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By Jiongtian Liu, Jianjun Wu, Yongzhou Wan, Li Feng

"Mechanical Thermal Expression (MTE) is a developing non-evaporative lignite dewatering technology. It has been shown to effectively dewater high moisture content in low rank coals via the application of mechanical force and thermal energy at elevated temperatures. In this paper, the dewatering behavior of Yunnan Xiaolongtang lignite during the MTE-process was studied. Furthermore, how variations in temperature and pressure during the MTE process affect the surface oxygen functional groups and pore structure were also discussed using Fourier transform infrared spectrometer (FTIR) and mercury intrusion porosimetry (MIP). Increases in MTE temperature and pressure resulted in significant reductions in residual moisture content and moisture holding capacity, along with the increase of fixed carbon content and reductions of other elements content, especially oxygen content, which have been largely attributed to the destruction of the surface oxygen functional groups and porosity in lignite. The optimized technology conditions are temperature 150~220°C and pressure 7~10MPa. The residual moisture content of the lignite treated by MTE under the conditions of 200°C and 10MPa is decreased to 8%, while the dewatering rate exceeds 76 % and the calorific value approaches 22 MJ/kg. The experimental results offer a deeper understanding of the influence of process parameters on the lignite stuctures and properties. The reduction in residual moisture content, surface oxygen functional groups and pore volume under increasingly severe MTE conditions are suggestive of the structure changes that accompany increased coalification (rank) within the lignitic range."

Jan 1, 2014

By Liu Yong

A complex rare metal ore, containing various valuable elements is used in this study. The mineralogy results indicate that the mineral composition of the raw ore is complex, and there are more than thirty-eight kinds of minerals in the raw ore, and the elements, such as Nb, Ti, Fe, REO, Be etc, always form isomorphism relationship. The REO content of the raw ore is 0.45%, and the contents of other rare metals Nb, Ta, Ti and Zr are 0.33%, 0.02%, 0.93% and 2.00% respectively, and the main gangue elements are Si and Al, and their contents are 71.84% and 8.5% respectively. The beneficiation-metallurgy combination process of ?preconcentration-reduction and magnetic separation-acidification and leaching-precipitation? is used to treat the raw ore. The preconcentration of raw ore is realized through high intensity magnetic separation, and the magnetic field intensity is 1.0T, and the rough concentrate with 2.88% REO and 1.95% Nbresidue can be obtained, and the iron recovery is 92.83%, and the REO recovery is 95.87%, and the Nbresidue is treated by hydrometallurgy process of ?acidification-leaching-precipitation?, then the rare earth oxide, niobium concentrate and zircon-bearing residue can be obtained, and the REO recovery is 80.10% and the Nbresidue and the gangue obtained from the high intensity magnetic separation process is separated by gravity separation, and then the zirconium concentrate can be obtained. The indexes of the beneficiation-metallurgy combination process used to treat the complex rare metal ore are as follows. The REO content of the rare earth oxide is 92.58% and the recovery is 58.44%. The Nb2O5 and 27.42% TFe can be obtained. Iron in rough concentrates is removed after reduction and low intensity magnetic separation, then the iron powder with Fe content over 88% and nonmagnetic rare-metal 2O5 recovery is 94.77%. The rare-metal 2O5 recovery is 80.04%. The mixture of the zircon-bearing 2O5 content of niobium concentrate is 28.34% and the recovery is 54.02%. The ZrO2 content of zirconium concentrate is 28.43% and the recovery is 52.35%. The TFe of iron powder is 89.53% and the recovery is 78.13%. Keywords: rare metal ore, separation and extraction, beneficiation-metallurgy combination, comprehensive utilization

Sep 1, 2012

By Kamalendu Bhunia

With the progressive depletion of known resources of good quality coal and minerals as well as the increasing demand of these minerals by different user industries, the emphasis has been shifted all over the world from selective mining to bulk mining followed by up- gradation to obtain the required quality of concentrate. The column flotation cell is one of the alternatives to reduce the gangue content of fines because of its inherent characteristics viz. easier to operate, low space required, no moving parts etc. A laboratory flotation column is used to conduct experiment. Present work has been undertaken to observe the effect of process variables (gas flow rate, feed/slurry flow rate, and frother concentration) on gas dispersion parameters (gas holdup, bubble surface area flux) in collection zone and to explore the effect of feed (slurry) inlet orientations and gas flow rate on column?s metallurgical performance. The effects of solid particle concentration, size and type (hydrophobic and hydrophilic) of solid on gas dispersion parameters have also been investigated. Test work has been performed in a continuously operating Perspex column (10 cm in diameter and 168 cm in height) using coal, sphalerite and dolomite as solid. Gas hold-up has been measured by phase separation method and mean bubble sizes are estimated from a drift flux analysis. The influence of operating parameters on bubble surface area flux has been discussed. It is observed that gas holdup in collection zone is affected by air as well as feed flow rates and also solid?s type. It is also found that addition of solid decreases the gas holdup and rate of decrease in gas holdup increases when solid concentration increases and particle size increases. Increase in gas flow rate increases recovery in collection zone due to increase in number of bubbles per unit volume of the column. From the experimental results it is evident that cross-current orientation of feed inlet shows slightly better metallurgical performance compared to other orientations. Keywords: column flotation, gas holdup, drifts flux, bubble size, bubble surface area flux, hydrophobicity, and recovery

Sep 1, 2012

In order to determine the optimal process parameters of agitation leaching and provide industrial process design parameters, experiments were carried out on leaching behaviors of copper oxide ore with high mud content. Condition tests show that the main factors affect the leaching efficiency as follows: Temperature, Initial acid concentration, leaching time and particle size. As the temperature increases, the copper leaching rate was increased. At 60 ?, the initial acid concentration 80g / L, leaching time 2h, liquid-solid ratio 2:1 and grinding fineness65%-0.074mm, the optimal copper extraction was 83.15%, the acid consumption was 187.91kg / t. ore. Keywords: agitation leaching, copper oxide ore, mud

Sep 1, 2012

By Bo Feng

The development of surface charge of serpentine mineral and implications for sulphide ?otation have been studied through flotation tests, sedimentation tests, zeta potential measurements and optical microscope photos. The results show that the serpentine mineral was positively charged at an extensive pH range, with an isoelectric point (IEP) of 11.9. The magnitude and sign of the pyrite particles were pH dependent and were negative for pH values above 2. At pH value 9, where ?otation of nickel sul?de ores is routinely performed, serpentine and pyrite particles attract through an electrostatic mechanism. Slime coatings of serpentine adhere to the surface of pyrite, reducing pyrite flotation recovery. The removal of magnesium ions from the serpentine surface by acid leaching results in a decrease of serpentine IEP and eliminates the adverse effect of serpentine on pyrite flotation. Therefore, it has been clearly established that the surface charge value developed in the serpentine/aqueous electrical interface is a function of the serpentine surface incongruently dissolution. As a result of hydroxyl dissolution, the magnesium ions are left in serpentine surface, which is responsible for serpentine surface charge. The methods, which can remove magnesium ions from serpentine surface, can be used to eliminate the adverse effect of serpentine on pyrite flotation.

Sep 1, 2012

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. Peszko

There are many measuring methods of grain sizes. Taking into consideration the fine grained materials, one of the existing techniques is measurement of grain size by the Coulter Counter method. This method is based on the measuring the changes of electrolyte resistance during grains flow through the calibrated diaphragm. This method is relatively simple to apply, significantly precise and the results are given quickly. However, the problem is that the measurements are limited by the size of diaphragm. Because of this situation, measurement of grain sizes by this instrument is possible in range from 10% to 60% of diaphragm diameter. This limitation causes the necessity of re-placing diaphragm in case when the measured grain size distribution concerns the material of large size range. In purpose of determining the total grain size distribution, the synthesis of some partial distributions, given for individual grain fractions (with different diaphragm applied), is required. This is possible to do by calculating the mixture of distribution functions, created from the partial distribution functions. Two materials were selected to research: quartzite and glass, which were comminuted in cylindrical crusher, additionally grinded, screened and then analyzed by Coulter Counter for five grain fractions: 0~125 µm, 0~80 µm, 0~56 µm, 0~40 µm and 0~25 µm. For each fraction, five different partial distributions were given (in case of glass ? four), which are the basis for the creating the joined grain composition. To assure the adequacy of the given distribution function, it is necessary to obtain the possibly best approximation of partial distributions. In the work, both the parametric and non-parametric methods of density approximations of investigated random variable. For each grain fraction the approximations were done by three traditional distribution functions: RRB, GSA and log-norm distribution functions and three methods of non-parametric approximation: Gauss kernel, Epanechnikov kernel and orthogonal Fourier series method. As the criterion of the certain distribution function acceptance, the value of the residual deviation was assumed, given by the formulae:

Jan 1, 2014

By J. Y. ` Xie

The paper introduced bio-oxidation plants of refractory gold concentrate in China and CCGRI cultures. CCGRI cultures are composed of bacteria and archaea. Archaea Ferroplasma acidiphilum is very thick and fills whole mineral surface. It plays a more dominant role in CCGRI process. Several years of practice has proved that the operating temperature in bioreactors between 38~52?,gold recovery is almost same. Pulp concentration has been increased each year and reached to 25%.

Jan 1, 2014

The ultimate goal of a mineral processing plant is to recover as much of the target mineral(s) as possible from the ore being treated to achieve the best economics. Selection of the mineral processing techniques is the most important step in achieving this goal. However, due to the complexity of the ore, the recoveries of valuable minerals may be not satisfactory even when the mineral processing technique(s) are well chosen. In other words, minerals of interest can be lost to the tailings for mineralogical reasons. For example, gold is mainly extracted from the ore by gravity, flotation, cyanidation, or a combination of these processes, and high recovery (>90%) can be achieved when gold occurs as coarse grains. However, when a refractory ore is being processed, gold extraction will be challenged by mineralogical factors, which often cause gold losses to various tailings. Mineralogical factors affecting gold recovery mainly include grain size, shape, surface coatings and rimmings, presence of cyanicides, oxygen consumers and preg-robbers, presence of slow-dissolving gold minerals and the refractory nature of submicroscopic gold. Among these factors, locking in sulphide, silicate and other minerals as fine-grained gold inclusions and/or as invisible submicroscopic gold is by far the most common factor leading to poor gold recovery encountered in gold ore processing. Processing of PGE ores faces the same challenges as gold. Small grain size and locking of PGM in sulphide and non-sulphide minerals often cause PGM losses. When silver ore contains significant amounts of pyrargyrite, proustite and stephanite, silver recovery by cyanidation can be very low because of the slow dissolving kinetics of these minerals. In the processing of base metal ores, high content of pyrite, intergrowth of chalcopyrite with sphalerite and presence of clay miner-als may cause problems in recovering Cu-, Pb- and Zn- bearing minerals. Process mineralogy helps address all issues and problems related to mineral processing with predicting and trouble-shooting being two major objectives. It provides useful information on process selection, flowsheet development, recovery improvement and reagent consumption optimization. The information acquired from a process mineralogical study can be used as a guide for a metallurgical testwork program for process design or optimization.

Jan 1, 2014

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

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

Jan 1, 2018

By C. G. Anderson

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

Jan 1, 2014

By F. L. Wang

The purification process of water-mining carnallite and rough potassium chloride concentrate from Qinghai Salt Lake Industry Group Co. Ltd. are investigated by the preprocessing-reverse flotation technology respectively. The results show that the impurities such as calcium sulfate and sodium chloride can be effectively removed from water-mining carnallite ore and rough potassium chloride concentrate by the new technology, the low-sodium carnallite is obtained and the final potassium chloride product greatly upgraded. The content and the recovery of KCl in the low-sodium carnallite are 25.78% and 97.50%, meanwhile the content of NaCl, CaSO4 in the low-sodium carnallite are 0.56% and 0.24%, and the removal of sodium chloride and calcium sulfate in the low-sodium carnallite are 97.48%, 85.10% respectively. The KCl content and recovery of high quality potassium chloride product are 98.25%, 96.70%, and CaSO4 content is 0.40% with 83.24% calcium sulfate removed in the high quality potassium chloride product.

Jan 1, 2014

By Bertil I. Pålsson, Sture V. Persson, Kent T. Tano

"Grinding is one of the most energy consuming unit operations and is also a very inefficient and costly process. Therefore, it is of great importance to run the grinding process as efficiently as possible. The most common way today to control grinding processes is by measuring the power draw of the mill and try to keep it at a maximum level. However, some studies (Kawatra, 1989, Koivistoinen, 1989, Moys, 1989) have shown that this measurement doesn.t reflect everything that takes place inside a mill. Among other parameters like slurry rheology, temperature and charge behaviour, the volumetric filling of a grinding mill seems to have a large influence on the grinding efficiency (Herbst, 1988, Koivistoinen, 1992, Vermeulen, 1988). A problem in attempting to measure those parameters has been to get a sensor that is both robust and sensitive enough for continuous on-line measurement.This paper presents a method for the measurement of the apparent filling level in a pilot ball mill equipped with the Metso Continuous Charge Measurement system (CCM). In this technique a strain gauge sensor is mounted on a flat steel spring which is fitted into a recess underneath a lifter bar. In addition, a conductivity probe, the Boliden Grinding Measurement System (GMS), is mounted in another lifter bar with the purpose of comparing the two measurements. To visualise the behaviour of the charge a DEM modelling technique is used.The results indicate that the system is capable of following the normal variation that occurs in the mill. The signal also very well reflect changes in operating variables such as ball charge level, pulp density and rotational speed. By studying the nature and different features of the signal one can get a better understanding of milling circuit dynamics. Another feature of the technique is the possibility for an operator to continuously follow the grinding process and thereby run the process under optimal conditions."

Jan 1, 2003

By J. E. Gebhardt, D. McBride, T. N. Croft, M. Cross

"Heap leaching is well-established as a relatively low-cost and low-energy method of extracting metals from low grade ores. However, the design methodology, attention to the engineering details during heap construction and the long time scale in metal recovery makes the process susceptible to significant variation in the success of a heap leach operation. Often the laboratory predicted recovery rates are not achieved on site due to poor understanding of the complex physics of flow and coupled solid-liquid-thermal reactions within the multi-dimensional heterogeneous ore body. Given the large scale of commercial operations, small changes in metal recovery can substantially change the operating profitability. While there are a variety of approaches to heap leach modeling, computational fluid dynamics (CFD) modeling coupled with leach kinetic models offers a methodology to describe and understand the complexities of heap leaching. The CFD model uses leach kinetics specific for the mineralogy of the ore, including gangue chemistry, and provides an energy balance to calculate and predict temperature. Coupled with the CFD model’s inherent capability for modeling complex fluid flow, the physics and the chemistry of the heap can be simulated. This provides a tool for engineering design, as well as forecasting heap production under different scenarios. The calibrated model is used to simulate a three-dimensional test heap under fluctuating meteorological data, such as precipitation events, periodic solution application, and notably temperature. These simulations provide support for a methodology to design and engineer heap leaching of low grade copper sulfide ore. INTRODUCTION Worldwide copper ore reserves are faced with decreasing head grades with copper sulfides, particularly chalcopyrite being the predominant mineralogy (Nesse, 2000). Heap leaching offers an economical way to recover copper from low grade ore. The ore is stacked and a leach solution is applied and allowed to trickle though the porous bed of ore to extract target metals. The heap can be built with run of mine material or crushed ore and is constructed in order to achieve percolation of the leach solution to all regions. Bartlett (1998) provides an authoritative overview of the solution mining process where the leach solution interacts with the solid, the lixiviant dissolves the target minerals from the solid into the solution, and the dissolved species are transported out of the heap for subsequent recovery. Petersen (2016) provides a recent review of heap leach technology and emerging and potential future applications, and Ghorbani et al. (2016) summarizes the current state and challenges of the technology. Early applications of heap leaching offered a low cost technique to achieve high recoveries from oxide ores, typically greater than 70% depending upon the kinetics of reaction. As world copper resources transition to mainly copper sulfide mineralogy, such as chalcopyrite based ores, achieving high recovery from these copper sulfide deposits is proving more difficult due to the complexity of the leach kinetics, which leads to low leaching efficiency."

Jan 1, 2018

The status quo of ecological rehabilitation in metal mine in China and progress in the technology for ecological rehabilitation are presented, including soil reconstruction, soil improvement, plant selection. The present and future research fields are suggested: basic theory of ecological rehabilitation, operative technology of ecological rehabilitation, new technology application research and ecological rehabilitation plan, management and policy.

Jan 1, 2014

By R. Singh

The present paper deals with the development of flotation based process for enrichment of a lead-zinc sulphide ore from Ganesh-Himal region of Nepal. Detailed characterisation and flotation studies were carried out under varying process conditions. The sample assayed 2.47% Pb with 13.6% Zn. The ore was predominantly made up of spahlerite and pyrite in association with subordinate amounts of galena, minor amounts of pyrrhotite and chalcopyrite. Dolomite was the main gangue. The modal analysis showed the probability of fair liberation of sulphides from gangues around 210 microns but the locking of galena with sphalerite and other sulphides continued to finer sizes. Under the optimum process conditions the rougher lead and zinc recoveries were 96.3% and 90% respectively. Multistage cleanings of rougher products proved helpful in improving the concentrate grade, meeting the required specification. Based on the studies undertake a process flow-sheet for the concentration of the ore to individual lead and zinc concentrates was developed.

Jan 1, 2014

By Jun Xiao, Yucai Zhou, Yanhong Dong, Daixiong Chen

"In this article research on the mineralogical characteristics and beneficiation process for a copper molybdenum deposits in Heilongjiang province of China has been carried out. Chemical analysis, X-ray diffraction(XRD) and Quantitative Evaluation of Minerals by SCANning electron microscopy (QEMSCAN) were conducted on samples. The bulk analysis results showed that: (1) Comprehensive recovery and separation of molybdenum & copper minerals was feasible by the flowsheet of first copper-molybdenum mixed flotation after grinding the ore samples to 61.88% -74µm and then separation flotation of copper and molybdenum after regrinding the Cu-Mo mixed concentrate to 83.26% -38 µm. The results highlight relationship between mineralogical characteristics of ore and comprehensive benefication method. (2) the combination of "" Sodium sulphide and sodium thioglycolate "" reagents are effective inhibitors of copper-molybdenum mixed concentrate, their selectivity performance is better than that of single reagent. Good flotation indexes were gained that might be directive experience to similar cases. KEYWORDS Mineralogical characteristics; molybdenite; chalcopyrite; flotation separation; inhibitor INTRODUCTION Copper and molybdenum metals are widely used in the field of metallurgy, aerospace, national defence, etc. Copper –molybdenum sulphide ore is an important source of copper and molybdenum metals. At present flotation is still the preferred methods to deal with the copper-molybdenum sulphide minerals (Yin, Z., Sun, W.et al. 2017; Ansari, A., & Pawlik, M. 2007; Hirajima, T., Miki, et al. 2017). Copper and molybdenum sulphide ores usually have the similarly good nature floatability(Miki, H., Matsuoka, et al. 2017), meanwhile most molybdenum sulphide ore has tiny grained-size(Castro, S., & Laskowski, J. S. 2015.) and closed relationship with other sulphide and gangue minerals which result in the coper and molybdenum separation problem. Base on the nature of the ore and flotation properties of the individual minerals contained in the ore, there are two methods are usually used to deal with the copper – molybdenum ore, including bulk molybdenum/copper flotation followed by separation of copper and molybdenum minerals, sequential molybdenum/ copper flotation(Liu, G. Y., Lu, et al. 2012). The latter method has the shortcoming of hard to activate the depressed copper minerals in the previous molybdenum flotation process, which may result in a large loss of the copper from concentrate, this disadvantage would avoid while adopting the former method. bulk flotation followed by separation process is to get the copper-molybdenum concentrate from raw ore first then separate flotation the molybdenum and copper minerals, benefit from the excellent floatability of both molybdenum and copper minerals ( Malhotra, D., Rowe, R. M., & Bhasin, A. K. 1986; Cao, Z., Yue, et al. 2017 ), it really easy to obtain the mixed concentrate. In order to get the high quality copper and molybdenum concentrate, the key technologies and difficulties are to realize the separation of the copper and molybdenum minerals which have the very similar natural floatability (Raghavan, S., & Hsu, L. L. 2015; Nakhaei, F. 2014)."

Jan 1, 2018

By Caitlin Rogers

The environmental and economic sustainability of froth flotation is dependent on effective management, which in turn improves the performance of a concentrator. In economic terms this means improved recovery of valuable minerals, in environmental terms this means effective management of acid generating tailings. Three indicators were selected to measure the performance of an integrated flotation system. The system consists of two stages of flotation; valuable mineral flotation followed by environmental desulfurisation by froth flotation. The suitable indicators were selected based on their fulfilment of four attributes. An attribute is a desired aspect of an indicator. The four attributes were: comprehensive, relevant, sensitive and quantitative. Two environmental indicators and one economic indicator were selected. They represent revenue generation from valuable minerals and environmental cost of management. The suitability of the selected indicators was shown using illustrative scenarios.

Jan 1, 2014

By Jaeheon Lee, Jae-Chun Lee, Doyun Shin, Minseuk Kim, Hyunsik Park

"The appropriate treatment of cyanide waste water is becoming an emerging issue because of the toxic residue and large quantity produced from gold processing plants. In the present article, we designed and operated a continuous biological cyanide treatment system using domestic sewage sludge and various microorganisms including a cyanide-producing and degrading bacterium, Chromobacterium violaceum. The synthetic wastewater containing 50 mg/L of cyanide was pumped continuously into the reactor at a flow rate of 500 mL/d for 21 days. When 50 mg/L of cyanide was fed, the cyanide concentration in the effluent of the reactor inoculated with activated sludge (S-50) decreased by 7.5 mg/L in the effluent. The other reactors did not show significant cyanide degradation and the reactor inoculated with C. violaceum showed increased cyanide concentration in the effluent. The microbial community in the reactors was analyzed by 16S rRNA-gene based pyrosequencing technique to investigate microbial response to cyanide addition and operation time. The microbial community analysis shows that the phylum Proteobacteria was detected in the reactors showing significant cyanide degradation (S-50), while Firmicutes and Bacteroidetes was dominant in the other reactors with very low cyanide degradation. Proteobacteria could not compete when the other phyla Firmicutes or Bacteroidetes were inoculated. This study shows the feasibility of the biological cyanide treatment system for gold processing plants and contributes new fundamental knowledge about the microbial community in the biological cyanide treatment system. INTRODUCTION Cyanidation has been widely used to recover gold from ores or secondary resources since first proposed by MacArthur and Forrest in 1888 (MacArthur et al., 1888) and it is used in many states of the USA, including Nevada, Arizona, California, Colorado, and Idaho (Laitos, 2012). Cyanide compounds are highly toxic and create serious problems for wildlife and water management (Solomonson, 1981; Donato et al., 2007). Furthermore, because many countries have imposed strict standards for cyanide discharge (USEPA, 1985), it is essential to develop a cost-effective and environmentally friendly technology for treating cyanide-containing wastewater."

Jan 1, 2018

By R. Venugopal

Hydrocyclones have been used extensively for more than 100 years to classify mineral slurries for recirculation in grinding circuits. Sometimes hydrocyclone classification is carried out in more than one stage to improve the efficiency of classification. Factors affecting separation efficiency include fluid velocity, density, and viscosity as well as the mass, size, and density of the particles. The geometric configuration also affects its efficiency; it includes parameters like cyclone diameter, underflow and overflow diameter, position of vortex finder, height of the cyclone, feed inlet geometry, and diameter etc. Besides changes in the basic parameters some modifications in cyclone has also been introduced from time to time which have affected its efficiency, some of these are :-(i).Introduction of magnetic force along with the centrifugal and drag force to control the flow of the magnetic particles inside the chamber.(ii). Introduction of sparger, air is introduced in the chamber in the form of bubbles, to control the flow of fine particles and hydrophobic particles. (iii). Introduction of dilution technologies for the dilution of thickened underflow. (iv).Introduction of new model. In spite of wide use and simple geometry, the real working principle of hydrocyclone chamber is extremely complex because of the swirling turbulent flow inside the device. In order to get more knowledge about hydrocyclones and to increase its efficiency, past 10-15 years simulation techniques are being developed. The simulation models also enabled a deeper insight into the static and dynamic behavior of hydrocyclones. Therefore, more emphasis on simulations by methods like Computational Fluid Dynamics (CFD), Finite Element method (FEM) is given. Overall, a status review of the work carried out on the analysis of hydrocyclone performance, modeling approaches and its contribution in the efficiency of mineral processing operation is highlighted.

Sep 1, 2012