References of "Gaydardzhiev, Stoyan"
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See detailIntegration of Composites for Greener Engine - Rapport scientifique & technique
Aatach, Mohamed ULg; Gaydardzhiev, Stoyan ULg

Report (2016)

The project's objective is to achieve a greater integration of composite materials in the low-pressure compressor, major product of Techspace Aero. The recycling of composite materials is one of the main ... [more ▼]

The project's objective is to achieve a greater integration of composite materials in the low-pressure compressor, major product of Techspace Aero. The recycling of composite materials is one of the main parts of this project. The focus is on the review of technologies, reuse and resulting properties on the recycling of fibre reinforced polymers and the development of new processes for end-of-life aerospace grade advanced carbon fiber reinforced composite materials (electrodynamic and conventional fragmentation, physicochemical characterization, environmental impact assessment, etc.) [less ▲]

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See detailIntegration of Composites for Greener Engine - Rapport scientifique & technique
Aatach, Mohamed ULg; Gaydardzhiev, Stoyan ULg

Report (2015)

The project's objective is to achieve a greater integration of composite materials in the low-pressure compressor, major product of Techspace Aero. The recycling of composite materials is one of the main ... [more ▼]

The project's objective is to achieve a greater integration of composite materials in the low-pressure compressor, major product of Techspace Aero. The recycling of composite materials is one of the main parts of this project. The focus is on the review of technologies, reuse and resulting properties on the recycling of fibre reinforced polymers and the development of new processes for end-of-life aerospace grade advanced carbon fiber reinforced composite materials (electrodynamic and conventional fragmentation, physicochemical characterization, environmental impact assessment, etc.) [less ▲]

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See detailERA-NET ECO-INNOVERA - Fragmentation électrodynamique des matériaux composites à haute valeur ajoutée contenant des substances récupérables - EDF-HVC: Rapport scientifique & technique annuel
Martino, Rémi ULg; Gaydardzhiev, Stoyan ULg

Report (2015)

The EDF-HVC project aims in evaluating the feasibility of electrodynamic fragmentation application to process end-of-life devices such as waste electrical and electronic equipments and secondary resources ... [more ▼]

The EDF-HVC project aims in evaluating the feasibility of electrodynamic fragmentation application to process end-of-life devices such as waste electrical and electronic equipments and secondary resources such as MSW incineration slags, EoL high-end composites, etc. Different target materials will be processed under varying operating parameters and characterized respectively, before and after a selective fragmentation in order to optimize the method and evaluate its economical and environmental perspectives. [less ▲]

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See detailEffects of process water recycling during flotation of copper and cobalt oxidised ores from Luiswishi deposit in the Democratic Republic of Congo
Shengo, Michel; Gaydardzhiev, Stoyan ULg; Kalenga, Pierre

in Desalination and Water Treatment (2015), 55(7), 117

Laboratory flotation tests with copper–cobalt oxidized ore from the Luiswishi deposit in the Katanga province were done using process water being recycled to different degrees. Grade and recovery of ... [more ▼]

Laboratory flotation tests with copper–cobalt oxidized ore from the Luiswishi deposit in the Katanga province were done using process water being recycled to different degrees. Grade and recovery of copper and cobalt were followed by 10, 20 and 80% process to fresh water addition with the results from these conditions being compared to those without water recycling. When process water was recycled at 10%, 83.7% copper and 84.1% cobalt were recovered at the rougher stage bringing the cleaner stage to a concentrate with recovery of 53 and 60% for copper and cobalt, respectively. However, recycling process water, up to 20 and 80%, has reduced the recovery of copper in the final concentrate to 23 and 6%, respectively, and of cobalt to 46 and 27%, respectively. Monitoring of dissolved oxygen content, pulp pH and Es potential during flotation, coupled with thermodynamic estimation of the predominant chemical compounds in the system, has enabled to evaluate the effects on flotation from the undesirable compounds’ formation during process water recycling. DRIFT spectroscopy was used to identify the nature of the chemical compounds formed on malachite and heterogenite surface during their sulphidisation in the presence of thiosulphate ions. Thiosulphate ions depending on their concentration could promote or hinder malachite and heterogenite flotation by inducing changes in pulp physicochemical parameters or by altering mineral surface properties. [less ▲]

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See detailCopper extraction from coarsely ground printed circuit boards using moderate thermophilic bacteria in a rotating-drum reactor
Rodrigues, Michael; Leão, Versiane; Gomes, Otavio et al

in Waste Management (2015), 41

The current work reports on a new approach for copper bioleaching from Printed Circuit Board (PCB) by moderate thermophiles in a rotating-drum reactor. Initially leaching of PCB was carried out in shake ... [more ▼]

The current work reports on a new approach for copper bioleaching from Printed Circuit Board (PCB) by moderate thermophiles in a rotating-drum reactor. Initially leaching of PCB was carried out in shake flasks to assess the effects of particle size ( 208 lm + 147 lm), ferrous iron concentration (1.25–10.0 g/L) and pH (1.5–2.5) on copper leaching using mesophile and moderate thermophile microorganisms. Only at a relatively low solid content (10.0 g/L) complete copper extraction was achieved from the particle size investigated. Conversely, high copper extractions were possible from coarse-ground PCB (20 mm-long) working with increased solids concentration (up to 25.0 g/L). Because there was as the faster leaching kinetics at 50 C Sulfobacillus thermosulfidooxidans was selected for experiments in a rotating-drum reactor with the coarser-sized PCB sheets. Under optimal conditions, copper extraction reached 85%, in 8 days and microscopic observations by SEM–EDS of the on nonleached and leached material suggested that metal dissolution from the internal layers was restricted by the fact that metal surface was not entirely available and accessible for the solution in the case of the 20 mm-size sheets. [less ▲]

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See detailCOPPER LEACHING FROM WASTE ELECTRIC CABLES BY BIOHYDROMETALLURGY
Lambert, Fanny ULg; Bastin, David ULg; Gaydardzhiev, Stoyan ULg et al

in Minerals Engineering (2015)

This study examines the leaching of copper from waste electric cables by chemical leaching and leaching catalysed by Acidithiobacillus ferrooxidans in terms of leaching kinetics and reagents consumption ... [more ▼]

This study examines the leaching of copper from waste electric cables by chemical leaching and leaching catalysed by Acidithiobacillus ferrooxidans in terms of leaching kinetics and reagents consumption. Operational parameters such as the nature of the oxidant (Fe3+, O2), the initial ferric iron concentration (0-10 g/L) and the temperature (21-50°C) were identified to have an important influence on the degree of copper solubilisation. At optimal process conditions, copper extraction above 90% was achieved in both leaching systems, with a leaching duration of 1 day. The bacterial leaching system slightly outperformed the chemical one but the positive effect of regeneration of Fe3+ was limited. It appears that the Fe2+ bio-oxidation is not sufficiently optimised. Best results in terms of copper solubilisation kinetics were obtained for the abiotic test at 50°C and for the biotic test at 35°C. Moreover, the study showed that in same operating conditions, a lower acid consumption was recorded for the biotic test than for the abiotic test. [less ▲]

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See detailIntegration of Composites for Greener Engine - Rapport scientifique & technique
Aatach, Mohamed ULg; Gaydardzhiev, Stoyan ULg

Report (2015)

The project's objective is to achieve a greater integration of composite materials in the low-pressure compressor, major product of Techspace Aero. The recycling of composite materials is one of the main ... [more ▼]

The project's objective is to achieve a greater integration of composite materials in the low-pressure compressor, major product of Techspace Aero. The recycling of composite materials is one of the main parts of this project. The focus is on the review of technologies, reuse and resulting properties on the recycling of fibre reinforced polymers and the development of new processes for end-of-life aerospace grade advanced carbon fiber reinforced composite materials (electrodynamic and conventional fragmentation, physicochemical characterization, environmental impact assessment, etc.) [less ▲]

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See detailSEM and EDS observations of carrollite bioleaching with a mixed culture of acidophilic bacteria
Nkulu, Guy; Gaydardzhiev, Stoyan ULg; Mwema, Edouard et al

in Minerals Engineering (2015), doi:10.1016/j.mineng.2014.12.005

Bioleaching of high purity carrollite minerals with mesophilic bacteria was carried out and monitored by observations in scanning electron microscopy (SEM) and elemental X-ray microanalysis (EDS) to ... [more ▼]

Bioleaching of high purity carrollite minerals with mesophilic bacteria was carried out and monitored by observations in scanning electron microscopy (SEM) and elemental X-ray microanalysis (EDS) to provide evidence of the interaction pattern between carrollite and microorganisms. A bacterial consortium involving three different acidophilic chemolithotrophs was adopted. The evolution of the surface topography, inside alteration effects and elemental composition of the mineral with leaching time was followed. It could be postulated that bacterial adhesion takes place on the mineral surface, resulting in the formation of dissolution pits of various shapes and continues by boring elongated channels deep inside the mineral grains. Enhanced concentration of ferric iron and sulphur could be assumed in vicinity of the zones where mineralized polymer substances are precipitated. It could be inferred that carrollite dissolution is governed by cooperative bioleaching involving oxidation induced by bacteria attached to the surface and ferric iron re-oxidized by planktonic bacteria in suspension. [less ▲]

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See detailPossibilities for Co(III) dissolution from an oxidized ore through simultaneous bioleaching of pyrite
Zeka, Leon; Lambert, Fanny ULg; Frenay, Jean ULg et al

in Minerals Engineering (2015)

Solubilisation of Co(III) from a heterogenite met in copper cobaltiferous oxide ore has been realized through reductive leaching using ferrous iron generated via bio-oxidation of pyrite. Biotic and ... [more ▼]

Solubilisation of Co(III) from a heterogenite met in copper cobaltiferous oxide ore has been realized through reductive leaching using ferrous iron generated via bio-oxidation of pyrite. Biotic and abiotic experiments at various pulp densities and redox potentials have been performed and results compared. Cobalt leaching at elevated redox potential is possible, offering cost reduction benefits due to reduced consumption of ferrous iron. At elevated potential of 625 mV, however, the initial rate of cobalt leaching has been found as 115 mg/(g ore)⋅(24 h), lower than the rate of 865 mg/(g ore)⋅(24 h) registered at 505 mV. Less stochiometric amount of ferrous iron was required when cobalt leaching was coupled to pyrite bioleaching, with 75% of cobalt recovered for 12 h at the optimally found conditions. It could be inferred that the Fe3+–Fe2+ cycle exists and is efficiently maintained through bacterial presence in the studied system. [less ▲]

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See detailPhysicochemical observations during process water reuse in flotation of oxide copper-cobalt ore
Shengo, Michel; Gaydardzhiev, Stoyan ULg; Kalenga, Pierre

in Yianatos, Juan (Ed.) Proceedings of the XXVII International Mineral Processing Congress (2014, October 20)

Lab-scale flotation of copper and cobalt oxidized ore from the Luiswishi deposit in the Katanga province (DRC) has been done focusing on the influence of the degree of process water recycling on metals ... [more ▼]

Lab-scale flotation of copper and cobalt oxidized ore from the Luiswishi deposit in the Katanga province (DRC) has been done focusing on the influence of the degree of process water recycling on metals recovery. Results have shown that at 20 % recycling rate, the recovery of copper and cobalt in the cleaner stage have been respectively reduced to 23 % and 45 % in comparison to 53 % Cu and 63 % Co if process water has not been recycled. At 10 % recycling rate however, the system could still tolerate the effect from recycling, since Cu and Co recovery has remained respectively at acceptable levels of 52 % and 60 %. In order to explain the reasons for the observed worsening of flotation results if process water was recycled at rate higher than 20 %, electrochemical investigation of the pulp has been performed. It has been established that the chemical compounds formed in the pulp when process water was recycled, do influence the sulfidization of malachite and heterogenite and impact further collector adsorption. To confirm these assumptions, the effect from thiosulphate ions presence during the sulfidization of high purity malachite has been studied. It has been found, that thiosulphate ions depending on their concentration in water induce variations in pulp properties such as DO content, pH, Es and contribute to formation of undesirable chemical compounds on mineral surface as identified by DRIFT spectroscopy. [less ▲]

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See detailInsights upon the adsorption mechanism of KAX on malachite
Kanda, Jean-Marie; Kongolo, Mukendi; Gaydardzhiev, Stoyan ULg et al

in Yianatos, Juan (Ed.) Proceedings of the XXVII International Mineral Processing Congress (2014, October 20)

The adsorption patterns of potassium amylxanthate on the surface of high purity malachite subjected to prior sulfidization with NaSH have been followed and elucidated. DRIFTS spectroscopy has been used to ... [more ▼]

The adsorption patterns of potassium amylxanthate on the surface of high purity malachite subjected to prior sulfidization with NaSH have been followed and elucidated. DRIFTS spectroscopy has been used to trace the associated physicochemical alterations as well as the chemical species present on the mineral surface. Varying the collector concentration from 5.10-4 to 1.10-2 mol/L has led to different degree of surface coverage of the alkyl groups in combination with formation of organometallic hydrophobic complexes of CuX and CuX – X2 type. The results reveal that the CuX complex formed on the malachite surface without sulfidizing agent is more unstable and prone to dissolution-precipitation phenomena. Based upon the constructed adsorption isotherms and upon the degree of statistical coverage, different zones of mineral-reagent interactions could be distinguished. They correspond respectively to the monolayer, bi-layer and tridimensional condensation domains. In each of the identified zones mono or double layer adsorption patterns of the collector are proposed leading respectively to formation of surface compounds with different degree of hydrophobicity. [less ▲]

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See detailAssessment of water quality effects on flotation of copper-cobalt oxide ore
Shengo, Michel; Gaydardzhiev, Stoyan ULg; Kalenga, Pierre

in Minerals Engineering (2014), 65

Results from lab scale flotation show that when process water was re-used copper and cobalt recovery from an oxidized ore decreased respectively with 25 and 30 percent at the rougher stage bringing lower ... [more ▼]

Results from lab scale flotation show that when process water was re-used copper and cobalt recovery from an oxidized ore decreased respectively with 25 and 30 percent at the rougher stage bringing lower grade concentrate as well. The presence of thiosulphate ions contributed to slow down of NaHS consumption during sulphidization of pure malachite and hindered collector adsorption. Elevated concentration of thiosulphate ions affected malachite surface properties and induced dissolution effects. DRIFT spectroscopy on activated malachite enabled to reveal the effects of thiosulphate ions presence with hydrophilic species being identified. [less ▲]

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See detailCharacterization of printed circuit boards from scrap printers
Silvas, Flávia; de Moraes, Viviane; Bortolini, Guilherme et al

in Yurko, James; Zhang, Lifeng; Allanore, Antoine (Eds.) Proceedings TMS 2014 143rd ANNUAL MEETING & EXHIBITION (2014, April)

Printed circuit boards (PCB) are particularly problematic to recycle because of the heterogeneous mix of organic materials, metals, and glass fiber. PCBs are found in almost every electroelectronic ... [more ▼]

Printed circuit boards (PCB) are particularly problematic to recycle because of the heterogeneous mix of organic materials, metals, and glass fiber. PCBs are found in almost every electroelectronic equipment and their recycling process involves a pre-treatment to separate the products which contain targeted metals. In this work, a physical processing involving sequential shredding and hammer milling were used to obtain a comminuted sample from scrap printers PCBs. The thus prepared sample was analyzed for particle size distribution and by optical microscopy as well was subjected to pyrolysis, leachabilty and chemical composition determination by XRF. The metals concentration was determined by ICP and AAS. The PCBs have been also analyzed by SEM-EDS (micro-analysis and X-ray mapping). The results show that the studied PCBs are lead free, multilayer with 4 copper layers, have 45% of metals and the copper is present in significantly higher concentration than the rest of the metals. [less ▲]

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See detailBiolixiviação de cobre contido em placas de circuito impresso (pci) com micro-organismos mesófilos.
Rodrigues, M; Gaydardzhiev, Stoyan ULg; Lopes, K et al

in Silva, André Carlos; Silva, Elenice Maria Schons (Eds.) ANAIS PROCEEDINGS (2013, October)

This work investigated the bioleaching of electronic waste, specifically printed circuit boards (PCB). The bio-assisted leaching was carried out with At. ferrooxidans in shake flasks in order to evaluate ... [more ▼]

This work investigated the bioleaching of electronic waste, specifically printed circuit boards (PCB). The bio-assisted leaching was carried out with At. ferrooxidans in shake flasks in order to evaluate the influence of presence of microorganisms on the dissolution of metallic copper. The effects of the initial Fe2+ concentration and the presence of pyrite, as a source of iron, on copper dissolution were analyzed. The experiments were performed in an orbital shaker under the following conditions: 34°C, stirring speed of 150 min-1, particle size below 420μm and 0.5% solids percent (w/v). The results indicated high extraction, around 100%, and proved the feasibility of copper recovering from PCB through bioleaching. [less ▲]

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See detailThe influence of grinding media alloys on the flotation performances at Ellatsite plant (Bulgaria)
Bastin, David ULg; Gaydardzhiev, Stoyan ULg; Jacques, Simon et al

in Proceedings of the XV Balkan Mineral Processing Congress (2013, June)

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See detailOverview of technologies for mineral/metal recuperation – challenges and technological gaps
Gaydardzhiev, Stoyan ULg

Conference given outside the academic context (2013)

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See detailAmenability for processing of oolitic iron ore concentrate for phosphorus removal
Ionkov, Krassimir ULg; Gaydardzhiev, Stoyan ULg; Correa de Araujo, Armando et al

in Minerals Engineering (2013), 46-47

Beneficiation routes aimed at dephosphorisation of oolitic gravity magnetic concentrate and involving a combination of roasting, re-grinding, magnetic separation and water and acid leaching are ... [more ▼]

Beneficiation routes aimed at dephosphorisation of oolitic gravity magnetic concentrate and involving a combination of roasting, re-grinding, magnetic separation and water and acid leaching are investigated. Roasting was carried out at 900ºC for one hour without or with lime or sodium hydroxide as roasting additives. When additives were used, cement phases of Si-Al-Na-Ca-O type were detected as well as the mineral giuseppettite. During the thermal process sodium silicate is liquefied and the newly formed phases coat the oolites and penetrate inside the cracks. Energy Dispersive Spectroscopy analysis has indicated that the zone surrounding the oolites consists of Na, Al and Si phases with part of phosphorus being captured there. As a result of the alkaline roasting, goethite is partly transformed to magnetite and this reduction is reinforced with an increase in sodium hydroxide dosage. Investigation of redistribution of phosphorous shows that it could be only partly separated if leaching is not accompanied by re-grinding and physical separation. The recommended dosage of the reductive agent for the final flowsheet is 8 % mass ratio to concentrate. Grinding to a mean size of 0.040 mm, with water and acid leaching and double magnetic separation creates conditions to obtain a high-quality iron concentrate with 65.97 % Fe and recovery of 92.43 %, with simultaneous decrease in the phosphorus content from 0.71 % to 0.05 %. [less ▲]

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See detailClean Coal Technologies and Carbon Capture and Storage in Kazakhstan – Reflections and ACCESS project results
Nesladek,, Milos; Helsen, S; Piessens, Kris et al

Book published by Royal Belgian Institute of Natural Sciences (2013)

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See detailStatistical analysis of bioleaching copper, cobalt and nickel from polymetalic concentrate originating from Kamoya deposit in the Democratic Republic of Congo
Nkulu, Guy; Gaydardzhiev, Stoyan ULg; Mwema, Edouard

in Minerals Engineering (2013), 48

The effects of five parameters, temperature, pH, leaching duration, stirring speed and pulp density on the bioleaching of copper, cobalt and nickel from a polymetallic flotation concentrate were ... [more ▼]

The effects of five parameters, temperature, pH, leaching duration, stirring speed and pulp density on the bioleaching of copper, cobalt and nickel from a polymetallic flotation concentrate were investigated. The leaching was carried out according to the L25 (55) orthogonal design. The optimal values of the parameters were determined using a Taguchi method through signal-to-noise analysis. ANOVA was applied to verify the individual contribution of each parameter and their degree of significance. It was found out that pulp density was the most influential factor on the bioleaching yield of the three metals altogether, followed by pH and temperature. For the copper bioleach, the following optimal parameters were determined: temperature - 37.5 °C, pH 1.6, leaching duration - 20 days, stirring speed - 350 rpm and pulp density - 7.5%. Verification experiments conducted according to these optimal parameters brought copper yield of 72.6%. For the cobalt bioleach, SEM observations of pure carrollite indicated a progressive bacterial colonization of mineral surface with time. [less ▲]

Detailed reference viewed: 98 (14 ULg)