Stoyan Gaydardzhiev

• University of Liège

We present an geometallurgical overview applied on Lithium deposit located in Manono , Republic Democratic of Congo

The use of Electro Dynamic Fragmentation (EDF) enables selective fragmentation of materials through generating electrical discharges as a means of fracturing. Liberated materials can be thus processed downstream in a more efficient way especially when value-added End-of-Life (EoL) electronic equipment is recycled. The aim of this study was to asses...

Electrodynamic fragmentation (EDF) is an innovative technique which enables selective fragmentation of material. Its inherent selective breakage principles enable liberation while avoiding fine grinding. In this study, the specific effects of the EDF on end-of-life printed wiring boards have been assessed. A novel methodology for their EDF processi...

The behavior of malachite and heterogenite was investigated during the process water recycling in flotation of copper-cobalt oxide ores from the deposit of Luiswishi located in Haut-Katanga province (DRC). A synthetic mill wastewater (SMWW) was utilized as feed water alone and in mixture with water recovered from the flotation tails in view to achi...

Laboratoryflotationtestswithcopper–cobaltoxidizedorefromtheLuiswishidepositinthe Katangaprovinceweredoneusingprocesswaterbeingrecycledtodifferentdegrees.Grade andrecoveryofcopperandcobaltwerefollowedby10,20and80%processtofreshwater additionwiththeresultsfromtheseconditionsbeingcomparedtothosewithoutwater recycling.Whenprocesswaterwasrecycledat10%,8...

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 (-208μm+147μm), ferrous iron concentration (1.25-10.0g/L) and pH (1.5-2.5) on copper leaching using m...

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 °...

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 chemoli...

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...

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 2...

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 concentrat...

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 900 °C for 1 h without or with lime or sodium hydroxide as roasting additives. When additives were used, cement ph...

The present study is devoted to improvement of the leaching efficiency during phosphorous removal from high phosphorous gravity-magnetic concentrate. Before leaching the concentrate has been subjected to roasting with the addition of either Ca(OH) 2 or CaO. The oolitic iron ore is roasted at 900°C for one hour. This reflects in reaction between alk...

The leaching step of an integrated hydrometallurgical process for the selective recovery of metals from polymetallic concentrates has been investigated. This concentrate has been produced by physical treatment of Fine Shredder Residues derived from a shredding plant processing a mixed feed of metallic scraps, waste electric equipments and end-of-li...

The oolitic iron ore reserves in Lisakovsky, North Kazakhstan represent quite a challenging deposit both from a technological and from a resource point of view. The diffi culties in processing such types of ore are connected with the extremely fi ne dissemination of phosphorus and gangue minerals inside the oolitic formations. The goethite crystals...

Results from the solvent extraction of copper and zinc from pregnant solutions after bioleaching of re-floated tailings from the Kipushi concentrator in DR of Congo are presented. LIX984N has been used as extractant for copper, while D2EHPA as such for zinc, following prior removal of the ferric iron via precipitation. The McCabe-Thiele diagrams co...

An experimental study aimed at re-flotation of laid down tailings from Kipushi (DRC) to bring sulphide concentrate suitable for further processing by hydrometallurgical means has been realized. The results from a bioleaching route chosen to accomplish the later task by use of moderate thermophilic and mesophilic microorganisms are reported. It has...

An approach using ceramic shaping by gel-casting and addition of natural tropical fibres as burnable pore developers has been explored for development of porous alumina materials with predetermined pore structures. The fibres used have been characterized in terms of size, shape, water uptake and surface charge. The degree of fibres loading in slurr...

The possibility of using natural fibres as template material for hollow ceramic tube manufacturing has been demonstrated. Two types of natural fibres have been used as template, which are hemp fibres and coconut fibres. Single fibres and fibre bundles have been coated with gel-cast slurry consisting of a 31 vol.% solid loaded nano-alumina and gelli...

The paper reports on the results of the study aimed at assessing of the influence of dispersant type on the electrochemical properties of highly concentrated alumina suspension. The relationship between the type of dispersant and the stabilization ability towards ultrafine alumina powder CT 3000 has been studied. The effectiveness was determined ma...

This paper deals with results from laboratory scale experiments with model dye effluents comprising of the commercially used textile diazo dye, CI “Reactive Black 5”, coagulated with ZETAG type primary coagulants. Size and structure analysis of flocs in coagulated dye sludge was undertaken in order to evaluate their separation abilities. The partic...

The choice of a reliable method for the testing of dispersant efficiency is an important issue in ceramics processing by emerging near net shape methods. The present paper presents the comparison of four methods for evaluation of the dispersibility properties of a commercial deflocculant Dolapix CE64, towards stabilization of submicron alumina powd...

The dispersing phenomenon of silicon nitride suspension has been investigated systematically by measuring surface charge density, sediment volume, and turbidity of the suspension. Dolapix A88 has been used as dispersant to improve the stability of the suspension, and assessed through measurement of the specific surface charge of the Si3N4 system. T...

The stability of a fumed aluminium oxide nano powder suspended in water has been assessed through measurement of zeta potential and streaming current, using the fact that the particles exhibit maximum repulsion at high magnitude of charge. Two commercial dispersants belonging to a Dolapix series have been tested. Dolapix CE 64 has shown a better de...

This article reports on results from a comparative study assessing a suitable method for dispersant efficiency evaluation in the case of water‐based suspensions of ultrafine alumina stabilized by a commonly used dispersant, Dolapix CE64. The following measurements were evaluated: zeta potential, specific surface charge, sedimentation behavior, and...

Chemical coagulation applied for colour removal from dye bearing solutions has been investigated from the point of view of surface charge progression. Two commercially used dyes, i.e. CI Acid Blue 113 and CI Disperse Blue 26 have been tested, employing three common coagulants: alum, aluminium chloride and ferric chloride. Coagulant type and dose le...