Pretreatment Of Ore Research Articles

Microwave Treatment of Minerals and Ores: Heating Behaviors, Applications, and Future Directions

The application of microwave technology in mineral metallurgy is a transformative approach to ore processing that offers new ideas about the current progressive depletion of resources and the environmental impact of mineral processing. This review delves into the principles, applications, and future directions of microwave treatment in mineral and ore processing. Microwave technology, characterized by its unique advantages such as rapid and uniform heating, selective heating, and energy efficiency, stands in contrast to traditional heating methods. It directly interacts with materials at the molecular level, enabling volumetric heating. The review encompasses a wide range of applications, including ore pre-treatment, drying, mineral processing, hydrometallurgy, smelting, and reduction. It highlights the role of microwave treatment in enhancing metal recovery, reducing energy consumption, and improving processing speeds. Future research directions are identified, focusing on enhanced equipment design, process optimization, integration with conventional methods, and technological innovations. The comprehensive overview assists researchers, engineers, and decision-makers in understanding the potential of microwave technology in mineral metallurgy, emphasizing its contribution to innovation and sustainability in the sector.

New approaches to improving efficiency of automated control over ore pretreatment process stages

New approaches to improving efficiency of automated control over ore pretreatment process stages

Effect of biogenic siderophores produced by Bacillus thuringiensis on gold and other element bioleaching from silicate ore

This comprehensive study delves into the role of silicate ore pretreatment and the biogenic siderophores produced by Bacillus thuringiensis in the bioleaching process of gold (Au) and various other elements. The results revealed that an effective pretreatment method involved subjecting silicate ore to ball milling (BM) at 200 rpm for 1 h, followed by ozonation (O3) for 10 min before initiating the bioleaching process. Subsequently, in the leaching of Au and other elements, the highest leachability was achieved through a two-step conditioning approach, involving the first and second stages of bioleaching with B. thuringiensis. The results strongly suggest that the mechanism of elements leaching is closely linked to the release of biogenic siderophores by B. thuringiensis, which possess remarkable potential as chelators and metal-binding agents, facilitating the formation of metal-siderophore complexes. Furthermore, the finding confirmed that commercial siderophores can effectively facilitate the leaching of Au and elements from silicate ore. Additionally, the presence of amino acids in nutrient broth (NB) medium provides the ability to bind with Au, forming Au-amino acids complexes. This finding underscores the effectiveness of the two-step conditioning approach with B. thuringiensis, particularly under mild alkaline pH conditions. This innovative technology offers numerous advantages, including its environmentally friendly and sustainable nature, safety, and cost-effectiveness. It presents a promising method for the efficient recovery of Au and other elements from pretreated silicate ore, especially those with low concentrations of valuable minerals, all through the remarkable capabilities of biogenic siderophores.

A Pretreatment of Refractory Gold Ores Containing Sulfide Minerals to Improve Gold Leaching by Ammonium Thiosulfate: A Model Experiment Using Gold Powder and Arsenic-Bearing Sulfide Minerals

The use of thiosulfate to extract gold from refractory ores is promising because of its non-toxicity and high selectivity. Sulfide minerals (i.e., pyrite, arsenopyrite, chalcopyrite), major gold carriers in refractory gold ores, however, hinder gold extraction due to the high consumption of a lixiviant. In this study, a new method to improve gold extraction from sulfide bearing gold ores is proposed based on the model experiments using a mixture of gold powder and arsenopyrite-bearing sulfide (HAsBS) ore. The effects of HAsBS ore on gold leaching in ammonium thiosulfate solutions were investigated, and it was found that gold extraction in the presence of HAsBS ore was suppressed because of the unwanted decomposition of thiosulfate on the surface of sulfide minerals. To improve gold extraction in the presence of the sulfide minerals, this study investigated the effects of the pretreatment of HAsBS ore using ammonium solutions containing cupric ions and confirmed that HAsBS ore was oxidized in the pretreatment and its surface was covered by the oxidation products. As a result, thiosulfate consumption was minimized in the subsequent gold leaching step using ammonium thiosulfate, resulting in an improvement in gold extraction from 10% to 79%.

Oxidative pretreatment of refractory gold ore using persulfate under ultrasound for efficient leaching of gold by a novel eco-friendly lixiviant: Demonstration of the effect of particle size and economic benefits

A novel pretreatment method for refractory gold ore using ultrasound-activated persulfate was developed to overcome the low extraction efficiency of gold in the leaching process. The feasibility of the pretreatment method was verified primarily by EPR (Electron paramagnetic resonance) and pre-oxidation tests. The free radicals generated by ultrasound-activated persulfate effectively promoted the oxidation of sulfide in the gold ore. The pretreatment efficiency of this process was higher than that of traditional heat activation, and the oxidation efficiency was two times higher. Furthermore, the gold leaching efficiency was higher under ultrasound activation conditions when using a novel eco-friendly lixiviant (Jinchan-its main effective component is Na3CN3C3H3N6O3, i.e., carbonized sodium cyanurate). Morphology analysis indicated that the synergistic effect of persulfate and ultrasound effectively reduced the particle size of the refractory gold ore, improved the specific surface area, and facilitated the oxidation of the enclosures, which benefited the subsequent leaching process. The maximum leaching efficiency of gold reached 86.9% after ultrasonic activated persulfate pretreatment for 3 h. This study provides a promising refractory gold ore pretreatment to improve gold leaching through persulfate oxidation using ultrasound activation.

Application of Microwave Technology in Different Fields for Energy Saving and Emission Reduction

In today's world, security of energy supply and greenhouse gas emissions due to rising energy demand are seriously threatening sustainable energy development, and it is urgent to promote energy structure reform. Microwave, as a clean and environmentally friendly green energy source, has developed rapidly in recent years. Unlike traditional heating methods, microwave heating generates heat through the random motion of polar molecules. This results in microwave heating having the advantages of selective heating, fast temperature rise, easy control and high heating efficiency. This allows microwaves to make a contribution in advancing the reform. of the energy mix. This paper investigates the use of microwave technology in different industries to save energy and reduce emissions. It finds that in the ironmaking industry, microwaves can speed up the reduction time of iron ore, reduce carbon dioxide emissions, while making iron ore more easier to crush and magnetically sort during iron ore pretreatment process. In the food industry, microwaves can reduce the time required to cook and dry, and maximise the retention of nutrients in food. In the field of waste recycling, microwaves reduce the volume of bottom radioactive waste in a shorter time and improve the efficiency of desulphurisation of waste rubber. In the Budur reaction, microwaves reduce the temperature required for the reaction and increase the conversion of carbon dioxide. After summarising the advantages of microwave technology, this paper also analyses the current shortcomings of microwave technology, introduces microwave-related patents and concludes with an outlook on the future of microwave technology.

Improvement of lead-zinc ore mining waste processing

Expansion of mineral reserves and resources in Russia is currently connected with larger scale commercialization of rebellious ore and mining waste, and the percentage of the latter continuously grows. Due to the complex material constitution of minerals, their similar physicochemical and processing properties, as well as because of deficient ore pre-treatment, up to 20% of valuable minerals and metals are lost with tailings, mostly with very fine particles less than 10 µm. It is of the great concern to improve processing technologies for ore and mining waste. This research aims to analyze mineral compositions of tailings after lead-zinc ore flotation, and to identify causes of lead and zinc losses with the flotation tailings. The technology tests reveal that the losses lead and zinc in the form of micron size grains of galena (PbS) and wurtzite (ZnS) are connected with their aggregation with other minerals (quartz, pyrite, magnetite, etc.). The tests with physical (radiation) treatment show dissociation ability of aggregates with subsequent separation of minerals by flotation. The presence of magnetic magnetite in flotation tailings makes it possible to implement magnetic separation to increase the contents of lead and zinc in the concentrate. The scientific novelty and practical significance of this research consists in the proved expediency of radiation treatment of minerals and mining waste toward modification of their processibilty to ensure reduction in loss of valued components with tailings and to enhance environmental safety of mining waste.

Laccase-mediator system for enzymatic degradation of carbonaceous matter in the sequential pretreatment of double refractory gold ore from Syama mine, Mali

The sequential bio-treatment of refractory carbonaceous gold ore is a promising solution to recover gold effectively by environmentally friendly technology, which includes bio-oxidation of sulfide and biodegradation of carbonaceous matter by lignin-degrading enzymes. There are several drawbacks in enzyme treatment using cell-free spent medium (CFSM), including lignin peroxidase and manganese peroxidase from Phanerochaete chrysosporium, in particular the poor stability of enzyme activities. In the present work, laccase-mediator system (LMS) was applied for the degradation of carbonaceous matter in real gold ore to improve the efficiency of gold extraction as well as handling. The LMS was intended to be a great alternative process of CFSM with utilizing purified laccase in the presence of 1-hydroxybenzotriazole as a mediator. The application of LMS provided several advantages including not only greater stability, greater efficiency to degrade carbonaceous matter, better handling, much saving the treatment time, but also wider availability in laccase. In addition, replacing bio-oxidation with ferric chloride leaching as the dissolution path of sulfides facilitated avoiding the formation of jarosite and saving the required time. The gold recovery by cyanidation was improved from 41.5 ± 0.3% for the starting material to 81.3 ± 3.9% (n = 2) for the solid residues after the modified sequential pretreatment. This is correspondent to 86.3% of gold recovery for the extractable maximum gold excluding the enclosed gold in acid-insoluble silicates. The improved process involving LMS can be proposed with valuable advantages to fit a sustainable metallurgical technology of gold ores.

Scandium Recovery Methods from Mining, Metallurgical Extractive Industries, and Industrial Wastes.

The recovery of scandium (Sc) from wastes and various resources using solvent extraction (SX) was discussed in detail. Moreover, the metallurgical extractive procedures for Sc recovery were presented. Acidic and neutral organophosphorus (OPCs) extractants are the most extensively used in industrial activities, considering that they provide the highest extraction efficiency of any of the valuable components. Due to the chemical and physical similarities of the rare earth metals, the separation and purification processes of Sc are difficult tasks. Sc has also been extracted from acidic solutions using carboxylic acids, amines, and acidic β-diketone, among other solvents and chemicals. For improving the extraction efficiencies, the development of mixed extractants or synergistic systems for the SX of Sc has been carried out in recent years. Different operational parameters play an important role in the extraction process, such as the type of the aqueous phase and its acidity, the aqueous (A) to organic (O) and solid (S) to liquid (L) phase ratios, as well as the type of the diluents. Sc recovery is now implemented in industrial production using a combination of hydrometallurgical and pyrometallurgical techniques, such as ore pre-treatment, leaching, SX, precipitation, and calcination. The hydrometallurgical methods (acid leaching and SX) were effective for Sc recovery. Furthermore, the OPCs bis(2-ethylhexyl) phosphoric acid (D2EHPA/P204) and tributyl phosphate (TBP) showed interesting potential taking into consideration some co-extracted metals such as Fe(III) and Ti(IV).

Impact of actinide-induced crystal defects on REE-bearing titanite reactivity

Titanite is a widespread accessory silicate which, in some deposits, hosts rare earth elements (REEs) at levels where it can be considered an important carrier. As titanite also accommodates Th and U at concentrations up to 2000 ppm, evidence of metamitctization, a process where radioactive decay of the actinides progressively damages the crystalline structure, is often observed. The current study aims to investigate how the extent of metamictization within a natural titanite specimen may impact its reactivity, principally in the context of REE recovery. Detailed structural characterization revealed the presence of crystalline domains coexisting with sectors having a dominant amorphous component. Compositionally, the density of irradiation-induced defects, leading to amorphization, shows a strong positive correlation not only with the abundance of actinides, but also with the REE concentration. Heat treatment of titanite performed at temperatures ranging from 400 to 800 °C indicates that, while the compositional zonation is maintained, thermal annealing of the defects results in progressive recovery of the crystalline structure. After treatment in sulfuric acid at 200 °C, the habit of reacted titanite grains is highly irregular, indicating distinct decomposition rates for specific sectors, where the more refractory regions coincide with the REE-depleted crystalline domains. A more detailed visualization of the impact of crystal properties on titanite reactivity, obtained by exposing polished grains to a 50% NaOH solution at 50 °C, reveals that, for pristine titanite, the extent of etching observed on crystal surfaces is controlled by the density of the actinide-induced defects, mainly concentrated in the REEs- and Th-enriched amorphous domains. On the other hand, for grains that were initially heat-treated, the etching features are much weaker, emphasizing that thermal annealing renders the crystals less reactive. From these observations, selective REE recovery, where only the more accessible amorphous titanite domains need to be decomposed, seems possible as long as the ore pre-treatment does not involve a high-temperature stage.

Projects which push the limits of efficient performance concepts of high-pressure grinding rollers

The ore pretreatment process evolution is briefly addressed, with some milestones and pioneer projects described. Two advanced projects of concentration mills based on the technology of the pioneer-level high-pressure roll milling are discussed. The operating Canadian Copper Mountain Mill is interesting for using the technology which eliminates bottlenecks of the classical semi autogenous milling circuit, with the resultant increase in the mill capacity more than two times as against the initial project value. This result has been achieved for the first time in the world owing to total rejection of the ore pretreatment circuit and thanks to complete transition to press roller milling. Design and engineering of high-pressure roll mill HRC3000, as well as auxiliary milling and flotation equipment is in progress. The high-capacity Iron Bridge Magnetite Mill under construction in Australia can be assumed as the breakthrough project owing to the world’s first time trial of Enduron high-pressure grinding rolls by Weir Minerals in milling of magnetite quartzite and in dry production of fine products suitable for further processing without ball milling. The power saving in dry milling using high-pressure rolls will make 30 % at the least as compared with the present-day ore pretreatment by wet milling. Ball mills are withdrawn from the processing circuit, water consumption drops, carbon emissions are decreased, and the tailing storage becomes simpler and safer. In dry tailing storage, the capital investment is cut down as the operation of thickening of wet tailings is rejected, dam construction for tailings ponds is eliminated, and the environmental impact related with contamination of surface and ground water bodies, which is intrinsic to operation of conventional tailings storage facilities, is mitigated.

Enhancing magnetite quartzite processing efficiency at Karelsky Okatysh

The article focuses on increasing efficiency of ferrous quartzite processing at Karelsky Okatysh JSC. The processing technology currently in use at Kostomuksha GOK is characterized by higher losses of fine magnetite (-0.02 mm) and by insufficient dissociation of aggregates, due to ore over-grinding and extended circulation of middlings along the process chain of the concentrator. To increase the production efficiency, it is proposed to withdraw the concentrate at each stage of grinding using the expanded-front fine screening and subsequent combined magnetic/gravity separation. This approach to improving the process flow chart takes into account the mineral and material composition of ore, the features of ore pretreatment and separation operations, and ultimately can ensure the production of a concentrate with the quality of 70% Fetotal at the concurrent increase in the technical and economic performance owing to the rational use of energy in the ore pretreatment processes. To implement the technology of stage-wise concentrate withdrawal, it is proposed to use TAPP Group’s Banan-type AURY high-performance multicyclone screens for the preliminary classification of crushed ore and Derrick Corporation’s Superstack fine vibrating screens in combination with magnetic gravity separators MGS-2.0 to produce the finished concentrate. The proposed technology is based on the general principles formulated by Academician L. A. Vaisberg, to whom this article is dedicated.

Strength analysis of gold-bearing ore of the Bam deposit

Due to the depletion of readily processible mineral reserves and to compensate for the growing shortage of high-quality minerals, the development strategy of the Russian mining industry has justified involvement of complex and unconventional deposits in operation. A distinctive feature of such raw materials is a complex mineralogical and geochemical composition, submicroscopic size grains, extremely heterogeneous textures and a variety of genetic processes of ore formation. All these raise costs and complicate flowcharts of both ore pretreatment and beneficiation already at the stage of design of a concentration plant. In order to optimize ore dressing cycles, it is proposed to use selective disintegration processes. This article presents the studies into applicability of selective mineral disintegration on the basis of in-depth analysis and identification of the relationships and mutual influence of mineralogical and geochemical features, textural and structural and technological properties of ores of the Bam deposit. The structural and textural peculiarities were studied by the methods of computer X-ray microtomography. The pore space analysis of ore samples reveals low porosity (0.35948 %), which implies the high strength of the rock. The microhardness tests at grain interfaces and in the monomineralization zones show that, depending on the point of measurement, it varies from 1256.31 N/mm2 (in quartz zone) to 354.894 N/mm2 (at interfaces). The destruction tests of Bam ore using different-type crushers find out that rock-forming minerals are concentrated in large classes; this is especially typical of impact crushers: up to 81.85% of siliceous minerals concentrate in the class –4+2 mm.The study was supported by the Russian Foundation for Basic Research, Grant No 20-55-12002 NNIO_a.

Modern trends of technological advancement in iron ore processing

The authors discuss evolution of technologies and procedures in iron ore processing. It is emphasized that an iron ore treatment approach is governed by the type and nature of dissemination of metallic and nonmetallic minerals. Iron ore is mostly processed using magnetic, magnetic–gravity or magnetic–flotation separation. High grade ore with the iron content of 60–63 % is utilized without dressing, immediately after crushing and size grading. Magnetic and flotation circuits are used in processing of the most rebellious and finely disseminated low-grade ore. The ore pretreatment technologies feature the trends of introduction of press–rollers, which reduces energy inputs by 10–30 % as compared with the semi autogenous grinding. The essential improvement of size grading efficiency is reached via inclusion of fine sifting in the grinding circuits. Due to persistently growing demand for high-quality concentrate, fine sifting is also included in the finishing processing of rough concentrates. One of the methods to produce ‘super concentrates’ is the reverse cation flotation of rough iron concentrates using collectors composed of mono-, di- and ether amines, as well as their mixtures, including alcohols. The need to dress ROM hematite ore and to after-treat magnetic separation tailings of magnetite ore initiated engineering, manufacturing and commercial-scale introduction of high-gradient and highduty magnetic separators based on permanent rare earth magnets with the field density to 1.7 T. These machines have much smaller weight and consume much less energy than the high-gradient separators based on electromagnets. The promising method for hematite ore treatment is the reverse cation flotation. The use of the described processes, technologies and equipment allows production of concentrates with the iron content higher than 70 % and the silicon content less than 2 % at the iron recovery more than 90 %.

Prospective Life Cycle Assessment at Early Stage of Product Development: Application to Nickel Slag Valorization Into Cement for the Construction Sector

Pyrometallurgical nickel industry in New Caledonia produces several tons of slag per year, which is stocked on site. There is no valorization today, except for a small transformation into sand. Pyrometallurgy highly consumes fossil-fuel energy and electricity for ore pre-treatment and nickel extraction inside electrical furnaces, which produces significant CO2 emissions. A new valorization approach is suggested to use these two local productions (slag and CO2) to mineralize slag and produce silico-magnesian cement for the construction sector. In order to ensure suitable environmental performances, many questions arise about the target valorized product: where and how to capture CO2 and produce cement, what constraints should be targeted for the mineralization process, can products be exported and where? Moreover, New Caledonia aims to develop renewable energies for electricity grid, which would mitigate local industries impacts in the future. A prospective Life Cycle Assessment (LCA) is used to define constraints on future product development. Two hundred scenarios are defined and compared as well as electricity grid evolution, using Brightway software. Thirteen scenarios can compete with traditional Portland cement for 12 of the 16 impacts of the ILCD midpoint method. The evolution of electricity grid slightly affects the performance of the scenarios by a mean of less than+/−25%, bringing a small difference on the number of acceptable scenarios. The main constraint requires improving the mineralization process by considerably reducing electricity consumption of the attrition-leaching operation. To be in line with scenarios concerning carbon neutrality of the cement industry by 2050, a sensitivity analysis provides the maximum energy consumption target for the mineralization process that is 0.9100 kWh/kg of carbonated slag, representing a 70% reduction of the current energy measured at lab scale. Valorization of nickel slag and CO2 should turn to carbon capture and utilization technology, which allows for the production of supplementary cementitious materials, another product for the construction sector. It will be the topic of a next prospective study.

Improvement of primary crushing technology for Stoilensky ferruginous quartzite using updated gyratory crushers manufactured KKD-1500/180

Primary crushing is one of the critical stages in mineral processing, which governs efficiency and capacity of the follow-on ore pretreatment. Given the present-day activity of Stoilensky GOK toward an increase in production capacity and efficiency, improvement of primary crushing is the first-order condition of the strategic mission accomplishment. This article describes the primary crushing productivity enhancement project at Stoilensky GOK through retrofitting of primary gyratory crushers manufactured at Uralmashplant, which has ensured the annual production output of 38 Mt/yr. The main engineering solutions on redesign of crushers KKD-1500/180, aimed at enhanced capacity and optimization of end product size in the conditions of coarse grinding shopfloor at Stoilensky GOK, consist in optimization of ore feed, intensification of crushing effect and primary breaking in the upper zone of crusher chamber, as well as in improvement of functioning of heavy-duty friction assemblies of crushers. The in-proof test conditions, methods and results obtained after modernization of crushers KKD-1500/180 are presented. The implementation of modernization solutions ensured the hourly efficiency increase from 400 to 5563 t/h at the product outlet width of 180 mm. The grain size composition evaluation proved the product quality improvement connected with stable size and reduction of medium size of the crushed product to d05 = 232.65 mm. As a consequence, it is possible to enhance capacities in the next following stages of medium and fine grinding due to better ore pretreatment quality.

Fine milling of Stoilensky oxidized quartzite

The development and technological advance strategy of Stoilensky GOK (Mining and Processing Plant) includes modernization of crushing and milling facilities. The top-priority objective in this regard is resource-saving based on higher energy efficiency of ore pretreatment. The pretreatment process flow is added with high pressure grinding rolls (HPGR) manufactured by Köppern, Germany. The test subject is ferruginous quartzite from Stoilensky deposit. This is a finely disseminated and very strong rock. Dissociation of metal and nonmetal phases takes place in milling to the size of –0.045 mm. Milling was implemented in three stages, with preliminary size screening of stage III product, which offered a finely milled product with the weighted average size dav of 5.5 mm at the content of size +15 mm up to 2.5 %. Some aspects of the roller technology introduction are discussed, and the main stages of the technology application at the commercial scale are described. The informational measures are selected to compare ferruginous quartzite pretreatment circuits with and without HPGR. Fine milling enhances efficiency of processing by 8 % owing to the reduced size of feed of the head-end mills at the maintained iron ore concentration quality.

Features of material constitution of quartz–feldspar ore from Quang Nam deposit in Vietnam

Feldspar is the largest group of aluminosilicate minerals making around 50% of the lithosphere mass. Feldspar is a high-value raw materials used in various industries in production of glass, ceramics, electrical insulators, abrasives, as well as an aggregate in production of plastics, paints, rubber, etc. A major source of high-grade feldspar is granitic pegmatites. The Social Republic of Vietnam possesses considerable feldspar reserves but mostly in weathered and semi-weathered pegmatite zones, which governs the complex material constitution of feldspar material and the diverse lattice architecture of feldspar weathering products. The article describes the integrated studies into the material constitution of quartz–feldspar ore from Quang Nam deposit in Vietnam. It is found that the ore has a rather complex composition. Alongside with the base useful component – feldspar represented by orthoclase and albite, the ore contains free quartz, mica group minerals (muscovite) and iron-bearing minerals as inclusions and coats in feldspar. The iron mineral coats are observed on the surface of muscovite grains. The mass percentage of Al2O3 is on average 14.20%; Fe2O3 – 0.75%; SiO2 – 75.27%. The total percentage of alkali metal oxides (K2O+Na2O) is similar in different size grades and makes on average 8.64%. The yield and distribution of useful component y size grades are relatively uniform. The analysis of the research findings allows drawing the conclusion that most efficient method to remove impurities of mafic minerals, including iron minerals, and free quartz is flotation. The feldspar ore flotation flow chart should include four stages: desliming (removal of clayey minerals); flotation of mina group minerals; flotation of iron-bearing minerals; flotation of feldspar. The proposed ore pretreatment circuit with selective milling and desliming enables production of mica concentrate with the size of +2 mm. The studies into material constitution of Quang Nam quartz–feldspar ore prove that this ore is processable toward production of valued products in high demand in many industries.

Disintegration of geomaterials in ore pretreatment–The role and significance

It is shown that all ore pretreatment processes including the stages of crushing and grinding, depending on the structural and texture features of geomaterials, have two interconnected sides: destruction and disintegration. Disintegration is considered as a process of selective separation of geomaterials by their weakest bonds and as a process concomitant with mechanical destruction. The paper justifies the methodology for determining the degree of geomaterial disintegration by the example of impact crushing using grain size composition of crushed products. The proposed procedure is based on isolating the fraction of material that is predominantly accumulated in the form of a mode, which depends on the energy of mechanical effect that is responsible for the process of actual geomaterial destruction and is determined as a lognormal distribution. In this case, the degree of disintegration is determined by subtracting the fraction of geomaterial formed directly by mechanical destruction (in percent or unit fractions) from total distribution sum of grain size composition. Examples of calculating the degree of disintegration for some ore geomaterials are given. Assessing the degree of disintegration according to the developed procedure can become an important characteristic of ore pretreatment and operating performance factor of crushing and grinding devices.

The mechanism of ultrasound oxidation effect on the pyrite for refractory gold ore pretreatment

The effect of ultrasonic cavitation on the oxidation of the crystal pyrite in deionized water has been discussed. The effect of solution alkalinity, ultrasonic power and temperature on the surface morphology of pyrite and the chemical forms of sulfur and iron was discussed. The surface of pyrite is severely corroded under ultrasound. The sulfur in the pyrite is oxidized to S2O32- and SO42-. Most of the iron is in the form of Fe2+, few of it is in the form of Fe3+. With the increase of alkalinity, ultrasonic power and temperature, the surface corrosion of pyrite becomes more and more obvious. With the increase of the NaOH concentration, the Fe(II) concentration in solution decreases and the deposition of iron oxides on the pyrite surface prevents pyrite oxidation. With the increase of the ultrasonic power, the Fe(II) concentration in solution increase. The effect of the NaOH concentration on the SO42- and S2O32- concentration indicates pyrite oxidation is in mild alkalinity under ultrasound. The concentration of SO42- and S2O32- increases along with increase of the ultrasonic power and decreases tremendously with increase of the temperature. The pyrite oxidation is initiated by hydroxyl radical and promoted by Fe3+.