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By Chris Plackowski, Bruckard. Warren J., Anh V. Nguyen

"Enargite is a significant penalty mineral in the copper industry and its separation from many copper sulfides by flotation is difficult. The separation may be crudely achieved using selective oxidation techniques or through the use of pulp potential control. This paper summarizes our latest contributions to a better understanding of enargite surface electrochemistry and hydrophobicity. Oxidation, roughness, hydrophobicity and species formation on the surface of natural enargite were examined by a novel experimental approach that combines electrochemical techniques, atomic force microscopy, X-ray photoelectron spectroscopy and droplet evaporation tensiometry. It allows for synchronized electrochemical control and examination of the oxidative surface morphology, speciation and hydrophobicity of enargite at pH 4 and pH 10. At low pH, surface layer formations consisting of metal deficient sulfide and elemental sulfur were identified associated with a limited increase in roughness and heterogeneous distribution of surface species produced by initial rapid dissolution of Cu, followed by diffusion limited surface layer deposition. At high pH, a similar diffusive mechanism associated with oxidation products consisting of copper sulfate and hydroxide and a significant increase in surface roughness were established. Receding contact angle measurements showed no significant difference in the contact angle on a surface oxidized at pH 10 and the freshly polished surface. Contact angle increased from 46° on the polished surface to 59° after oxidation at pH 4. Competing effects of hydrophilic copper oxides and hydroxides, and hydrophobic species of elemental sulfur on the mineral surfaces under oxidizing conditions at pH 4, and the change in surface roughness at pH 10, contribute to the changes in enargite hydrophobicity under electrochemically-controlled oxidation conditions. Most likely, both surface species and surface roughness produced by oxidation are critical to the changes in the wettability of enargite and other sulfide minerals."

Jan 1, 2014

By Luis Bergh, Juan Yianatos, Luis Vinnett

"Process automation as an engineering discipline is more than control systems since it includes industrial instrumentation, such as sensors, transmitters and actuators, as well as control and supervision systems, collection and transmission of data and real-time software applications to supervise and control the operation of plants or industrial processes. In the last several decades, accelerated technological development has provided a variety of software and hardware tools to aid development, maintenance and continuous improvement of automated systems. These developments however seldom reach their full potential in real plants. There are many factors to be considered, among them human capital specific training and the organization model. In this paper, a methodology for training engineers in advanced control and supervision of flotation plants is presented based on study of the application of these technologies in hybrid pilot plants. Since experimentation in real plants may present undesirable risks and costs, and simulation studies are usually limited to some unrealistic conditions, a laboratory where on-line measurements of the hydrodynamic behaviour of a pilot plant is mixed with phenomenological models has been created. In this form, an environment as close as possible to a real plant can be recreated. A flotation column and a circuit of three pneumatic cells are fully instrumented and connected to a PLC and PC network. In the control room, students learn applications of classical PID control in a DCS environment, advanced predictive control, on-line process operation diagnosis, fault analysis, virtual sensors and expert-fuzzy systems. Several undergraduate and graduate courses and theses are supported by this Process Control Laboratory infrastructure. Examples of these applications are discussed."

Jan 1, 2014

By S. A. Kondratyev

"The present research work aims at disclosing the dependence of flotation concentrate recovery and its grade on the physically adsorbed collecting reagent properties, viz., surface pressure in the reagent film at gas-liquid interface, velocity of reagent species spreading over the said interface, relation between interaction energies of collector molecules within a film and with water dipoles.When using a single collecting reagent it is possible to improve the flotation concentrate grade in two ways, namely, by reducing collector consumption rate or using a weaker reagent. According to the proposed mechanism, a decrease in the physically sorbed species of the collector leads to a decrease in the rate of removal of the kinetic restriction of a flotation contact formation. As a result, the recovery of the useful component is reduced and the content of valuable components in the flotation concentrate is increased. The relationship between the spreading velocity of physically sorbed species at the gas-liquid interface and the recovery and quality of the flotation concentrate has been experimentally proved. Reduction in collector consumption lowered the valuable component recovery at a higher grade of the concentrate.The reasons were established for a rise of valuable content in the flotation concentrate if a weaker collector was used. It is justified that the use of a weaker collecting reagent with a shorter hydrocarbon fragment declines physically sorbed species of collector. The spreading velocity of collector derivatives at gas-liquid interface tends to lower along with less participation physically sorbed species of collector in formation of a flotation aggregate. The spreading velocity is determined for products of interaction between butyl-and ethyl-xanthates and lead nitrate at gas-liquid interface. It is found that the spreading velocity of butyl-xanthate derivatives is higher than that of ethylxanthate derivatives.The research work gets insight into the nature of relation between useful component content in the flotation concentrate and the useful component recovery. It is pointed out that adjusting the collecting activity of a collector makes it possible to influence a useful component content in the froth product thus gaining a compromise between wanted grade and recovery parameters."

Jan 1, 2018

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

By F. Boylu

In this study, Ca-bentonite was subjected to a series of systematic hydrocyclone tests with the aim of developing separation procedures and in turn achieving optimum recoveries. In hydrocyclone tests, vortex and apex diameters and also feed pressures were investigated. In each hydrocyclone set, vortex diameter was kept constant while the other two parameters varied to produce bentonites con-centrates of various smectite contents. The separation efficiencies were evaluated based on the cation exchange capacity (CEC), particle size and swelling index. The detailed hydrocyclone tests showed that, upgrading of Ca-bentonites require procedures different from the bentonites reported in the literature. Sodium and mixed bentonites are easy- to-disperse and easy-to-separate whereas calcium types need to be scrubbed rigorously for disintegration. Scrubbing properties of ca-bentonite were investigated as a function of scrubbing time and percent solids by weight (PS). The scrubbing conditions at 700 rpm for 1.5 hours and percent solids of 30 % were found more effective for achieving a better quality bentonite. In addition to the parameters mentioned above, the effect of percent solids on hydrocyclone separation was also studied. Although Ca-bentonites permit studying at higher percent solids, increasing solids content of the pulp deteriorated the quality of the clean products. Application of an appropriate separation scheme enabled the development of a unique separation procedure involving stage wise scrubbing followed by hydrocycloning which yielded calcium bentonite concentrates with CEC of 90 meq/100 g and high swelling indexes of 12 mL from the original bentonite of 65 meq/100 g and 7.0 mL, respectively. These results indicate that upgraded bentonite products can be conveniently used in various diverse industrial applications including bleaching earth, desiccant, cat litter, paper etc.

Jan 1, 2014

By Dave Deglon

The Western Cape Mineral Processing Facility (WCMPF) is a collaborative educational initiative between the Departments of Chemical Engineering of the University of Cape Town, the University of Stellenbosch and the Cape Technikon. The WCMPF was established in 1989 with the aim of improving mineral processing education in the Western Cape. Since its inception the WCMPF has had a number of successes in this area, especially in improving the quality of mineral processing practical training. In addition, the WCMPF has played an important role in promoting liaison and interaction between tertiary educational institutions teaching mineral processing in the Western Cape. Over the past decade the WCMPF has played a key role in the education of over five hundred mineral processing graduates and diplomates. This paper presents an overview of the activities of the WCMPF and attempts to encapsulate the ‘lessons learned’ from over a decade of successful functioning as a collaborative educational initiative in mineral processing.

Jan 1, 2003

By S. M. Narbekova, L. V. Semushkina, Zh. A. Aldybayeva, A. A. Mukhanova, D. K. Turysbekov, N. K. Tussupbayev

More complex and heavy-concentrating oxidized and mixed sulphidic oxidized ores are involved in production because of increasing needs for non-ferrous metals. Extraction of the oxidized minerals of non-ferrous metals general in current technologies. The problem is solved to oxidized polymetallic ores the preliminary selective sulphidization is the oxidized surface of the components by means of hydrogen sulphide, sulphide and calcium polysulphide, and also element sulphur, etc. The task was to study details of flotation of the oxidized lead-bearing ore of the Zarechnoe deposit (Kazakhstan) with calcium polysulphide as sulphidation. According to chemical analysis initial samples of the ore contain, %: lead – 4.8; zinc – 0.1; general iron – 0.81. Phase structure lead is characterized by the oxidized form of 57.76-64.5 %; by sulphidic status of 25.5-32.64 %, and by plyumboyarosite of 19.0-23.02 %. Researches on flotation beneficiation of oxidized lead-bearing ore are conducted. Sulfidizator gave to grinding, on flotations there were used the collector (butyl xanthogenate of sodium) and frother (T-80). Experiments were conducted with a new sulphidizator – calcium polysulphide. The latter is obtained by interaction of CaO calcium oxide with sulfur and water at high temperature with component mass the following ratio S:CaO:H2O =10:5:85. Extent of mill initial ore was optimised (88.42 % of - 0.071 mm grade). For the optimum mill mode the studies on matching of an optimized consumption of sulphidizators are performed. On basic technology with application of sulphide of sodium as a sulphidizator at optimum mill, the lead concentrate with the content of lead 64.4 % at extraction of 86.6 % was received. The content of cerussite in a concentrate was about 14.9 % at extraction of 82.1 %. With application of calcium polysulphide as a sulphidizator the lead concentrate with the content of lead 68.0 % at extraction of 88.0 % was received. The content of cerussite has made 16.0 % at extraction of 85.0 %. Application of a new sulphidizator allows to increase extraction of lead in a concentrate from 64.4% to 68% and cerussite extraction – from 82.1 % to 85.0 %. The possibility of application of calcium polysulphide as a sulphidizator instead of conventional sulphurous sodium was established.

Jan 1, 2018

By Shuoshi Lu

The Cu-Co ore studied here belongs to the oxide type. The oxidation rates of copper and cobalt are69.30% and 78.78%, respectively. The content of Cu in ROM is 1.34% and that of Co is 0.096%. The ore contains 4.64% carbon.Based on the process mineralogy and previous metallurgy tests, the principalprocess flow-sheet of ?grinding fines 80% -0.074mm, sulphide flotation followed by oxide flotation, and flash flotation for oxides? has been determined.The handling of carbon is determined through tests. The depressant PNL-1 depressed carbon effectively, improved the recovery of sulphide minerals and reduced the reagents consumption.The operation of the flow-sheet was also changed to better at the same time. Keywords: Cu-Co oxide ore, process mineralogy, carbon depression, efficient depressant of carbon

Sep 1, 2012

By Juan Estrada, Mirtha Frómeta, Rubén Alcalá, Emilio Montejo, José Castellanos, Juan Berto, María Rivas

"The oxidized nickel ores from San Felipe deposit are composed mainly Smectites which gives to the pulps very unfavorable rheological .properties (cinematic viscosity and high shearing strength) for transportation processes (pumping), very low settling velocities and very low thickened pulps. These properties do not allow the preparation of high % solids, which affects the economic efficiency if a high pressure acid leach (HPAL) process is used. Pulps of close to 30% solids have very high BYS making pumping impossible. CIPIMM developed three technologies to solve these problems and to substantially increase the % solids in the pulps to be leached without a thickening step. These technologies are: • CIPIMM 2. At Preparation of pulps using additives. This method is based on the effect of some additives (inorganic salts) to improve the pulp’s properties. The use of this method allows increasing the % solids in the pulp up to 40% with good rheological properties • CIPIMM 2B. Preparation of pulps by thermal treatment of the ore previous to the preparation of the pulps. This method is based on the thermal destruction of the clays structure. Its use allows to obtain pulps with 50 - 60 % solids with excellent rheological characteristics. As a collateral effect, the Ni and Co grades increases by 10 - 15%. • CIPIMM 2C. Pulp preparation by chemical treatment. This method is based on the chemical transformation of clays, to obtain without thickening, pulps with 43- 45% solids and excellent rheological properties. The use of one of the three technologies depends on the chemical and mineralogical composition of the ores and the results of technical-economical evaluations to determine which one is the best alternative before running higher scale tests."

Jan 1, 2014

By A. A. Sirkeci

In the scope of this investigation comparison between impact breakage and compression breakage were carried out for the separation efficiency of minerals using a chromite ore sample. The ore sample was broken below 1 mm employing a laboratory type roll crusher and an impact crusher. Concentration tests were conducted on -1+0.5 mm, -0.5+0.2 mm and -0.2 mm size fractions using a Wilfley type shaking table. Test results showed a remarkable difference between two types of breakage. Both concentrate grade and recovery was in the favour of impact crushing. Furthermore, the shape of the broken particles also showed differences such that in the case of impact breakage they were more spherical compared to compressive crushing. The results of the shaking table con-centration tests showed that a concentrate assaying 48.4% Cr2O3 were obtained with 78.5% recovery in the case of impact breakage. On the other hand the concentrate grade and recovery values were 48.8% Cr2O3and 52.4% respectively in the case of compression crushing. The losses in the tailings were also in favour of impact breakage proving that differential breakage occurred between chromite and gangue minerals.

Jan 1, 2014

By Andrzej Luszczkiewicz, Magdalena Duchnowska, Jan Drzymala

A selected flotation system of beneficiation of the copper ore at KGHM Polska Miedz S.A. has been analyzed in the article. It was found that a proper assessment of upgrading must be based on two elements, that is the upgrading process selectivity and working point of the considered flotation unit, both determined, preferentially by means of the Fuerstenau recovery-recovery upgrading curve. The Cu recovery - non-Cu components recovery upgrading curve was selected for calculations because its background lines (no separation and ideal separation) are insensitive to changes in the grade of feed of the processed material. This approach allows a comparison of upgrading results for feeds having different grade, being upgraded in various flotation machines and under different physicochemical conditions. It was shown in the paper that the main criterion for comparison of two working in parallel systems is selectivity of upgrading. However, when two flotation machines, despite of the same selectivity, produce concentrate and tailing of different grades, it is necessary to analyze their working points using upgrading curves. The proper position of the working point depends on the criterion imposed on the process and is a result of not only basic parameters of the upgrading process such as feed, concentrate and tailing grades but also on economic parameters such as costs associated with the production of concentrates and the time needed for their production.

Jan 1, 2014

In this paper, various methods, such as XPS, XRD, SEM and zeta potential measurement are applied to investigate the action mechanism of sodium sulfide in flotation of lead and zinc oxysalt minerals. The experimental results show that the mechanisms of sodium sulfide in flotation of lead oxysalt minerals and zinc oxysalt minerals are different: on the surface of cerusite, there is lead sulfide phase formed under the reaction of sodium sulfide, resulting that the cerusite surface shows the form of galena, which is advantageous to the adsorption of anion collector and improves the floatability of cerusite as a result. On the surface of zinc oxysalt minerals, there is no zinc sulfide phase formed, but the sodium sulfide increases its surface electronegativity, and enhances the adsorption of cation collector lauryl amine, so the floatability of zinc oxysalt minerals is improved. The difference of action mechanisms of sodium sulfide on lead and zinc oxysalt minerals exactly explains the reason why different collectors are selected in the flotation of cerusite and smithsonite, which are both carbonate minerals although.

Jan 1, 2014

By I. Gombköto, G. Mucsi, S. Nagy, F. Kristály, Á. Rácz, R. Szabó, B. Egyed

"Present paper deals with the investigation of a Hungarian pumice. Grinding experiments were carried out in a stirred media mill for various residence time. Ground samples were tested with laser particle size analyzer to determine and calculate the material fineness (particle size distribution and specific surface area). The lime adsorption capacity was measured to monitor the reactivity. Alkali activated cement paste was prepared using ground pumice with various alkali activators. Cube shaped specimens were produced from the paste and the uniaxial compressive strength was measured at the age of 7 days. The resulted alkali activated material structure was investigated by XRD and FTIR. The results of the experiments show that pumice fineness has strong impact on its hydraulic activity, hence on the compressive strength and the structure of the resulted binder. Relationships between grinding fineness, material structure and strength of the raw and mechanical activated material as well as the alkali activated cement were revealed. INTRODUCTION Pumice is a natural pozzolan which can be used as raw material for cementitious materials in limited portion owing to its low reactivity. Furthermore, due to its mineralogical composition it can be used for developing a new environmental friendly binder, namely alkali activated cements (AAC) which are inorganic alumina-silicate materials with good cementitious properties (Almalkawi et al., 2017; Özodabas and Yilmaz, 2013; Najimi et al. 2018; Yadollahi et al., 2015). Despite being a rather recent research topic, many papers and books have been published focusing on various aspects of alkali activation. There is great variety of raw materials that can be utilized for AAC production. However, primary raw materials are very expensive and secondary materials are heterogenous in composition. Therefore, a more homogeneous and low price silicate would help to balance the properties and cost of resulting cement and easing the way for commercialization of AAC. However, the control of its reactivity is of great importance which can be realized using mechanical activation by grinding (Juhász and Opoczky, 1990; Djobo et al., 2016; Mádai et al., 2015). The goal of present paper is to investigate the effect of mechanical activation of pumice on the properties of the resulted alkali activated cement."

Jan 1, 2018

By B. Friedrich, A. Weyhe, H. Heegn

"Nickel-metal hydride batteries (Ni-MH) are storers of electrochemical energy, which have a higher specific storage capacity than lead or nickel-cadmium batteries. The demand for Nickel-metal hydride batteries is increasing rapidly since their market launch in the early 1990’s. Today there is no suitable and sustainable recycling process to recover nickel, cobalt and rare-earth metals. The discarded batteries are used today in the steel industry as alloy material because they contain nickel. Cobalt and rare-earth metals (RE) are lost; they are non-recycleable.In a German governmental funded research project, IME Aachen, ACCUREC Mühlheim and UVR-FIA Freiberg are cooperating in processing as well as in creating a feasibility study. The target of this project is the development of a new recycling process for metal recovery from Ni-MH-batteries. The proposed process described in this paper consists of a combination of mechanical, pyrometallurgical and hydrometallurgical processing steps. This process is capable of treating all types of Ni-MH-batteries. After comminution steel and organics are separated. The separated Ni-MH is smelted in an electric arc furnace. The products are a nickel-cobalt alloy and a slag phase enriched with rare-earth oxides for further treatment to ‘mischmetal’. Both the Nickel-Cobalt alloy and the ‘mischmetal’ will be directly used in battery production."

Jan 1, 2003

By G. Mucsi

This paper deals with the laboratory investigation of cathode ray tube (CRT) glass based glass foam, a relatively new product so called ?Geofil bubbles?. The main process engineering material properties of raw materials, such as particle size distribution, moisture content, density and specific surface area are shown. Then the preparation of raw cathode ray tube glass waste is presented including the following steps: crushing in impact crusher, grinding in laboratory scale ball mill, mixing, pelleting and sintering. We found that it was possible to produce foam glass (with proper mechanical stability and particle density) from the investigated waste CRT glass. The material characteristics of the final product strongly depend on the sintering conditions. Optimum conditions were determined particle size fraction was found to be 4-6 mm, temperature 800 0C, residence time 7.5 min. Keywords: waste CRT glass, grinding, pelleting, sintering, glass foam

Sep 1, 2012

By Z. L. Huang

A new porous apatite product was prepared using phosphorite from Yichang China by a tem-plate-directed method in self-made reaction equipment under constant temperature and pressure. The product was characterized by XRD, FT-IR and SEM. The results showed that the product was a kind of micrometer porous sphere three-dimensionally structured by apatite nanoflakes, that the average thickness of nanoflakes was about 50 nm, that the average pore size was about 1.2 µm and that the particle average size was about 20 µm. Great amounts of Ca2+channel, high special surface area and regular spherical shape show the potential promising applications of this special porous apatite product in the fields of catalyst, medication, chemical engineering and environment engineering

Jan 1, 2014

By A. P. Das

Biomining technology focuses on achieving effective recovery of precious metals from their ores and concentrates using microbial techniques. Biomineral extraction of manganese from low-grade manganese ores using bioleaching was investigated in this paper. Five fungal strains were selected for screening of bioleaching of low-grade Mn ore collected from Sanindpur iron and manganese mines, Koira Sector, Keonjhar, Odisha, India. A fungal strain, Aspergillus niger was selected as it showed high efficiency of manganese leaching. Growth of the fungus was determined in terms of sbiomass dry weight and the final pH was monitored. The selected fungal strain was used for bioleaching of low-grade manganese ore of -150µm size particle size at 2 % pulp density with 2g/100ml sucrose concentration for duration of 20 days. About 60 % of Mn bioleaching was obtained with A. niger. The fungal species proved to be useful for manganese biomining.

Sep 1, 2012

By P. Han

The preparation technological conditions and regeneration method of two novel granulated adsorbing materials of rectorite/fly ash composite (Material 1) and rectorite/water quenched - slag composite (Material 2) and the use of them to remove heavy metals from copper smelting plant wastewater have been studied. The experimental results showed that under the preparation conditions with the ratio of rectorite to fly ash or water - quenched slag of 1:1, the amount of the additive (Industrial Starch, IS) of 15% (Material 1) or 10% (Material 2), the addition of 50% water, and the calcination temperature of 500? (Material 1) or 400? (Material 2), the efficiency of heavy metal removal with the granulated materials was the best, whereas the ratio of disintegration loss was the lowest. Under the treatment conditions of natural pH, and with the addition of the granulated materials of 0.07g/cm3 (Material 1) or 0.05g/cm3 (Material 2), a reaction time of 60 minutes (Material 1) or 40 minutes (Material 2), and the adsorption temperature of 25?, the efficiency for the granulated materials to remove Cu2+Pb2+Zn2+Cd2+ and Ni2+ from the copper smelting plant wastewater was 98.9, 97.5, 96.7, 90.2, and 79.1, (Material 1) or 98.2, 96.3, 78.6, 86.2, and 64.2, (Material 2), respectively, and the quality indexes of the wastewater after treatment conformed with the first level of integrated wastewater discharge standard (GB8978-1996). When the adsorption of heavy metal ions on the surface attained saturation the granulated materials could be regenerated by washing with 1 mol/L sodium chloride (NaCl) solution and still with quite good heavy metal removal efficiency. The granulated adsorbing materials had the advantages of high efficiency of wastewater treatment, easy method of solid-liquid separation and regeneration, and a broad prospect of applications.

Jan 1, 2014

By Cuim R., M. L. Li

Fankou Lead-Zinc Mine produced pyrite concentrate (P.C.) from the zinc tailings by rougher and scavenger flotation before 2010, with the averaged S grade of 40.54% at recovery of 79.34% ( to the feed of S circuit). On the one hand, the economic value of P.C. increases with its purity, on the other hand, when the S grade of P.C. feed to sulfuric acid manufacturer is over 47%, the pyrite cinder can reach a high Fe grade of 62% which can be directly sold as iron concentrate. On this background, engineers in Fankou Mine set the P.C. with S grade of 47% as target. The direct way to reach that goal was to clean the rougher P.C.. Lots of cleaning flotation tests were conducted and the compromised strategy was to produce two ranks P.C. with the S grade of 47% and 38% at the recovery of 44.20% and 36.17%, respectively. The dual-product flowsheet was successfully industrialized in 2010. In order to further improve the quality of P.C., gravity separation was introduced into the flowsheet. The numerical simulation and separation tests were performed to evaluate the beneficiation and classification performance of hydrocyclone as it treated the rougher P.C.. It was shown that the underflow of hydrocyclone could addressed the S grade of 47%, and the finer size overflow could also be enriched to P.C. with S grade of 47% by flotation, due to the contained pyrite with well liberation. That is to say, with the ingenious addition of hydrocyclone to treat the rough P.C., single P.C. with S grade of 47% could be achieved. The new flotation-gravity separation flowsheet was commissioned to produce the high quality P.C. at the end of 2013. The averaged S grade is 47.20% at recovery of 82.26% in 2014. The two steps flowsheet improvement maximizes the enterprise benefits and leads to simple utilization of Fe in pyrite in downstream industry.

Jan 1, 2018

By Tingting Li, Guodong Li, Dezhou Wei, Cong Han, Shuling Gao, Yanbai Shen

"The aim of this study is to solve the problem of tungsten leaching from scheelite concentrate using sodium hydroxide in the presence of phosphate by an autoclaving process, which is one of main development techniques for tungsten recovery. To understand the applicability and leaching performance of tungsten leaching from scheelite concentrate, the main work is to investigate the effects of leaching parameters such as initial concentrations of NaOH and Na3PO4, reaction temperature, stirring speed, liquid-to-solid ratio and reaction time on WO3 dissolution rate to obtain the optimal leaching conditions. The chemical composition and phase composition of the samples were evaluated by means of XRF and XRD. The content of WO3 in the leaching residue obtained via washing, filtering and drying was analyzed by thiocyanate spectrometric method. The optimal leaching conditions were found to be NaOH concentration of 6.76 mol·L-1, Na3PO4 concentration of 1.35 mol·L-1, reaction temperature of 180°C, stirring speed of 400 rpm, liquid-to-solid ratio of 2.0 and reaction time of 90 min. The results showed that tungsten leaching rate of 99.20% was reached under the optimal conditions. The technology exhibited superior leaching performance, which not only reduced the consumption of sodium hydroxide but also greatly decreased reaction time in comparison to a conventional autoclaving process. INTRODUCTION Tungsten is an important strategic metal, which is widely utilized in a variety of industries due to its high melting point, superior mechanical properties and heat-resistant performance [1-3]. The chief raw materials for the production of tungsten in nature are wolframite and scheelite [4, 5]. Among them, approximately two-thirds of the tungsten reserves contain scheelite deposits in the world [6, 7]. With the progressive exhaustion of high-quality wolframite resources, scheelite has become a predominant primary resource for the production of tungsten [8, 9]."

Jan 1, 2018