Dusica Vucinic - Academia.edu (original) (raw)

Papers by Dusica Vucinic

Research paper thumbnail of Mechanism of stearic acid adsorption to calcite

Powder Technology, 2013

ABSTRACT This paper presents the interpretation of binding mechanism of stearic acid for calcite ... more ABSTRACT This paper presents the interpretation of binding mechanism of stearic acid for calcite surface in two modification methods.In the “dry” method, a surface dissociation of stearic acid is assumed where H+ ion goes to a surface carbonate ion and stearic ion is chemisorbed on primary surface center of − Ca+ ion which is only available for chemisorption. The structure of adsorbed layer indicates chemisorption of stearate, but due to steric effects, and the oblique or gauche conformation of hydrocarbon chains. A part of surface − Ca+ centers can be blocked, which is explained by the result that physical adsorption dominates over 1.5%.In the “wet” method, by adding stearic acid, at concentration above the critical concentration of micelle formation in base solution, micelles are formed, and on the other side free stearic acid molecules or molecules from developed micelle dissociate. The resulting stearic ions can be chemisorbed on primary centers of − Ca+ ions or participate in ion exchange with OH− ions from secondary surface centers. With increasing adsorption density, the adsorbed ions and molecules, due to interactions of hydrocarbon chains, and thickness of double electrical layer, achieve a vertical orientation and keep the trans-conformation of hydrocarbon chains.

Research paper thumbnail of PVC mixtures’ mechanical properties with the addition of modified calcite as filler

Hemijska industrija, 2012

In this study mechanical properties of PVC mixtures (PVC, stabilizer, lubricant, filler) such as ... more In this study mechanical properties of PVC mixtures (PVC, stabilizer, lubricant, filler) such as tensile strength, tensile elongation, breaking strength, and breaking elongation were investigated. Unmodified calcite, as well as calcite modified by stearic acid, were used as fillers in wet and dry processes. The PVC mixtures containing the calcite modified by wet procedure have better mechanical properties compared to those with the calcite modified by the dry process. Tensile and breaking strength of the PVC mixture containing the calcite modified with 1.5% stearic acid using wet process, are higher for 2.8% and 5.2%, respectively, compared to the PVC mixture containing the calcite modified with the same amount of acid used in the dry process. The tensile strength difference between the mixtures increases with the increase of the concentration of used stearic acid up to 3%. The strength of PVC mixture with the calcite modified by wet process is 3.1% higher compared to the mixture co...

Research paper thumbnail of 10.5937/mmeb1402131r = Definition the technology method of apatite flotation concentration from the phosphate deposit 'Lisina

Mining and Metallurgy Engineering Bor, 2014

This paper presents the importance of phosphate in the world, and the problems that arise in the ... more This paper presents the importance of phosphate in the world, and the problems that arise in the process of preparing the low-grade phosphate ore for obtaining the phosphate concentrate using the flotation concentration. The apatite concentrates are obtained using the selective flotation from the silicate and oxide minerals while defining the process of selective flotation of apatite from carbonate deposits is the major problem worldwide. The experimental part of this paper presents the results of laboratory flotation tests of phosphate ore from the surface part of the location "Panjevica" of the deposit "Liina". The results have enabled definition of the flotation process in continuous conditions of work.

Research paper thumbnail of Surface Properties of Natural Calcite Filler Treated With Stearic Acid

Ceramics– …, 2009

Page 1. Original papers 268 Ceramics – Silikáty 53 (4) 268-275 (2009) SURFACE PROPERTIES OF NATUR... more Page 1. Original papers 268 Ceramics – Silikáty 53 (4) 268-275 (2009) SURFACE PROPERTIES OF NATURAL CALCITE FILLER TREATED WITH STEARIC ACID SLAVICA MIHAJLOVIĆ, ŽIVKO SEKULIĆ, ALEKSANDRA DAKOVIĆ ...

Research paper thumbnail of Effect of Na2O/SiO2 mole ratio on the crystal type of zeolite synthesized from coal fly ash

Journal of the Serbian Chemical Society, 2003

Coal fly ash was modified to zeolitic materials by hydrothermal treatment at 90 ?C. The zeolite s... more Coal fly ash was modified to zeolitic materials by hydrothermal treatment at 90 ?C. The zeolite synthesis was studied as a function of the mole ratio of Na2O/SiO2 in the reaction mixtures. The results showed that NaP1 zeolite is obtained when the Na2O/SiO2 mole ratio was 0.7. Hydroxysodalite is the dominant zeolite phase in modified fly ash treated with a higher Na2O concentration solution (Na2O/SiO2 = 1.3). The IR and XRD methods were used to determine the phases present in the starting sample and in the zeolitic materials.

Research paper thumbnail of Influence of the modification method on the surface adsorption of stearic acid by natural calcite

Journal of the Serbian Chemical Society, 2010

In order to obtain hydrophobic materials, the surface of natural limestone with the high content ... more In order to obtain hydrophobic materials, the surface of natural limestone with the high content of calcite was treated with different amounts (0.5, 1, 1.5, 2, 3 and 4 %) of stearic acid. Two methods were used for the modification: the solution and the dry coating methods. Using the solution method, it was suggested that at lower initial concentrations of stearic acid, the surfactant monomers initially sorbed forming a monolayer on the calcite surface, which then in the presence of excess surfactant develops into a bilayer configuration. When the dry coating method was applied, some form of bilayer existed on the calcite surface, even when the amount of stearic acid was low. The effect of surface modification by both methods was evaluated by the floating test, which represents the ratio of the floating product to the overall weight of the sample after mixing in water and stirring vigorously. This ratio is called the active ratio. Measurement of the active ratio showed that at the lowest surface coverage of calcite with stearic acid, the active ratio for the solution method was 65.5 % and 55.5 % for dry coating. Using the solution method, an active ratio over 99.9 % was achieved with 1.5 % stearic acid, while by dry coating, the same active ratio was obtained with 3 % stearic acid.

Research paper thumbnail of Electrokinetic properties of hydroxyapatite under flotation conditions

Journal of Colloid and Interface Science, 2010

The effect of calcite supernatant, calcium, and carbonate ions on the hydroxyapatite (HA) zeta po... more The effect of calcite supernatant, calcium, and carbonate ions on the hydroxyapatite (HA) zeta potential without and in the presence of sodium oleate (1x10(-4) mol L(-1)) was examined within the pH range from 4 to 12. The interpretation of results was based on the HA surface and oleate solution chemistry, and on some floatability tests. HA, with different positive and negative surface sites formed depending on its solubility and pH, had a negative zeta potential over the whole pH range. This mineral is not naturally floatable (flotation recovery, 5%<R<18%). The oleate ions (Ol(-)), present in a very low concentration in an acidic medium (pH from 4.8 to 6), chemisorb individually on HA surface centers [triple bond]Ca(+), [triple bond]HPO(4)Ca(+), and [triple bond]OH(2)(+), increasing the negative zeta potential of the mineral. Within the pH range from 7 to 9, the dominant oleate species Ol(-) ion and ion-molecule complex, H(Ol)(2)(-), adsorbed on HA by head groups toward the solid and associated due to chain-chain interaction in hemimicelles, made the HA surface with zeta potential about -22/-23 mV, and more floatable (R=80-100%) than in 4<pH<7 (R=15-35%) or in pH>9.3. The HA surface is less negatively charged in calcite supernatant than in water from pH 6.6 to 9.2 due to the adsorption on HA negative surface active centers ([triple bond]HPO(4)(-) and [triple bond]PO(4)(2-)) of the Ca(2+), and CaOH(+) ions (present in the calcite supernatant), producing more surface sites [triple bond]HPO(4)Ca(+), [triple bond]PO(4)Ca, [triple bond]HPO(4)CaOH, and [triple bond]PO(4)(-) CaOH, and new centers [triple bond]HPO(4)CaHCO(3) and [triple bond]PO(4)(-) CaHCO(3). In the presence of 1x10(-3) mol L(-1) CaCl(2), the HA sample has positive zeta potential, the same as calcite from the same deposit, up to IEP at pH 11.25. Carbonate ions (1x10(-3) mol L(-1) Na(2)CO(3)) do not affect the HA zeta potential. However, a possible process can be the ion-exchange reaction between bicarbonate (or carbonate) and some anion from the surface sites formed on HA. The obtained values of the HA zeta potential with the collector (1x10(-4) mol L(-1) Na-oleate) added into hydroxyapatite/calcite supernatant suspensions corroborate the weak chemisorption of Ol(-) and H(Ol)(2)(-). The likely processes in this system also are the ion-exchange reactions on [triple bond]HPO(4)CaOH and [triple bond]PO(4)(-) CaOH, [triple bond]HPO(4)CaHCO(3) and [triple bond]PO(4)(-) CaHCO(3) between oleate ion and surface hydroxyl and bicarbonate ions, surface and bulk precipitations of calcium oleate, Ca(Ol)(2), and the surface and bulk precipitations of Ca[H(Ol)(2)(-)](2) over the pH range from 7 to 9. Calcite supernatant does not influence natural floatability of the mineral. However, calcite supernatant depresses the hydroxyapatite flotation in the presence of 1x10(-4) mol L(-1) Na-oleate (pH 9, R approximately 50%), a likely result of the weak chemisorption due to the steric effect of heterogeneous HA surface formed in calcite supernatant, Ca(Ol)(2) and Ca[H(Ol)(2)(-)](2) surface and bulk precipitations.

Research paper thumbnail of Effect of dissolved lead ions on the ethylxanthate adsorption on sphalerite in weakly acidic media

International Journal of Mineral Processing, 1989

ABSTRACT

Research paper thumbnail of Ethyl xanthate adsorption and adsorption kinetics on lead-modified galena and sphalerite under flotation conditions

Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2006

... Trahar et al. [23] found sphalerite floated upon addition of lead ions up to pH 9. Also, Houo... more ... Trahar et al. [23] found sphalerite floated upon addition of lead ions up to pH 9. Also, Houot and Raveneau [22] and Rey and Formanek [48] observed increased sphalerite recovery in bath flotation tests when galena and oxidized lead minerals were added. ...

Research paper thumbnail of Influence of the modification method on the surface adsorption of stearic acid by natural calcite

Journal of The Serbian Chemical Society, 2010

In order to obtain hydrophobic materials, the surface of natural limestone with the high content ... more In order to obtain hydrophobic materials, the surface of natural limestone with the high content of calcite was treated with different amounts (0.5, 1, 1.5, 2, 3 and 4 %) of stearic acid. Two methods were used for the modification: the solution and the dry coating methods. Using the solution method, it was suggested that at lower initial concentrations of stearic acid, the surfactant monomers initially sorbed forming a monolayer on the calcite surface, which then in the presence of excess surfactant develops into a bilayer configuration. When the dry coating method was applied, some form of bilayer existed on the calcite surface, even when the amount of stearic acid was low. The effect of surface modification by both methods was evaluated by the floating test, which represents the ratio of the floating product to the overall weight of the sample after mixing in water and stirring vigorously. This ratio is called the active ratio. Measurement of the active ratio showed that at the lowest surface coverage of calcite with stearic acid, the active ratio for the solution method was 65.5 % and 55.5 % for dry coating. Using the solution method, an active ratio over 99.9 % was achieved with 1.5 % stearic acid, while by dry coating, the same active ratio was obtained with 3 % stearic acid.

Research paper thumbnail of Mechanism of stearic acid adsorption to calcite

Powder Technology, 2013

ABSTRACT This paper presents the interpretation of binding mechanism of stearic acid for calcite ... more ABSTRACT This paper presents the interpretation of binding mechanism of stearic acid for calcite surface in two modification methods.In the “dry” method, a surface dissociation of stearic acid is assumed where H+ ion goes to a surface carbonate ion and stearic ion is chemisorbed on primary surface center of − Ca+ ion which is only available for chemisorption. The structure of adsorbed layer indicates chemisorption of stearate, but due to steric effects, and the oblique or gauche conformation of hydrocarbon chains. A part of surface − Ca+ centers can be blocked, which is explained by the result that physical adsorption dominates over 1.5%.In the “wet” method, by adding stearic acid, at concentration above the critical concentration of micelle formation in base solution, micelles are formed, and on the other side free stearic acid molecules or molecules from developed micelle dissociate. The resulting stearic ions can be chemisorbed on primary centers of − Ca+ ions or participate in ion exchange with OH− ions from secondary surface centers. With increasing adsorption density, the adsorbed ions and molecules, due to interactions of hydrocarbon chains, and thickness of double electrical layer, achieve a vertical orientation and keep the trans-conformation of hydrocarbon chains.

Research paper thumbnail of PVC mixtures’ mechanical properties with the addition of modified calcite as filler

Hemijska industrija, 2012

In this study mechanical properties of PVC mixtures (PVC, stabilizer, lubricant, filler) such as ... more In this study mechanical properties of PVC mixtures (PVC, stabilizer, lubricant, filler) such as tensile strength, tensile elongation, breaking strength, and breaking elongation were investigated. Unmodified calcite, as well as calcite modified by stearic acid, were used as fillers in wet and dry processes. The PVC mixtures containing the calcite modified by wet procedure have better mechanical properties compared to those with the calcite modified by the dry process. Tensile and breaking strength of the PVC mixture containing the calcite modified with 1.5% stearic acid using wet process, are higher for 2.8% and 5.2%, respectively, compared to the PVC mixture containing the calcite modified with the same amount of acid used in the dry process. The tensile strength difference between the mixtures increases with the increase of the concentration of used stearic acid up to 3%. The strength of PVC mixture with the calcite modified by wet process is 3.1% higher compared to the mixture co...

Research paper thumbnail of 10.5937/mmeb1402131r = Definition the technology method of apatite flotation concentration from the phosphate deposit 'Lisina

Mining and Metallurgy Engineering Bor, 2014

This paper presents the importance of phosphate in the world, and the problems that arise in the ... more This paper presents the importance of phosphate in the world, and the problems that arise in the process of preparing the low-grade phosphate ore for obtaining the phosphate concentrate using the flotation concentration. The apatite concentrates are obtained using the selective flotation from the silicate and oxide minerals while defining the process of selective flotation of apatite from carbonate deposits is the major problem worldwide. The experimental part of this paper presents the results of laboratory flotation tests of phosphate ore from the surface part of the location "Panjevica" of the deposit "Liina". The results have enabled definition of the flotation process in continuous conditions of work.

Research paper thumbnail of Surface Properties of Natural Calcite Filler Treated With Stearic Acid

Ceramics– …, 2009

Page 1. Original papers 268 Ceramics – Silikáty 53 (4) 268-275 (2009) SURFACE PROPERTIES OF NATUR... more Page 1. Original papers 268 Ceramics – Silikáty 53 (4) 268-275 (2009) SURFACE PROPERTIES OF NATURAL CALCITE FILLER TREATED WITH STEARIC ACID SLAVICA MIHAJLOVIĆ, ŽIVKO SEKULIĆ, ALEKSANDRA DAKOVIĆ ...

Research paper thumbnail of Effect of Na2O/SiO2 mole ratio on the crystal type of zeolite synthesized from coal fly ash

Journal of the Serbian Chemical Society, 2003

Coal fly ash was modified to zeolitic materials by hydrothermal treatment at 90 ?C. The zeolite s... more Coal fly ash was modified to zeolitic materials by hydrothermal treatment at 90 ?C. The zeolite synthesis was studied as a function of the mole ratio of Na2O/SiO2 in the reaction mixtures. The results showed that NaP1 zeolite is obtained when the Na2O/SiO2 mole ratio was 0.7. Hydroxysodalite is the dominant zeolite phase in modified fly ash treated with a higher Na2O concentration solution (Na2O/SiO2 = 1.3). The IR and XRD methods were used to determine the phases present in the starting sample and in the zeolitic materials.

Research paper thumbnail of Influence of the modification method on the surface adsorption of stearic acid by natural calcite

Journal of the Serbian Chemical Society, 2010

In order to obtain hydrophobic materials, the surface of natural limestone with the high content ... more In order to obtain hydrophobic materials, the surface of natural limestone with the high content of calcite was treated with different amounts (0.5, 1, 1.5, 2, 3 and 4 %) of stearic acid. Two methods were used for the modification: the solution and the dry coating methods. Using the solution method, it was suggested that at lower initial concentrations of stearic acid, the surfactant monomers initially sorbed forming a monolayer on the calcite surface, which then in the presence of excess surfactant develops into a bilayer configuration. When the dry coating method was applied, some form of bilayer existed on the calcite surface, even when the amount of stearic acid was low. The effect of surface modification by both methods was evaluated by the floating test, which represents the ratio of the floating product to the overall weight of the sample after mixing in water and stirring vigorously. This ratio is called the active ratio. Measurement of the active ratio showed that at the lowest surface coverage of calcite with stearic acid, the active ratio for the solution method was 65.5 % and 55.5 % for dry coating. Using the solution method, an active ratio over 99.9 % was achieved with 1.5 % stearic acid, while by dry coating, the same active ratio was obtained with 3 % stearic acid.

Research paper thumbnail of Electrokinetic properties of hydroxyapatite under flotation conditions

Journal of Colloid and Interface Science, 2010

The effect of calcite supernatant, calcium, and carbonate ions on the hydroxyapatite (HA) zeta po... more The effect of calcite supernatant, calcium, and carbonate ions on the hydroxyapatite (HA) zeta potential without and in the presence of sodium oleate (1x10(-4) mol L(-1)) was examined within the pH range from 4 to 12. The interpretation of results was based on the HA surface and oleate solution chemistry, and on some floatability tests. HA, with different positive and negative surface sites formed depending on its solubility and pH, had a negative zeta potential over the whole pH range. This mineral is not naturally floatable (flotation recovery, 5%<R<18%). The oleate ions (Ol(-)), present in a very low concentration in an acidic medium (pH from 4.8 to 6), chemisorb individually on HA surface centers [triple bond]Ca(+), [triple bond]HPO(4)Ca(+), and [triple bond]OH(2)(+), increasing the negative zeta potential of the mineral. Within the pH range from 7 to 9, the dominant oleate species Ol(-) ion and ion-molecule complex, H(Ol)(2)(-), adsorbed on HA by head groups toward the solid and associated due to chain-chain interaction in hemimicelles, made the HA surface with zeta potential about -22/-23 mV, and more floatable (R=80-100%) than in 4<pH<7 (R=15-35%) or in pH>9.3. The HA surface is less negatively charged in calcite supernatant than in water from pH 6.6 to 9.2 due to the adsorption on HA negative surface active centers ([triple bond]HPO(4)(-) and [triple bond]PO(4)(2-)) of the Ca(2+), and CaOH(+) ions (present in the calcite supernatant), producing more surface sites [triple bond]HPO(4)Ca(+), [triple bond]PO(4)Ca, [triple bond]HPO(4)CaOH, and [triple bond]PO(4)(-) CaOH, and new centers [triple bond]HPO(4)CaHCO(3) and [triple bond]PO(4)(-) CaHCO(3). In the presence of 1x10(-3) mol L(-1) CaCl(2), the HA sample has positive zeta potential, the same as calcite from the same deposit, up to IEP at pH 11.25. Carbonate ions (1x10(-3) mol L(-1) Na(2)CO(3)) do not affect the HA zeta potential. However, a possible process can be the ion-exchange reaction between bicarbonate (or carbonate) and some anion from the surface sites formed on HA. The obtained values of the HA zeta potential with the collector (1x10(-4) mol L(-1) Na-oleate) added into hydroxyapatite/calcite supernatant suspensions corroborate the weak chemisorption of Ol(-) and H(Ol)(2)(-). The likely processes in this system also are the ion-exchange reactions on [triple bond]HPO(4)CaOH and [triple bond]PO(4)(-) CaOH, [triple bond]HPO(4)CaHCO(3) and [triple bond]PO(4)(-) CaHCO(3) between oleate ion and surface hydroxyl and bicarbonate ions, surface and bulk precipitations of calcium oleate, Ca(Ol)(2), and the surface and bulk precipitations of Ca[H(Ol)(2)(-)](2) over the pH range from 7 to 9. Calcite supernatant does not influence natural floatability of the mineral. However, calcite supernatant depresses the hydroxyapatite flotation in the presence of 1x10(-4) mol L(-1) Na-oleate (pH 9, R approximately 50%), a likely result of the weak chemisorption due to the steric effect of heterogeneous HA surface formed in calcite supernatant, Ca(Ol)(2) and Ca[H(Ol)(2)(-)](2) surface and bulk precipitations.

Research paper thumbnail of Effect of dissolved lead ions on the ethylxanthate adsorption on sphalerite in weakly acidic media

International Journal of Mineral Processing, 1989

ABSTRACT

Research paper thumbnail of Ethyl xanthate adsorption and adsorption kinetics on lead-modified galena and sphalerite under flotation conditions

Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2006

... Trahar et al. [23] found sphalerite floated upon addition of lead ions up to pH 9. Also, Houo... more ... Trahar et al. [23] found sphalerite floated upon addition of lead ions up to pH 9. Also, Houot and Raveneau [22] and Rey and Formanek [48] observed increased sphalerite recovery in bath flotation tests when galena and oxidized lead minerals were added. ...

Research paper thumbnail of Influence of the modification method on the surface adsorption of stearic acid by natural calcite

Journal of The Serbian Chemical Society, 2010

In order to obtain hydrophobic materials, the surface of natural limestone with the high content ... more In order to obtain hydrophobic materials, the surface of natural limestone with the high content of calcite was treated with different amounts (0.5, 1, 1.5, 2, 3 and 4 %) of stearic acid. Two methods were used for the modification: the solution and the dry coating methods. Using the solution method, it was suggested that at lower initial concentrations of stearic acid, the surfactant monomers initially sorbed forming a monolayer on the calcite surface, which then in the presence of excess surfactant develops into a bilayer configuration. When the dry coating method was applied, some form of bilayer existed on the calcite surface, even when the amount of stearic acid was low. The effect of surface modification by both methods was evaluated by the floating test, which represents the ratio of the floating product to the overall weight of the sample after mixing in water and stirring vigorously. This ratio is called the active ratio. Measurement of the active ratio showed that at the lowest surface coverage of calcite with stearic acid, the active ratio for the solution method was 65.5 % and 55.5 % for dry coating. Using the solution method, an active ratio over 99.9 % was achieved with 1.5 % stearic acid, while by dry coating, the same active ratio was obtained with 3 % stearic acid.