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By Aldo Cipriano, Fernando Estrada

The mining industry is in search of control strategies that allow considering a global optimization of their processes, ensuring their stability. This has led to the application of recently developed control techniques on large-scale systems in the mining processes. One of the most important process of the mining industry is the mineral grinding, as the product particle size impacts, in a significant manner, the recovery rate of the valuable mineral in the separation stages. As a solution, a centralized hybrid model predictive control (HMPC) is presented; this control approach maintains the product particle size on a defined range and minimizes energy consumption, maintaining the grinding plant in a stable operation. As a comparison, a conventional model predictive control with an expert system to handle discrete events was developed, showing HMPC is a suitable solution that can used in the grinding process, with the benefit that it handles in the same controller both discrete and continuous dynamics and events.

Jan 1, 2014

By Kazutoshi Haga, Batnasan Altansukh, Shirchinnamjil Nyamdelger, Atsushi Shibayama, Narankhuu Ariunbolor, Gunchin Burmaa

In this study, the authors investigated the capability of an acidic thiourea solution and silicon-organic polymers (PSTM-3c, PSTM-3T) as ion-exchange resins to recover of gold from gold-bearing ore concentrates. Firstly, elemental gold present in flotation concentrates was dissolved by leaching with a solution of nitric acid and thiourea under the optimized conditions. The best result on gold thiourea leaching was obtained under a nitric acid concentration of 2 N, thiourea concentration of 2 %, and oxidant (Fe2(SO4)3) concentration of 3 %, solid:liquid ratio (S:L) of 1:20, leaching time of 6 hours at 20 °C with a gold recovery of 93.7 % for a gold flotation (unroasted) concentrate. For the roasted gold concentrate, the dissolution of gold was 94.8% under the optimized leaching condition as nitric acid concentration of 0.5 N, thiourea concentration of 2 %, and the oxidant concentration of 1 %, S:L ratio of 1:10, leaching time of 4 hours at 50 °C. Secondly, a series of sorption tests was carried out on a pregnant leach solution containing gold complex Au[S=C(NH2)2]2+ using silicon-organic polymers (PSTM-3c and PSTM-3T), respectively. The effects of solution pH, adsorption time and temperature in the sorption process are also studied. As the results, the PSTM-3c and PSTM-3T polymers were adsorbed about 94.4 % and 95.1 % gold from the pregnant leach solutions under the optimum sorption conditions, respectively. It was found that the both PSTM-3c and PSTM-3T polymers were effective for the recovery of gold from the pregnant leach solution of thiourea. Adsorption activity of the PSTM-3c and PSTM-3T polymers was confirmed by new peaks near 1700 cm-1 in the FT-IR spectrum of the gold-adsorbed polymers, respectively.

Jan 1, 2014

By J. Vilcáez

The copper extraction yield from thermophilic bioleaching of chalcopyrite depends on temperature, pH, and the oxidation-reduction potential (ORP), as well as the activity of the microbe used. We studied copper extraction yields obtained from chalcopyrite with three thermophiles, Acidianus brierleyi, Sulfolobus metallicus, and Metallosphaera sedula, under various pH and temperature conditions and with different initial amounts of ferric iron. The results indicated that the capacity of each thermophile strain to leach iron as Fe3+ differed, which affected the influence of pH, temperature, ORP, and microbial activity level on the yield of copper. Microbial activity can cause ORP to be close to the critical value (450 mV) at which copper extraction at 65 °C can be higher than that at 80°C. An initial pH of 1.5 retards the precipitation of jarosite, allowing temperatures as high as 80°C to result in copper extraction yields close to 100%. However, if a thermophile with a poor capacity to form Fe3+ is employed, 100% copper extractions can also be obtained at pH 2.5, because ORP is low as result of low amounts of Fe3+ in solution. Optimum temperatures for the growth of thermophiles did not always mean high copper extraction yields. Conversely, high biomass concentrations depending on the capacity of the thermophile strain to leach iron as Fe3+, can result in excess Fe3+ in solution, leading to the precipitation of large amounts of Fe3+ as jarosite. The bioleaching capacity of A. brierleyi was reduced or suppressed when insufficient initial Fe3+ was pro-vided to trigger the leaching reaction, whereas S. metallicus and M. sedula were less sensitive to the initial availability of Fe3+. This result confirmed that a direct enzymatic attack on the mineral surface could initiate the leaching reaction, but later ORP governed the leaching rate of chalcopyrite.

Jan 1, 2014

"The thiosulfate leaching process developed by Barrick to treat sulfidic high preg-robbing gold ores uses calcium thiosulfate as the leaching reagent for ores pre-treated by pressure oxidation, resin for gold recovery with sulfite/trithionate elution and reverse osmosis as a means of reagent recovery. A large portion of the research that led to the development of the technology was based on previous studies completed by different groups over the years, mainly focused on the ammonium thiosulfate system. Operational limitations in the use of the ammonia-containing recycled water in the pressure oxidation circuit were some of the main drivers for the change from ammonium to calcium thiosulfate for the development of the industrial scale process. One of the main aspects for successful gold extraction and recovery in the thiosulfate system is the pseudo-equilibrium reactions that drive distribution of the different gold species (in solids, solution and on resin) in the system. Previous studies have been focused on the thiosulfate reactions and equilibrium constants for the oxysulfur ions (thiosulfate, trithionate, tetrathionate). However, the literature around the effects of the different metal-oxysulfur complexes (Cu and Hg complexes) that form when the ore is in contact with the leaching reagents, and the related effects on stability of the gold complex is limited. The main changes in the gold complex chemistry and stability in the calcium thiosulfate system as compared to the ammonium and sodium equivalents, as well as related effects on gold recoveries, were investigated in the presence of different types of double refractory ores. INTRODUCTION Barrick has developed a thiosulfate leaching process to treat double refractory gold ores, by combining the use of acidic and alkaline autoclave pre-treatment with thiosulfate resin-in-leach (RIL). The process currently in operation at the Goldstrike mine (the TCM process), uses calcium thiosulfate as the leaching reagent, resin for gold recovery with sulfite/trithionate elution and reverse osmosis as a mean of reagent recycle. The main feed to the process plant is highly preg-robbing sulfidic ore from Goldstrike’s open pit. Prior to feeding the pressure oxidation circuit, the ore is processed through the crushing and grinding circuits and treated in preparation for acid or alkaline autoclave processing (POX)."

Jan 1, 2018

By Ernesto de la Torre, Karla Velín, Alicia Guevara

"The following study shows the improvement and simulation of a gold recovery plant of 24 t/day of capacity by gravity concentration, flotation and leaching. The ore processed had grades of 6 g/t Au, 15 g/t Ag, and 0.69 %Cu with the mineralogy consisting of 2 %chalcopyrite, 12 %pyrrhotite, 7 %plagioclase and 50 %quartz. The recovery process starts with crushing the ore followed by grinding it further in a ball mill. The ground ore is then concentrated in a Falcon centrifugal concentrator with concentrate being processed by amalgamation process. Gravity tails are sent to a flotation circuit where the copper minerals and some gold are concentrated. Lastly, the flotation tailings undergo cyanidation for gold recovery. Currently, the overall recoveries are 82.8 %Au, 49.6 %Ag and 99.1 % Cu. The optimization was developed in the laboratory using a Wilfley table by gravity concentration. Flotation tests in the laboratory were performed using potassium amyl xanthate and pine oil. Lastly, cyanidation was then performed on the flotation tailings. The results showed the optimum concentration of sodium cyanide in cyanidation is 2 g/L, which produced an increase in gold recovery from 30% to 44%. The reduction of diameter particle from 132 to 80 µm also produces an incremental recovery of gold and silver from 11% to 21% Au and 0.4 to 3% Ag in gravity concentration. Likewise in the cyanidation the recovery of gold and silver has shown a rise from 44 to 62% and 8 to 32% for Au and Ag respectively. However, the flotation method the gold recovery is reduced from 68 to 30% Au by reducing the particle size. Computer simulations using the programs, Moly-Cop and ModSim were performed to determine optimum parameters for the recovery of precious metals at the gold recovery plant."

Jan 1, 2014

By Luis Bergh, Francisco Díaz, Isabel Panire, Juan Yianatos, Luis Vinnett

"In this paper, industrial data of residence time distribution (RTD) in mechanical flotation cells is presented, which were measured in several plants using the radioactive tracer technique. Results include mechanical flotation cells of 100 - 300 m3, which were operated with effective residence times from 2 to 7 min. Tests were developed in forced air and self-aerated cells for liquid and solids (non-floatable) per size classes. Different RTD model structures including perfect mixer, Large and Small Tanks in Series (LSTS) and by-pass flow plus perfect mixer were evaluated and compared for single cells. The actual mixing regime was related to the effective residence times and cell designs based on the model fitting. By-pass flow percentages were typically lower than 10%, therefore the perfect mixer model plus a dead time was a suitable model structure in most cases. On the other hand, the arrangement of cells in series was effective in reducing the bypass flow observed in single cells (by-pass flow percentage greater than 5%). In addition, the N perfectly mixed reactor in series model was used to represent the mixing regime along flotation banks, which were operated with mean residence times in the range of 18 - 53 min. Results showed that N tanks in series plus dead time were closer to the actual values in most cases."

Jan 1, 2014

By Ljubisa Obradovic, Baisui Han, Batnasan Altansukh, Zoran Stevanovic, Atsushi Shibayama, Jonovic Radojka, Daizo Ishiyama, Kazutoshi Hag, Radmila Markovic, Ljiljana Avramovic

This paper discussed a combined froth flotation and high pressure leaching (HPL) process to recover copper from mine tailings. At first, froth flotation were carried out using the mine tailings sample under various conditions in the presence of different pH (3.5-10) and sulfurizing reagent value (0-1000 g/t), respectively. As a result, optimum condition (sulfurizing reagent of 1000 g/t, pH of 10, PAX (collector) of 100 g/t and MIBC (frother) of 200 g/t) was found for froth flotation of copper. The effects of sulphuric acid concentration, leaching temperature, total pressure (steam pressure plus oxygen pressure) on high pressure leaching (HPL) of mine tailing were investigated using sulphuric acid solution in the presence of oxygen. The best conditions for HPL were obtained to be sulphuric acid concentration: 0 mol/L (water), leaching temperature: 170 ?, total pressure: 2 MPa, leaching time: 1 hr and pulp density: 100 g/L. The leaching rate of copper reached nearly 99 % and the concentration of copper in pregnant leach solution (PLS) was 0.24 g/L. Finally, copper in the mine tailing was recovered using froth flotation followed by HPL. As a result of a combined froth flotation and HPL, the vast majority of copper (99 %) from the mine tailings was extracted.

Jan 1, 2014

By Masakazu Niinae, Tasuma Suzuki, Mai Moribe, Yohhei Okabe

Bench-scale electrokinetic experiments were performed to elucidate the electrokinetic remediation mechanisms of arsenate from artificially contaminated kaolinite. The electrokinetic experiments in which a constant voltage was applied demonstrated that high soil pH favored arsenate remediation with respect to both the remediation time and electricity consumption. It was also demonstrated that applying a pulse voltage (1 hour ON, 1 hour OFF) significantly improved the electricity consumption efficiency when the soil pH was maintained at the initial value during the experiments; this trend was not observed when the soil pH was gradually increased from the cathode side. These electrokinetic experimental results indicate that the remediation rate-limiting step varied with soil pH. When the soil pH was maintained at the initial value of 7.2 during the experiments, arsenate desorption was the remediation rate-limiting step rather than the migration of dissolved arsenate toward the anode. Conversely, when the cathode pH was not controlled and the soil pH was correspondingly increased gradually from the cathode side, the migration of hydroxyl and desorbed arsenate ions toward the anode played a more important role in the control of the overall remediation efficiency.

Jan 1, 2014

By B. Rath

An effective process plan is an important part of maintaining consistent recoveries in mineral processing operations. Traditionally, Mineralogical studies are completed using chemical and metallurgical methods to monitor recovery and elemental distribution. The development of mineralogy and more efficient processes in mineral analysis techniques means that mineralogy is now more accessible as an efficient and comprehensive study tool. As operating costs increase and feed grades decrease it is important to maintain tight control of process and ensured maximum recovery is maintained at all times. Just a few days of losses in recovery caused by changes in ore type or processing conditions can have a large effect on total metal recovery and profit. Mineralogical audits can be used to minimize these losses by monitoring the fundamental behavior of feed ore on a regular basis. Smart use of mineralogical studies can develop mineralogical and ore type benchmarks in a detailed, which can be used in process control and monitoring. Geological ore types can be used to identify key mineralogical parameters that may be used in routine and cost effective analysis. Mineralogical systems ideally suited to this because of the depth of information on everything from modal mineralogy to locking/liberation characteristics and mineral associations. Mineralogical studies can equally be applied to specific unit operations within the process, which can allow more detailed information to be gathered on areas of the process that have been identified as critical. This will be especially effective for flotation or oxidation processes where process parameters can be very sensitive to small changes in mineralogy. This paper deals with the Ore Morphology, Ore Mineralogy, Gangue mineralogy, Photo micrographs under reflected, transmitted light and XRD studies Ore, Mineral studies of Sub grade Iron ore of Bacheli Complex, Bailadila Sector, India. Keywords: mineralogy, liberation, liberation studies, ore mineral, gangue mineral, morphology, jasper, ferruginous clay

Sep 1, 2012

By G. Granata, C. Tokoro, T. Kato

The rare earth elements (REE) are composed of 17 elements that are 15 elements of lanthanide added scandium and yttrium. REE are divided into light rare earth elements (LREE) and heavy rare earth elements (HREE). Although the supply source of LREE is distributed around the world, the supply sources are unevenly distributed. Thus, the development of a new HREE supply source is required. In this study, we focused on the weathered residual rare earth ore as a new HREE supply source. Since so far this weathered residual rare earth ore could not be treated neither by flotation nor by wet high intensity magnetic separation, it was not considered as HREE resource before. In this study, we investigated the leaching of HREE from the weathered residual rare earth ore and elucidated the effectiveness of planetary milling with sodium hydroxide as a method to enhance their recovery. For this purpose, the weathered residual rare earth ore was first grinded by planetary mill in the presence of sodium hydroxide and then leached by sulfuric acid. The influence of planetary milling on HREE recovery was investigated by assisting the leaching experiments with X-ray absorption fine structure (XAFS) in cerium and yttrium K-edge. Since yttrium was the most contained HREE in the weathered residual rare earth ore used in this study, we focused on yttrium in XAFS analysis. Results clearly showed that the recovery of HREE increased by planetary milling with sodium hydroxide. XAFS analysis revealed that a part of the yttrium in the weathered residual rare earth ore was changed to yttrium hydroxide by planetary milling with sodium hydroxide. It is supposed that all HREE were affected like yttrium due to a similar behavior observed in leaching.

Jan 1, 2018

The flotation of nickel sulphide minerals is normally difficult in the presence of serpentine minerals due to the coating of serpentine particles on the nickel mineral surface. To improve the flotation, dispersants such as polyphosphate and carboxy methyl cellulose are normally used to remove the slime coating. However, in the flotation using high ionic strength process water, these dispersants are invalid due to their ionic nature. In this study, a new type of non-ionic dispersants, Pluronic triblock copolymers were examined with an objective of improving the flotation of ultrafine pentlandite (a nickel sulphide mineral) in the presence of lizardite (a serpentine mineral) in saline water. Three Pluronic triblock copolymers varying in solubility and hydrophile-lipophile balance (HLB) values were studied by flotation tests, settling tests and froth measurement. It was found that two of the copolymers improved pentlandite flotation against lizardite, and one copolymer deteriorated the flotation. The effect of Pluronic triblock copolymers on the flotation was actually linked to their dispersibility and foamability, which were governed by their physical properties. The two copolymers with a higher solubility or HLB value produced more stable mineral suspensions and more stable froth in the flotation resulting in better nickel grade and recovery in both rougher and cleaner flotation. Keywords: ultrafine particle, flotation, slime coating, dispersion, saline water, triblock copolymers

Sep 1, 2012

By Komar Kawatra, Joseph Halt

"Bentonite clay has been the traditional binder for iron ore pellets. However, bentonite increases pellets’ silica contents and is expensive. Researchers have proposed lowering bentonite doses by mixing it with other common binders. These mixtures may only be successful if the fundamental bonding mechanisms are understood. For example, what happens when bentonite (physical bonding) is mixed with fly-ash (chemical bonding)? What happens when bentonite is mixed with cornstarch (physical bonding)? In this paper, experiments are described where bentonite was mixed with various ratios of cornstarch and fly-ash, and pellets were agglomerated using 0.66 % w/w binder. Ca(OH)2 and CaCl2 were added as activator and accelerator, respectively, to the bentonite-fly ash mixture. Curves of pellet dry strength vs. bentonite-starch ratio were linear, suggesting the physical-physical bonding mechanisms were compatible - acceptable strengths (> 22 N) were produced at all bentonite-to-starch ratios. This was contrary to bentonite-fly ash mixtures, which displayed dry strength curves with a noticeable minimum due to competing binding mechanisms. Bentonite alone and fly ash alone produced acceptable strengths (> 22 N), but their mixtures resulted in weak pellets. Due to the positive results using cornstarch (CS) binders, the effects of CS solubility in water were investigated using two CS with high and low solubility (60 and 7.5 %). CS was premixed with bentonite at various ratios (0, 20, 40, 60, 80, 100 %). Pellets were agglomerated using 0.66 % w/w binder. The dry strength of pellets ranged from 50-300 N using the high solubility CS mixtures, and from 50-85 N using the low solubility CS mixtures. Fired strengths exceeded 2200 N/pellet at all bentonite-cornstarch ratios. This research showed that cornstarch solubility is an important factor in determining its effectiveness as a binder for iron ore concentrates, but significant work is still necessary before it can be used as a bentonite replacement."

Jan 1, 2014

By Dilip. Makhija, Asim. K. Mukherjee, Tamal Ghosh, Abhay Patra

In India around 15-20% of Run of Mine (ROM) from any iron ore deposit reports to slime dams as byproduct of iron ore beneficiation process. The proportion of iron ore slime to ROM will increase in future with higher proportion of lean grade ores in ROM. Furthermore, tonnages of iron ore slime will also increase with increasing demand of iron concentrate. Presently, this slime is stored in the dam in the absence of beneficiation technology. A beneficiation flowsheet has been developed at Tata Steel. This process produced concentrate of 2.2% alumina with 40 % yield from slime of 7-9% alumina. The iron content in the reject will be less than 40% thus adhering to the regulatory norm. Pilot scale study show waste from slime beneficiation is a good raw material for making a variety of building materials. Waste from slime beneficiation also has soil amendment properties. Pilot scale studies show productivity of rice increased when the waste of slime beneficiation process is mixed with soil. On commercialization of this zero waste technology slime generated from the iron ore washing plant will be completely used. In this paper the result of the pilot scale studies on slime beneficiation and utilization processes towards soil making and making of building materials are discussed in detail.

Jan 1, 2014

By Robert Peretti, Antonio Zucca, Andrea Manni, Silvia Serranti, Paolo Massacci, Marcello Ghiani

"This research study aims to identify the best way of processing colemanite concentrates, which is sometimes characterised by a high content of As sulphides, finely disseminated in the matrix of the boron mineral.Scanning Electron Microscopy analyses have been carried out to identify all the mineralogical constituents and to evaluate their distribution, frequency and mutual relationships.Colemanite concentrates are mainly used by chemical plants producing boric acid and gypsum. A high As content is unacceptable for further use of tailings coming from the leaching process and is very dangerous if the tailings are released into the environment.Grinding tests were conducted under dry and wet conditions in order to assess how As sulphide minerals are released from colemanite minerals.Some of the difficulties involved in obtaining selective liberation of As sulphides from colemanite minerals were overcome, although a certain decrease in As grade in the higher size classes was registered.All comminution products have been analysed by SEM, monitoring the degree of liberation of the mineralogical constituents.Flotation tests have been carried out, following different comminution flow sheets and adopting different modulating conditions in order to evaluate the influence of the following parameters:- collector concentration versus contaminants concentration (As minerals) in the froths;- kind and quantity of the frothing agent to maximise mineral recovery in the froths;- kind and quantity of the modulating agents to maximise the selectivity of the process;- conditioning modalities in order to obtain a suitable dispersion of fines and avoid segregation of Asbearing particles together with colemanite ones;- solid/liquid ratio of the pulp to minimise the water flow into the plant.Information obtained from SEM analysis has been adopted to evaluate segregation phenomena in pulp and in flotation products."

Jan 1, 2003

By P. Hatefi, O. Rahmani, M. Noor-Mohammadi, A. Tohry

"Depressants play an important role in the selective separation of impurities from iron minerals by direct or inverse flotation. In this paper, sodium co-silicate (SCS) with chemical formula of Na4SiCO6, as a depressant with pH modifier features, has been synthesized and used for phosphorus bearing iron ore in anionic reverse flotation. In this process, phosphorus is floated while the iron oxides are depressed, using fatty acids as collector in an alkaline medium. Batch and pilot flotation tests were carried out to investigate the influence of SCS on the separation selectivity of phosphorus from iron oxides. Also the depression mechanism of SCS on hematite surface was investigated by microflotation tests and FTIR spectroscopy measurements. The flotation results indicated that without using a pH modifier, the pH of pulp could reach up to 10, when SCS was used as depressant. In this condition, a better depression performance was observed compared to sodium silicate (SS). Using the SCS, phosphorus and total iron content in iron concentrate was 0.046% and 66.29%, respectively, compared to SS where these values were 0.06% and 65.75%, respectively. As a result the weight recovery of iron concentrate was increase by around 4%, compare to SS. It was also found that 238 g/t of SCS could be used instead of 3 types of reagents collectively, including 32 g/t of NaOH, 151 g/t of Na2CO3 and 400 g/t of SS gel.INTRODUCTIONThe phosphorous presents in iron ore minerals is mainly in the form apatite mineral. The apatite is separated from iron ore minerals by magnetic and flotation methods (Ma, 2012). The reverse anionic flotation of iron is one of the most common method for removing phosphorus from iron concentrate (Araujo et al., 2005).Usually apatite minerals are readily floated using anionic collectors such as fatty acids (Ma, 2012). In this conditions the iron minerals are depressed and by modifying the pH in alkaline conditions, selective separation of phosphorus from iron concentrate can be achieved. Depressants including; sodium silicate (SS), starch, dextrin, guar gum and humic acids play an important role in the reverse flotation of iron ore (Kar et al., 2013; Ma, 2012; Turrer and Peres, 2010; Araujo et al., 2005). Studies have shown that SS has a better effect on iron recovery and phosphorous reduction, compared with other depressants (Tohry and Dehghani, 2016; Qi et al., 1992, Dho and Iwasaki, 1990). In most flotation processes, modifiers are used to adjust the pH. To achieve alkaline conditions, mainly pH modifiers such as carbon dioxide and sodium carbonate are used."

Jan 1, 2018

By Olga D. Khmelnitskaya

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

Jan 1, 2014

By G. H. Li

Preparation strontium carbonate with celestite concentrate by flotation is studied by agglomeration-reduction roasting process. It is shown that, the drop strength of green pellet is greater than 4 times?(0.5m) -1 under the balling conditions of moisture of 9% and time of 18~20min. Lignin xanthate obviously improves the ballability of the celestite concentrate due to the increase of surface hydrophilicity, therefore, the balling rate is increased, as well as green ball strength. The drop strength of 7 times?(0.5m) -1 can be obtained when the lignin xanthate dosage is 0.5%~1%. Reduction roasting with anthracite shows that the SrSO4 conversion is 82%~83% for celestite concentrate pellet, under the optimal conditions of roasting temperature of 1100~1150? and time of 30min, and it is 10% higher than conversion of celestite lump under the same conditions. The strontium carbonate are prepared after roasted pellets are leached, purified and carbonated, and the SrCO3 content is higher than 97% , while the content of CaCO3 is less than 0.3%.

Jan 1, 2014

By A. A. Novoselov, U. Kelm

"Large volumes of mine tailings accumulated in surroundings of porphyry copper deposits represent a growing threat to environment. They contain significant concentrations of toxic metal and metalloids which can contaminate river runoff, ground waters or can be transported by wind. Both extreme pH of fluids in tailings impoundments and high surface areas of processed mineral grains provide their increased reactivity. As a result, during only a few decades, As, Cu, and Mo can be mobilized, redistributed through the tailing column and accumulated through post-deposition leaching, evaporation and contamination with natural fluids. Those processes are reflected in the forming of secondary minerals. Gypsum, Fe oxides/hydroxides, efflorescent salts and clay minerals are typical alteration products in tailings. Here we present the results of reactive transport simulations implemented on the base of PHREEQC and SUTRA codes. The one-dimension model emulates the mass balance between rainfall, evaporation and subsurface runoff, the kinetically- and thermodynamically-driven dissolution of tailing minerals, advective and diffusive transport of tailing fluids, and precipitation of secondary phases. A typical tailing column is composed of four unequal layers with predominance of (i) evaporation, (ii) secondary mineralization above, (iii) below water table, and (iv) near the bottom of dump. Those horizons are characterized by contrasting pH, chemical composition and bulk mineralization of pore fluids, distinct accessibility of atmospheric oxygen and, as a consequence, distinct intensity of sulfide oxidation. The modeling and its verification on Chilean tailings impoundments reveal the complexity and high rates of secondary mineralization. The accumulation of toxic alteration products is controlled by fluid transport through the tailing column induced by both rainfall/evaporation and exchange with subsurface runoff. The geochemical modeling is a powerful approach which allows comparing the processes in tailing deposits produced by distinct flotation regimes and providing the long-term predictions of their environmental impact as well as identifying sectors of tailings for possible re-processing."

Jan 1, 2018

By A. Collings, A. Farmer

Power ultrasound may be used in the processing of mineral suspensions to clean the particle surfaces of oxidation products and fine coatings, mainly through the large, but very localised forces, produced by cavitation. This effect may be utilised in lowering the level of iron contamination in silica sand used for glass making, in improving the sharpness of electrostatic separation of heavy mineral concentrates, in shortening the time of leaching of minerals and in improving the selectivity and recovery of flotation processes. Parameters affecting the efficiency of these processes, such as input power and levels of reagent addition, are discussed. In particular, we present data showing the relationship between power input and the particle size of surface coatings removed, which can be explained by the Derjaguin approximation for the energy of interaction between a sphere and a flat surface. Pilot scale studies, using commercially available components, are currently being used to assess process viability and will be compared with laboratory scale results.

Jan 1, 2003

By R. Chowdhury

Axis House manufactures and supplies alkylhydroxamate reagent of various carbon chain lengths for application in flotation of oxide copper and other minerals. As part of reagent performance improvement the structural factors of hydroxamate are examined by various analytical tools in particular with X-ray diffraction of single crystals. In a recent publication, the structure of n-octylhydroxamic acid and its corresponding potassium salt are presented with findings of hydroxamic functional group geometric preference, H-bonding, keto-enol tautomerisation, acid-salt aggregation and alignment of carbon chain. In this paper an example of branched alkylhydroxamate 3, 5, 5-trimethylhexylhydroxamate will be presented and compared with the result of linear alkylhydroxamate.

Sep 1, 2012