References of "Gaydardzhiev, Stoyan"
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See detailProcess Oriented Characterisation of Copper Slag Processed by Flotation in View Metals Recovery
Aatach, Mohamed ULiege; Milen, Kadiyski; Stoilov, Viktor et al

in Proceedings of the 7th International Slag Valorisation Symposium: Shifting Gears to a Climate-neutral & Resource Efficient Society (in press)

Profound process oriented characterisation on samples collected during plant survey of the slag flotation plant belonging to Aurubis AD, Bulgaria has been realized in order to evaluate the form under ... [more ▼]

Profound process oriented characterisation on samples collected during plant survey of the slag flotation plant belonging to Aurubis AD, Bulgaria has been realized in order to evaluate the form under which Cu, Ni, Mo and Co bearing phases occurred and likewise their mineralogical composition. The slag subjected to flotation consisted in majority of fayalite, magnetite-iron oxides and a glass-resembling phase. Ni and Mo have been found to be closely associated to iron-bearing phases. The flotation tailings sample has been subjected to sulphation roasting followed by water leaching as a hydrometallurgical route to recover the remaining Cu, Mo, Ni and Co. Based on the various sulphation roasting process conditions (acid dosage, duration, temperature), copper, nickel and cobalt were brought in solution to a different extent. Sulphation roasting performed at 350 °C has secured the best extraction degree for Mo and Co, while maximum recovery of Ni and Cu has been documented when roasting was done at 150 °C and 450 °C respectively. EDS-SEM observations of various products do support the experimental findings. [less ▲]

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See detailExtraction of Ta and Nb from a Coltan Bearing Ore by Means of Ammonium Bifluoride Fluorination and Sulfuric Acid Leaching
Shikika, Alidor; Zabene, François; Muvundja, Fabrice et al

in Minerals (2021)

A novel approach for Ta and Nb extraction consisting of the pre-treatment of a coltan-bearing ore with an ammonium bifluoride sub-molten salt and subsequent acid leaching has been stud-ied. The effects ... [more ▼]

A novel approach for Ta and Nb extraction consisting of the pre-treatment of a coltan-bearing ore with an ammonium bifluoride sub-molten salt and subsequent acid leaching has been stud-ied. The effects from ore granulometry, ammonium bifluoride (ABF) to ore mass ratio, temper-ature and duration of fluorination on the degree of Ta and Nb extraction were examined. The ABF to ore ratio and process temperature were found to have the most pronounced impact on extraction efficiency. The following optimal process conditions were determined: ore granulo-metric fraction (−75 + 45 µm), ABF-ore (5/1), fluorination temperature (200 °C) and fluorination time (2.5 h). Maintaining these parameters enabled about 94% of Ta and 95% of Nb to be brought into solution during the sulfuric-acid-leaching stage. A comparison of the proposed method with previously reported studies suggests that due to the effects of mechanical agitation and the re-circulation of the HF-containing gaseous phase back into the process, the dosage rate of ABF at the fluorination stage could be reduced significantly without sacrificing the overall recovery of Ta and Nb. In such a way, the approach could offer added environmental benefits since release of fluoride-containing effluents into the environment could be limited. [less ▲]

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See detailExtraction of Nb and Ta from a coltan ore from South Kivu in the DRC by alkaline roasting - thermodynamic and kinetic aspects
Shikika, Alidor; Muvundja, Fabrice; Mugumaoderha, Mac et al

in Minerals Engineering (2021), 163

An alkaline roasting of a coltan bearing ore from the Numbi deposit (South Kivu, the DRC) was investigated with particular focus on the extraction kinetics of Ta and Nb. Isothermal roasting experiments ... [more ▼]

An alkaline roasting of a coltan bearing ore from the Numbi deposit (South Kivu, the DRC) was investigated with particular focus on the extraction kinetics of Ta and Nb. Isothermal roasting experiments were carried out to study the effects from KOH to ore mass ratio, particle size and roasting temperature on the degree of Ta and Nb recoveries. The roasting efficiency was found to be affected by all the parameters being studied with their optimal values being found as following: particle size range +75-45 µm, KOH to ore ratio 3/1, roasting temperature 550 °C and roasting duration of 1 hour. Under these conditions, 80% of Ta and 87% of Nb were recovered from the ore. The kinetic data analysis by different kinetic models indicated that the caustic potash roasting of the Numbi coltan ore is governed by a chemical reaction at particle surface. The apparent activation energies for Ta and Nb were estimated as 40.9 and 46.1 kJ.mol^(-1) respectively. The obtained results demonstrated that it is possible to bring Ta and Nb into solution without using hydrofluoric acid and deliver a pregnant leach solution (PLS) suitable for downstream treatment. [less ▲]

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See detailBioprocessing of spent lithium ion batteries for critical metals recovery – A review
Sethurajan, Manivannan ULiege; Gaydardzhiev, Stoyan ULiege

in Resources, Conservation and Recycling (2021), 165

The increasing demand for metals and the concomitant depletion of the primary metallic resources is one of the most important environmental and societal challenges nowadays. Critical metals, rare earth ... [more ▼]

The increasing demand for metals and the concomitant depletion of the primary metallic resources is one of the most important environmental and societal challenges nowadays. Critical metals, rare earth elements, base and precious metals demand is growing day-by-day and driving many metals towards the edge of supply risk. On the other hand, the problems linked to waste generation (especially waste electrical and electronic equipment (WEEE)) are also increasing globally. These end-of-life electronic wastes contain significant concentration of critical raw materials accompanied by harmful substances. Spent Li ion batteries is a kind of WEEE stream, bearing considerable concentrations of valuable metals (like Co, Li, Mn and Ni). If the end-of-life Li ion batteries are not managed properly, there is a high risk that these valuable metals and toxic substances could end into the environment. In order to address the environmental complications, sustainable resource management and boost circular economy, it is important to properly manage and recycle these spent Li ionbatteries. Conventional methods based on high-temperature pyro-metallurgical routes together with hydro-metallurgical processing have been widely studied for the recovery of metals from spent LiBs. However, bio-metallurgical approaches have an edge over their counter parts because of their environmentally friendly nature. Microbe-metal interactions have received special attention both in terms of leaching metals from WEEE and also in recovering metal ions from aqueous streams. Microbial technologies are promising for removing metal ions because of less cost, technical feasibility for large scale applications and no need for addition of toxic chemicals thereby avoiding generation of toxic or hazardous byproducts. In this study, particular emphasis is placed on reviewing the progress made in biohydrometallurgy (i.e. bacterial and fungal leaching practices as one and two-step mode) for the leaching of critical metals from waste lithium ion batteries. Biotechnological methods (e.g. biosorption, bioprecipitation and bioelectrochemical treatment) for the recovery of critical metals from pregnant leachates and aqueous streams are also discussed. [less ▲]

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See detailIncreased liberation and flotation performance of bulk copper flotation concentrate following its regrinding in a stirred media mill
Stefanov, Alexander; Grossman, Karsten; Peuker, Urs et al

in Proceedings of the XXX International Mineral Processing Congress (2021, January)

Flotation concentrate originating from the Asarel-Medet porphyry copper mining and processing complex in Bulgaria has been subjected to regrinding using a Ro-Star mill and the effects from which on the ... [more ▼]

Flotation concentrate originating from the Asarel-Medet porphyry copper mining and processing complex in Bulgaria has been subjected to regrinding using a Ro-Star mill and the effects from which on the downstream metallurgical behavior are discussed. Particularly the effect on the liberation degree was studied through an optical microscopy and MLA-SEM automated mineralogy. On the other side, copper selective flotation of the reground bulk concentrate was realized to evaluate the anticipated metallurgical improvement. Process parameters such as involvement of prior hydrocycloning and variation of collector dosage have been evaluated. Within a 2-minute residence time inside the Ro-Star mill, an improved liberation degree of the copper bearing minerals has been observed. As a consequence, enhanced copper recovery and selectivity against pyrite was noted. It has been found, that in order to guarantee efficient flotation of the resulting ultrafine particles a modified flotation regime (i.e. changing collector suite and dosages) should be followed. [less ▲]

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See detailCharacterisation and recovery of non-ferrous metals met in a copper-slag processed by flotation
Aatach, Mohamed ULiege; Kadiyski, Milen; Stoilov, Viktor et al

in XXX International Mineral Processing Congress, IMPC 2020 (2021)

Detailed process oriented characterisation on representative samples from plant survey of the slag flotation plant belonging to Aurubis, Bulgaria has been realised in order to evaluate the mineralogical ... [more ▼]

Detailed process oriented characterisation on representative samples from plant survey of the slag flotation plant belonging to Aurubis, Bulgaria has been realised in order to evaluate the mineralogical occurrences of Cu, Ni, Mo and Co bearing phases. The slag subjected to flotation consisted in majority of fayalite, magnetite-iron oxides and a glass-like phase. Ni and Mo have been found to be closely associated to magnetite and fayalite. The tailing from the slag flotation has been subjected to sulphation roasting followed by water leaching as a hydrometallurgical means to recover the remaining Cu, Mo, Ni and Co. Based on the various sulphation roasting conditions (acid dosage, duration, temperature) copper, nickel and cobalt were brought to solution to a different extent. Molybdenum was the most difficult to be rendered soluble due to its close association with iron, suspected to form an insoluble compound with it. Sulphation roasting performed at 350ºC has secured the best extraction degree for Cu, Mo and Co, while maximum recovery of Ni has been documented when roasting was done at 150°C. [less ▲]

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See detailA review on extractive metallurgy of tantalum and niobium
Shikika, Alidor; Sethurajan, Manivannan ULiege; Muvundja, Fabrice et al

in Hydrometallurgy (2020)

On-going technological developments, especially in the field of microelectronics and communication have reflected in concomitant increase in the demand for strategic metals such as tantalum (Ta) and ... [more ▼]

On-going technological developments, especially in the field of microelectronics and communication have reflected in concomitant increase in the demand for strategic metals such as tantalum (Ta) and niobium (Nb). The extraction of these two metals from ore deposits and secondary resources is based on the generic extractive metallurgical techniques known from the non-ferrous metals value chains. However, their operational particularities and especially the downstream refining remain a particular challenge. To this end, the existing and emerging processes from the Ta and Nb raw materials preparation and leaching to pure metals elaboration are reviewed. The upstream operations and the downstream extractive metallurgical processes are discussed. The different sub-processes making part of the hydrometallurgical processing of the two metals, including leaching and solvent extraction are described, with their advantages and limitations highlighted. The selective recovery of Ta and Nb from the leachates is most commonly realized by solvent extraction and stripping which are therefore extensively covered. In the same context, the most widely used and promising extractants are compared in the light of their separation efficiency and level of handling hazard. [less ▲]

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See detailCharacterisation and recovery of non-ferrous metals met in a copper-slag processed by flotation
Aatach, Mohamed ULiege; Kadiyski, Milen; Stoilov, Viktor et al

in Proceedings of the XXX International Mineral Processing Congress (2020, October)

Detailed process oriented characterisation on representative samples from plant survey of the slag flotation plant belonging to Aurubis, Bulgaria has been realized in order to evaluate the mineralogical ... [more ▼]

Detailed process oriented characterisation on representative samples from plant survey of the slag flotation plant belonging to Aurubis, Bulgaria has been realized in order to evaluate the mineralogical occurrences of Cu, Ni, Mo and Co bearing phases. The slag subjected to flotation consisted in majority of fayalite, magnetite-iron oxides and a glass-like phase. Ni and Mo have been found to be closely associated to magnetite and fayalite. The tailing from the slag flotation has been subjected to sulphation roasting followed by water leaching as a hydrometallurgical means to recover the remaining Cu, Mo, Ni and Co. Based on the various sulphation roasting conditions (acid dosage, duration, temperature) copper, nickel and cobalt were brought to solution to a different extent. Molybdenum was the most difficult to be rendered soluble due to its close association with iron, suspected to form an insoluble compound with it. Sulphation roasting performed at 350ºC has secured the best extraction degree for Cu, Mo and Co, while maximum recovery of Ni has been documented when roasting was done at 150°C. [less ▲]

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See detailCharacterisation and recovery of non-ferrous metals met in a copper-slag processed by flotation
Aatach, Mohamed ULiege; Kadiyski, Milen; Stoilov, Viktor et al

in Proceedings of the XXX International Mineral Processing Congress (2020, October)

Detailed process oriented characterisation on representative samples from plant survey of the slag flotation plant belonging to Aurubis, Bulgaria has been realized in order to evaluate the mineralogical ... [more ▼]

Detailed process oriented characterisation on representative samples from plant survey of the slag flotation plant belonging to Aurubis, Bulgaria has been realized in order to evaluate the mineralogical occurrences of Cu, Ni, Mo and Co bearing phases. The slag subjected to flotation consisted in majority of fayalite, magnetite-iron oxides and a glass-like phase. Ni and Mo have been found to be closely associated to magnetite and fayalite. The tailing from the slag flotation has been subjected to sulphation roasting followed by water leaching as a hydrometallurgical means to recover the remaining Cu, Mo, Ni and Co. Based on the various sulphation roasting conditions (acid dosage, duration, temperature) copper, nickel and cobalt were brought to solution to a different extent. Molybdenum was the most difficult to be rendered soluble due to its close association with iron, suspected to form an insoluble compound with it. Sulphation roasting performed at 350ºC has secured the best extraction degree for Cu, Mo and Co, while maximum recovery of Ni has been documented when roasting was done at 150°C. [less ▲]

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See detailInsights on the effect of pyrite liberation degree upon the acid mine drainage potential of sulfide flotation tailings
Mafra, Caroloina; Bouzahzah, Hassan ULiege; Stamenov, Lachezar et al

in Applied Geochemistry (2020), 23

A new insight into the way in which the mineralogical composition and texture of sulfides govern the geochemical behavior of the tailings in terms of acid mine drainage (AMD) generation is presented. Two ... [more ▼]

A new insight into the way in which the mineralogical composition and texture of sulfides govern the geochemical behavior of the tailings in terms of acid mine drainage (AMD) generation is presented. Two samples were taken from a tailings management facility. They were likewise subjected to flotation to recover reactive (liberated and middling) pyrite whilst the unreacted (locked) pyrite was kept in the tailings fraction. Geochemical (static and kinetic) tests were performed on the collected samples and tailings after flotation and a secondary electron microscope based automated mineralogy system (AM) was used to characterize them in terms of modal mineralogy, liberation degree and particle size. The absolute acidification potential (AP) defined by the Sobek method overestimates the effective AP when pyrite is partially locked. Hence, considering the locked pyrite may unfavorably lead to acidity overestimation and increased tailings management costs. Therefore, automated mineralogy data was used to calculate the effective AP of the tailings taking into account pyrite grade and its liberation degree. Based on the findings it could be assumed that the amount of lime required to neutralize the acidity produced by pyrite oxidation could be considerably reduced (in the studied case nearly 4 times) if environmental desulfurization by flotation is practiced and the liberation degree of the acid-producing minerals is taken into account. [less ▲]

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See detailCEReS – Co-processing of Coal Mine & Electronic Wastes: Novel Resources for a Sustainable Future
Bryan, Christopher; Williamson, Ben; Calus-Moszko, Johanna et al

in Hydrometallurgy (2020)

Most coal mines produce waste which has the potential to generate acid mine drainage (AMD). If not properly managed, this can cause environmental damage through contamination of ground and surface waters ... [more ▼]

Most coal mines produce waste which has the potential to generate acid mine drainage (AMD). If not properly managed, this can cause environmental damage through contamination of ground and surface waters and soils for hundreds of years. At the same time, the pace of technological development means that most electrical and electronic equipment becomes obsolete within a matter of years, resulting in the generation of vast quantities of electronic waste (e-waste). Where this cannot be recycled, it must be discarded. The CEReS project developed a co-processing approach for both waste streams to produce metals and other valuable products, and to reduce or eliminate the their environmental impact. This brings together two waste streams from opposite ends of the supply chain; turning each into a novel resource in a single, coherent ‘grave-to-cradle’ process. This industrial ecology approach is key to supporting a circular economy whilst securing the sustainable supply of critical raw materials. The project successfully elaborated a novel co-processing flow-sheet comprising: (i) the accelerated bioweathering of AMD-generating coal production wastes to generate a biolixiviant; (ii) the pyrolysis and catalytic cracking of low-grade PCBs to produce hydrocarbon fuel, a halogen brine and a Cu-rich char; (iii) the leaching of base metals from the char using the biolixiviant; (iv) the reuse of stabilised coal wastes; and (v) the full or partial (as enriched substrates) recovery of valuable metals. These individual process units were demonstrated individually at lab-pilot scale. The data were then used to validate the entire flow-sheet in an integrated process simulator and determine the economic balance. Finally, an LCA approach was used to demonstrate the environmental benefits of the CEReS process over the status quo. [less ▲]

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See detailBioleaching of metals from e-waste using immobilized biomass of mesophilic Acidithiobacillus ferrooxidans
Vardanyan, Arevik; Vardanyan, Narine; Gaydardzhiev, Stoyan ULiege

Conference (2019, October 22)

Among the secondary post-consumption wastes, e-wastes represent the fastest growing waste stream in the world being heterogeneous and diverse in terms of structure and composition. Consequently, it is ... [more ▼]

Among the secondary post-consumption wastes, e-wastes represent the fastest growing waste stream in the world being heterogeneous and diverse in terms of structure and composition. Consequently, it is difficult to feed such waste into conventional recycling streams. Biometallurgy could prove a competitive and applicable technique for recovering valuable metals from these materials. The objective of the study is to test the feasibility of biometallurgy for recycling secondary raw materials, rendering the presently uneconomic raw materials economically viable, thus contributing directly to the circular economy. Long-term objective is to study the peculiarities of bioleaching of secondary raw materials, reveal the role of bacteria in these processes and develop the concept on the mechanism of bioleaching of secondary raw materials. Comparative chemical leaching of printed circuit boards (PCBs) by ferric sulfate Fe2O12S3xH2Osolution and biogenic Fe3+ obtained by immobilized biomass ofAcidithiobacillus ferrooxidans 61 (Armenia) and Acidithiobacillus GR1 (Bulgaria) has been performed. The intensity of zero valent copper oxidation was correlated to the ratio of Fe3+/Fe2+ ions in the solution. It was revealed that recovery of metals from PCBs by biogenic Fe3+ occurred 2-3 times more intensively than that by Fe2O12S3xH2O solution. The use ofFe2O12S3xH2O solution for leaching of PCBs resulted in intensive precipitation of Fe3+ andgeneration of jarosite, while in case of biogenic Fe3+ the amount of jarosite was significantly lower. It is supposed that Fe3+ in biogenic solution is mainly in the form of complexes with organic compounds produced by bacteria, which prevent its precipitation as jarosite. It is as-sumed that chemical leaching by biogenic Fe3+ integrated into the processes of leaching of PCB's may contribute to intensification of extraction of copper and other valuable metals from different secondary resources. [less ▲]

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See detailBioleaching of Metals from Pyrolised Printed Circuit Boards using Coal as External Sulphur Source
Arinanda, Muhammad ULiege; van Haute, Quentin; Lambert, Fanny et al

Conference (2019, October 21)

Copper-rich char from pyrolysis of obsolete printed circuit boards (PCBs) was processed using bio- and hydrometallurgical means. Preliminary results demonstrated the potential of copper leaching using an ... [more ▼]

Copper-rich char from pyrolysis of obsolete printed circuit boards (PCBs) was processed using bio- and hydrometallurgical means. Preliminary results demonstrated the potential of copper leaching using an acidic, ferric iron lixiviant derived from coal waste containing pyrite and subjected to accelerated bioleaching. The presented results report on the role bacterial presence plays in the leaching system, the main challenge being to outline the optimal con-ditions under which bacteria survive in the harsh leaching environment. The results are highlighting the importance of finding an appropriate sulphur source to be added in the char leaching system in order to keep the moderate thermophile microbial consortia viable. Tail-ings fraction derived from gravity beneficiation of coal was chosen as such due to its sulphur content and in view of its reutilization potential. The influence of the coal addition degree (%wt ratio) to the char, on the dissolution of the zero valent metals (copper, aluminum) and bacterial activity was studied. Other process relevant parameters such as pH, redox potential and ferric-ferrous iron balance were followed as well. It was found out, that an addition of coal fraction, do stimulate bacterial activity inside the reactor which results in higher degree of copper dissolution (97%) after 168 hours, in comparison to the abiotic system (89%) and biotic system where coal is absent (93%) over the same time span. Although a very fine granulometric fraction of the coal was explicitly used, there was virtually no indication of metal back-sorption onto coal particles. The fact that copper was brought into solution by ferric iron at starting concentrations well below the stoichiometric requirement, implies bacterial regeneration of the ferric iron and its cycling in the system. [less ▲]

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See detailCEReS Deliverable 4.3: Extractive Metallurgy Unit Development Report
Arinanda, Muhammad ULiege; Gaydardzhiev, Stoyan ULiege

Report (2019)

WP4 Char Leaching aims to demonstrate the feasibility for utilisation of the acidic leachates (biolixiviant) generated from coal wastes bioleaching (WP3) as leaching agent for extraction of the base and ... [more ▼]

WP4 Char Leaching aims to demonstrate the feasibility for utilisation of the acidic leachates (biolixiviant) generated from coal wastes bioleaching (WP3) as leaching agent for extraction of the base and high-value metals contained in the char originating from the pyrolysis of PCB’s (WP2). The main tasks of this WP consist of three components: 1) investigation on the suitable reactor design and its working parameters for treating such material, which is unique compared to conventional materials treated in (bio)hydrometallurgy reactors, e.g. mineral ores, PCBs, etc., 2) exploring the option to extract metal(s) of interest and recover it/them to obtain a high-purity product, and 3) exploring the option to valorise the residue and excess iron in the char treatment system. Stirred-tank reactor (STR) is the most commonly employed since the early days of biohydrometallurgy campaigns, ranging from lab-scale to industries, treating from mineral ores to electronic wastes and residues. The main advantage of this type of reactor is achieving the desired levels of mass transfer, mixing, and agitation, in which STR outperforms other types of reactors. Due to that, STR has been given priority during WP4 of CEReS project. Despite the advantages, STR faces the challenge linked to the char’s special physical characteristics. The disintegration of fibres followed by their suspension inside reactor needs a careful hydrodynamic design to maintain sustained mixing and mass transfer. Moreover, the high shear stress of impeller rotation may harm the presence of biofilm, risking the elimination of microorganisms from the biolixiviant. As an alternative, leaching performance of rotary-drum reactor (RDR) has also been studied in this WP4. Step-leaching has also been studied in order to outline the possibility to increase the kinetic rate of copper dissolution by doing the leaching in several successive steps. Different from mineral ores, char (or pyrolyzed PCBs) contains various metals and elements, oftentimes in high grades. More often than not, the leaching of the char is non-selective, meaning that other than metals of interest, the un-desired ones should also be dissolved at high concentration. This is proven to be problematic for recovery stage, thus highlight the importance of extraction stage as intermediate between leaching and recovery. The solvent extraction stage consists of two steps; extraction step to transfer metal ions from solution (aqueous) to extractant (organic), and stripping step to transfer metal ions back from organic to aqueous. Concentrated metal ions in the aqueous phase are then transferred to recovery stage to produce metal product with high purity. This report will subsequently summarize the result on investigation of solvent extraction to produce concentrated electrolyte solution, followed by the results on recovery stage by electrowinning to produce metal product. The treatment of residues came after the char leaching and solvent extraction-electrowinning occurred. The residue from char leaching still contains fairly high grade of precious metals (gold, silver) as well as platinum group metals (PGMs). Although the processing of such by-products is not in the scope of CEReS, the possibility of such treatment has been explored in relation to CEReS applying the concept of biohydrometallurgy. The bleeding of iron from the system is important to maintain balanced level of accumulative iron from overall process, and has been explored by performing jarosite precipitation. [less ▲]

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See detailEffects of operational parameters on the bio-assisted leaching of metals from pyrolyzed printed circuit boards
Arinanda, Muhammad ULiege; van Haute, Quentin; Lambert, Fanny ULiege et al

in Minerals Engineering (2019), 134

End-of-life printed circuit boards have been subjected to proprietary pyrolysis resulting in a copper-rich char. This study details their downstream processing by hydrometallurgy for copper recovery. The ... [more ▼]

End-of-life printed circuit boards have been subjected to proprietary pyrolysis resulting in a copper-rich char. This study details their downstream processing by hydrometallurgy for copper recovery. The pyrolysed PCBs were reacted with two different bioleaching solutions containing mixed mesophilic microbial consortia and a synthetic chemical solution for comparative purposes. The influence of char pre-treatment, reactor type, working temperature, and the origin of leaching solution on the dissolution of the zero valent copper was studied. It was found, that the type of reactor had a more pronounced effect than the origin of bacterial solution in bringing copper in solution. Characterisation of the leached char confirmed the importance of the pre-treatment step. Other than ferric iron concentration and temperature, the leaching effciency and kinetics were largely influenced by the bacterial activity. The fact that copper was brought into solution by ferric iron at starting concentrations well below the stoichiometric requirement, implies bacterial regeneration of the ferric iron and its cycling in the system. [less ▲]

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See detailEffects of operational parameters on the bio-assisted leaching of metals from pyrolyzed printed circuit boards
Arinanda, Muhammad ULiege; van Haute, Quentin; Lambert, Fanny ULiege et al

in Minerals Engineering (2019), 134

End-of-life printed circuit boards have been subjected to proprietary pyrolysis resulting in a copper-rich char. This study details their downstream processing by hydrometallurgy for copper recovery. The ... [more ▼]

End-of-life printed circuit boards have been subjected to proprietary pyrolysis resulting in a copper-rich char. This study details their downstream processing by hydrometallurgy for copper recovery. The pyrolysed PCBs were reacted with two different bioleaching solutions containing mixed mesophilic microbial consortia and a synthetic chemical solution for comparative purposes. The influence of char pre-treatment, reactor type, working temperature, and the origin of leaching solution on the dissolution of the zero valent copper was studied. It was found, that the type of reactor had a more pronounced effect than the origin of bacterial solution in bringing copper in solution. Characterisation of the leached char confirmed the importance of the pre-treatment step. Other than ferric iron concentration and temperature, the leaching effciency and kinetics were largely influenced by the bacterial activity. The fact that copper was brought into solution by ferric iron at starting concentrations well below the stoichiometric requirement, implies bacterial regeneration of the ferric iron and its cycling in the system. [less ▲]

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See detailCoupling mineralogy with physicochemical parameters in view copper flotation efficiency improvement
Naumov, Dejan; Stamenov, Lachezar; Gaydardzhiev, Stoyan ULiege et al

in Physicochemical Problems of Mineral Processing (2019)

The Chelopech epithermal arsenic bearing high-sulphidation, copper-gold deposit located in Bulgaria is often considered as the richest European gold deposit. Selected physicochemical parameters have been ... [more ▼]

The Chelopech epithermal arsenic bearing high-sulphidation, copper-gold deposit located in Bulgaria is often considered as the richest European gold deposit. Selected physicochemical parameters have been measured at key flotation streams inside the processing plant. Sampling campaign has followed with samples being submitted to chemical analysis and MLA. Quantitative analysis has enabled to link copper flotation response to the type of copper bearing minerals and physiochemical parameters such as Eh, DO, EDTA extractable Cu and Fe. Data from mineral liberation analysis have highlighted an important process-relevant information explaining the variable floatability in different particle size ranges. The low chalcopyrite recovery can be linked to the non-sufficient amount of dissolved oxygen inside the copper selective flotation. Given the finely-disseminated copper bearing minerals, copper losses due to particle locking could be suggested as well. [less ▲]

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See detailInversigation on the flotation recovery of copper sulphosalts through an integrated mineralogical approach
Rincon Gamero, Jonathan Jose ULiege; Gaydardzhiev, Stoyan ULiege; Stamenov, Lachezar

in Minerals Engineering (2019), 130

Investigation on the flotation behaviour of enargite (Cu3AsS4) and tennantite ((Cu, Fe)12As4S13) during selective copper flotation was performed using an integrated mineralogical approach. To this end ... [more ▼]

Investigation on the flotation behaviour of enargite (Cu3AsS4) and tennantite ((Cu, Fe)12As4S13) during selective copper flotation was performed using an integrated mineralogical approach. To this end, samples taken from a production block at the Chelopech mine were subjected to a laboratory scale flotation and products characterized through multi-element chemical analyses and mineral mapping using a SEM-based automated mineralogy. Chemistry, modal mineralogy, copper-sulphosalts’ liberation and associations were quantified. Principal component analysis (PCA) was employed to look for relationships between mineralogical features and flotation recovery. High variability in head copper grade was observed in the studied block, with deportment results attributing it to the varied content of enargite and tennantite. Chalcopyrite content was low in the majority of the samples. The close association and the frequently observed interlocking of pyrite and Cu-sulphosalt grains can explain pyrite (and gold) recovery during copper cleaner flotation. Linear equations based on PCA results allow the prediction of Cu-sulphosalts’ recovery with a root mean square error of ±1.32%. [less ▲]

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See detailCoupling comminution indices and mineralogical features as an approach to a geometallurgical characterization of a copper ore
Rincon Gamero, Jonathan Jose ULiege; Gaydardzhiev, Stoyan ULiege; Stamenov, Lachezar

in Minerals Engineering (2019), 130

A production block of the underground mine exploiting the Chelopech high sulphidation epithermal copper-gold deposit was subjected to geometallurgical modelling. This study details the used procedure ... [more ▼]

A production block of the underground mine exploiting the Chelopech high sulphidation epithermal copper-gold deposit was subjected to geometallurgical modelling. This study details the used procedure based on traditional comminution and mineralogical indices. Drop weight and batch grinding tests were performed on representative samples to yield parameters related to Axb and operating work OWi indices. These were further correlated with the ore mineralogical features using principal component analysis. Modal mineralogy data processed by a set of linear equations has enabled the estimation of the aforementioned indices with a deviation of ±2.4 for Axb and ±9.08 kWh/t for OWi respectively. Based on ore textural characteristics and non-sulphide gangue (NSG) minerals content, two geometallurgical domains were identified as a first approach to modelling of the studied block [less ▲]

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See detailHSC SIM® simulation model of the assarel copper flotation circuit based on process mineralogy and metallurgical testing
Korolev, I.; Remes, A.; Stoilov, V. et al

in Chanturia, Vladimir (Ed.) Proceedings of the 29 International Mineral Processing Congress (2019)

The process modeling and simulation studies aim for better process operation and favorable environmental impact. The objective of this work is to set up a simulation model of the Assarel copper flotation ... [more ▼]

The process modeling and simulation studies aim for better process operation and favorable environmental impact. The objective of this work is to set up a simulation model of the Assarel copper flotation circuit for planning and optimization of the process with the aim of increased metal recovery. The model is parameterized based on laboratory flotation tests of ore samples from the Assarel mine together with mineralogical studies by X-ray diffraction (XRD) and Mineral Liberation Analysis (MLA). A combination of several techniques allows reliable identification of mineralogical composition of the selected samples. The changes in the proportion between sulfide minerals in various products along the circuit have been also documented. Further, this information is used in the simulation model and in data reconciliation procedures for establishing mass balance. The simulation accuracy is studied by comparing the simulations with the plant survey based mass balance. Constructed simulation model can be used to run alternative process scenarios. As an example, the flotation circuit performance with different reagent regimes is simulated based on data from batch flotation tests. Two reagents were considered for this purpose, dithiocarbamate-based one and xanthogen formate/mercaptan blend. It has been revealed that these reagents do not have the same influence on the selective flotation. The one improves flotation of gold and overall recovery but without notable selective action. In contrast, the other showed better selectivity towards copper, rejecting more gangue and lowering gold recovery. The model is also applicable for process optimization studies with different feed compositions, flowrates and circuit configurations. © IMPC 2018 - 29th International Mineral Processing Congress. All rights reserved. [less ▲]

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