decades. According to statistics presented by Balde et al. (2015), total WEEE produced around the world was 41.8 million tonnes in 2014 and expected to rise to approximately 50 million tonnes by 2018. Kumar et al. (2017) estimated that annual growth rate for the WEEE stream is 3–5% (Singh et al., 2016). The aim of this paper is to provide an overview of physical separation and hydrometallurgical methods available for the treatment of WEEE."

Jan 1, 2018

By Fengming Li, Baocheng Song, Yuemin Zhao, Hailin Dong, Liping Peng, Chusheng Liu, Chenlong Duan

The large-scale vibrating screens with high processing capacity and efficiency are now in great demand in the mineral processing industry of China. However, as the equipment is always suffering from the strong external harmonic exciting force, the inertial force and the impact from the minerals, the fracture of the beam and the crack of the lateral plate are easy to occur, which has a negative effect on the reliability of the equipment itself and the industrial production. Considering the essential high reliability of the equipment, a new large-scale vibrating screen with duplex statically indeterminate mesh beam structure (VSDSIMBS) was developed. The natural characteristics, namely, the natural frequency (or the modal frequencies) and the natural mode, and the dynamic characteristics of the VSDSIMBS were obtained by the modal analysis and the harmonic response analysis. In addition, the dimensions and the constructions of the statically indeterminate plate and the mesh beam were chosen as the design parameters, to which the sensitivity of the whole mass, the maximum deformation and the maximum stress of the duplex statically indeterminate mesh beam structure (DSIMBS) were summarized for the optimization of the DSIMBS. Now the large-scale VSDSIMBS is being well used in China.

Jan 1, 2014

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

By Yuemin Zhao

Pre-combustion cleaning of coal plays a key role in the process of efficient and clean utilization of coal resources. Recently, wet beneficiation of coal is predominant around the world. Nevertheless, wet beneficiation processes are limited by the increasingly serious problem of worldwide shortage of water, especially in China. Thus, it is imperative to develop efficient dry coal beneficiation techniques. Currently, several technologies such as air dense medium fluidized bed, compound dry cleaning and air jigging have successfully achieved high-efficiency separation of 50~6 mm coal. However, in recent years, a large amount of fine coal is generated as the mechanized mining technology has been progressively deployed in coal sector. Thus, it is necessary to develop efficient dry beneficiation techniques for fine coal. In recent years, many countries including China, India, Canada, Germen, and Australia have carried out many research works on fine coal dry beneficiation techniques. China University of Mining and Technology has carried out systematic researches on the introduction the vibrated energy to traditional air dense medium fluidized bed for fine coal beneficiation. This paper studied air dense medium vibrated fluidized beds (ADMVFB) for fine coal dry beneficiation. The experimental results show that the coal of <6 mm size can be beneficiated in an ADMVFB efficiently with the E value of 0.065~0.085, the separating density can be adjusted in the range of 1.45~2.2 g/cm3, and the lower limit of beneficiation can reach to 0.5 mm. Keywords: fine coal, air dense medium vibrated fluidized bed, coal separation, dry separation

Sep 1, 2012

By John A. Rumball, Martin R. Houchin

"For gold leaching of oxide ores, the optimum cyanide : oxygen ratio is approximately 106 mg/L NaCN : 10 mg/L O2 (6.9:1 by mole). In sulphide ores, galvanic coupling of the gold with the electrically conductive sulphides significantly increases this ratio such that leaching may occur in a relatively low dissolved oxygen (DO) environment.RESULTS AND DISCUSSIONGold leaching in a carbon in pulp (CIP) and carbon in leach (CIL) circuit is driven by the supply of cyanide and oxygen, as described by Elsner’s equation (1):• 4Au + 8CN- + O2 + 2H2O ? 4Au(CN)2 - + 4OH- (1)Equation 1 suggests that the ideal molar cyanide : oxygen ratio should be 8:1, or 122.5 mg/L NaCN to 10 mg/L of DO. It is generally accepted however, that oxygen is not completely reduced to hydroxide at the gold surface, and that equation (2) better represents the gold leaching reaction (Marsden and House, 1992):• 4Au + 8CN- + 2O2 + H2O ? 4Au(CN)2 - + 2OH- + H2O2 (2)Additionally, since gold leaching is limited by either the diffusion of cyanide or oxygen to the gold surface (Habashi, 1993), then the relative diffusion rates of cyanide and oxygen must also be taken into account. Marsden and House (1992) suggest that the ideal molar cyanide : oxygen ratio is 6:1, while a more recent investigation using laboratory and plant observations (Heath and Rumball, 1998) suggested a molar ratio of 6.9:1.In practice, although a cyanide : oxygen mole ratio of 6.9:1 applies to some circuits, there are many instances when this is not the case.In sulphide ores, galvanic coupling of the gold with the electrically conductive sulphides significantly increases this ratio. Galvanically connected sulphides, and possibly carbon, provide a large surface area for oxygen reduction. As the cathode surface area increases, the oxygen concentration required to sustain the same rate of gold oxidation decreases proportionately.Galvanically connected particles may be composite particles, however they may simply be liberated sulphides in the same suspension as the gold. Particle collisions within a slurry are sufficient to provide momentary galvanic connection (Greet, 1995)."

Jan 1, 2003

By M. Z. He

Attractive particle interactions which underpin the sliming of gangue mineral particles onto valuable mineral phases are encountered in a number of flotation circuits. Sliming leads to poor flotation recovery of the valuable minerals and high recovery of the gangue particles in the concentrate. To mitigate sliming, low molecular weight poly-electrolytes are commonly used as dispersants during pulp conditioning prior to flotation separation of the valuable and gangue mineral phases. In the present work, the sliming mechanism of sericite onto chalcocite and the influence of interfacial chemistry and two anionic copolymer dispersants (carboxylate substituted polyacrylamide, polymer Cyquest 3223 and sulfonate substituted polymaleic acid, polymer P80) on the sliming interactions were probed in the pH range 5~9. It was shown that the sliming occurred under solution conditions where both chalcocite and sericite particles were negatively charged, as evidenced by their apparent particle zeta potentials. The suspension pH had a profound effect on sliming process as the extent was markedly greater at lower than higher pH. The sliming was found to be due to the chalcocite dissolution, Cu (I) release and oxidation to Cu (II), followed by hydrolysis and specific adsorption, leading to sericite particle surface charge reversal and the formation of electropositive sites on chalcocite surface in the pH range 5~9. Addition of polymer Cyquest 3223 or P80 not only increased the magnitude of zeta potentials of both sericite and chalcocite particles but also reduced the formation of Cu (II) ions and complexes, which mitigated the sliming behaviour. The adsorption of polymer Cyquest 3223 or P80 at 3 g polymer / kg solid or more had a significant impact on the zeta potentials of both sericite and chalcocite particles. Sericite-chalcocite particulate adsorption studies showed that sliming was completely suppressed via an electro-steric repulsion mechanism resulting from anionic polymeric dispersant adsorption at dosages > 3 g polymer / kg solid.

Jan 1, 2014

By T. Inoue, K. Okaya

"Movement of mill charge in the centrifugal mill is essentially different from that in the vibration mill with circular path despite the apparently similar mode in the motion of mill body. As proved e.g. in [11], this results in substantial advantage regarding the comminution intensity of the centrifugal mill over the conventional vibration mill accounting approximately to one order of magnitude.Back in 1983, Bradley et al. presented a model of the centrifugal mill based on the kinetics of the mill charge by regarding it as a lumped mass. On the other hand, numerical modeling by ‘discrete element method (DEM)’ enabled us to observe the movement of each ball in the centrifugal mill with an extremely minute time intervals (Inoue et al., XX IMPC in 1997). The former approach rendered simple, even though approximate, expression of the mill behavior, while the latter method was advantageous in describing the behavior of the mill in terms of individual events taking place in the mill body, even though the result did not reduce to a simple expression. The characteristics of the centrifugal mill described by both these approaches proved to be in a degree of agreement. Thus, the kinetic approach was capable of presenting the overall view of the mill, while the DEM model was informative of the details that could not be depicted well enough by the simple math expressions."

Jan 1, 2003

By V. Avzian Belozersky reg 453524, Vasily V. Lodeischikov, Adolf F. Panchenko, Til E. Vidusov, Olga D. Khmelnitskaya, Vladimir E. Dementyev

"Presently, there is a number of gold deposits which cannot be developed using the conventional technologies with acceptable economic indices due to low gold content, high depth of ore occurence and other conditions. For such ores, an innovation technology of underground gold leaching in the place of their occurrence is of special interest. The technology excludes ore mining and hoisting to the surface. This enables the production cost of 1 g of gold to be considerably reduced in comparison with conventional methods of gold recovery.The Maminskoye deposit oxidized ores were chosen as the subject of underground leaching because they are ideally suited for this purpose due to their composition and hydrological parameters. The ore reserves within the underground leaching block are 90, 000 t with 0.7 g/t average gold grade.An experimental system for underground leaching with a throughput of 15 cubic m solutions per hour was developed. A combined filtration-and-infiltration system of the ore massif development by holedrillingwhere pregnant solutions are air-lifted was worked out.The underground leaching flowsheet includes Au dissolution by chlorine-containing solutions, Au adsorption from solution onto active carbon, carbon concentrate ashing and calcine melting to produce Dore metal."

Jan 1, 2003

By Fengnian Shi

In the current energy-sensitive world, sustainable development in the mineral industry will require new, better and more efficient processes. Novel comminution methods, which offer the prospect of achieving the required outcomes of size reduction and mineral liberation at lower energy consumption, are continually being sought. In the past five years, extensive research using high voltage pulse electrical comminution technology has been carried out at the Julius Kruttschnitt Mineral Research Centre (JKMRC), in collaboration with selFrag AG. The major outcome of this research is the development of the concept of pre-weakening ore particles by electrical comminution procedures to reduce the energy consumption in the downstream grinding circuit. The research has also verified the preferential liberation of valuable minerals by electrical comminution. Given the advantages, several potential applications of electrical comminution in the mineral industry are proposed, including AG/SAG mill feed pre-weakening, pebble treatment, ball mill feed pre-weakening, early recovery of the liberated valuable minerals, crack/micro crack generation for improved leaching, and smelter slag treatment. For the mineral industry to utilize electrical comminution, two emerging issues identified from the research need to be address. They are the energy consumption by electrical comminution in the locked cycle treatment and the facilities scale up necessary to move this technology from the laboratory to the plant. Keywords: high voltage pulses, electrical comminution, energy efficiency, mineral liberation

Sep 1, 2012

By G. Alfano

We have investigated the breakage actions of solid particles observed in a new generation fluid energy micronizer being set up at our laboratories. The attention has been focussed in particular on breakage caused by interparticle collision, particle impact against a fixed surface, interparticle attrition and particle against wall of jet mill attrition. We have also studied the influence of grain size distribution, maximum particle size, flow rate and characteristics of the solid to be processed, as well as of flow rate and pressure of injected air on the above mechanism. Lastly, the operating parameters of a dynamic air classifier in closed circuit with the micronizer for recovering the fine fraction and automatically recycling the oversize, have been optimized. The findings of this investigation have been used to design, build and fine tune a micronizer capable of controlling the top size of a product having average particle size that meets market requirements for fine powders, while keeping power consumption relatively low.

Jan 1, 2014

By Dmitriy Makarov

The paper presents the modeling and analysis of oxidation of pyrite copper-zinc ore samples from the Letnee, Yaman-Kasy and Valentorskoye deposits. It is found, that the oxidized samples contain copper and zinc sulfates that are leached under the sample and water contact. It is shown, that sulfide floatability is decreased by the longer-term oxidation.We advise to improve nonferrous metals recovery by joint leaching and ultrasonic treatment of oxidized compounds. Study of the geotechnological processes of non-ferrous metal extraction, on the basis of two copper-zinc ore deposits shows, that heap leaching is of little use for the ores of the Letnee deposit. Leaching results for the Yaman-Kasy ore showed more promise.

Sep 1, 2012

By Mohammad Kor, David Beattie, Agnieszka Mierczynksa-Vasilev

The selectivity of polymer adsorption in mixed mineral systems is the basis for polymer depression of gangue minerals in flotation. Effective polymer depressants not only reduce gangue mineral recovery, they also have minimal effect on the recovery of the value phase, presumably through targeted adsorption on the gangue phase, and minimal uptake on the value phase. Traditionally, polymer depressant design has been guided by single mineral phase adsorption tests, with affinity and maximum adsorbed amount determined for gangue and value phases separately. However, there is a need to determine the actual extent of adsorption on the gangue phase while in the presence of the value phase. In this work, we report on the development of in situ atomic force microscopy (AFM) imaging for determination of polymer depressant coverage and morphology on mixed mineral surfaces. Our group has previously used AFM imaging on single minerals to connect adsorbed layer characteristics with bubble-particle attachment and flotation outcomes. Two sample types were used to test the methodology: (i) a mixture of two crushed/ground minerals encased in resin; and (ii) a composite mineral sample containing macroscopic regions of three different mineral phases. The samples have been used to probe the selective uptake of two modified dextrin polymers (octenyl succinate anhydride dextrin). AFM images acquired in situ (while all surfaces are immersed in the same polymer solution) of each mineral phase have revealed the natural selectivity of the polymer for the mineral surfaces. In all cases, the polymers adsorb on the all mineral surfaces present, but to a varying extent.

Jan 1, 2014

By D. Tang

The froth zone in a flotation cell is recognised as a region which contributes to the overall flotation performance. Froth recovery is a measure of the efficiency with which the froth phase delivers particles arriving at the pulp-froth interface to the concentrate. Poor froth recovery in scavenger stages is generally attributed to poor froth stability. The key indicators of froth performance: froth recovery, entrainment and water recovery were measured in an OK3 pilot cell installed at a zinc concentrator in Australia and supplied with scavenger feed. Cell hydrodynamic and pulp chemical conditions during the operation of the cell were also measured as well as bubble growth across the froth phase. The objective of the work was to assess the impact of a number of commercial frothers on the froth performance in the OK3 cell and assess the suitability of using bubble growth as an indicator of froth stability.

Jan 1, 2014

By D. Steele, B. Ndlovu

"Adequate characterisation of clays is becoming increasingly important as operating mines move into areas of more complex ores. The processing therefore needs better mineralogical characterisation to identify problematic ores for better planning before issues arise. While a number of instrumental mineral characterisation methods are available, X-ray Diffraction (XRD) is widely recognised as perhaps the best technique for the identification and quantification of minerals, particularly clays. When an appropriate sequential and systematic sample preparation and treatment protocol is employed with instrumental XRD analysis individual clays can be uniquely identified, and the proportions of interstratified clays can also be quantified. The effect of sample preparation on the XRD analysis and identification of clays was investigated in this study. The results showed that sample preparation protocol is indeed critical to accurately analysis and characterisation of clays. For example, both dry grinding and micronizing affected the degree of crystallinity of kaolinite leading to the formation of reactive surfaces or changes in the physicochemical behavior. It was also found that the apparent degree of preferred orientation in platy minerals correlates directly with the amount of force/pressure applied during the preparation of backfilled powder samples. This work showed that manual preparation can produce highly variable peak intensities especially with minerals that show any preferred orientation. KEYWORDS Clay; XRD; kaolinite INTRODUCTION Clays are important in our life and they have numerous applications in modern world from cosmetics to environmental remediation. Therefore, clays have been extensively investigated for many years. Adequate characterisation of clays is becoming increasingly important as the mineral processing industry faces more complex mineralogy with the need for better mineralogical characterisation to identify problematic ores and plan accordingly. In most studies, X-ray diffraction (XRD) method has shown the unique capability to characterise mineralogy, especially for the fine grained size materials. The XRD technique is particularly diagnostic for clays. It is known that under ideal conditions, the peak intensities of an XRD diffractogram are proportional to the concentrations of individual minerals present in the sample. Hence, the qualitative mineralogical data obtained from XRD can be quantified, using either the internal or external standard methods. However, it is also known that clays are particularly sensitive to the influences of sample preparation method due to their physical characteristics (e.g. fine grain size, morphology, relative physical softness, crystallinity, thermal sensitivity) that could be destroyed by inappropriate preparation prior to the analysis. Thermal and mechanical treatment and grinding of clays can change their crystalline structure, and consequently, their characterisation results by XRD analysis. The behaviour of clays in grinding has been widely studied, especially for kaolinite (Miller and Oulton, 1970, Milocevic et al., 1992, Tomasevic-Canovic et al., 1992). With prolonged grinding time, the crystallinity of the clays can decrease (Filipovic-Petrovic et al., 2002). It has been shown that grinding may gradually cause the loss of hydroxyl ions of kaolinite (Gonzalez Garcia et al., 1991)."

Jan 1, 2018