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Papers by Vakhtang Gabunia
Preparation of Ultradispersed Crystallites of Modified Natural Clinoptilolite with the Use of Ultrasound and Its Application as a Catalyst in the Synthesis of Methyl Salicylate, Feb 6, 2017
The ultradispersed crystallites (300 – 325 nm) of the acid modified natural clinoptilolite (CL, ν... more The ultradispersed crystallites (300 – 325 nm) of the acid modified natural clinoptilolite (CL, ν(SiO2)/ν(AI2O3) = 8.9) from Dzegvi (Georgia) deposit with the use of simplest method – of the indirect effect of ultrasound – were prepared. Under the influence of ultrasound the happening changes of structure and the sizes of clinoptilolite particles are shown, by the XRD, FTIR spectroscopy and by means of laser particle size analyzer, respectively. Catalytic activities of the initial acid form of the clinoptilolite (H–CL, ν(SiO2)/ν(AI2O3) = 23.3) and its form processed by ultrasound (H–CL (UlS)) in reaction of esterification of salicylic acid by methanol into methyl salicylate were compared. The indirect irradiation with ultrasound of acid form of clinoptilolite has led to sharp improve its catalytic properties in the formation of methyl salicylate. The best catalytic performance is achieved with ultrasound treated catalyst. The conversion of the salicylic acid and the selectivity to m...
Advanced Science, Engineering and Medicine, 2015
The synthesis of gold nanoparticles by cells of the thermoacidophilic archaeon Sulfolobus islandi... more The synthesis of gold nanoparticles by cells of the thermoacidophilic archaeon Sulfolobus islandicus for technological purposes has been studied. A complex of optical and analytical methods has been used in order to characterize produced nanoparticles. It was shown that in the biomass of Sulfolobus islandicus the extracellular as well as intracellular formation of gold nanoparticles of spherical shape with sizes in the range of 20–80 nm (50 nm average) takes place. Energy-dispersive analysis of X-rays was used for examining the elemental content of the Sulfolobus islandicus biomass. Neutron activation analysis and atomic absorption spectrometry have been applied for characterizing the dynamics of gold accumulation in the Sulfolobus islandicus biomass. It was shown that the growing formation of gold nanoparticles in the biomass of Sulfolobus islandicus takes place mainly at few hours. The ultrasound was applied for intensification production of gold nanoparticles by biomass of Sulfol...
The present paper studies hydrothermal transformation of natural zeolites analcime and phillipsit... more The present paper studies hydrothermal transformation of natural zeolites analcime and phillipsite, widespread in Georgia, in order to obtain valuable products. It is found that phasepure zeolite NaA with Si/Al~1 can be prepared in the form of cubic/rhombus crystallites with uniform micrometric (3-5 μm) dimensions by hydrothermal crystallization of aged at room temperature gel (4.5Na2O: 0.45Al2O3: 1SiO2: 178H2O) obtained from natural analcime, treated with hydrochloric acid before suspending in water and mixing with sodium hydroxide. Phase-pure zeolite NaX with Si/Al~1.5 can be prepared in the form of octahedral crystallites with uniform micrometric (2-7 μm) dimensions by hydrothermal crystallization of aged at room temperature gel (2.9Na2O: 0.26Al2O3: 1SiO2: 150H2O) obtained from water suspension of natural phillipsite, treated with hydrochloric acid and mixed with sodium hydroxide. Crystal structure of both zeolites is testified by X-ray diffraction patterns and infra-red spectra....
Nano zero-valent iron (nZVI) is widely used to remediate groundwater and wastewater from heavy me... more Nano zero-valent iron (nZVI) is widely used to remediate groundwater and wastewater from heavy metals and stable organic pollutants (Permeable Reactive Barriers). This is caused by the fact that Fe0 reduces several halogenous hydrocarbons, chlorine-containing pesticides, organic dyes, nitrozo compounds, explosives and others. The restoring ability is used for reduction of CrO4-2, Cr2O7-2, ClO4-, NO3- ions and elimination of Hg+2, Ni+2,Cd+2, Pb+2 as well as of a number of radionuclides from water. nZVIs had found wide application in the USA but in Europe this method appeared later. The cost of these methods for remediation of water depends on many factors (type of pollution, cost of reagents, the purpose and degree of remediation, remediation methods and other). That is why revealing of new reductants and methods for reduction of Fe+2 and Fe+3 up to Fe0 is an actual problem. The objective of the present research is impregnation of nZVL in bioorganic materials and obtaining of hybrid ...
Science and Technology of Polymers and Advanced Materials, 2019
The synthesis of gold nanoparticles by two novel strains of Arthrobacter sp. 61B and Arthrobacter... more The synthesis of gold nanoparticles by two novel strains of Arthrobacter sp. 61B and Arthrobacter globiformis 151B isolated from basalt rocks in Georgia was studied. The complex of optical and analytical methods was applied for investigation of experimental samples after exposure to gold chloroaurate (HAuCl4) for different time intervals. To characterize formed gold nanoparticles UV-Vis spectrometry, Transmission electron microscopy (TEM), Scanning electron microscopy (SEM), Energy-dispersive analysis of X-rays (EDAX), and X-ray diffraction (XRD) were used. It was shown that after 1.5-2 days the extracellular formation of nanoparticles of spherical form with size in the range of 8-40 nm (on average of 20 nm) took place. To determine gold concentrations in the bacterial biomass neutron activation analysis (NAA) and atomic absorption spectrometry (AAS) were applied. The results obtained evidence that the concentration of gold accumulated by bacterial biomass is rapidly growing in the ...
In this work, obtaining methods of ultrafine alumina powdery composites and high temperature pres... more In this work, obtaining methods of ultrafine alumina powdery composites and high temperature pressing technology of matrix ceramic composites with different compositions have been discussed. Alumina was obtained by solution combustion synthesis and sol-gel methods. Metal carbides containing powdery composites were obtained by homogenization of finishing powders in nanomills, as well as by their single-step high temperature synthesis .Different types of matrix ceramics composites (α-Al2O3-ZrO2-Y2O3, α-Al2O3Y2O3-MgO, α-Al2O3-SiC-Y2O3, α-Al2O3-WC-Co-Y2O3, α-Al2O3B4C-Y2O3, α-Al2O3B4C-TiB2 etc.) were obtained by using OXYGON furnace. Consolidation of powders were carried out at 15501750°C (hold time 1 h, pressure 50 MPa). Corundum ceramics samples have been obtained and characterized by high hardness and fracture toughness, absence of open porosity, high corrosion resistance. Their density reaches 99.5-99.6% TD. During the work, the following devices have been used: High temperature vacu...
Thermal treatment (>1200C) of unstable intermediate phases of aluminum hydroxides and aluminum... more Thermal treatment (>1200C) of unstable intermediate phases of aluminum hydroxides and aluminum oxides inspires formation of thermodynamically stable α-Al2O3 which is widely applied in the production of ceramics with different functional purposes. Low-temperature phase transformation and obtaining of α-Al2O3 nanopowders is possible , if in the reaction mixture is added a small amount of up to 5% α-Al2O3 (during decomposition, hydrolysis, drying-heating and annealing of precursors). Modified polymer-precursor and solution combustion techniques were used for obtaining α-alumina. Aluminum nitrates, aluminum alkoxydes, oxidants and bifunctional compounds for producing organic-inorganic gels were used as initial precursors. Organic-inorganic gels were obtained by homogenization of aluminum and organic compounds within the range of 80-200°C and by carbonization of the obtained mass within the temperature range of 300-800°C. The addition of 3-5% α–Al2O3 seeds in the initial reactive mixt...
The ultradispersed crystallites (300 – 325 nm) of the acid modified natural clinoptilolite (CL, ν... more The ultradispersed crystallites (300 – 325 nm) of the acid modified natural clinoptilolite (CL, ν(SiO2)/ν(AI2O3) = 8.9) from Dzegvi (Georgia) deposit with the use of simplest method – of the indirect effect of ultrasound – were prepared. Under the influence of ultrasound the happening changes of structure and the sizes of clinoptilolite particles are shown, by the XRD, FTIR spectroscopy and by means of laser particle size analyzer, respectively. Catalytic activities of the initial acid form of the clinoptilolite (H–CL, ν(SiO2)/ν(AI2O3) = 23.3) and its form processed by ultrasound (H–CL (UlS)) in reaction of esterification of salicylic acid by methanol into methyl salicylate were compared. The indirect irradiation with ultrasound of acid form of clinoptilolite has led to sharp improve its catalytic properties in the formation of methyl salicylate. The best catalytic performance is achieved with ultrasound treated catalyst. The conversion of the salicylic acid and the selectivity to m...
Analcime is a fairly widespread zeolite in the territory of Georgia and other countries, but its ... more Analcime is a fairly widespread zeolite in the territory of Georgia and other countries, but its practical application is limited due to the peculiarities of its compact structure with small pores and irregular channels. This work describes a method developed by us for hydrothermal recrystallization of analcime into a widely used ion exchanger of the LTA type in the form of micrometric crystals or nanosized crystals, depending on the synthesis conditions. Silver-, copper-and zinc-containing analcimes and synthetic LTA zeolites with bacteriostatic activity were obtained by ion exchange. It has been shown that the highest bacteriostatic activity is possessed by a silver-containing synthetic zeolite, and analcimes enriched with relatively cheap copper and zinc exhibit activity sufficient for practical use in water treatment, paper production and other applications.
Advanced Science, Engineering and Medicine, 2015
Advanced Science, Engineering and Medicine, 2015
ABSTRACT The synthesis of gold nanoparticles by cells of the thermoacidophilic archaeon Sulfolobu... more ABSTRACT The synthesis of gold nanoparticles by cells of the thermoacidophilic archaeon Sulfolobus islandicus for technological purposes has been studied. A complex of optical and analytical methods has been used in order to characterize produced nanoparticles. It was shown that in the biomass of Sulfolobus islandicus the extracellular as well as intracellular formation of gold nanoparticles of spherical shape with sizes in the range of 20–80 nm (50 nm average) takes place. Energy-dispersive analysis of X-rays was used for examining the elemental content of the Sulfolobus islandicus biomass. Neutron activation analysis and atomic absorption spectrometry have been applied for characterizing the dynamics of gold accumulation in the Sulfolobus islandicus biomass. It was shown that the growing formation of gold nanoparticles in the biomass of Sulfolobus islandicus takes place mainly at few hours. The ultrasound was applied for intensification production of gold nanoparticles by biomass of Sulfolobus islandicus.
Materials Methods Technologies, 2014
Thermal treatment (>1200 o C) of unstable intermediate phases of aluminum hydroxides and aluminum... more Thermal treatment (>1200 o C) of unstable intermediate phases of aluminum hydroxides and aluminum oxides inspires formation of thermodynamically stable α-Al 2 O 3 which is widely applied in the production of ceramics with different functional purposes. Low-temperature phase transformation and obtaining of α-Al 2 O 3 nanopowders is possible , if in the reaction mixture is added a small amount of up to 5% α-Al 2 O 3 (during decomposition, hydrolysis, drying-heating and annealing of precursors). Modified polymer-precursor and solution combustion techniques were used for obtaining α-alumina. Aluminum nitrates, aluminum alkoxydes, oxidants and bifunctional compounds for producing organic-inorganic gels were used as initial precursors. Organic-inorganic gels were obtained by homogenization of aluminum and organic compounds within the range of 80-200°C and by carbonization of the obtained mass within the temperature range of 300-800°C. The addition of 3-5% α-Al 2 O 3 seeds in the initial reactive mixture decreases γ→α phase transformation temperature (1200°C) to 1020-1080°C. It was established, that during the interaction between aluminum nitrates and urea, adding of aluminum caused obtaining of amorphous aluminum oxide, annealing of which for 2h at 800°C on the open air gave α-Al 2 O 3. There were studied possibilities of obtaining nano-phase powders by low-temperature (20-90 o C). corrosion of aluminum activated with mercury. Subsequent annealing of the obtained Al2O3•nH 2 O amorphous powder at 1000-1100 o C resulted in the formation of α-Al 2 O 3 fibers. XRD analysis showed that Al 2 O 3 fibers contained particles with primary crystallites of 10-30 nm sizes.
Preparation of Ultradispersed Crystallites of Modified Natural Clinoptilolite with the Use of Ultrasound and Its Application as a Catalyst in the Synthesis of Methyl Salicylate, Feb 6, 2017
The ultradispersed crystallites (300 – 325 nm) of the acid modified natural clinoptilolite (CL, ν... more The ultradispersed crystallites (300 – 325 nm) of the acid modified natural clinoptilolite (CL, ν(SiO2)/ν(AI2O3) = 8.9) from Dzegvi (Georgia) deposit with the use of simplest method – of the indirect effect of ultrasound – were prepared. Under the influence of ultrasound the happening changes of structure and the sizes of clinoptilolite particles are shown, by the XRD, FTIR spectroscopy and by means of laser particle size analyzer, respectively. Catalytic activities of the initial acid form of the clinoptilolite (H–CL, ν(SiO2)/ν(AI2O3) = 23.3) and its form processed by ultrasound (H–CL (UlS)) in reaction of esterification of salicylic acid by methanol into methyl salicylate were compared. The indirect irradiation with ultrasound of acid form of clinoptilolite has led to sharp improve its catalytic properties in the formation of methyl salicylate. The best catalytic performance is achieved with ultrasound treated catalyst. The conversion of the salicylic acid and the selectivity to m...
Advanced Science, Engineering and Medicine, 2015
The synthesis of gold nanoparticles by cells of the thermoacidophilic archaeon Sulfolobus islandi... more The synthesis of gold nanoparticles by cells of the thermoacidophilic archaeon Sulfolobus islandicus for technological purposes has been studied. A complex of optical and analytical methods has been used in order to characterize produced nanoparticles. It was shown that in the biomass of Sulfolobus islandicus the extracellular as well as intracellular formation of gold nanoparticles of spherical shape with sizes in the range of 20–80 nm (50 nm average) takes place. Energy-dispersive analysis of X-rays was used for examining the elemental content of the Sulfolobus islandicus biomass. Neutron activation analysis and atomic absorption spectrometry have been applied for characterizing the dynamics of gold accumulation in the Sulfolobus islandicus biomass. It was shown that the growing formation of gold nanoparticles in the biomass of Sulfolobus islandicus takes place mainly at few hours. The ultrasound was applied for intensification production of gold nanoparticles by biomass of Sulfol...
The present paper studies hydrothermal transformation of natural zeolites analcime and phillipsit... more The present paper studies hydrothermal transformation of natural zeolites analcime and phillipsite, widespread in Georgia, in order to obtain valuable products. It is found that phasepure zeolite NaA with Si/Al~1 can be prepared in the form of cubic/rhombus crystallites with uniform micrometric (3-5 μm) dimensions by hydrothermal crystallization of aged at room temperature gel (4.5Na2O: 0.45Al2O3: 1SiO2: 178H2O) obtained from natural analcime, treated with hydrochloric acid before suspending in water and mixing with sodium hydroxide. Phase-pure zeolite NaX with Si/Al~1.5 can be prepared in the form of octahedral crystallites with uniform micrometric (2-7 μm) dimensions by hydrothermal crystallization of aged at room temperature gel (2.9Na2O: 0.26Al2O3: 1SiO2: 150H2O) obtained from water suspension of natural phillipsite, treated with hydrochloric acid and mixed with sodium hydroxide. Crystal structure of both zeolites is testified by X-ray diffraction patterns and infra-red spectra....
Nano zero-valent iron (nZVI) is widely used to remediate groundwater and wastewater from heavy me... more Nano zero-valent iron (nZVI) is widely used to remediate groundwater and wastewater from heavy metals and stable organic pollutants (Permeable Reactive Barriers). This is caused by the fact that Fe0 reduces several halogenous hydrocarbons, chlorine-containing pesticides, organic dyes, nitrozo compounds, explosives and others. The restoring ability is used for reduction of CrO4-2, Cr2O7-2, ClO4-, NO3- ions and elimination of Hg+2, Ni+2,Cd+2, Pb+2 as well as of a number of radionuclides from water. nZVIs had found wide application in the USA but in Europe this method appeared later. The cost of these methods for remediation of water depends on many factors (type of pollution, cost of reagents, the purpose and degree of remediation, remediation methods and other). That is why revealing of new reductants and methods for reduction of Fe+2 and Fe+3 up to Fe0 is an actual problem. The objective of the present research is impregnation of nZVL in bioorganic materials and obtaining of hybrid ...
Science and Technology of Polymers and Advanced Materials, 2019
The synthesis of gold nanoparticles by two novel strains of Arthrobacter sp. 61B and Arthrobacter... more The synthesis of gold nanoparticles by two novel strains of Arthrobacter sp. 61B and Arthrobacter globiformis 151B isolated from basalt rocks in Georgia was studied. The complex of optical and analytical methods was applied for investigation of experimental samples after exposure to gold chloroaurate (HAuCl4) for different time intervals. To characterize formed gold nanoparticles UV-Vis spectrometry, Transmission electron microscopy (TEM), Scanning electron microscopy (SEM), Energy-dispersive analysis of X-rays (EDAX), and X-ray diffraction (XRD) were used. It was shown that after 1.5-2 days the extracellular formation of nanoparticles of spherical form with size in the range of 8-40 nm (on average of 20 nm) took place. To determine gold concentrations in the bacterial biomass neutron activation analysis (NAA) and atomic absorption spectrometry (AAS) were applied. The results obtained evidence that the concentration of gold accumulated by bacterial biomass is rapidly growing in the ...
In this work, obtaining methods of ultrafine alumina powdery composites and high temperature pres... more In this work, obtaining methods of ultrafine alumina powdery composites and high temperature pressing technology of matrix ceramic composites with different compositions have been discussed. Alumina was obtained by solution combustion synthesis and sol-gel methods. Metal carbides containing powdery composites were obtained by homogenization of finishing powders in nanomills, as well as by their single-step high temperature synthesis .Different types of matrix ceramics composites (α-Al2O3-ZrO2-Y2O3, α-Al2O3Y2O3-MgO, α-Al2O3-SiC-Y2O3, α-Al2O3-WC-Co-Y2O3, α-Al2O3B4C-Y2O3, α-Al2O3B4C-TiB2 etc.) were obtained by using OXYGON furnace. Consolidation of powders were carried out at 15501750°C (hold time 1 h, pressure 50 MPa). Corundum ceramics samples have been obtained and characterized by high hardness and fracture toughness, absence of open porosity, high corrosion resistance. Their density reaches 99.5-99.6% TD. During the work, the following devices have been used: High temperature vacu...
Thermal treatment (>1200C) of unstable intermediate phases of aluminum hydroxides and aluminum... more Thermal treatment (>1200C) of unstable intermediate phases of aluminum hydroxides and aluminum oxides inspires formation of thermodynamically stable α-Al2O3 which is widely applied in the production of ceramics with different functional purposes. Low-temperature phase transformation and obtaining of α-Al2O3 nanopowders is possible , if in the reaction mixture is added a small amount of up to 5% α-Al2O3 (during decomposition, hydrolysis, drying-heating and annealing of precursors). Modified polymer-precursor and solution combustion techniques were used for obtaining α-alumina. Aluminum nitrates, aluminum alkoxydes, oxidants and bifunctional compounds for producing organic-inorganic gels were used as initial precursors. Organic-inorganic gels were obtained by homogenization of aluminum and organic compounds within the range of 80-200°C and by carbonization of the obtained mass within the temperature range of 300-800°C. The addition of 3-5% α–Al2O3 seeds in the initial reactive mixt...
The ultradispersed crystallites (300 – 325 nm) of the acid modified natural clinoptilolite (CL, ν... more The ultradispersed crystallites (300 – 325 nm) of the acid modified natural clinoptilolite (CL, ν(SiO2)/ν(AI2O3) = 8.9) from Dzegvi (Georgia) deposit with the use of simplest method – of the indirect effect of ultrasound – were prepared. Under the influence of ultrasound the happening changes of structure and the sizes of clinoptilolite particles are shown, by the XRD, FTIR spectroscopy and by means of laser particle size analyzer, respectively. Catalytic activities of the initial acid form of the clinoptilolite (H–CL, ν(SiO2)/ν(AI2O3) = 23.3) and its form processed by ultrasound (H–CL (UlS)) in reaction of esterification of salicylic acid by methanol into methyl salicylate were compared. The indirect irradiation with ultrasound of acid form of clinoptilolite has led to sharp improve its catalytic properties in the formation of methyl salicylate. The best catalytic performance is achieved with ultrasound treated catalyst. The conversion of the salicylic acid and the selectivity to m...
Analcime is a fairly widespread zeolite in the territory of Georgia and other countries, but its ... more Analcime is a fairly widespread zeolite in the territory of Georgia and other countries, but its practical application is limited due to the peculiarities of its compact structure with small pores and irregular channels. This work describes a method developed by us for hydrothermal recrystallization of analcime into a widely used ion exchanger of the LTA type in the form of micrometric crystals or nanosized crystals, depending on the synthesis conditions. Silver-, copper-and zinc-containing analcimes and synthetic LTA zeolites with bacteriostatic activity were obtained by ion exchange. It has been shown that the highest bacteriostatic activity is possessed by a silver-containing synthetic zeolite, and analcimes enriched with relatively cheap copper and zinc exhibit activity sufficient for practical use in water treatment, paper production and other applications.
Advanced Science, Engineering and Medicine, 2015
Advanced Science, Engineering and Medicine, 2015
ABSTRACT The synthesis of gold nanoparticles by cells of the thermoacidophilic archaeon Sulfolobu... more ABSTRACT The synthesis of gold nanoparticles by cells of the thermoacidophilic archaeon Sulfolobus islandicus for technological purposes has been studied. A complex of optical and analytical methods has been used in order to characterize produced nanoparticles. It was shown that in the biomass of Sulfolobus islandicus the extracellular as well as intracellular formation of gold nanoparticles of spherical shape with sizes in the range of 20–80 nm (50 nm average) takes place. Energy-dispersive analysis of X-rays was used for examining the elemental content of the Sulfolobus islandicus biomass. Neutron activation analysis and atomic absorption spectrometry have been applied for characterizing the dynamics of gold accumulation in the Sulfolobus islandicus biomass. It was shown that the growing formation of gold nanoparticles in the biomass of Sulfolobus islandicus takes place mainly at few hours. The ultrasound was applied for intensification production of gold nanoparticles by biomass of Sulfolobus islandicus.
Materials Methods Technologies, 2014
Thermal treatment (>1200 o C) of unstable intermediate phases of aluminum hydroxides and aluminum... more Thermal treatment (>1200 o C) of unstable intermediate phases of aluminum hydroxides and aluminum oxides inspires formation of thermodynamically stable α-Al 2 O 3 which is widely applied in the production of ceramics with different functional purposes. Low-temperature phase transformation and obtaining of α-Al 2 O 3 nanopowders is possible , if in the reaction mixture is added a small amount of up to 5% α-Al 2 O 3 (during decomposition, hydrolysis, drying-heating and annealing of precursors). Modified polymer-precursor and solution combustion techniques were used for obtaining α-alumina. Aluminum nitrates, aluminum alkoxydes, oxidants and bifunctional compounds for producing organic-inorganic gels were used as initial precursors. Organic-inorganic gels were obtained by homogenization of aluminum and organic compounds within the range of 80-200°C and by carbonization of the obtained mass within the temperature range of 300-800°C. The addition of 3-5% α-Al 2 O 3 seeds in the initial reactive mixture decreases γ→α phase transformation temperature (1200°C) to 1020-1080°C. It was established, that during the interaction between aluminum nitrates and urea, adding of aluminum caused obtaining of amorphous aluminum oxide, annealing of which for 2h at 800°C on the open air gave α-Al 2 O 3. There were studied possibilities of obtaining nano-phase powders by low-temperature (20-90 o C). corrosion of aluminum activated with mercury. Subsequent annealing of the obtained Al2O3•nH 2 O amorphous powder at 1000-1100 o C resulted in the formation of α-Al 2 O 3 fibers. XRD analysis showed that Al 2 O 3 fibers contained particles with primary crystallites of 10-30 nm sizes.