Oznur Onel | Virginia Tech (original) (raw)

Papers by Oznur Onel

Synthesized rare earth ion-adsorption clays (La, Ce, Nd, Dy and Y, ~ 400 ppm each) were prepared ... more Synthesized rare earth ion-adsorption clays (La, Ce, Nd, Dy and Y, ~ 400 ppm each) were prepared from kaolinite at various basic pH in open-air conditions. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma mass spectrometry (ICP-MS) were used to characterize the effect of pH on the adsorption mechanism of rare earth elements (REEs) on kaolinite. The crystal structure of kaolinite by XRD analysis is not altered after REE adsorption, suggesting that REEs are bound to the surface of kaolinite. Elemental analysis by XPS and ICP-MS show that the surface concentration of REEs on kaolinite is pH dependent, and a local maximum of the surface concentration is achieved at pH 10. Three characteristics of the La 3d 5/2 XPS photoemission feature were measured and compared to those of standard La compounds to probe the speciation of REEs, and electrostatically bound hydroxides such as REE(OH) 2 + are identified as the primary species on the surface of kaolinite. Compared to the typical ion-adsorption clays with intrinsic acidic pH, clays synthesized at basic pH exhibit similarly high rare earth ion-exchange efficiency with ammonium sulfate (AS), suggesting that rare earth ion-adsorption clays can exist in both acidic and basic environments.

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The uptake mechanism and influence of iron (Fe) co-adsorption on the binding of rare-earth elemen... more The uptake mechanism and influence of iron (Fe) co-adsorption on the binding of rare-earth elements (REEs) on kaolinite have been investigated. REEs and varying concentrations of Fe were co-adsorbed onto kaolinite at pH 10.5. Inductively coupled plasma mass spectrometry (ICP-MS), powder X-ray diffraction (PXRD), and X-ray photoelectron spectroscopy (XPS) were used to characterize how Fe co-adsorption influenced the uptake mechanism of REEs on kaolinite. Elemental analysis by ICP-MS revealed that the REE concentrations on kaolinite were unaffected by the presence of Fe. Crystal structure of kaolinite, determined by PXRD, was not altered after REE and Fe co-adsorption. XPS suggests that the adsorbed Fe is in the form of FeOOH, while the greatly attenuated REE XPS signals upon Fe co-adsorption implies that REEs are encapsulated by Fe species. Based on these results, we conclude that FeOOH layers were formed on top of REEs on the surface of kaolinite. Synthesized REE-Fe-kaolinite samples respond poorly to ion-exchange leaching, indicating that Fe is detrimental to the REE ion-exchange efficiency. The inhibition of ion-exchange REE extraction appears to be due to the passivating FeOOH layers. In contrast to ion-exchange methods, reductive leaching was found to dissolve the FeOOH passivating layers and liberate REEs such that they became available for ion-exchange leaching.

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Inżynieria Mineralna, 2021

The fly ash as a byproduct of coal-fired power plants constitutes vital ecological problems. In T... more The fly ash as a byproduct of coal-fired power plants constitutes vital ecological problems. In Turkey, approximately 15 million tons ofashes are generated via the combustion of 40 million tons of lignite yearly. Worldwide, a number of investigation and applications wereundertaken to utilize fly ash in order to overcome the environmental problems. One of the application area of fly ashes is the production of building bricks. Characterization of fly ash samples from Seyitomer and Yatagan coal-firing power plants were conducted inthis study. TCLP 1311, ASTM3987-85 and EN 12457-2 leaching tests on the cylindrical fly ash/lime brick (FA/LB) samples which wereproduced from Seyitömer and Yatagan thermal power plant fly ash-lime mixtures were performed to determine the leachability ofsome chosen trace elements. The results show that the release of all trace elements was lower than the hazardous material limit valuesof waste acceptance. Thus, non- fired fly ash bricks are an advantageous wa...

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Applied Clay Science

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This study presents the results of the application of the laboratory gravity-recoverable-gold (GR... more This study presents the results of the application of the laboratory gravity-recoverable-gold (GRG) determination procedure on a Turkish gold ore using a Falcon concentrator. The study had two major goals; as investigating the compatibility of Falcon concentrator for GRG procedure (which was originally developed for Knelson concentrator); and finding out the gravity recoverable gold content in Gümüşhane/Mastra gold ore. It was seen that a concentrate enriched in Au content could be successfully achieved: After the first stage a product with an Au grade of 41.09 mgAu/tonne at %10.95 fractional gold recovery at the first stage of the procedure. Au content in the concentrate increased to 98.84 mg after the second stage and finally 59.74 mg Au was obtained by the third stage. As a result of the application, it was found that the GRG content of Gümüşhane/Mastra gold was 48.28%, corresponding to a significant potential for obtaining an Au-enriched preconcentrate.

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Applied Clay Science

Abstract Synthesized rare earth ion-adsorption clays (La, Ce, Nd, Dy and Y, ~ 400 ppm each) were ... more Abstract Synthesized rare earth ion-adsorption clays (La, Ce, Nd, Dy and Y, ~ 400 ppm each) were prepared from kaolinite at various basic pH in open-air conditions. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma mass spectrometry (ICP-MS) were used to characterize the effect of pH on the adsorption mechanism of rare earth elements (REEs) on kaolinite. The crystal structure of kaolinite by XRD analysis is not altered after REE adsorption, suggesting that REEs are bound to the surface of kaolinite. Elemental analysis by XPS and ICP-MS show that the surface concentration of REEs on kaolinite is pH dependent, and a local maximum of the surface concentration is achieved at pH 10. Three characteristics of the La 3d5/2 XPS photoemission feature were measured and compared to those of standard La compounds to probe the speciation of REEs, and electrostatically bound hydroxides such as REE(OH)2+ are identified as the primary species on the surface of kaolinite. Compared to the typical ion-adsorption clays with intrinsic acidic pH, clays synthesized at basic pH exhibit similarly high rare earth ion-exchange efficiency with ammonium sulfate (AS), suggesting that rare earth ion-adsorption clays can exist in both acidic and basic environments.

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IOP Conference Series: Earth and Environmental Science

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Physicochemical Problems of Mineral Processing

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Synthesized rare earth ion-adsorption clays (La, Ce, Nd, Dy and Y, ~ 400 ppm each) were prepared ... more Synthesized rare earth ion-adsorption clays (La, Ce, Nd, Dy and Y, ~ 400 ppm each) were prepared from kaolinite at various basic pH in open-air conditions. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma mass spectrometry (ICP-MS) were used to characterize the effect of pH on the adsorption mechanism of rare earth elements (REEs) on kaolinite. The crystal structure of kaolinite by XRD analysis is not altered after REE adsorption, suggesting that REEs are bound to the surface of kaolinite. Elemental analysis by XPS and ICP-MS show that the surface concentration of REEs on kaolinite is pH dependent, and a local maximum of the surface concentration is achieved at pH 10. Three characteristics of the La 3d 5/2 XPS photoemission feature were measured and compared to those of standard La compounds to probe the speciation of REEs, and electrostatically bound hydroxides such as REE(OH) 2 + are identified as the primary species on the surface of kaolinite. Compared to the typical ion-adsorption clays with intrinsic acidic pH, clays synthesized at basic pH exhibit similarly high rare earth ion-exchange efficiency with ammonium sulfate (AS), suggesting that rare earth ion-adsorption clays can exist in both acidic and basic environments.

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The uptake mechanism and influence of iron (Fe) co-adsorption on the binding of rare-earth elemen... more The uptake mechanism and influence of iron (Fe) co-adsorption on the binding of rare-earth elements (REEs) on kaolinite have been investigated. REEs and varying concentrations of Fe were co-adsorbed onto kaolinite at pH 10.5. Inductively coupled plasma mass spectrometry (ICP-MS), powder X-ray diffraction (PXRD), and X-ray photoelectron spectroscopy (XPS) were used to characterize how Fe co-adsorption influenced the uptake mechanism of REEs on kaolinite. Elemental analysis by ICP-MS revealed that the REE concentrations on kaolinite were unaffected by the presence of Fe. Crystal structure of kaolinite, determined by PXRD, was not altered after REE and Fe co-adsorption. XPS suggests that the adsorbed Fe is in the form of FeOOH, while the greatly attenuated REE XPS signals upon Fe co-adsorption implies that REEs are encapsulated by Fe species. Based on these results, we conclude that FeOOH layers were formed on top of REEs on the surface of kaolinite. Synthesized REE-Fe-kaolinite samples respond poorly to ion-exchange leaching, indicating that Fe is detrimental to the REE ion-exchange efficiency. The inhibition of ion-exchange REE extraction appears to be due to the passivating FeOOH layers. In contrast to ion-exchange methods, reductive leaching was found to dissolve the FeOOH passivating layers and liberate REEs such that they became available for ion-exchange leaching.

Bookmarks Related papers MentionsView impact

Inżynieria Mineralna, 2021

The fly ash as a byproduct of coal-fired power plants constitutes vital ecological problems. In T... more The fly ash as a byproduct of coal-fired power plants constitutes vital ecological problems. In Turkey, approximately 15 million tons ofashes are generated via the combustion of 40 million tons of lignite yearly. Worldwide, a number of investigation and applications wereundertaken to utilize fly ash in order to overcome the environmental problems. One of the application area of fly ashes is the production of building bricks. Characterization of fly ash samples from Seyitomer and Yatagan coal-firing power plants were conducted inthis study. TCLP 1311, ASTM3987-85 and EN 12457-2 leaching tests on the cylindrical fly ash/lime brick (FA/LB) samples which wereproduced from Seyitömer and Yatagan thermal power plant fly ash-lime mixtures were performed to determine the leachability ofsome chosen trace elements. The results show that the release of all trace elements was lower than the hazardous material limit valuesof waste acceptance. Thus, non- fired fly ash bricks are an advantageous wa...

Bookmarks Related papers MentionsView impact

Applied Clay Science

Bookmarks Related papers MentionsView impact

This study presents the results of the application of the laboratory gravity-recoverable-gold (GR... more This study presents the results of the application of the laboratory gravity-recoverable-gold (GRG) determination procedure on a Turkish gold ore using a Falcon concentrator. The study had two major goals; as investigating the compatibility of Falcon concentrator for GRG procedure (which was originally developed for Knelson concentrator); and finding out the gravity recoverable gold content in Gümüşhane/Mastra gold ore. It was seen that a concentrate enriched in Au content could be successfully achieved: After the first stage a product with an Au grade of 41.09 mgAu/tonne at %10.95 fractional gold recovery at the first stage of the procedure. Au content in the concentrate increased to 98.84 mg after the second stage and finally 59.74 mg Au was obtained by the third stage. As a result of the application, it was found that the GRG content of Gümüşhane/Mastra gold was 48.28%, corresponding to a significant potential for obtaining an Au-enriched preconcentrate.

Bookmarks Related papers MentionsView impact

Applied Clay Science

Abstract Synthesized rare earth ion-adsorption clays (La, Ce, Nd, Dy and Y, ~ 400 ppm each) were ... more Abstract Synthesized rare earth ion-adsorption clays (La, Ce, Nd, Dy and Y, ~ 400 ppm each) were prepared from kaolinite at various basic pH in open-air conditions. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma mass spectrometry (ICP-MS) were used to characterize the effect of pH on the adsorption mechanism of rare earth elements (REEs) on kaolinite. The crystal structure of kaolinite by XRD analysis is not altered after REE adsorption, suggesting that REEs are bound to the surface of kaolinite. Elemental analysis by XPS and ICP-MS show that the surface concentration of REEs on kaolinite is pH dependent, and a local maximum of the surface concentration is achieved at pH 10. Three characteristics of the La 3d5/2 XPS photoemission feature were measured and compared to those of standard La compounds to probe the speciation of REEs, and electrostatically bound hydroxides such as REE(OH)2+ are identified as the primary species on the surface of kaolinite. Compared to the typical ion-adsorption clays with intrinsic acidic pH, clays synthesized at basic pH exhibit similarly high rare earth ion-exchange efficiency with ammonium sulfate (AS), suggesting that rare earth ion-adsorption clays can exist in both acidic and basic environments.

Bookmarks Related papers MentionsView impact

IOP Conference Series: Earth and Environmental Science

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Physicochemical Problems of Mineral Processing

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