The present work is performed to photocatalytically reduce Cr(VI) by means of metal deposited ano... more The present work is performed to photocatalytically reduce Cr(VI) by means of metal deposited anodized TiO 2 tubes, which are prepared by anodization of Ti foil followed by metal deposition. Stably immobilized photo-reactive materials are favored in the field of detoxification in a conventional aqueous medium, preventing gradual loss of efficiency and process malfunction due to detachment of the materials. The prepared samples are characterized by SEM, TEM, EDAX, and photocurrent. The metal deposited-TiO 2 electrode shows higher efficiency for Cr(VI) reduction (ca. 20%) and higher ability for adsorption (4～5 times) than pure one.KEY WORDS : Photoanode(광전극), Anodized nanotublar TiO 2 electrode(ATTE, 양극산화 TiO 2 전극), Electrolyte deposition(전해질 담지법), Cr(VI), Photocatalytic reduction(광환원) 한국수소 및 신에너지학회 논문집(2010. 8), 제21권 제4호Trans. of the Korean Hydrogen and New Energy Society(2010. 8), Vol. 21, No. 4, pp. 301~306 † Corresponding author : hkjoo@kier.re.kr [ 접수일 : 2010.5.27 수정일 : 2010.7.22...
The purpose of this study was to correlate between photoelectrochemcial hydrogen production rate ... more The purpose of this study was to correlate between photoelectrochemcial hydrogen production rate and electron transfer with various types of metal doped TiO 2 nanotubes as photoanodes. In order to fabricate light sensitized photoanode, CdS, WO 3 , and Pt were doped by electrodeposition method. As the results of experiments, the electron transfer was favorable from higher position to lower position of conduction band (CB). In consequence, the higher hydrogen production rate was as follows, CdS/TiO 2 (100 umol/hr-cm 2 ) > WO 3 /TiO 2 (20 umol/hr-cm 2 ) > Pt/TiO 2 (10 umol/hr-cm 2 ). The surface characterizations exhibited that crystal structure, morphological and electrical properties of various metal depoed TiO 2 nanotubes by the results of SEM, TEM, XPS, and photocurrent measurements.KEY WORDS : Anodization(양극산화), Conduction band(전도대), Photoanode(광어노드), CdS(황화카드뮴), WO 3 (삼산화텅스텐), Hydrogen(수소) 한국수소 및 신에너지학회 논문집(2011. 10), 제22권 제5호Trans. of the Korean Hydrogen and New Energy Soc...
In this study, a flat-type photocatalytic reactor is applied under solar irradiation for simultan... more In this study, a flat-type photocatalytic reactor is applied under solar irradiation for simultaneous treatment of target pollutants: reduction of Cr(VI) to Cr(III) and oxidation of EDCs (BPA, EE2, E2). An immobilized type of photocatalyst was fabricated to have self-grown nanotubes on its surface in order to overcome limitations of powdery photocatalyst. Moreover, Ti mesh form was chosen as substrate and modified to have both larger surface area and photocatalyst content. Ti mesh was anodized at 50V and 25°C for 30min in the mixed electrolytes (NH4F-H2O-C2H6O2) and annealed at 450°C for 2 hours in ambient oxygen to have anatase structure. Surface characterization was done with SEM and XRD methodologies. Fabricated NTT was applied to water treatment, and coexisting Cr(VI) and organics (EDCs) enhanced each other's reactions by scavenging holes and electrons and thus impeding recombination. Also, several experiments were conducted outdoor under direct sunlight and it was observed ...
Journal of Korean Society of Water and Wastewater, 2006
In the drinking water treatment, the aesthetic and color problem are caused by the manganese whic... more In the drinking water treatment, the aesthetic and color problem are caused by the manganese which is occurring and present in the surface, lake and ground water. The most common treatment processes for removing manganese are known for oxidation followed by filtration. In this study, the manganese sand process was used for removing manganese with river bank filtrate as a source. In the manganese sand process, the residual chlorine and pH are important factors on the continuous manganese oxidation. In addition, space velocity (SV) and alum dosage are play a role of manganese removal. Even though manganese removal increased with increasing chlorine concentration, the control of residual chlorine is actually difficult in this process As the results of tests, the residual chlorine concentration as well as manganese removal were effectively achieved at pH 7.5. The optimum attached manganese concentration on manganese sand was confirmed to 0.3mg/L by the experimental result of a typical s...
In this study, a Pd catalyst was prepared with promoters such as CeO2, BaO and SrO in a washcoate... more In this study, a Pd catalyst was prepared with promoters such as CeO2, BaO and SrO in a washcoated form on a metallic monolith for autothermal reforming of methane to syngas for the Fischer-Tropsch synthesis. A reactor was installed with an electric heater in the form of the metallic monolith as a start-up device instead of a burner with which
Hindered (effective) diffusion of perchlorate anion (ClO4−) through negatively-charged porous nan... more Hindered (effective) diffusion of perchlorate anion (ClO4−) through negatively-charged porous nanofiltration and ultrafiltration membranes was determined by means of diffusion cell experiments. Three electrolytes, KCl, K2SO4, and CaCl2, were employed to determine their effects on the effective diffusion of perchlorate through membrane pores under varying pH levels (4, 6, 8, and 10). In addition, the effect of electrolyte concentration on effective diffusion was investigated, given that conductivity can affect electrostatic repulsion associated with the membrane surface/pore charge. All diffusion cell measurements were performed by reusing the same membrane in order to minimize artifacts from membrane variation based on membrane pore geometry (size) and membrane surface charge. In general, the results indicate that target ion (in this case ClO4−) transport by diffusion through the negatively charged membrane pores can be significantly affected by the presence of co- and counter ions and pH conditions, which significantly influence partitioning of the perchlorate ion due to mainly electrostatic repulsion occurring between the perchlorate anion and the negatively charged membrane.
Titanium foil and mesh(anodized tubular electrode, ATTE) were anodized in a bath at with 20V exte... more Titanium foil and mesh(anodized tubular electrode, ATTE) were anodized in a bath at with 20V external bias applied, then annealed at different temperatures() to obtain tubular on the Ti substrate. The prepared sample was used to investigate rate of hydrogen production as well as Cr(VI) reduction. The ATTEs annealed at relatively lower temperatures showed higher activity than those at relatively higher temperatures. In particular, the Cr(VI) reduction was pH-dependent. To improve photocatalytic Cr(VI) reduction with the ATTEs, two configurations, fixing foil type and rotating mesh type, were also compared. As a result, the rotating mesh type was much more effective for Cr(VI) reaction than the former due to the more efficient use of the light. In the rotating type reactor, as the rotating speed increased, the rate of the Cr(VI) reduction was getting faster.
Anodized tubular TiO2 electrodes (ATTEs) with three noticeably different lengths are prepared to ... more Anodized tubular TiO2 electrodes (ATTEs) with three noticeably different lengths are prepared to determine their optimum length for the photo-driven activity in the reaction of Cr(VI) reduction and hydrogen evolution. The ATTEs with ethylene glycol have longer TiO2 tubes (7-15.6 μm) than those with hydrfluoric acid (0.6-0.8 μm). These samples, which differ only in the length of the tubes, with a wall thickness of ca. 20 nm, consist mainly of an anatase crystalline phase after heat treatment at 650℃, since the anatase crystallites at the tube walls do not undergo transformation into rutile phase, due to the constraints imposed by the wall thickness. Among them, the medium size (ca. 8 μm) tubes provide the optimum conditions, irrespective of the light intensity, which is explained in terms of the correlation between the amount of photons and the adsorbed electron acceptors and their location. Photocatalytic Cr(VI) reduction leads to ca. 60% reduction of Cr(VI) even under 1 sun irradia...
Enhanced oxidation of organic pollutant, methylene blue (MB) was conducted using a newly designed... more Enhanced oxidation of organic pollutant, methylene blue (MB) was conducted using a newly designed rotating photoelectrocatalytic process (PECP), compared with photocatalysis. A significant synergy of photoelectrocatalytic reaction was observed such that the degradation of methylene blue (MB) by the photoelectrocatalytic mode was 80% higher than that (61.6%) of photocatalytic mode. To confirm the potentials in the application of water treatment, the effects of various parameters affecting reaction performance were studied with the newly designed rotating photoelectrocatalytic reactor consisting of TiO2 nanotubes and Ti lath as the photoanode and cathode, respectively, for applying electrical potential under UV irradiation. As the result of parameter studies, such as applied electrical potential (voltage), UV light intensity, rotating speeds, the highest degradation efficiencies of MB were achieved at 2.5 V or less (electrical potential), 90 rpm (rotating speed), and higher UV intensity. In addition, the stability and activity of TiO2 nanotubes electrode were studied through repeated experiments and showed a good performance, excellent stability, and reliability in the rotating photoelectrocatalytic process (PECP). This study provides an basis for the development of a rotating PECP to water treatment.
The present work is performed to photocatalytically reduce Cr(VI) by means of metal deposited ano... more The present work is performed to photocatalytically reduce Cr(VI) by means of metal deposited anodized TiO 2 tubes, which are prepared by anodization of Ti foil followed by metal deposition. Stably immobilized photo-reactive materials are favored in the field of detoxification in a conventional aqueous medium, preventing gradual loss of efficiency and process malfunction due to detachment of the materials. The prepared samples are characterized by SEM, TEM, EDAX, and photocurrent. The metal deposited-TiO 2 electrode shows higher efficiency for Cr(VI) reduction (ca. 20%) and higher ability for adsorption (4～5 times) than pure one.KEY WORDS : Photoanode(광전극), Anodized nanotublar TiO 2 electrode(ATTE, 양극산화 TiO 2 전극), Electrolyte deposition(전해질 담지법), Cr(VI), Photocatalytic reduction(광환원) 한국수소 및 신에너지학회 논문집(2010. 8), 제21권 제4호Trans. of the Korean Hydrogen and New Energy Society(2010. 8), Vol. 21, No. 4, pp. 301~306 † Corresponding author : hkjoo@kier.re.kr [ 접수일 : 2010.5.27 수정일 : 2010.7.22...
The purpose of this study was to correlate between photoelectrochemcial hydrogen production rate ... more The purpose of this study was to correlate between photoelectrochemcial hydrogen production rate and electron transfer with various types of metal doped TiO 2 nanotubes as photoanodes. In order to fabricate light sensitized photoanode, CdS, WO 3 , and Pt were doped by electrodeposition method. As the results of experiments, the electron transfer was favorable from higher position to lower position of conduction band (CB). In consequence, the higher hydrogen production rate was as follows, CdS/TiO 2 (100 umol/hr-cm 2 ) > WO 3 /TiO 2 (20 umol/hr-cm 2 ) > Pt/TiO 2 (10 umol/hr-cm 2 ). The surface characterizations exhibited that crystal structure, morphological and electrical properties of various metal depoed TiO 2 nanotubes by the results of SEM, TEM, XPS, and photocurrent measurements.KEY WORDS : Anodization(양극산화), Conduction band(전도대), Photoanode(광어노드), CdS(황화카드뮴), WO 3 (삼산화텅스텐), Hydrogen(수소) 한국수소 및 신에너지학회 논문집(2011. 10), 제22권 제5호Trans. of the Korean Hydrogen and New Energy Soc...
In this study, a flat-type photocatalytic reactor is applied under solar irradiation for simultan... more In this study, a flat-type photocatalytic reactor is applied under solar irradiation for simultaneous treatment of target pollutants: reduction of Cr(VI) to Cr(III) and oxidation of EDCs (BPA, EE2, E2). An immobilized type of photocatalyst was fabricated to have self-grown nanotubes on its surface in order to overcome limitations of powdery photocatalyst. Moreover, Ti mesh form was chosen as substrate and modified to have both larger surface area and photocatalyst content. Ti mesh was anodized at 50V and 25°C for 30min in the mixed electrolytes (NH4F-H2O-C2H6O2) and annealed at 450°C for 2 hours in ambient oxygen to have anatase structure. Surface characterization was done with SEM and XRD methodologies. Fabricated NTT was applied to water treatment, and coexisting Cr(VI) and organics (EDCs) enhanced each other's reactions by scavenging holes and electrons and thus impeding recombination. Also, several experiments were conducted outdoor under direct sunlight and it was observed ...
Journal of Korean Society of Water and Wastewater, 2006
In the drinking water treatment, the aesthetic and color problem are caused by the manganese whic... more In the drinking water treatment, the aesthetic and color problem are caused by the manganese which is occurring and present in the surface, lake and ground water. The most common treatment processes for removing manganese are known for oxidation followed by filtration. In this study, the manganese sand process was used for removing manganese with river bank filtrate as a source. In the manganese sand process, the residual chlorine and pH are important factors on the continuous manganese oxidation. In addition, space velocity (SV) and alum dosage are play a role of manganese removal. Even though manganese removal increased with increasing chlorine concentration, the control of residual chlorine is actually difficult in this process As the results of tests, the residual chlorine concentration as well as manganese removal were effectively achieved at pH 7.5. The optimum attached manganese concentration on manganese sand was confirmed to 0.3mg/L by the experimental result of a typical s...
In this study, a Pd catalyst was prepared with promoters such as CeO2, BaO and SrO in a washcoate... more In this study, a Pd catalyst was prepared with promoters such as CeO2, BaO and SrO in a washcoated form on a metallic monolith for autothermal reforming of methane to syngas for the Fischer-Tropsch synthesis. A reactor was installed with an electric heater in the form of the metallic monolith as a start-up device instead of a burner with which
Hindered (effective) diffusion of perchlorate anion (ClO4−) through negatively-charged porous nan... more Hindered (effective) diffusion of perchlorate anion (ClO4−) through negatively-charged porous nanofiltration and ultrafiltration membranes was determined by means of diffusion cell experiments. Three electrolytes, KCl, K2SO4, and CaCl2, were employed to determine their effects on the effective diffusion of perchlorate through membrane pores under varying pH levels (4, 6, 8, and 10). In addition, the effect of electrolyte concentration on effective diffusion was investigated, given that conductivity can affect electrostatic repulsion associated with the membrane surface/pore charge. All diffusion cell measurements were performed by reusing the same membrane in order to minimize artifacts from membrane variation based on membrane pore geometry (size) and membrane surface charge. In general, the results indicate that target ion (in this case ClO4−) transport by diffusion through the negatively charged membrane pores can be significantly affected by the presence of co- and counter ions and pH conditions, which significantly influence partitioning of the perchlorate ion due to mainly electrostatic repulsion occurring between the perchlorate anion and the negatively charged membrane.
Titanium foil and mesh(anodized tubular electrode, ATTE) were anodized in a bath at with 20V exte... more Titanium foil and mesh(anodized tubular electrode, ATTE) were anodized in a bath at with 20V external bias applied, then annealed at different temperatures() to obtain tubular on the Ti substrate. The prepared sample was used to investigate rate of hydrogen production as well as Cr(VI) reduction. The ATTEs annealed at relatively lower temperatures showed higher activity than those at relatively higher temperatures. In particular, the Cr(VI) reduction was pH-dependent. To improve photocatalytic Cr(VI) reduction with the ATTEs, two configurations, fixing foil type and rotating mesh type, were also compared. As a result, the rotating mesh type was much more effective for Cr(VI) reaction than the former due to the more efficient use of the light. In the rotating type reactor, as the rotating speed increased, the rate of the Cr(VI) reduction was getting faster.
Anodized tubular TiO2 electrodes (ATTEs) with three noticeably different lengths are prepared to ... more Anodized tubular TiO2 electrodes (ATTEs) with three noticeably different lengths are prepared to determine their optimum length for the photo-driven activity in the reaction of Cr(VI) reduction and hydrogen evolution. The ATTEs with ethylene glycol have longer TiO2 tubes (7-15.6 μm) than those with hydrfluoric acid (0.6-0.8 μm). These samples, which differ only in the length of the tubes, with a wall thickness of ca. 20 nm, consist mainly of an anatase crystalline phase after heat treatment at 650℃, since the anatase crystallites at the tube walls do not undergo transformation into rutile phase, due to the constraints imposed by the wall thickness. Among them, the medium size (ca. 8 μm) tubes provide the optimum conditions, irrespective of the light intensity, which is explained in terms of the correlation between the amount of photons and the adsorbed electron acceptors and their location. Photocatalytic Cr(VI) reduction leads to ca. 60% reduction of Cr(VI) even under 1 sun irradia...
Enhanced oxidation of organic pollutant, methylene blue (MB) was conducted using a newly designed... more Enhanced oxidation of organic pollutant, methylene blue (MB) was conducted using a newly designed rotating photoelectrocatalytic process (PECP), compared with photocatalysis. A significant synergy of photoelectrocatalytic reaction was observed such that the degradation of methylene blue (MB) by the photoelectrocatalytic mode was 80% higher than that (61.6%) of photocatalytic mode. To confirm the potentials in the application of water treatment, the effects of various parameters affecting reaction performance were studied with the newly designed rotating photoelectrocatalytic reactor consisting of TiO2 nanotubes and Ti lath as the photoanode and cathode, respectively, for applying electrical potential under UV irradiation. As the result of parameter studies, such as applied electrical potential (voltage), UV light intensity, rotating speeds, the highest degradation efficiencies of MB were achieved at 2.5 V or less (electrical potential), 90 rpm (rotating speed), and higher UV intensity. In addition, the stability and activity of TiO2 nanotubes electrode were studied through repeated experiments and showed a good performance, excellent stability, and reliability in the rotating photoelectrocatalytic process (PECP). This study provides an basis for the development of a rotating PECP to water treatment.
Uploads
Papers by Jaekyung Yoon