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By T. S. Qiu

In view of the bad effect that Na-bentonite direct adsorb Pb2+-containing wastewater, this article has carried out two kinds modification treatment on Na-bentonite: the direct microwave radiation modification and microwave radiation organic modification by adding quaternary ammonium salt?cetyltrimethylammonium bromide,and analysis the main influencing factors of the modification effect. In static conditions, preparing Pb2+-containing wastewater as the research object, it has respectively studied the effects of Na-bentonite, microwave soil of direct microwave modification and microwave soil of organic modification on the process of adsorption Pb2+, and discusses the effects of pH value, temperature, adsorbent dosage, stirring time on the adsorption Pb2+ in wastewater by modified bentonite, at the same time it does a verification test to the practical Pb2+-containing wastewater. Comparison the effects of adsorption Pb2+ in wastewater, the results show that organic modified microwave bentonite is obviously better than direct microwave modified bentonite and Na-bentonite, and can make 6 mg/L Pb2+-containing wastewater meet the national discharge standards. Through scanning electron microscope, the result of test is that organic modified microwave bentonite is the cause of improving adsorption Pb2+ in wastewater. Preparing modified bentonite by microwave heating will not only shorten the response time, reduce energy consumption and work-load, but also modified effect is good.

Jan 1, 2014

By Alain Broussaud

The lecture is about the growing role and the evolution of advanced process control (APC) in the mining and mineral processing industry, taking into account major trends in Information Technology. It reflects the standpoint of a team, which has already successfully developed APC technology for more than 20 years. Advanced process control systems tend to rely on combinations of artificial intelligence techniques or algorithms that complement each other and cooperate. Each technique or algorithm makes it possible to use certain type of knowledge about the process, so that the advanced control systems benefit at any time from the combined knowledge of process and control engineers and plant operators, from knowledge derived from past research work and process modeling, from a considerable amount of data provided by advanced instrumentation in real time, and from knowledge that can be extracted automatically and at any time from past data and images. The lecture will first review and compare the role, merits and limitations of algorithms that are used for online decision making in mineral processing plants: expert systems, fuzzy logic, neural networks, soft sensors, optimizers, and MPC controllers. The lecture will also review the role of online image analysis and sound analysis in process control. Recent developments in this area open new dimensions, in particular the ability for advanced process control algorithms to automatically explore the past, move back and forth in time in order to make better informed decisions, and the ability to cooperate with the operators for better performance. Applications will be presented. Recent progress in process simulation makes it possible to design, configure, check, and pre-tune APC systems before plant startup, opening new options for implementing APC. In conclusion, the author will share his experience about the key ingredients for sustainable success in APC Keywords: mineral processing plants, APC, MOC controllers

Sep 1, 2012

By W. Pawlos

"The paper will present the methods of visual observation and recording of movement paths of coal grains of different physical properties in the paramagnetic liquid. The paths were recorded with a video camera in the working chamber by means of a specially constructed device, acting as a periscope, which were then transformed into digital images.Experimental movement paths were confronted to the paths obtained in a theoretical way by means of solving differential equations of movement. The outlet level of a grain of the same physical properties from the separator is a random variable with normal distribution which modal value is equal to the outlet level of a spherical grain, calculated from the solution of grain movement equations. At these assumptions it is possible to calculate the height of the passage from the separator working chamber to separate a given product with a given separation accuracy, measured by a probable error and to determine separation conditions."

Jan 1, 2003

By T. C. Rao

This presentation identifies how mineral (coal included) processing profession should look at the challenges (threats) being faced by mineral industry. Presently, the focus is more on supply and demand on minerals. In addition, the R&D activities in the chain of mine-to-metal are paying more attention (if not only on) the processes being adopted, development of new equipments and modeling and simulation. But the profession is grossly ignoring aspects such as impact of the processes on other resources, of the ways we extract, use and dispose them socio-economically and efficiently. A business model which may encompass all these dimensions are essential for the sustainable development of mineral industry and a possible approach in this direction is presented. To start with, for the sustainable growth and existence, the profession must be aware of the prospective impacts of their activities on critical factors such as ? political (changing government policies), geographical (environment, land, water and habitat), which have major bearing on the survival and growth of the industry. Mineral Processing professionals have to join hands with mining engineers to answer some relevant questions related to the impact of mineral industry on society. Mining can become economically viable only if mineral processing engineers come out with innovative solutions to reduce capital and operating costs. The solutions have to be adoptable and practically feasible so that industry looks at us for directions. In fact, we have to move towards beneficiation of nano particles striving towards zero waste. Some of the gaps in the knowledge of procedures being followed in the design and operation of processing plants are highlighted. Enhancing the knowledge base for solving unexplored possibilities, solutions to evolve sustainable development measures which demands innovation both at academic and practicing levels is the need of the future. Well-structured academic programmes are to be formulated so that the graduates of these programmes can make an effort to look at processes/concepts with a new insight and approach; the profession should excite the young brains with challenges. R&D funding agencies have to have a long-term perspective on mineral processing so that closer interactions between academic institutes, industry and R&D organizations are sustainable and that innovations are at least a few years ahead of needs of future challenges. Keywords: sustainable growth

Sep 1, 2012

By Ersin Yazici, Ahmet Bas, Haci Deveci

Pregnant leach solutions from waste of printed circuit boards (WPCB) leaching contain many impurity metals (Fe in particular) at significant levels. These impurities should be reduced to acceptable levels to avoid problems in downstream recovery processes e.g., low current efficiencies in electro-winning of copper from sulfate solutions in the presence of ferric. In this study, removal of iron in the form of goethite from synthetic (30 g/L Cu2+ and 1 M SO42-) and real leach solutions of WPCB was studied in some detail. The influences of initial concentration of iron (1-4.5 g/L Fe3+), pH (2.5-4.0), temperature (80-90°C) and seeding (23.5 g/L) were investigated over a period of 4 h. A significant increase in the iron precipitation was observed (i.e., from 68% to 96% over 4 h) with rising the pH from 2.5 to 4.0. The addition of seeds had also increased the removal rate over 4 h albeit to a limited extent i.e., from 96% to 99%. For the real leach solutions of sulfate (H2SO4-H2O2) and sulfate/chloride leaching (H2SO4-CuSO4-NaCl), precipitation of iron was found to be 63-73% (pH 2.5) and 93-98% (pH 4.0), respectively. The precipitates were further characterised by SEM-EDS analysis which showed the presence of copper (1-25%) in the precipitates indicating significant copper co-precipitation from the solution. These copper losses can be attributed to the formation of copper compounds such as anthlerite and brochantite within the range of pH (2.5-4.0) tested. This study showed that iron can be readily removed from synthetic/real leach solutions of WPCBs to a large extent (=93%) at the expense of high copper losses particularly at pH 4.0.

Jan 1, 2014

The Arctic is a region of special economic, geopolitical, research, socio-ethnic, and defense interests of both Russia and other countries of the Arctic zone. Introduction of innovation technologies at ore-processing factories is a direct responsibility of the state and this problem should be solved on the basis of coordination of interests of different stakeholders. The task of elaboration of scientific principles of rational state regulation in the North is very topical. Innovations require considerable investments first of all from private capital. However as an investment object innovations are not attractive for investors as they require large expenditures for long-term projects, and they are connected to high risks because market incentives form striving to get quick profits of private companies and result in a certain behaviour strategy while innovations need ?long money?. Under such conditions without state regulation of investment and innovation activities development of the mining sector in the Arctic practically has no prospects. At innovation development of mining enterprises economic growth is provided at the expense of active state innovation activities. The elaborated strategy of ore-processing enterprises should correspond to the modern paradigm of the ore-processing industry development which is not only for extraction of minerals but also for multi-profile structure having comprehensive use of the resources on the rational basis intended for rational complex utilization of mineral resources of the AZR which by the definition includes maximally full use of the whole aggregate of resources on the economically rational basis with obligatory environmental with resource reproductive and socio-economic functions and deterrents. The main principle of creation of innovation technologies is to obtain more products of higher quality with minimal costs. This allows increasing ?productivity of the resources? several times. This principle makes increasing productivity of the resources the most important and in this case efficiency of use of the resources brings extra profits at the expense of lack of new costs such as payment for protection and utilization of wastes. According to the economic theory only ratio between demand and supply is able to fix optimal proportions in economy and to give necessary signals for investment activities of mining enterprises. In this context market for minerals and increase of mineral resources productivity do not create incentives for investment activities without which neither sustainable economic growth nor solution of macroeconomic tasks are possible. Nevertheless countries should not reject this idea in spite of economic efficiency of the enterprises. Extraction degree of useful components and especially oil in the Arctic zone is one of the lowest in the world. This can lead to crisis of oil industry and other mining sectors. The reason for that is lack of a state policy of realization of innovation technologies in the mining sector in the Arctic.

Jan 1, 2014

By I. Nishkov, I. Grigorova, M. Ranchev, S. Dzhamyarov

"Chelopech concentrator (part of Dundee Precious Metals) is located in central-western Bulgaria. The current process plant utilizes conventional primary crushing and SAG mill grinding, copper and pyrite rougher and cleaner flotation stages to produce a marketable gold-rich copper and pyrite concentrates. As in the most processing plants, the pyrite depression is carried out alkaline media using lime. The subsequent activation of pyrite mineral is achieved by adding sulfuric acid, which has an adverse effect on the flotation equipment. Therefore, a series of laboratory flotation experiment for activation of lime depressed pyrite by ammonium salts, such as ammonium chloride (NH4Cl), ammonium sulfate (NH4)2SO4 and ammonium bicarbonate (NH4HCO3), have been conducted. The obtained results showed that ammonium bicarbonate proved to be the most appropriate reagent choice for pyrite mineral activation. These results are confirmed by X-ray photoelectron spectroscopy (XPS), performed to determine the surface chemistry of pyrite in its natural state, after lime treatment and subsequent treatment by NH4HCO3. The registered XPS spectra indicate that the hydrophilic phases on the pyrite surface could be efficiently removed by using the ammonium salt NH4HCO3. The industrial use of NH4HCO3 as an activator of lime-depressed pyrite is a possible alternative for sulfuric acid replacement as a most widely used pyrite activator. Flotation experiments with addition of 200, 400, 600 and 800 g/t from each of the studied ammonium salts have been conducted. Furthermore, the impact of the flotation pulp pH within the scope of 9.00 – 10.50 was also investigated. The obtained results from the laboratory flotation experiments, showed that the pyrite activation with ammonium bicarbonate is an excellent possibility for replacing the sulfuric acid as main pyrite activator reagent, in order to eliminate the gypsum accumulation during the flotation of pyrite in Chelopech concentrator.INTRODUCTION The Chelopech deposit, located about 60 km east of Sofia is one of the largest Cu-Au deposits in Europe. The ore have complicated mineralogical and chemical composition. The main ore minerals are represented by pyrite, enargite (luzonite), tennantite, chalcopyrite and bornite. The average copper content of the mined ore is about 1.1 % and the gold content is about 4.0 g/t."

Jan 1, 2018

By N. Karapinar

Ferrihydrite, a member of iron oxides family, has been used as an adsorbent for the removal of heavy metal ions from industrial wastewater. The success of the operation depends mainly on the efficient removal of ferrihydrite from the aqueous phase. Hence, the emphasis of this study was given on the separation of ferrihydrite by high gradient magnetic separation (HGMS) method to overcome solid-liquid separation difficulties of ferrihydrite. Magnetic seeding technique in which the magnetite mineral was chosen as a seeding reagent was used to make magnetic separation available. The method clearly involves the attachment of ferrihydrite to a magnetic seed material and subsequent magnetic separation of ferrihydrite ? magnetite coagulates. Seeding of ferrihydrite with magnetic particles was achieved by exceeding the solubility limit of the ions in the presence of dispersed magnetite. Magnetic separation results of seeded ferrihydrite showed that maximum seeding performance is obtained in the pH range of 7.0~10.0. Iron/magnetite ratio had a marked effect on the separation of seeded iron oxide precipitate by HGMS. This ratio determines the operation parameters such as magnetic field strength and flow rate. It was concluded that when used with magnetic seeding technique, HGMS can be used to surpass separation difficulties of ferrihydrite used in adsorption-based treatment techniques.

Jan 1, 2014

By Igor P. Solozhenkin, Peter M. Solozhenkin, Sanda Krausz

"In this work, authors will show the efficiency of computer technology and chemical programs at studying collectors for flotation of minerals of elements of platinum group (EPG). Clusters various minerals EPG (flotation reagents) are created, named us clusters minerals (reagents) as their structure corresponds to the chemical formula, and the distance between separate atoms corresponds to the known tabulated data. By molecular modeling are investigated clusters sperrylite PtAs2, stumpfilyte PtSb, sadberryte PdSb, sobolevskite PdBi, palladoarsenyte Pd2As, paolovyte Pd2Sn, rustenburgyte (Pt3Sn, Pt6Sn2) and their computer parameters (absolute rigidity, electronegativity, transfer factors of carry, charges of the atoms) are determined. Tellurides of palladium (IV, II) merenskyite PdTl2 and kotulskyte PdTe and platinum clusters are investigated: PtFe4, Pt3Fe, PtFe (Pt2Fe2), Pt2Fe (Cu) Ni. The technique of attachment of the collector (composites) to cluster atoms EPG is offered. For the first time, it is established that at linkage of flotation collectors on monodentate, bidentate and bridged to circuits with atoms clusters the minerals containing atoms As, Sb, Bi, Pb, Sn, reaction of connection with change of a degree of oxidation of these atoms and occurrence of a proton operates. It is executed virtual skirling organic compounds connections by the developed criteria from accessible libraries of a database. The principle of an estimation of interaction energy for flotation reagents with mineral clusters is offered. It is developed the prognosis of collector activity evaluation (P?AE) and his values for candidates in collectors for flotation of minerals EPG are calculated. For flotation of ores containing Pt and Pd minerals, a number of reagents, including compounds on basis P (III), for innovational technology of Pt, Pd mineral flotation are recommended. Key words: flotation, minerals, flotation reagents on the basis of phosphorus (III), molecular modelling, chemical programs, program ????? , electronic energy."

Jan 1, 2014

By P. K. Arya

Huge quantity of copper is lost in Crown, Sill, Rib Pillars, hanging wall, foot wall and unexploited ore bodies in several closed underground copper mines and old worked out stopes of Hindustan Copper Limited at Mosaboni and other places. These mines might have been uneconomical to work with conventional mining methods. However, huge quantity of mineral reserves is lost due to their closure. Chemical and in-situ bio-wash leaching, if tried can provide an answer to facilitate the recovery of metallic values economically. Encouraging results were obtained during an experiment at North Badia Mines at Mosabani in the past. Though the experiments were not completed but whatever results obtained were very encouraging and can be successfully tried to make it viable. The results of the experiments are discussed here and a plan is suggested to recover copper from such mines.

Jan 1, 2014

By M. V. S. Cavalcante

The quality of iron ore pellets, represented in terms of parameters such as cold compressive strength (CCS) and Tumble Index (TI), has a strongly influence on the productivity and energy of reduction furnaces like the blast furnace and on the quality of hot metal or liquid iron. The main objective of pelletization operations is to produce iron ore pellets of desirable specifications and ensure high levels of plant productivity and energy efficiency. Advanced process control of an industrial iron ore pellet induration process using a soft sensor for pellet quality and fuzzy-logic based control algorithm is described in this paper. The pellet quality soft sensor consists of a rigorous mathematical model of the induration process and a statistical model for the pellet quality parameters. The mathematical model is based on the fundamental principles of heat and mass transfer between gases and pellets, kinetics of drying and condensation of moisture, combustion of coke, calcination of limestone, and melting and solidification of pellets. The predictions of wind-box temperature profiles are in close agreement with the measured profiles. The time-temperature profiles of the pellets during induration, along with raw material characteristics and induration process operating conditions, are used as inputs to the quality model to predict cold compressive strength and the Tumble Index. The predictions of the quality soft sensor along with the rules based on fuzzy-logic derived from simulation results and operator experience are then utilized to control the induration process to achieve precise control of the quality parameters and to optimize the induration process in terms of fuel efficiency and productivity. The mathematical model is also utilized as a soft sensor for temperature, moisture and composition profiles of pellets and gases. Results of implementation of this model-based control strategy on an industrial scale induration process will be presented. Keywords: iron ore, pelletization, simulation, process control, optimisation

Sep 1, 2012

By John A. Herbst

Professor A.M. Gaudin and his students at MIT were dedicated to understanding the fundamentals of mineral processing and as a consequence were constantly searching for better quantatative descriptions of size reduction, liberation and mineral separations. I have had the good fortune of meeting Professor Gaudin and working with many the modeling pioneers who followed him. I have observed first hand the refinement of mineral processing models as they increased in realisticness moving up the steps of the pyramid (see figure below) from pure empiricism to the current pinacle of physics based models. During this journey our industry benefited significanbtly as model prediction errors were reduced from ± 20% to ± 1%. Unit operation and plant simulations improved in accuracy and speed of calculations.

Sep 1, 2012

As a leading global company in the mining sector, we are committed to sustainable development. To this end, we invest in the responsible, integrated management of economic, environmental and social issues. Vale?s objective is for our businesses to produce local, regional and global prosperity, enabling the construction of a positive legacy throughout the lifecycle of our activities. This covers everything from talking with stakeholders and preventing failures to complying with legislation, paying constant attention to environmental issues and respecting ethics in business. Keywords: sustainable development

Sep 1, 2012

By V. F. Petrov, E. P. Olberg, S. V. Petrov

"The study was carried out using process solutions produced during cyanidation of gold-bearing concentrates from a gold-processing plant. It was found that the water contained a significant portion of thiocyanate (7910.0 mg/L), cyanide was virtually not present. The metals occurred primarily as iron (355.0 mg/L) in the form of ferrocyanide. Cyanide recovery was conducted using an ozone treatment process with reactors developed by the Environmental Department of Irgiredmet. The process design ensured complete utilization (100%) of O3, thus equipment operation safety increased.The recovery of free cyanide from thiocyanate was 76.6%, which corresponded to 5.12 kg of NaCN (100%) per 1 m3 of solution. Recovered NaCN can be used for recycling in hydrometallurgical processes.The operating costs estimation showed that the production cost of a tonne of recovered cyanide was US$1288.7, considering the prices of energy and commercial sodium cyanide in Russia in 2017, i.e. recovered cyanide is cheaper than commercial cyanide by 55.8%.INTRODUCTION Depletion of oxidized gold-bearing ores readily amenable to cyanidation has shifted focus to large-scale processing of primary ores with high sulphide content. Primary ores processing flow sheets involve gravitational and/or flotation concentration with subsequent treatment of produced gold-bearing concentrates. Typically, concentrates reporting to cyanidation contain considerable amounts of sulphur that can interact with CN- and further formation of SCN-. The use of refractory gold liberation methods (bacterial liberation, ultra-fine grinding) provides activation of this side reaction up to complete consumption of free cyanide in a short period. This makes water recycling unviable and impractical.The interaction of the sulphur content in concentrates and cyanide contributes substantially to consumption of NaCN required for efficient gold recovery. Inappropriate consumption of the main reagent achieves dozens of kilogram per tonne of material to cyanidation, and reaches approximately 100% when gold is recovered from activated sulphide-containing products (e.g. by ultra-fine grinding)."

Jan 1, 2018

By Kaioeng Wang, Qi Liu, Yahui Xiang

"In the differential metal sulfide ore flotation it is desirable to replace the toxic inorganic depressants with environmentally benign chemicals. Chitosan, as a natural and non-toxic polymer, has been proven to be an efficient depressant for chalcopyrite while allowing galena to be floated by xanthate collectors. However, the poor solubility of chitosan limits its potential applications as the flotation could only be carried out at about pH 4 where chitosan is soluble. A carboxymethyl derivative of chitosan, named N-carboxymethyl chitosan (N-CMC), was synthesized by substituting the amino groups of chitosan with carboxymethyl groups. The substitution significantly improved the solubility of chitosan. The structure of N-CMC was studied and compared with chitosan via Fourier transform infrared spectroscopy (FTIR). Flotation tests were performed on single minerals and mineral mixtures (with weight ratio of 1:1) with the addition of appropriate amount of potassium ethyl xanthate (KEX) and N-CMC. The solution pH was varied from neutral to alkaline. The flotation concentrates and tailings were collected and analysed for the contents of copper and lead. FTIR measurements showed that new peaks of C=O stretching of -COOH and N-H deformation of -NH- appeared in N-CMC, which indicated that the carboxymethyl groups were introduced and the amino groups were the sites for the substitution. Flotation results indicated that N-CMC could depress either chalcopyrite or galena depending on the pH. The results were not affected by the sequence of KEX and N-CMC addition. Therefore, N-CMC is potentially useful in Cu-Pb sulfide separation following a bulk Cu-Pb flotation. The N-CMC was also found to have surface cleaning functions, and was able to remove contaminating copper ions from galena surfaces. Therefore, its application in sulfide ore flotation is expected to be more robust than the original chitosan."

Jan 1, 2014

By Olga D. Khmelnitskaya

The paper presents the results of research on the development of gold recovery technology from oxidized gold-copper ore of one of deposits in Russian Federation. Gold and copper grades in the ore are 9.5 g/t and 0.4%, respectively. Various options of flowsheets, such as direct cyanidation, thiourea leaching, flotation and gravity concentration followed by subsequent cyanidation of con-centration products, were tested. It was established that gravity-cyanidation technology with filtra-tion leaching tails and the use of solutions in the recirculation is the optimal option for ore treatment. The proposed flowsheet provides gold recovery for 91.0% at NaCN consumption 2.5 kg/t ac-cording to the results of pilot testing. Ammonia-cyanide gold leaching was also examined. In comparison with cyanidation, gold leaching solution in system NaCN-NH4OH-(NH4)2CO3 allows NaCN consumption to be reduced three times from 4.5 kg to 1.5 kg per 1 ton of the ore and provides the same gold recovery. Based on the laboratory and pilot plant tests results of gravity-cyanidation technology of gold dissolution, process design criteria were developed.

Jan 1, 2014

By V. Sheikhzadeh, M. Saghaeian, R. Hejazi, M. Zare

High Pressure Grinding Roll (HPGR) plays a major role in increasing specific surface area of iron ore concentrate for producing pellet feed. HPGR grinding mechanism implies that material be compressed between the two rolls, therefore layer of material must be able to resist required pressure for achieving suitable grinding conditions. In this study for determining a simple relationship between material pressure resistance ability and HPGR main design parameters, piston press tests were performed on different iron ore concentrate samples along with HPGR Blaine increasing tests. Piston press tests results showed that by decreasing moisture content, material pressure resistance increased and in constant moisture content this parameter will change based on material specifications. HPGR Blaine increasing tests results showed that by decreasing moisture content, HPGR specific throughput and working gap increased and in constant moisture content this parameter will change based on material specifications. For all of the studied samples at worst condition, we got the results including: HPGR delta gap equal to zero, specific throughput lower than 200 ts/hm3.According to the tests results, HPGR Applicability Index (HAI) can be introduced at four different class types from 1 (weak) to 4 (excellent). This index determines achievable specific throughput and possibility of using HPGR according to material specifications, i.e. for HAI 1-4 the pressure resistance is <90, 90 to<125, 125 to <150 and = 150 bar, respectively. Similarly for HAI 1-4 specific throughput is <200, =200, =220 and =250, respectively. So based on design moisture content, if concentrate HAI is 3 or 4, HPGR is a correct choice. For HAI 2, HPGR can also be used. But for a material with HAI equal to 1, HPGR is not a good solution. As a result in order to apply HPGR for HAI 1, material condition such as moisture or slime content should be decreased.

Jan 1, 2018

By Herman Mendoza, Luisa Ciriaco

An investigation of the seeding mechanism using heterocoagulation and the Derjaguin - Landau - Verwey - Overbeek (DLVO) theory of two pure minerals is the objective of this study. The seed was silica with modal diameters of 4.529 µm (fine particles) and 5.216 µm (coarse particles) and the test powder was hematite with a modal diameter of 0.883 µm. Parameters included variations in the concentration and particle size of silica. Both particles were first subjected to size determination and settling tests via Stoke’s Law. The silica-hematite system was then suspended in 0.001 M KNO3 electrolyte solutions where pH was adjusted. Afterward, the suspension was agitated and was allowed to settle at different time intervals while obtaining turbidity readings. Results through settling time and turbidity vs. pH graphs indicate that maximum heterocoagulation occurs from pH 2 to 5 while minimum heterocoagulation occurs from pH 6 to 7. At these pH levels the zeta potentials of silica and hematite are negative and positive, respectively. On the contrary, repulsive forces dominate the system from pH 8 to 11 due to the particles’ negative zeta potentials. Furthermore, the attachment of hematite to silica increases when the parameters become larger thereby increasing the effectivity of heterocoagulation at acidic to neutral pH levels.

Jan 1, 2014

By Edson Charikinya, Pierre-Henri Koch

"The extraction of mineral values from ore requires liberation followed by separation steps. Liberation is achieved by size reduction operations which are energy inefficient processes typically dominating the energy consumption in a mineral concentrator. As the grade of ore reserves declines, future viability of mineral operations will be determined by energy costs of comminution. The application of high power microwave energy to secondary crusher products has been suggested as a possible commercially viable thermal treatment method for reducing comminution energy and improving value mineral liberation. Recent studies have shown that microwave pre-treatment of coarse sphalerite ore particles (> 5mm) at specific microwave heating energies (1-3 kWh/t), induces microfractures and creates new crack surfaces. This suggests that subsequent crushing of these microwave treated particles could yield enhanced liberation. However, limited studies have been carried out investigating the mode of breakage and the extent of enhanced liberation in that case. The objective of this study is to develop numerical methods for quantifying the extent of enhanced liberation and mode of breakage in crushed microwave treated and untreated particles. Sphalerite ore particles representing small (-5+4.75) mm, medium (-16+9.5) mm, and large (-25+19) mm HPGR and cone crushed particles were microwave treated at specific energies between 1-3 kWh/t. Cracks in the ore particles before and after microwave treatment were analysed with QEMSCAN and numerical models of the measured particles (before and after microwave treatment) were developed in MATLAB. The propagation of random and non-random cracks was investigated by simulating comminution of the modelled treated and untreated particles. Results of this study demonstrate that the breakage mechanism and the liberation of valuable minerals from gangue in microwave treated and untreated particles is significantly different. This study contributes to the development of numerical tools to quantify crack propagation in heterogeneous ore particles."

Jan 1, 2018

By S. Jeon, N. Hiroyoshi, N. Kitajima, S. Tanaka, M. Ito, R. Pongsumrankul, C. B. Tabelin

"Gold (Au) extraction is inefficient when crushed waste mobile phones (WMPs) are directly leached by ammonium thiosulfate likely because of the cementation/precipitation of dissolved Au in the presence of base metals like copper (Cu), iron (Fe) and/or aluminum (Al). This study applied physical separation techniques to remove base metals as well as plastics and concentrate the Au containing fractions from WMPs prior to leaching. Coarse fraction of crushed WMP (+2-5.6 mm) was pretreated by jig and magnetic separation to remove plastics and base metals like Fe, Cu, and Al, while the fine fraction (-2 mm) was pretreated by flotation, and float and sink separation. The leaching results showed that Au extraction increased in both of the size fractions. In the coarse fraction, Au extraction increased by as much as 2-fold after pretreated (from 4 to 7%). Improvement of Au extraction in the fine fractions after pretreatments were even more dramatic. Au extraction increased from 4 to 61%. These results indicate that physical pretreatment to remove co-existing common metals and plastics is effective to improve Au extraction from WMPs. INTRODUCTION Global sales of mobile phones are expected to increase steadily in the foreseeable future because a lot of people buy newer phones with upgraded and more advanced functions almost every two years, which leads to the higher generation of waste mobile phones (WMPs). WMPs contain a wide variety of materials including plastics, glasses, base metals and precious metals such as gold (Au). Among all the valuable materials in WMPs, Au accounts for over 80% of its total metal price (Park et al., 2017), so recovery of Au from WMPs is needed."

Jan 1, 2018