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By C. A. Perez

Estimation of rock composition in mineral plants is important to determine rock size and grindability which in turn may improve control of the grinding process. Variations in ore grindability and size distribution directly affects mills power consumption and throughput. Therefore, it is desirable to develop new tools to estimate rock lithological composition. In this paper, a new method for lithological classification based on machine vision is proposed. The method is based on a single video camera and employs information about texture using several different spatial scales. Texture information is extracted from rock images using Gabor filters that can be adjusted at different spatial scales and orientations. After feature extraction, rock images are classified using support-vector machine (SVM). The method was tested on a database containing sub-images of 64x43 pixels of five ore types as follows: massive sulphide (MS), disseminated sulphide (DS), net textured (NT), gabbro (G), and peridotite (P). These ore types were assigned to three grindability classes: soft (MS), medium (DS and NT) and hard (G and P). The database was divided in 2 subsets for training, cross validation, and for test. Classification accuracy is compared with previously published results on a dataset with three different classes of rocks according to their hardness. Results show that our proposed method reached significant improvements (between 13%-20%) in classification accuracy relative to previously published results. Keywords: rock classification, lithological classification, grindability estimation, Gabor feature extraction, texture features

Sep 1, 2012

By P. Gao, J. W. Yu

"Pre-concentration is a necessary step for upgrading low-grade iron ores, and its aim is to remove gangue minerals for improving efficiency of downstream separation process. The most important pre-concentration technique for iron ores, including hematite, siderite and limonite, is magnetic separation based on the appreciable differences between the desired iron minerals and gangue minerals in magnetic susceptibility. In this paper, the separation efficiency of one-stage low-intensity magnetic roughing combined with two-stage high-gradient magnetic scavenging for the pre-concentration of a low-grade hematite from Donganshan was investigated. It is a BIF type of ore containing hematite, magnetite and a bit of siderite, and an average content of Fe is about 34.6%. The effects of grinding fineness and magnetic field intensity for scavenging I and II were studied and optimized. The results showed that a magnetic preconcentrate assaying 42.7% with a recovery of 95.4% was obtained under the conditions of ore grinding fineness of -74 µm 70%, magnetic field intensity of 300 mT and 800 mT for scavenging I and II, respectively. Over 20% of the feed was rejected as the final tailings assaying 6.4% Fe. Meanwhile, the XRD, iron chemical phase and SEM analyses of different stage products revealed that hematite, magnetite and siderite could be recovered successfully by magnetic separation. However, some ultra-fine hematite particles (-10 µm) were difficult to be captured by magnet, and lost in the final tailing, resulting in lower iron recovery.INTRODUCTION Donganshan iron ore belongs to sedimentary-metamorphic iron formation called banded iron formation (BIF), which is formed in the Precambrian with a layered structure composed of ore bodies (Shen, 2012). Such type of iron deposit contains various iron-bearing minerals like hematite, magnetite, and siderite, suggesting it may be amenable to pre-concentration with magnetic separation. The pre-concentration process is effectively applied in recovering hematite, magnetite and siderite from iron ore, due to its benefits of further upgrading iron ore and improving separation efficiency. The most important pre-concentration technique for iron ore is magnetic separation, including low-intensity magnetic separation and high-gradient magnetic separation, based on the fact that there are appreciable differences between the desired hematite, magnetite or siderite and the gangue minerals in magnetic susceptibility."

Jan 1, 2018

In this paper, the recovery of copper minerals and molybdenite in the rougher/scavenger banks of two separate mineral processing plants is compared with recovery in laboratory (batch) cells. A number of metallurgical surveys were conducted in two plants treating porphyry copper and molyb-denum ore. Batch flotation tests were performed on plant conditioned flotation feed slurry, in parallel with the plant metallurgical surveys. The effect of flotation feed density on recovery of copper minerals and molybdenite in the plant and batch laboratory cells was investigated. Changes in flotation pulp density had little effect on copper mineral recovery, in both plant and laboratory cells. The ultimate recovery for molybdenite, on the contrary, increased considerably when the pulp density was reduced, both at plant and laboratory scale. Recovery of copper minerals in the plant and laboratory cells was comparable, while molybdenite recovery in laboratory flotation cells was 3%~13% higher than in plant. It is hypothesised that the flotation rate of molybdenite is sensitive to cell hydrodynamic conditions (i.e. local turbulent energy dissipation) more than the flotation rate of copper. The flotation behaviour of molybdenite particles is likely to be predominantly controlled by bubble-particle collision frequency, which is enhanced in high local turbulent energy dissipation environment. For chalcopyrite, the flotation recovery is mostly determined by attachment and stability efficiencies. An increase in local turbulent energy dissipation, while increasing collision efficiency, may negatively impact on attachment and stability efficiencies. The outcomes may have a considerable impact on increasing molybdenite recovery from porphyry ores.

Jan 1, 2014

By N. Vorob?ev-Desyatovskii

The process of gold(I) adsorption on activated carbon (AC) from aqueous Na[Au(CN)2] and the state of the adsorbed gold cyanide complex on the adsorbent surface was investigated by photometry, XPS, XANES methods. By DFT method, quantum-chemical calculations were performed of the gold cyanide species on activated carbon surface. It was established that the binding of gold(I) with the surface of carbon involved several simultaneous processes governing the selective adsorption of gold(I) from the cyanide solutions.

Sep 1, 2012

Coal preparation plants usually operate with water in a closed circuit mode. In this practice, large quantities of water is continuously being recycled. To compensate the natural losses, only small quantity of fresh make up water is added into the circuit. As a result, a gradual build up of residual concentrations of flotation reagents (frothers, collectors, coagulates etc.) take place in the water and the concentration levels of the contaminants increase. Besides, the recycled water accumulates higher amounts of total dissolved components (1600 ppm) and hardness (740 ppm) than the fresh water. Nearly 80 ? 85% of the process water used in a coal preparation plant is utilized in treating the coal fines in flotation circuit. The presence of certain alkali earth metal ions (e.g., Ca++, Mg++) may adversely affect the flotation performance as they precipitate sparingly soluble hydroxyl complexes on the coal surface and change its surface charge. These studies showed that the use of recycled water in flotation has a significant effect on the selectivity and kinetics of the flotation process because, the dissolved compounds, both inorganic and organic, alter the chemistry radically. By treating the recycled water through a softening process, the concentrations of alkali earth metals and hardness were reduced significantly. The concentration of alkali earth metals and hardness were reduced to 10 ppm and 35 ppm respectively in the softened recycle water. From the selectivity studies, it has been observed that the flotation yield and recoveries increased by four to seven units by softening the recycled water. The kinetic studies indicated that the clean coal particles followed first-order kinetics. The kinetic parameters namely, flotation rate constant (k) and maximum recoveries (R8) of flotation, were found higher with softened recycle water than the recycled water. This reduces the residence time in the flotation cell and thereby, increases its productivity. Keywords: coal flotation, hardness of water, water chemistry, softening process, selectivity, kinetics, flotation rate constant and maximum recovery

Sep 1, 2012

By M. M. Yahyaei

The Sarcheshmeh new concentration plant uses a 32 ft×16 ft constant speed (10.5 RPM) SAG mill with two 5500 hp motors which could rotate in two directions. The mill liners are chrome-molybdenum steel casting type with a Brinnell hardness between 325 and 375 with the lifter face angle of 14° and lifter height of 152 mm. The shell liner consists of 120 (two 60 rows) pieces with a High-High configuration in a rail design. A specially designed liner wear profile measuring device enabled fast and accurate measurements inside the mill during the mill shut-down periods. The measurements indicated that the liner wear profile along the liner length is non-uniform and the highest wear occurs between 1.25m and 2.75m of the mill length. The average weight of liners at the time of removal was 47% of the original weight indicating a significant metal loss. The modification of liner shape was undertaken with the aim of having a uniform profile at the liner removal time. The proposed liner unlike the pervious type did not have a uniform shape with a lifter height of 187mm at the section where the wear rate was high. It was believed that this new profile could arrive at a uniform profile at the liner change out time. A study was also directed to the possible change of charge motion due to the liner profile modification. The dynamic behaviour of charge was investigated through the analysis of forces acting on a single ball using mill characteristics such as mill diameter, rotational speed, lifter height and release angle. The simulation of charge motion with this method and Milltraj TM software indicated that the impact position of charge will change only one degree due to the maximum increase of 35 mm in the lifter height. This assured that the installation of the modified liner would not have any adverse effect on the mill because of ball impacting the mill shell. It was predicated that the amount of scrap metal will reduce to 30% from the current value of 47% beside 1500 h increase in the liner life time.

Jan 1, 2014

By X. O. Xia

This paper introduces a kind of flotation machine for nonferrous metal, ferrous metal and non-metal minerals. With the application and development of flotation machine, researching the designment of master parts, including tank, impeller, stator, false bottom. Through the commercial run to validate the correctness of designment, achieving satisfied technical and economic target and supplying a kind of efficient and reliable flotation machine.

Jan 1, 2014

By G. J. Mei

Separation of hematite and iron-containing silicate gangue - aegirine by Flotation using fatty acid collector and (NH4)2SiF6 depressant was investigated in this paper. The flotation tests with single minerals show Ammonium hexafluorosilicate (AHFS) is a selective depressant for aegirine in hematite flotation in weakly acidic medium, which can strongly reduce the flotation recovery of aegirine in the pH range of 4~5 while has no evident effect on the flotation of hematite. The results of flotation tests with actual ores show the separation of hematite from aegirine gangue by forth flotation was possible, and good selectivity was achieved. Chemisorptions were observed on aegirine mineral surface treated by AHFS solution by using SEM and IR spectrum measurements. On the basis of coordination chemistry, a comprehensive mechanism, which reasonably explains the selective depression of AHFS for iron-containing silicate, is also proposed.

Jan 1, 2014

By S. L. Gubin, T. V. Ignatova, A. V. Levshin, D. O. Sharkovsky

"Flotation process applied for concentration of unoxidized ferruginous quartzites by PJSC Mikhailovsky GOK (MGOK) is based on wet magnetic separation of strong magnetic minerals. However quality of the resulting concentrate (Fe65-66%) is insufficient for production of metallics. Quality upgrade of magnetite concentrate via flotation has been implemented by MGOK to produce premium quality magnetite concentrate.Flotation is a challenging process due to sensitivity to varied amounts of reagents, fine and coarse mineral ratio, particle contact (retention) time and temperature of feed. Tomah’s PA-14 reagent (USA) has proven efficient for application in flotation of MGOK’s magnetite concentrate.Objective of this work is to select and prove applicability of selective agents for flotation upgrade of magnetite iron ore concentrate.Series of flotation tests has been carried out with application of new highly selective collecting agents produced by Akzo Nobel (Sweden), Clariant (Germany) as well as Akzo Nobel’s and Tomah’s cationic collector mix to improve performance efficiency of flotation process. Tomah’s flotation agents and Akzo Nobel’s Lilaflotproved to be the most effective for purposes of concentrate quality upgrade to Fe69.0% via flotation.Testing Method: Following scientific research methods were applied for testwork: system analysis, mathematical statistics, observation, comparison, trial (experiment).To determine key process factors a series of pilot tests was carried out. Most of the testwork was performed by PJSC Mikhailovsky GOK’s Central Process Laboratory.Work Results:-optimized flotation performance modes were defined to ensure production of three types of low-silica concentrate, i.e. containing SiO25%, SiO24% and below SiO23% by weight. Most efficient selective agents applicable for flotation have been defined. Mixture of higher aliphatic amines has proven to intensify selective flotation of quartz. It enables higher yield of chamber product maintaining desired quality of concentrate.Achieved process operation and performance factors have been revaluated.Value for Advancement and Expansion of Mineral Processing:Flotation of concentrate has enabled expansion of PJSC Mikhailovsky GOK’s production capacity, improved production quality, helped to maintain sustainability and competitive advantage of the company."

Jan 1, 2018

By T. Onnela

Metso Mining and Construction Technology is one of the world leading suppliers of equipment and knowhow for aggregate and mining industry. The processing capacity, ease of use, and reliability are featuring Metso?s state-of-the-art cone crushers. Crushing is a complicated process affected by numerous parameters. The optimized crusher kinematics is one of the key factors for high performance. To fine tune the crusher kinematics and crushing chambers one needs to know how different parameters affect. The main cone crusher parameters are head angle and diameter, gyration point, shaft speed, eccentricity, stroke length, and inclination and design of crushing cavity. Selecting the correct combination of these parameters is a multi task optimization challenge. In practical life there are more factors to achieve satisfactory performance, like crushing chamber wear and profile management keeping the performance constant over the whole wear life, control of crusher frame loads, ability to handle disturbances in feed material etc. The extensive research work has lead to a solution that enables the highest possible material density in the crushing chamber. This design provides maximum reduction of processed material and thus increased share of 0/10 mm product. High density in the cavity offers further benefits, such as high throughput capacity, less material contact with wear parts and even load on crusher frame and bearings. The challenge that an equipment supplier involved with high density crushing is how to design a robust cone crusher, which is able to cope with the high crushing forces due to high resistance from the crushed material against the gyration movement. Metso has launched a new series of cone crushers HP3, HP4 and HP5 that are all able to work in high density crushing applications The test results and evidence from over 300 installations clearly prove the effectiveness and importance of high density crushing. Keywords: cone crusher, crushing chamber, crusher kinematics

Sep 1, 2012

By John O. Marsden

"Technology development and innovation has played a crucial role in the copper industry throughout history. The effective development and implementation of new technologies allows mankind to produce copper at progressively lower cost of production at a given feed grade and mineral type. This progress serves to counteract cost inflation/escalation over time and, depending on the magnitude of the cost benefit, allows ore cut off grades to be reduced thereby improving the availability, accessibility and utilization of resources. Two broad categories of technology development and innovation play a key role in this process: (i) incremental improvements and optimization of existing technology provide benefits in the near- to medium-term, and (ii) step change technologies provide value over the longer term. A key issue for potential developers and implementers of new step change technology is how to justify resource allocation and expenditures for such initiatives. This paper examines this issue with reference to specific case studies in the copper industry. INTRODUCTION AND BACKGROUND Technology development and innovation has played a crucial role in the commodity minerals industry throughout history, and none more important than the copper industry. As new, cost-efficient technologies are commercialized, the cost of production in real terms at a given ore feed grade and mineral type decreases. This progress enables ore cut off grades to be reduced allowing lower grade material to be processed economically, which in turn increases the availability and supply of the metal or mineral of interest. Cost inflation/escalation works in the opposite direction, squeezing margins for operations utilizing incumbent technology to process material from a given ore deposit. A prior review by the author considered the issue of technology development and sustainable competitive advantage. This review concluded that first movers and fast followers can achieve competitive advantage for periods of 10-15 years through effective deployment of new technologies (Marsden, 2004). A new, more comprehensive study and evaluation was completed in 2014. This paper presents a portion of the results from the 2014 study."

Jan 1, 2018

By M. Karamoozian

Modelling and optimisation of the power draw of large SAG mills are important due to the large power draw which modern mills require (5~10 MW). The cost of grinding is the single biggest cost within the entire process of mineral processing. Traditionally, modelling of the mill power draw has been done using empirical models. Although these models are reliable, they cannot model mills and operating conditions, which are not within the model database boundaries. Also, due to their static nature, the impact of the changing conditions on the power draw, within the mill, cannot be deter-mined using such models. Despite advances in computing power, on-line modelling of large plant scale mills could be a time consuming task. On the other hand, using on-line parameters for model-ling, result in more reliable control of SAG mill without performing any more costly tests. In this paper, SAG mill power draw is modelled using neural network approach. Six inputs, namely: solid percent, two bearing pressures, noise, recycle and feed rate were used to model the power draw. The produced model shows an acceptable correlation coefficient, R2 =0.9623.

Jan 1, 2014

By D. M. R. Sekhar

Certain types of rock phosphates of sedimentary origin are applied to acidic soils as fertilizer directly. Recent research in India showed that high grade rock phosphate in fine size when used as a mix with organic manure works as efficiently as di-ammonium phosphate (DAP) in alkaline soils. The rock phosphate from Jhamarkotra, India (sedimentary origin), Egypt (sedimentary origin) and South Africa (volcanic origin) showed good agronomic efficiency when used as Phosphate Rich Organic Manure (PROM). Further PROM shows equal residual effect. The results of efficiency of PROM made using two grades (+ 24% P2O5 and 34% P2O5) of rock phosphate mineral from Jordan show that low grade rock phosphate slimes are as effective as high grade phosphate concentrate when used in PROM. Also PROM is very effective in the saline soil of Eshidiya desert where DAP is not at all effective.

Jan 1, 2014

By Ivan Bonchev, Elisaveta Djurova, Evgeni Visariev, Viktor Stoilov

"Two types of slag cooling is used world wide - cooling in ladles and cooling in pits. The flotation comparison of the type cooling regimes was done at Aurubis Bulgaria. In Copper smelter Aurubis Bulgaria (Pirdop), the residual copper in the slags from Flash furnace and Converters is recovered by flotation. The slag flotation plant processes blend of three parts FSF and one part converter slag. The slag processing comprises: pit cooling, crushing, two stages grinding (autogenous and ball) and flotation. The copper content in flotation concentrate is over 20 % and in flotation tail is under 0.5 %. In order to improve the copper recovery, different cooling rate of the liquid slags should be achieved. Three cooling experiments with flash smelting furnace (FSF) slag have been done: two of them in pits with different volume and one cooling experiment in metallic ladle. The ambient air temperature during the cooling tests was from -4 to +4 OC. Laboratory flotation tests in open cycle were done with an aim to compare the slags behaviors cooled at different conditions. In this paper the effect of different cooling on the flotation process will be presented. The copper recovery and distribution by sizes in the tails, copper content in the rougher concentrate, and the concentrate yield are discussed."

Jan 1, 2014

By Hao Zhang, Dezhou Wei, Qiang Zhao, Caie Zhang, Baoyu Cui, Xuetao Wang

"Nowadays, long periods of relatively low iron ore prices have made the steel industry get the greater pressure. To develop appropriate processing technology based on characteristics of the iron ore, so as to reduce the beneficiation costs, is crucial to the improvement of iron and steel enterprise competition. For a typical low-grade iron ore from northeast China, beneficiation process research was conducted based on the in-depth studies of ore characteristics. Results show that the iron grade of the ore was 31.56%, the content of FeO was 6.59%, the main iron minerals were hematite and magnetite with fine dissemination sizes and partly scattering in gangue; With the grinding fineness of 65% passing 0.074mm, and regrinding fineness of 90% passing 0.074mm, the concentrate with 66.80% iron and recovery of 82.90% was obtained via the combined flowsheet of stage grinding – classification – gravity concentration – low and high intensity magnetic separation – reverse flotation. Ratios of gravity concentration and low intensity magnetic separation were 70.21% and 7.57% respectively in 40.42% of total concentrate yield; The loss of micro-size fractions can be reduced by feeding spiral tailings into magnetic separation and flotation; It’s helpful in reducing the dosage of reagents and beneficiation costs by increasing the throughput of gravity concentration and outputting concentrate of low intensity magnetic separation.INTRODUCTION Iron and steel industries are facing the increasing pressures in the continued falling iron ore prices. In order to improve the competitiveness, it is extremely urgent for them to develop more appropriate separation process for the reduction in iron ore beneficiation cost. As a typical low-grade iron ore, Anshan-type iron ore is one of the most important iron ore resources in China [1-3]. The flowsheet of stage grinding and separation contained the classification of the coarse particles and the fine particles, the gravity concentration, the magnetic separation and the anionic reverse flotation has been widely applied for Anshan-type iron ore. With the appropriate separation progress as well as equipment, satisfactory separation results had been obtained, and mineral particles with different size were recovered separately [4-7]. However, the low recovery of fine mineral particles and the relatively high beneficiation costs still prevented the efficient application of the process [8]. For a Anshan-type low-grade iron ore, a typical process flowsheet, as mentioned earlier, with stage grading, classification of the coarse particles and the fine particles, gravity concentration, magnetic separation, anionic reverse flotation was adopted currently. And the concentrate with 67.10% iron and recovery of 75.50% was obtained and the gravity concentrate accounted for 39% of the total concentrate. However, a large amount of fine liberated iron ore particles were lost in the tailings."

Jan 1, 2018

By Alex Joseph

A tertiary amine containing polyamine in its back bone was grafted to exfoliated graphite oxide by means of a series of chemical reactions.The synthesized amine functionalized polyaniline grafted to exfoliated graphite oxide (EGAMPANI) was characterized using various techniques such as, FTIR, TGA, Raman, and X-Ray diffraction.The synthesized EGAMPANI was blended with carbon paste electrode, and used to study the response of Hg2+ in acetate buffer solution.Preliminary analysis showed that the anodic current intensity using the EGAMPANI modified electrode was higher during a potential sweep and 10-4 M concentration of mercury could be detected which could be improved to 10-6 M using anodic stripping voltammetric technique. Keywords: metal sensor, exfoliated graphite oxide, functionalization, polyaniline

Sep 1, 2012

By V. A. Ivanova, T. N. Perunkova, N. O. Dorozhanova, G. V. Mitrofanova

"Oxyethylated compounds are used as reagents-regulators in the flotation of non-sulfide ores, in particular, apatite-containing ores. Thus, the necessary degree of selectivity in the flotation separation of two calcium-containing minerals of apatite and calcite is achieved only by using, in addition to a collector, regulators-reagents from the nonylphenol ethoxylates class. In order to establish the most optimal structures, this paper presents a comparative assessment of the physical-chemical and flotation properties of several classes of oxyethylated compounds - alkylphenol ethoxylates, aliphatic alcohol ethoxylates and oxyethylated carboxylic acid. The authors have studied their dispergating ability with respect to the air phase and calcium soaps of the carboxylic collector. Dependences of foaming properties of regulators on the degree of oxyethylation have been determined. Adsorption isotherms of sodium oleate on apatite and calcite in the presence of regulators have been obtained. It has been shown that the presence of oxyethylated compounds in the solution reduces the amount of the adsorbed fatty acid collector. The influence of the considered classes of regulators on apatite flotation has been studied. The interrelation of flotation properties of oxyethylated compounds and their molecular structure has been established.INTRODUCTION Flotation plays a leading role in complex apatite-containing ores processing. However, two calcium-containing minerals - apatite and calcite, which compose apatite-carbonate ores, are characterized by close flotation properties. Selective separation of these minerals is a difficult task, the solution of which is impossible without using reagents-regulators. One of the ways to ensure the selectivity of the flotation separation of calcium-containing minerals is the use of reagents-depressants such as sodium silicate, starch, cellulose derivatives, and others (Liu et al., 2016; Rao et al., 1989). Another method is the application of nonionic reagent regulators (Filippov et al., 2016; Filippova et al., 2014; Ignatkina, 2017), which contribute to the adsorption of the ion collector (Filippov and Filipova, 2006 Rao and Forssberg, 1997) and stability of formed froth (Sis and Chander, 2003)."

Jan 1, 2018

By M. Zolghadri

MIBC and sodium metasilicate are used as a frother and a dispersant in coal flotation respectively. In order to study interaction between them, flotation experiments were performed on fine coal (<150 microns). It was found that if the frother (MIBC) dosage is in excess of a certain limit, it has an activation effect on the gangue minerals associated with coal. In addition, it was found that however sodium metasilicate can disperse clay slimes eliminating slime coating, but in the case of excess dosage, could intensify activation effect of MIBC, which is undesirable in coal flotation. Keywords: coal flotation, sodium silicate, frother, dispersion, activation

Sep 1, 2012

By P. A. Bepswa

A numerical study done to test the efficacy of heuristics developed for the design of measurement networks for high precision metallurgical accounting is presented in this paper. The heuristics considered were designed to maximise variance reduction of terminal stream measurements through data reconciliation for observable linear flow systems. A complex metallurgical process flow sheet from the mineral sands industry was used as a case study. Monte Carlo type simulations coupled with a non-linear programming based steady state data reconciliation algorithm were used as tools to investigate the heuristics. The results obtained suggested a close correlation between magnitudes of measured variances and the respective levels of variance reduction obtained through data reconciliation for both internal and terminal streams. It was observed that variance reduction through data reconciliation was maximised for terminal stream measurements in networks characterised by high precision measurement of internal streams and/or in flow sheets characterised by high ?stream to node ratios?. Terminal streams attached to highly interconnected parent nodes were observed to experience higher reductions in variance compared to terminal streams attached to less interconnected parent nodes. The results generally highlight the additional benefits of highly interconnected flow sheets and high precision internal stream measurement regimes on the maximisation of variance reduction of terminal stream measurements through data reconciliation. These findings are significant to metallurgical accounting and to process accounting applications in general in that they provide a conceptual basis for design decision making regarding the construction of measurement networks aimed at maximising variance reduction of targeted streams through data reconciliation.

Jan 1, 2014

By A. E. Sobolev

The kinetics of hydrochemical oxidation of antimonite in solutions of nitric acid was studied using the rotating disk method and the factor experiment design. The dependences of the antimonite?s oxidation rate on concentration of nitric acid solutions, temperature, disk rotation frequency, and duration of interaction were determined. The adequate kinetic models allowing calculating the specific oxidation rate at any combination of the values of the influencing factors were obtained. The oxidation process is found to proceed in a mixed mode, close to chemically controlled. Gradually, as the sediments of elemental sulphur and Sb2O5 accumulate on the disk surface, the process becomes controlled by internal diffusion. The observed high (more than second) order of the oxidation rate with respect to the concentration of nitric acid was explained by the autocatalytic action of the acid reduction products. The apparent activation energy depends on the stage of interaction. At the initial stage (in a mixed mode of the process proceeding), it depends on nitric acid concentration and varies from 31.5 kJ?mol?1 (in 2 M HNO3) to 36.1 kJ?mol?1 (in 10 M HNO3). This trend indicates the weakening of diffusion limitations with a nitric acid concentration increase. When the process is controlled by internal diffusion, the apparent activation energy was found to be 14.5 kJ?mol?1. The obtained kinetic characteristics enlarge the database on hydrochemical oxidation kinetics of sulphides and can be used for the elaboration of the recommendations for the effective comprehensive exploitation of antimony-bearing ores and concentrates.

Jan 1, 2014