References of "Gaydardzhiev, Stoyan"
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See detailColour removal from wastewater by means of microbial treatment
Janeczko, M.; Georgiev, P.; Nicolova, M. et al

in Fecko, P. (Ed.) 10-th Conference on Environment and Mineral Processing (2006)

Water solutions of different dyes used in textile industry (Reactive Black 5, Acid Orange 7 and Disperse Yellow 5) were treated under laboratory conditions by means of different microorganisms or their ... [more ▼]

Water solutions of different dyes used in textile industry (Reactive Black 5, Acid Orange 7 and Disperse Yellow 5) were treated under laboratory conditions by means of different microorganisms or their metabolites. The following organisms were used in this study: Bacillus megatherium, B.subtilus, B.circulans, activated sludge from industrial w. w. teratment plant and a mixed enriched culture of flocculating bacteria. It was find out that the microbial effect towards the dyes was quite specific and the extent of colour removal varied in broad range. Very good results were achieved also by means of permeable reactive barriers inhabitated by flocculating bacteria and other independent microorganisms and operating under continuous flow conditions. The colour removal in these case varied in the range of about 80 - 90 % and was similar to that achieved by the well known chemical reagents used in the textile industry. [less ▲]

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See detailComparative studies of dispersant optimisation techniques for evaluating the stability of concentrated alumina slurries
Gaydardzhiev, Stoyan ULg; Ay, Peter; Janeczko, Marta

in Particle & Particle Systems Characterization (2006), 23

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See detailSize and structure characterization of dye flocs during chemical coagulation of Reactive Black 5 dye
Janeczko, Marta; Gaydardzhiev, Stoyan ULg

in Particle & Particle Systems Characterization (2006), 23

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See detailStabilization of aqueous silicon nitride suspension with Dolapix A 88
Singh, Bimal; Gaydardzhiev, Stoyan ULg; Ay, Peter

in Journal of Dispersion Science & Technology (2006), 27(1), 91-97

The dispersing phenomenon of silicon nitride suspension has been investigated systematically by measuring surface charge density, sediment volume and turbidity of the suspension. Dolapix A 88 has been ... [more ▼]

The dispersing phenomenon of silicon nitride suspension has been investigated systematically by measuring surface charge density, sediment volume and turbidity of the suspension. Dolapix A 88 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. The isoelectric point (iep) of Si3N4 powder has been found to be at pHiep = 6.91 and there was no shift in iep due to presence of dispersant indicating that the interaction between the powder and the dispersant Dolapix A88 is purely physisorbing in nature. Good agreement has been observed between dispersion characteristics, surface charge and streaming potential inflection. The paper also describes the selection and optimisation of the dispersant in controlling stability of an aqueous suspension of Si3N4. It can be concluded from this investigation that the PCD technique for measurement of specific surface charge can be conveniently used for the assessment of dispersibility of ceramic suspension in both dilute as well as in concentrated suspensions [less ▲]

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See detailCharacterisation of aqueous suspensions of fumed aluminium oxide in presence of two Dolapix dispersants
Gaydardzhiev, Stoyan ULg; Ay, Peter

in Journal of Materials Science (2006), 41

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 ... [more ▼]

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 deflocculating action than Dolapix A 88. The iso electric point of the powder suspension has been found close to pH 9. A notable shift in the pH of iso electric point when Dolapix CE 64 was present, indicating that the interaction between particles and dispersant has involved chemical sorption. It has been found out, that at the relative low solids loading studied and within the limits of the pH measurement accuracy, a dispersant supplied in dose levels from 12 to 24 mg/g, has confined the pHiep to a relatively narrow range. A capillary suction time technique has been tried for evaluation of suspension fluidity as function of dispersant concentration and pH. For the dispersant stabilised suspensions, a correlation between their CST and pHiep has been documented [less ▲]

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See detailEvaluation of dispersant efficiency for aqueous alumina slurries by concurrent techniques
Gaydardzhiev, Stoyan ULg; Ay, Peter

in Journal of Dispersion Science & Technology (2006), 27(3), 413-417

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See detailColour removal from model solutions by coagulation - surface charge and floc characterisation aspects
Gaydardzhiev, Stoyan ULg; Karthikeyan, J.; Ay, P.

in Environmental Technology (2006), 27

Chemical coagulation applied for colour removal from dye bearing solutions has been investigated from point of view of surface charge progression. Two commercially used dyes, i.e. CI Acid Blue 113 and CI ... [more ▼]

Chemical coagulation applied for colour removal from dye bearing solutions has been investigated from 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 level and pH of the dye solution have been studied as process parameters affecting surface charge and degree of colour removal after filtration of coagulated dye. It has been found, that both dyes could be almost completely removed with the tested coagulants, when supplied however at different dosages. From one side, the correlation between surface charge and colour removal suggests that destabilization of colour colloids occurs as a result of charge neutralization followed by removal by filtration. From other side, the lack of re-stabilization and continued high colour removal even at increased coagulant dosages implies enmeshment of destabilized dye colloids into the hydroxy flocs/precipitates of metal coagulant by “sweep coagulation”. Finally, flocs from selected sludge samples have been examined for particle size and shape by image analysis and their key characteristics summarised [less ▲]

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See detailImplication of surface charge effects in color removal from effluents by chemical coagulation - the case of CI Reactive Blue 4 dye
Gaydardzhiev, Stoyan ULg; Ay, Peter

in Pratsinis, S. (Ed.) Proceeedings CD of Partec 2004 Inetrnational Congress of Particle Technology (2004, March)

Characterisation of dye flcos during colour removal from synthetic waste water is presented. Surface charge and floc size and shapes are measured and an implications towards the predominant removal ... [more ▼]

Characterisation of dye flcos during colour removal from synthetic waste water is presented. Surface charge and floc size and shapes are measured and an implications towards the predominant removal emchanisms is made. [less ▲]

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See detailMineralogical characteristics of copper flotation products from Cayeli mine, Turkey and their influence to mineral processing
Strashimirov, S.; Dobrev, S.; Stamenov, S. et al

in Annual of the University of Mining and Geology, Sofia, 47, I, 147-153 (2004)

The paper presents mineralogical characteristics and pecularities of minerals distribution in products from Cu cycle of clastic ore mineral processing in Cayeli concentrator, Turkey. Special attention has ... [more ▼]

The paper presents mineralogical characteristics and pecularities of minerals distribution in products from Cu cycle of clastic ore mineral processing in Cayeli concentrator, Turkey. Special attention has been drawn to the mineralogical pecularities of sphalerite. The study has covered 16 samples from Cu flotation feed, Cu rougher concentrate, Cu final concentrate and tailing, each sieved in 4 granulometric classes. Significant quantity of sphalerite charactarized by higher amount of Cu and Fe as isomorphic impurities or extemely fine crystals of chalcopyrite are present in the Cu concentrate. Based on the performed studies, an improvement in the processing circuit has been suggested - especially in the grinding and hydrocycloning circuits. [less ▲]

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See detailSurface charge studies - an important approach for investigation of color removal from textile wastewaters by chemical coagulation
Gaydardzhiev, Stoyan ULg; Ay, P.

in Rao; Misra (Eds.) MPT 2004 Conference Proceedings (2003)

Results concerning surface charge characterizations of coagulated dye with an aim to evaluate the predominant destabilization mechanism taking place during colour removal by chemical coagulation are ... [more ▼]

Results concerning surface charge characterizations of coagulated dye with an aim to evaluate the predominant destabilization mechanism taking place during colour removal by chemical coagulation are presented. A model wastewater comprising of commercially used dye with a CI “Reactive Red 2” was studied. The effect of the combination coagulant/flocculant on colour removal by filtration and sedimentation was evaluated in terms of progression of sludge surface charge. On that basis, an implications about the predominant colour removal mechanisms have been drawn. On selected sludge samples, floc characterisations in terms of size by laser scattering and shape were performed. The measurement techniques used have encompassed for particle size and Small Angle Light Scattering (SALS) for fractal dimension. [less ▲]

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See detailImprovement of a syllabus on environmental protection designed for mineral and mining engineering students in Bulgaria
Gaydardzhiev, Stoyan ULg

in 6th International auDes Conference Bridging Minds & Markets, Venice, 5 – 7 April 2001 (2001)

The University of Mining and Geology in Sofia as a unique academic Institution engaged in training graduates to work in the field of mining and geological prospecting faces the need for modification and ... [more ▼]

The University of Mining and Geology in Sofia as a unique academic Institution engaged in training graduates to work in the field of mining and geological prospecting faces the need for modification and updating its curriculum, for being able to meet the challenges of European educational standards like Institution accreditation, ECTS, etc. In a smaller scale, this is particularly relevant to the Department of Mineral Processing which is one of the largest Departments (in the University) and is engaged in training students for the entire raw materials (non-petroleum) industry: ores, coal and industrial minerals. Despite the drastic reduction in great number undergraduate specialisations, the specialization “Mineral Processing” remains in the Governmental Register released by the Ministry of Education, Science and Technologies. Therefore in this new situation, there is a necessity to verify and to parallel the existing syllabus to the one practiced in a similar Departments in the EU countries and more precisely to develop undergraduate and graduate courses to include risk and hazard assessment, environmental protection and related matters. [less ▲]

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See detailThiourea leaching of gold bearing mine wastes from Madjarovo processing plant in SE Bulgaria
Gaydardzhiev, Stoyan ULg

in Nath, B. (Ed.) Proceedings of NATO ARW “Sustainable Solid Waste Management in the Southern Black Sea Region”, September 1999, Sofia, Bulgaria (2000)

Flotation tailings derived from processing of complex sulphide gold-bearing ores have been repropcessed by means of thiourea leaching. Before leaching takes place the materials has been subjected to ... [more ▼]

Flotation tailings derived from processing of complex sulphide gold-bearing ores have been repropcessed by means of thiourea leaching. Before leaching takes place the materials has been subjected to magnetic separation, flotattion and hydrocloric leaching. An environmental and economic benefits could be expected provided the approach is implementyed on site. [less ▲]

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See detailOn the influence of the disturbed conditions in the centrifugal concentration of heavy fine particles
Patchejieff, B.; Gaydardzhiev, Stoyan ULg; Stoev, S.

in Ozbayoglu, G. (Ed.) Proceedings of the 8-th IMPS Antalya, Turkey, 16-18 X 2000, 167-170 (2000)

Model investigations were carried out with the aim to improve the method for accelerated gravity separation of heavy fine mineral particles. The effects of feed particle size has been studied with the aim ... [more ▼]

Model investigations were carried out with the aim to improve the method for accelerated gravity separation of heavy fine mineral particles. The effects of feed particle size has been studied with the aim to generate disturbed conditions inside the riffle zones of a bowl-type centrifuge and thus to avoid material packing leading to better separation conditions. [less ▲]

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See detailNatural clinoptiolite in contaminated soil and effluent handling
Gaydardzhiev, Stoyan ULg

in Salatic, D. (Ed.) Proceedings of the 8th Balkan Conference on Mineral Processing, Belgrade, Yugoslavia (1999)

Natural zeolite has been used as adsorbent for heavy metals from effluents and as soil ammendment for imobilzation of phytotoxic heavy metals. The principal technological factors being investigated were ... [more ▼]

Natural zeolite has been used as adsorbent for heavy metals from effluents and as soil ammendment for imobilzation of phytotoxic heavy metals. The principal technological factors being investigated were pH, soil/zeolite ratio and zeolite granulometry. A second order regression analysis has been used to outline their influence on th degree of metal immobilisation. [less ▲]

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See detailMagnetically supported zeolite adsorbents for effluent treatment
Pramatarova, R.; Gaydardzhiev, Stoyan ULg

in Gaballah, Hager and Solozabal (Ed.) REWAS’99 - Proceedings of the Global Symposium on Recycling, Waste treatment and Clean Technology, San Sebastian, Spain, 2469-2474. (1999)

Zeolite adsorbents packed in magnetic carrier beds have been used for metals removal from synthetic multielemental effluent solution. Prolonged operation of the bed at high mass transfer rates and good ... [more ▼]

Zeolite adsorbents packed in magnetic carrier beds have been used for metals removal from synthetic multielemental effluent solution. Prolonged operation of the bed at high mass transfer rates and good regeneration degree have been achieved. Some of the loaded zeolite samples have been subjected to X-ray mapping for revealing the adsorption mechanism. [less ▲]

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See detailMicroscopic and laser granulometric analyses of hydrating cement suspensions
Lilkov, V.; Dimitrova, E.; Gaydardzhiev, Stoyan ULg

in Cement & Concrete Research (1999), 29

The results from microscopic and laser granulometric analyses of hydrating cement suspensions, containing active mineral additives are presented. Conclusions are drawn about the specific hydration ... [more ▼]

The results from microscopic and laser granulometric analyses of hydrating cement suspensions, containing active mineral additives are presented. Conclusions are drawn about the specific hydration processes of the investigated cements, as well as the applicability of laser granulometry for the study of cement and hydration products. [less ▲]

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See detailApplication of zeolite minerals as an in-situ amendments for heavy metals polluted soils
Gaydardzhiev, Stoyan ULg; Atanasov, S.

in Pasamehmetoglu and Ozgenoglu (Ed.) Proceedings of SWEMP’98, International Symposium (1998)

Metal fixation from simulated rain water onto zeolite adsorbents has been studies using a column filtration mode. Further on, soil artificially contaminated with heavy metals have been brought into ... [more ▼]

Metal fixation from simulated rain water onto zeolite adsorbents has been studies using a column filtration mode. Further on, soil artificially contaminated with heavy metals have been brought into contact with the zeolites. The loaded adsorbents have been studied via IR spectroscopy wih the aim to reveal the predominant mechanism of metal uptake. [less ▲]

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See detailHydrometallurgy of precious metals - effects on the environment
Gaydardzhiev, Stoyan ULg

in Gallios and Matis (Ed.) Proceedings of a NATO-ASI, NATO-ASI Series 2, v. 43 (1998)

Factors which affect the release of toxic substabces to the environment during the hydrometallurgical processing of precious metals bearing ores are discussed. The environmental notions of the cyanidation ... [more ▼]

Factors which affect the release of toxic substabces to the environment during the hydrometallurgical processing of precious metals bearing ores are discussed. The environmental notions of the cyanidation process are presented together with a review about the work in the field of alternative gold lixiviants. [less ▲]

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See detailCoal-gold agglomeration of alluvial gold
Gaydardzhiev, Stoyan ULg; Kireva, R.; Stoev, S.

in Kemal, Arslan, Akar and Canbazoglu (Ed.) Proceeding of VI-th International Mineral Processing Symposium (1996)

The study concerns feasibility testing of the coal-gold agglomeration process as alternative to the amalgamation for upgrading of alluvial gold fractions found in a dredge line. Different process ... [more ▼]

The study concerns feasibility testing of the coal-gold agglomeration process as alternative to the amalgamation for upgrading of alluvial gold fractions found in a dredge line. Different process parameters such as oild and coal type, coal/oil and agglomerates/gold ratio have been varied with the aim to optimise the degree of gold recovery. The addition of quartz and heavy mineral particles in the slury in view outlining process selectivity is also discussed. [less ▲]

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See detailOpportunities for using two low-cost methods for treatment of metal bearing aqueous streams
Gaydardzhiev, Stoyan ULg; Hadjihristova, M.; Tichy, R.

in Minerals Engineering (1996), 9

The feasibility of two non-traditional approaches - reedbeds as a natural wetland and adsorption on lignite and its maceral fractions - for their application in metal bearing effluent treatment is ... [more ▼]

The feasibility of two non-traditional approaches - reedbeds as a natural wetland and adsorption on lignite and its maceral fractions - for their application in metal bearing effluent treatment is discussed. The main mechanisms of metals uptake are otulined. The preliminary results from a pilot scale wetland operation for metallurgical effluents purification are analysed. For the second approach - the different maceral fractions derived from coal refining have shown different metal uptake apptitude. Zeta potential studies and adsorption isotherms have explained these findings. [less ▲]

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