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By Jerzy A. Mielczarski

The separation of albites from quartz by flotation applying the conventional HF-methods is no longer acceptable from an environmental and health point of view. Therefore, the search for a new reagent scheme without using HF depressor for separation of albite from quartz is under consideration. The flotation behaviour of ore mineral components depends on the produced hydrophobic or hydrophilic surface coverage (chemical functionalization). Currently we have excellent possibility of monitoring surface composition and structure at molecular and atomic levels at surfaces of natural minerals contacted with aqueous solutions of collectors, activators, depressants which is vitally important for the understanding of the surface chemistry that govern selective and efficient flotation. Detailed surface characterization of minerals before and after their exposition to different solution conditions was performed by the most modern spectroscopic techniques such as developed by us the infrared external reflection technique combined with spectral simulation and X-ray photoelectron spectroscopy (XPS). It is possible to monitor surface reactions which facilitate the separation process and those which bring disadvantage to selective flotation. At first we found that a small amount of ?mineral impurity? presented in natural ore could play important role in selective hydrophobization process. It was found that the pH of solution (parameter possible to control) and natural mineral impurities present in mineral samples (parameter related to ore origin) play a very important role in the separation process. Another important parameter is interaction between minerals, quartz and albite, present in aqueous solution. The limitation of flotation separation resulting from chemistry will be discussed. Moreover, the most promising scheme for separation of albites from quartz will be examined.

Jan 1, 2014

By P. T. Nguyen

The analysis of particle capture by an air bubble by two separate phenomena of collision and attachment has been difficult due to the uncertainty in determining when and where the two phenomena begin and terminate at the bubble surface, respectively. Therefore, a unified analysis was developed by solving the motion equation for the particle capture as one process. No distinction be-tween collision and attachment was made. Both the liquid film described by the micro-hydrodynamic resistance functions and the surface forces were included in the new model. The model predictions with the DLVO (Derjaguin-Landau-Verwey-Overbeek) surface forces did not agree with the experimental trajectories of latex and silica spheres. The model predictions with the inclusion of the non-DLVO attractive surface force agreed with the experimental data. The non-DLVO force reduced the repulsion between the non-attaching particle and the bubble, and significantly increased the attraction between the attaching particle and the bubble. The unified analysis is capable of predicting particle capture without the use of the induction time. The unified analysis also shows significant influence of the short-range hydrodynamic interactions on the collision which has been previously ignored.

Jan 1, 2014

By Carlos Gualdron, Elizabeth Gomez, Rafael Bolivar

The productivity index of the Coopracarcegua Ltda., a mid-size coal mining company of Norte de Santander, Colombia, was related absenteeism using accident, productivity and profit data four years. The analysis was based on type, severity and frequency of accidents, number of absentee days; price per metric ton, and other relevant parameters. The enterprise is formed by 5 different mines of thermic coal, each one with different exploitation technologies and different productivity. Each mine was analysed separately and the loss of profit due to absenteeism was calculate for each one. The study showed that the foregone earnings due to absenteeism in terms of the whole productivity of the enterprise was about of 6.6% of the total profit average the 4 years, with calculated values of 14.7%, 3.5%, 8.4% and 4% per year in the evaluated period. The study identified that the most important cause of absenteeism was "General Disease". The foregone earnings in 2009, the highest loss for the analysed period, was about US$ 0.937 million and during the whole evaluated period was US$ 2.46 million.

Jan 1, 2014

By Haghi. Hamed, Javad Vazifeh Mehrabani, Mehdi Sedigh

In this investigation, the possibility of physical separation methods such as attrition scrubbing, hydro-cycloning and also reverse flotation were investigated for silica and calcite removal from relatively low grade kaolin. The head sample was provided by the Iran China Clay Company and the major oxides contained in the head sample were Al2O3, SiO2, CaO and Fe2O3 with grades of 15.07%, 71.05%, 4.35% and 0.52% respectively. The liberation degree of calcite and iron impurities from kaolin particles were over 80% for particles finer than 210µm and 53µm respectively. Attrition scrubbing tests were carried out with scrubber cell of the conventional Denver flotation cell model D-12. Laboratory scale hydro cyclone was applied for the beneficiation of kaolin. Attrition scrubbing tests with control screen of 106µm did not achieve the desirable yield for purification of this kaolin sample, but hydro cyclone experiments resulted in better results. Hydro cyclone with 2.54 cm diameter used and the only variable was the cyclone inlet pressure ranging from 68.65kPa to 98.07kPa. The best inlet pressure was found to be 68.65kPa. Based on the optimized condition, Al2O3 and CaO amount in the hydro-cyclone overflow was 23% and 1.47% respectively. However weight recovery of the overflow in each cyclone experiment was less than 30% and multi stages of hydro-cyclones would have to be applied for higher weight recovery and better yield. All of the flotation tests were carried out in the conventional Denver flotation cell model D-12. Reverse floatation tests for calcite removal were carried out under alkali pH based on full factorial design of variables in 2 levels including one center point. The three parameters tested were collector dosage (gr/ton), pH and depressant dosage (gr/ton). The collected data from flotation tests were analyzed and optimized collector and depressant dosage were 1000 gr/ton and optimized pH was 8.5. Under the above mentioned conditions, calcite removal was about 75% and CaO content in the final product was reduced from 4.35% to 1.33%. However calcite removal will increase to more than 83% if the feed particle size in flotation tests is reduced from 210µm to finer than 53µm. Finally after optimization, the best working condition and possible flow sheet were developed.

Jan 1, 2014

By T. X. Hu

Pyrite ore is one of the main raw materials in the production of sulfuric acid. For a long time, the raw material containing the pyrite, which is used to produce sulfuric acid, generally contains S only 32%~45%. A plenty of residue from the sulfuric acid production contains 40%~50% Fe and 1%~2% S. Some of the residue also contains Cu, Pb, Zn and other harmful elements like As, thus it pollutes environment seriously and is solid waste. The research on comprehensive utilization of the residue has been made by many scholars. Through the study, the residue can only be used to pro-duce iron concentrate and the iron oxide red pigment. But because of the complex techniques, the low recovery, the low grade of iron concentrate , high sulfur in iron concentrate, causing second waste residue and the environmental pollution, the residue is mainly used as an accessory material in the production of cement, and is of a low value. Therefore, the iron resource in pyrite has not been used efficiently until now. In the paper, the flotation condition test, the flotation open circuit test and the flotation closed circuit test to produce high-purity pyrite concentrate with the low-grade pyrite ore in oceanic ore deposit have been carried on. Flotation reagent scheme of sulfuric acid used as activator and butyl xanthate as collector is determined. After four times depth cleaning, high-purity pyrite concentrate containing 52.82% S, 44.29% Fe, and only 2.89% impurities has been obtained. The S recovery is 99.13%, and the Fe recovery is 96.00% in the high-purity pyrite concentrate. The oxidizing roasting depth desulfurization experiment of the high-purity pyrite concentrate has been conducted. The results show that the Fe grade in the residue obtained is 68.58%, the content of S is 0.25%, the content of P is 0.0084%, the content of As is 0.0065%. The residue is a kind of high-quality iron-smelting raw material. Based on the above experiments, the industrial experiments on producing high-purity pyrite concentrate with the low-grade pyrite ore, and producing sulfuric acid and iron concentrate with high-purity pyrite concentrate have been done. The results indicate that the high-purity pyrite concentrate with the S grade of 51.24%, the Fe grade of 44.15% has been obtained. The iron concentrate obtained with 65.73% Fe and 0.23% S is a sort of high-quality iron-smelting raw material applied to the production of steel and iron smelting. Through the experimental study, the sulfur and iron resources in the pyrite ore have been recovered and utilized efficiently.

Jan 1, 2014

Cyanide is reactive to copper minerals and is not suitable to extract the gold from the copper bearing ores. Ammoniacal thiosulfate is considered an excellent alternative lixiviant for leaching copper bearing gold ores. Unfortunately the results of high reagent consumption and poor gold ex-traction were found by thiosulfate leaching of synthetic gold ores containing chalcopyrite, chalcocite or bornite and a mild refractory copper-bearing sulfidic gold ore. In this investigation, several processes have been applied to reduce the impacts of these minerals on gold leaching. The process included: the pre-oxidation of copper sulphide minerals in water or ammonia solution, the reduction of dissolved oxygen in the lixiviant (0.3 ppm DO or 0.7% oxygen), adding phosphate anion in the leach or pre-leach stage, and the addition of a strong copper ligand (e.g., EDA and DETA). The results indicated that the gold extraction could be improved to 93% with the thiosulfate consumption being reduced to less than 8 kg/t. The dissolution of copper minerals was found to be the major reason for increased consumption of thiosulfate and the highly reductive leached surfaces are responsible for the reduced gold extractions.

Jan 1, 2014

By D. Tao

A novel rotary triboelectrostatic separator has been developed and patented recently at the University of Kentucky with unique features, including a high efficiency rotary charger, charger electrification, laminar air flow, etc. A parametric study has been performed with a coal combustion fly ash sample to investigate the effects of major operating parameters on the process performance. Most significant operating variables and optimum conditions were identified. Separation tests performed with four fly ash samples indicated that the rotary triboelectrostatic separator showed effective fly ash separation.

Jan 1, 2014

By Thomas Mütze, Petya Atanasova, Kai Bachmann, Urs A. Peuker, Thomas Leißner

"A method is presented for the evaluation of mineral processing by liberation and upgrading. The method bases on the plot of recovery of valuables versus the recovery of gangue (Fuerstenau upgrading curve). The locking curve of a feed material was plotted together with the upgrading curve in a Fuerstenau diagram. The assessment of liberation and upgrading is done by a comparison of surfaces formed by the curves and some characteristic lines of the diagram. This plot allows the calculation of two new quantitative measures for liberation and upgrading. Both parameters can be combined to a third parameter describing the quality of the whole technical setup for mineral processing by subtracting the upgrading parameter from the liberation parameter. The third parameter shows a positive value in cases of upgrading determined processes, a negative value in cases of liberation affected processes and about zero for processes affected equally by liberation and upgrading. Thus it is easily possible to distinguish between poor results in the mineral processing caused by insufficient liberation or poor results caused by insufficient upgrading. Preliminary results from two case studies, performed on two different ore types, are very promising illustrating the practical use of such an approach."

Jan 1, 2014

By G. Merazchiev

In the selection of copper ? molybdenum concentrates with the use of reagents containing sulfide ion ? sodium sulfide, sodium hydrosulfide etc for depression of copper minerals and pyrites, big part of depressor is oxidized by oxygen, which is dissolving in pulp during aeration with air in flotation machines and it is expended unproductively. This is the main reason for the big expenditures of depressor, reaching up 15~20 kg/t collective concentrate and the high exploitation expenditures for the copper ? molybdenum selection. Effective direction for lowering expenditure of depressor and increasing of the technical ? economical effectiveness of moly production is the conducting of the selection in nitrogen medium. In the paper are shown the results, obtained by applying of this direction in selection of collective copper ? molybdenum concentrate from the porphyry copper deposit ?Ellatzite? ? Bulgaria, in which the ratio Mo:Cu is over 1:120. In laboratory conditions, through comparative experiments in medium of air and nitrogen are defined: expenditure and initial concentration of NaHS in pulp for effective depression of copper minerals and pyrites; kinetics of flotation process of molybdenite; influence of pulp density; emf (negative milivolts) of pulp and the expenditure of nitrogen on tech-nological indexes of molybdenum flotation. When working in nitrogen medium decrease of NaHS in rougher molybdenum flotation from 40% to 45% is settled. When nitrogen is also fed in cleaner stages, the total expenditure of depressor is lowered by 64%. The quality of end molybdenum con-centrate is raised with over 5%. On the ground of the results of laboratory studies and of world practice data, an industrial installation for selection of copper ? molybdenum concentrate in nitrogen medium in Wemco inert ? gas machines.

Jan 1, 2014

By G. X. Du

Reaction kinetics of serpentine and hydrochloric acid is theoretical basis for optimizing reaction process conditions of serpentine and hydrochloric acid. Kinetics of serpentine and hydrochloric acid was studied in this paper. The results indicated that apparent reaction order to hydrochloric acid was two and reaction kinetic equation could be expressed as: 2HClHCl,ddtckct-=·. The diffusion rates of hydrogen ions in liquid film on surface of serpentine particle and in amorphous silica layer generated in the reaction and chemical reaction velocity during the reaction had important effects on to-tal reaction velocity. And chemical reaction velocity had the most significant influence. The relation of conversion rate of magnesia xMgO with reaction time could be expressed as: 1(1)xkt--=·.

Jan 1, 2014

By A. Schönecker, P. Y. Pichon, B. Kraaijveld, Y. Meteleva-Fischer

"Ribbon-growth-on-substrate is a casting method, which offers a possibility to control heat flow, nucleation and subsequent crystal growth at the liquid-substrate interface. This technology allows for low-cost and high throughput shaping of silicon sheets with controlled crystal grain size and orientation for use in solar cells. In this work, sheets of silicon- metal silicide composite materials were produced and their microstructure was studied. It was shown that depending on the relevant phase diagram and casting conditions, a micro/nano-sized eutectic structure of the casted sheet can be formed. Such composite materials possess properties promising for various applications in energy generation, storage and conservation. The advantages, potential and challenges of the ribbon-growth-on-substrate technique for production of composite sheet materials as well as novel areas of application for such materials are discussed.IntroductionThe Ribbon Growth on Substrates (RGS) process is well known in the solar industry as a process to produce multicrystalline silicon wafers. An industrial size pilot production line for continuous casting of silicon wafer was developed by RGS Development B.V. in the Netherlands (Figure 1). A comprehensive review of this technology and properties of the produced silicon wafers were reported by Schönecker et al [1]. The principle of the RGS process is explained in Figure 2. The relatively cold substrate extracts the crystallization heat from the liquid silicon in the casting frame. This results in the growth of a silicon ribbon (Vc) in contact with the substrate. When the substrate (Vp) is transported from the casting zone into the cooling section, the crystal growth stops, the wafer can be removed and the substrate can be re-used. Last few years large work was done on the industrialization and market development of RGS wafers for the solar industry. Part of this work was discussed by Schönecker et al [2]. Although there is still a good perspective on the middle and long term solar market for the RGS wafers, the current market situation was found to be unfavorable for new entrants."

Jan 1, 2014

By L. S. Zhou

Germany-made AFX-100 multi-grade fluidized classifier, with exquisite built-in structure and unique novel design, materializes not only advanced and efficient classification, but also precise particle distribution and safe operation, in addition to lower energy consumption and operational cost. It, simultaneously in place of screw grader, water cyclone, and fine mesh sieve, is equipped with multi-function, and indicates superior advantage in comparison with other else grading facilities. As the third-generation equipment, which is efficient and modern, it, in China and therefore all over the world, will find wide application in processing both fine and ultra-fine iron ore resources. Industrial test, carried out in Benxi Steel?s Waitoushan Iron Mine, shows efficient classification, i.e., ?74µm particle contents in coarse, medium and fine products come to 6.09%,11.82% and 82.73%, respectively, while qualitative and quantitative efficiencies end up by 74.38% and 87.66%, respectively. Its separation efficiencies amount to 2.2 times as many as spiral classifiers, 1.8 times as hydrocyclones, and 1.3 times as vibration high-frequency fine screens. Another industrial test, which was practiced in Anshan Steel?s Donganshan Sinter Plant, indicates that classification qualitative efficiency comes to 65.06%, equal to 1.51 times as many as hydrocyclones; yield, 55.79%; -71µm particle contents in medium and coarse products, 42.02%; -71µm content in fine product, 95.42%; and concentration, 12.33%. Estimated separation indexes are as follows: Yield for concentrate at 31.22%, up 0.22% than that from general processing line; concentrate grade at 66.42%, up 1.13%; recovery ratio comes to 65.84%, up 1.28%, which, based on pilot study, results in 20 million yuan of economic return for Donganshan Floatation Plant.

Jan 1, 2014

By William Skinner, Jennifer MacCarthy, Jonas Addai-Mensah, Ataollah Nosrati

"Acid leaching in agitated tanks is central to hydrometallurgical processing for valuable metals’ (e.g., copper, gold, nickel and cobalt) recovery from low grade (e.g., < 2 wt.%) ores. In this study, atmospheric leaching behaviour of Australian saprolitic nickel (Ni) laterite ore using sulfuric acid was investigated under isothermal, batch conditions at pH 1. The effect of primary process variables comprising time (4 h) and temperature (70 and 95 oC) on the leaching mechanisms and kinetics was established for -2 mm, low grade (~1 % Ni) saprolitic ore dispersions at 40 wt.% solid loading. Leaching proceeded incongruently, reflecting the proliferation of gangue minerals’ constituent elements (e.g., Mg, Al, Fe) alongside Ni and Co in the pregnant leach solutions (PLS). Subsequent analysis showed that 89% Ni and 78% Co were extracted after 4 h at 95 oC whilst at 70 oC the recoveries of these metals were markedly low (< 25 %). Overall, 177 and 644 kg H2SO4 /t dry ore were consumed at 70 and 95 oC, respectively. Activation energy of 79.0 ±1.0 kJ/mol was estimated for the mechanism of Ni and Co leaching and associated kinetics. Particles size analyses indicated that when the breakage of frail laterite particles due to shear is taken into consideration, differences in feed and leached product particle size distributions were insignificant , despite a remarkable increase in BET specific surface area of the product. Mineralogical analyses of the feed ore and leached solid products revealed a sub-crystalline silica phase enrichment of the latter. The overall results suggest that the mechanism of acid leaching of saprolitic Ni laterite may be described by a chemical reaction-controlled, shrinking core model."

Jan 1, 2014

By T. Neesse

In many cases, the use of hydrocyclone control is desirable for the stabilization of separation in the setting of changing feed conditions. Control concepts based on exact mathematical models are not satisfactory due to the complexity of the physical process. In this case, fuzzy control is a suitable solution. The data are primarily derived from an optical sensor that monitors the outside view of the free underflow stream. A throttling valve, serving as an actuator, is installed in the overflow pipe that regulates the volume split of the cyclone. Applications in closed circuit grinding and in separation plants for tunnel driving, fine sand dewatering, and classification of kaolin demonstrate the typical use of this development. Additionally, the technological characteristics of the cyclone may be improved by this control, which is mainly caused by the increased discharge capacity of the un-der flow nozzle. A further advantage is the option to operate at an optimal operation point. In many cases, this point is located at the transition spray/rope discharge. The improved operation characteristics present new options for extensive applications of fuzzy cyclone control.

Jan 1, 2014

By V. A. Chanturiya

The results of development of new collecting reagents selectively interacting with the metals of platinum group (MPG) are presented. A new approach to the concentration of the platinum minerals from the fine grade platinum containing products with the use of cloud point polymers for the first time proposed for this purpose is discussed. An original method for the investigation of complexing reagents with the platinum under flotation conditions developed by authors is described. The influence of the complexing reagents on the xanthate adsorption and on the electrochemical properties of the platinum arsenide surface (sperrylite) as well with the interaction mechanism between the reagent and metallic platinum were investigated by means of the modern physical and physicochemical methods of the solid and fluid phase studies. The results of tests of some complexing reagents with the rich copper-nickel ore in the cycle of nickel-pyrrhotite flotation are given. The data obtained makes it possible to mark the complexing reagent containing phosphine group as the most effective additional collector for MPG. Cloud point polymers containing thioamide, aminosulphide, and phosphine functional groups were examined. It is shown that all the reagents tested increase the platinum and palladium extraction to the nickel-pyrrhotite concentrate without quality loss. Platinum containing particles flocculate selectively.

Jan 1, 2014

By A. Oleynik

The paper presents the modeling and simulation experience in field of research into the mineral row material separation. Features of the subject domain generate a need of different approaches using for modeling and simulation. The general scheme of separation modeling process and some examples of developed simulators are presented. Due to different features and standards of knowledge, different formal models should be used to describe and analyze separation processes in the frame of general scheme. The main types of simulators are modeling tools based on statistical, analytical or expert (logical) methods. Advantages and disadvantages of each method above are mentioned in the paper. Based on the studies in the field considered, an aggregated mathematical model of a separation process has been generated. The aggregated model is presented by two combined equations. The actual apparatus model is formed by substitution of the particular functional expressions of the forces acting in the apparatus into the aggregated model. The developed simulation tools are based on integration of limited experimental data and on ex-pert knowledge available on separation processes. Simulation does not allow producing an optimal, in terms of mathematics, solution. But it gives an opportunity to produce and compare quite adequate solution variants in real time. The results obtained are the theoretical and methodological base for integrated information technologies to support studies in the field of mineral processing.

Jan 1, 2014

By C. Van Den Heuvel, C. B. Van Buuren

BIOX® has been successfully demonstrated over the past 2 decades for the recovery of gold from refractory sulphide concentrates. To date 12 successful BIOX® plants have been installed in 8 countries spanning 4 continents with the 13th installation currently nearing completion in the Philippines. In 2010 BIOMIN introduced the ASTER™ process for improved water balances in commercial BIOX® applications by supporting tightening environmental legislation on water usage and availability in both arid and tropical regions. Previously, a common challenge for BIOX® plants was the inability to recycle thiocyanate containing water due to the low tolerance of the organisms. ASTER™, a biological thiocyanate and cyanide destruction process, renders a non-toxic solution for re-use in BIOX®. Two commercial ASTER™ plants are in operation with the 3rd ASTER™ plant under construction in the Philippines. A 3rd BIOMIN technology, specifically developed for double refractory ores is available for implementation. The HiTeCC process has shown considerable success on ores where competition from disseminated carbon has rendered ineffective gold recoveries. Through HiTeCC, gold is desorbed from the carbonaceous matter by manipulating the ionic strength and temperature of conventionally treated CIL product. One Australian commercial plant utilises HiTeCC while a 2nd installation is set for commissioning 4th Quarter 2014. BIOMIN’s premier solutions for refractory gold processing are described herein.

Jan 1, 2014

By M. Rehor

The importance of brown coal as a raw material is currently given by growing energy needs of Czech Republic. More than 70% of mined brown coal comes from North Bohemian Basin these days. Mining of brown coal is run in four mining locations. They are geologically different and the parameters of mining coal are quite different too. This requires a little bit different methodology of both extraction and reclamation. Methods of reclamation works in the region are given mainly by the characteristics of overburden rocks appearing in the upper horizon of recuperated localities. The difficulties of the North Bohemian mine dumps reclamation works are caused by extremely unfavourable properties of rocks poured down to the majority of mine dumps. These are mainly rocks of the overlaying strata and the rocks strata of brown coal bed. Main materials poured down to the mine dumps are sands, clayey sands and kaolin ? illitic clays. Admixtures in filled rocks consist of organic (coal) mass, siderite and pyrite. These rocks are mechanically instable with respect to the wind and water erosion and during weathering they are getting unfavourable, acid (phytotoxic) nature, due to the influence of SO3 and Al ions. External and internal dumps of open pit mines are significant part of the North ? Bohemian landscape sustained by excavation. Their as fast as possible preparation and gradual integration into ecosystem of the area is interest of both citizens of region and mining companies. The paper briefly summarizes the methodology of restoration of the largest dumps of the North Bohemian Brown Coal Basin and the results of analyses and evaluation of samples taken on restored localities Rado-vesice dump, Strimice dump, Ru?odol dum pand internal dump of Bilina mine. An example of modern non-tradicional restoration methods is the restoration of internal dump of Bilina mine (application of power plant stabilizer). According to observations and results of sample analyses the methods of restoration were selected to limit the erosion influence, adjust the chemical and physical composition of surface of Radovesice and Strimice dumps. The application of marlites and bentonite prevent the unfavourable weathering processes on dump surface. Compensation of Quaternary sediments was artifically formed here. The need of marlite ploughing in, application of organical substrates and vegetation preparation was proved on Radovesice dump. The conception of landscape reclamation of the largest dumps after finishing of mining, methodology of technical reclamation and well considered using of fertilizable soils are main results presented in this article.

Jan 1, 2014

By A. J. Ren

The ore, dealt with in this paper, is a certain rutile in Shanxi province, China. A trunk flowsheet with gravity concentration is used, and the TiO2 grade of rutile concentrate is about 90%, but the TiO2 recovery is less than 50%. In order to increase the rutile recovery, the laboratory test, using the truck flowsheet with flotation, is carried out. The flowsheet is that firstly floatable gangue is re-moved by flotation; secondly rutile is recovered by flotation; and thirdly impurity is separated by LIMS, HIMS, gravity concentration and flotation from the rutile concentrate. In rutile flotation, BK423, a phosphonic acid, is used as rutile collector, and Na2SiF6 is used as silicates depressant. The experimental result shows that the recovery of rutile concentrate is improved obviously, and the recovery of ultimate rutile concentrate is 68.01% TiO2 and 84.88% rutile. The TiO2 grade of first concentrate is 95.98%, and the TiO2 recovery is 45.60%. The TiO2 grade of second concentrate is 80.53%, and the recovery is 22.41%. Furthermore, magnetite and ilmenite are recovered in the flowsheet.

Jan 1, 2014

By V. A. Leão, A. M. Silva, S. M. Bertolino, B. C. S. Ferreira, D. Guimarães

Although not considered a high risk pollutant as compared to toxic metals and acidity, environmental agencies worldwide are proposing regulations to control sulphate in effluents and drainages by setting a threshold value varying between 250 mg/L and 500 mg/L. The aim of this study was thus to compare four different techniques for removing sulphate ions from mining/metallurgy effluents. The first alternative studied was sulphate removal by precipitation as ettringite. Treating a synthetic solution containing 1650 mg/L sulphate at 22±1 ºC resulted in removals close to 85% during continuous precipitation. Sulphate sorption was also investigated using three different ion exchange resins as well as limestone. Fixed bed experiments produced sulphate loadings of up to 70 mg SO4 2-/L resin, at pH 2.0. In neutral wastewaters, limestone is also a potential adsorbent producing a maximum particle loading of 19 mg/g. Sulphate sorption on limestone seems to be an alternative to treating mine waters with sulphate concentrations below the 1200-2000 mg/L range, where lime precipitation is not effective. Subsequently, sulphate removal by sulphate reducing bacteria was also investigated and it was observed that reactor’s hydrodynamic conditions and the choice of substrate are important factors for the process. The different technical aspects of each technology are addressed.

Jan 1, 2014