• Title/Summary/Keyword: Photocatalytic oxidation

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Synthesis and Characteristics of Pd/r-TiO2 Nanotube Arrays Hetrojunction Photocatalyst (Pd/r-TiO2 나노튜브 이종결합 광촉매의 합성과 특성)

  • Lee, Jong-Ho;Lee, Young-Ki;Kim, Young-Jig;Jang, Kyung-Wook;Oh, Han-Jun
    • Korean Journal of Materials Research
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    • v.32 no.1
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    • pp.14-22
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    • 2022
  • To improve light absorption ability in the visible light region and the efficiency of the charge transfer reaction, Pd nanoparticles decorated with reduced TiO2 nanotube photocatalyst were synthesized. The reduced TiO2 nanotube photocatalyst was fabricated by anodic oxidation of Ti plate, followed by an electrochemical reduction process using applied cathodic potential. For TiO2 photocatalyst electrochemically reduced using an applied voltage of -1.3 V for 10 min, 38% of Ti4+ ions on TiO2 surface were converted to Ti3+ ion. The formation of Ti3+ species leads to the decrease in the band gap energy, resulting in an increase in the light absorption ability in the visible range. To obtain better photocatalytic efficiency, Pd nanoparticles were decorated through photoreduction process on the surface of reduced TiO2 nanotube photocatalyst (r10-TNT). The Pd nanoparticles decorated with reduced TiO2 nanotube photocatalyst exhibited enhanced photocurrent response, and high efficiency and rate constant for aniline blue degradation; these were ascribed to the synergistic effect of the new electronic state of the TiO2 band gap energy induced by formation of Ti3+ species on TiO2, and by improvement of the charge transfer reaction.

Kinetics of Photocatalytic Reactions with Porous Carriers Coated with Nano-$TiO_2$ Particles (나노-$TiO_2$ 입자로 코팅된 다공성 담체의 광촉매 반응에 관한 동력학)

  • Park, Seong-Jun;Rittmann, Bruce E.;Bae, Woo-Keun
    • Journal of Korean Society of Environmental Engineers
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    • v.31 no.10
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    • pp.927-932
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    • 2009
  • Toxic and recalcitrant organic pollutants in wastewaters can be effectively treated when advanced oxidation and biodegradation are combined, ideally with intimate coupling, in which both processes occur simultaneously in the same system. One means to achieve intimate coupling is to coat nanoscale $TiO_2$ on the outside of macroporous biofilm carriers. This study investigated the kinetics of photocatalysis with $TiO_2$-coated porous carriers. The carriers were made of polyvinyl alcohol (PVA) and coated with $TiO_2$ using a low-temperature sol-gel process. The $TiO_2$-coated carriers catalyzed the oxidation of methylene blue (MB) effectively under irradiation of UV light. The overall reaction rate with adsorption and photolysis saturated at high MB concentration, and approached the adsorption rate, which was first order for all MB concent rations. This result indicates that adsorbed MB may have slowed photocatalysis by blocking active sites for photocatalysis. The overall kinetics could be described by a quasi-Langmuir model. The estimated maximum specific (per unit mass of $TiO_2$) transformation rate of MB by the $TiO_2$-coated carriers was four times larger than that obtained from slurry-$TiO_2$ reactors. This observation demonstrated that the $TiO_2$ present as a coating on the carriers maintained high efficiency for transforming recalcitrant organic matter via photocatalysis. These findings serve as a foundation for advancement of an intimate coupling of photocatalysis to biodegradation.

Synthesis of Polyaniline/WO3 Anode for Lithium Ion Capacitor and Its Electrochemical Characteristics under Light Irradiation (리튬이온커패시터용 Polyaniline/WO3 음극 제조 및 이의 광 조사에 따른 전기화학적 특성 변화)

  • Park, Yiseul
    • Korean Chemical Engineering Research
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    • v.56 no.6
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    • pp.884-889
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    • 2018
  • In this study, polyaniline $(PANI)/WO_3$ electrode was prepared as an anode of a lithium ion capacitor, and its electrochemical characteristics were measured and analyzed. When PANI was electrochemically deposited on the surface of $WO_3$ electrode, the capacity of $PANI/WO_3$ was improved with increase of the deposited amounts of PANI. Furthermore, the effect of light irradiation on capacity and coulombic efficiency was examined by irradiating sunlight during charging and discharging. When the light was irradiated to the $WO_3$ electrode and the $PANI/WO_3$ electrode, those capacities and coulombic efficiencies were increased compared to that measured under the dark condition. It is attributed to the photocatalytic property of $WO_3$ that can generate photoelectrons by light irradiation. In $PANI/WO_3$ electrode, PANI also can be excited under the light irradiation with affecting the electrochemical property of electrode. The photoelectrons improve the capacity by participating in the intercalation of $Li^+$ ions, and also improve the coulombic efficiency by facilitating electrons' transport. Under the dark condition, the capacity of $PANI/WO_3$ was gradually reduced with increase of cycles due to a poor stability of PANI. However, the stability of PANI was significantly improved by the light irradiation, which is attributed to the oxidation-reduction reaction originated from the photogenerated electrons and holes in $PANI/WO_3$.

Treatment of Cu(II)-EDTA using Solar/$TiO_2$ Photocatalysis (태양광/$TiO_2$ 광산화를 이용한 Cu(II)-EDTA의 제거)

  • Shin, In-Soo;Lee, Seung-Mok;Yang, Jae-Kyu;Shin, Won-Tae
    • Journal of Korean Society of Environmental Engineers
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    • v.27 no.2
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    • pp.163-169
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    • 2005
  • Photocatalytic oxidation of Cu(II)-EDTA has been studied using solar/$TiO_2$ photocatalysis as an energy source. Photocatalysis efficiency on the treatment of Cu(II)-EDTA was investigated using different types of solar collectors as well as by variation of the angles of solar collector solar light intensities, flow rates, and areas of solar collector. effect of $H_2O_2$ and types of $TiO_2$ catalyst on the treatment of Cu(II)-EDTA was also investigated. Removal of Cu(II) and DOC was favorable with a hemispherical collector than with a flat collector Removal of Cu(II) and DOC increased with increasing angles of solar collector up to $38^{\circ}$. Slurry type $TiO_2$ showed four-times higher removal efficiency than immobilized type $TiO_2$. Removal of both Cu(II) and DOC at a clear sky of solar light intensity ranging from 0.372 to $2.265\;mW/cm^2$ was greater than removal at a cloudy day of solar light intensity ranging from 0.038 to $1.129\;mW/cm^2$. From the result of this research that the removal efficiency of Cu(II) and DOC increased as the solar light intensity increased, it can be inferred that quantum yield in the destruction of Cu(II)-EDTA may directly related with the solar light intensity. Removal of Cu(II) increased as increasing the area of solar collector and was similar at lower flow rates white removal of Cu(II) was interfered at higher flow rates. When immobilized $TiO_2$ was used, removal efficiency of Cu(II) increased in the presence of $H_2O_2$ while negligible effect was found in the use of $TiO_2$ slurry.

The Photocatalytic Degradation of Humic Acid by TiO2 Sol-Gel Coating -Characterization of Humic Acid in the Chemical Oxidation Treatment (II)- (TiO2 졸-겔 코팅 막에 의한 Humic Acid의 광분해 -화학적 산화법에 의한 부식산의 분해처리 기술에 관한 연구 (II)-)

  • Seok, Sang Il;Ahn, Bok Yeop;Suh, Tae Soo;Rhee, Dong Seok
    • Journal of Korean Society of Environmental Engineers
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    • v.22 no.4
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    • pp.765-773
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    • 2000
  • The degradation of humic acid using $TiO_2$ coatings was studied, $TiO_2$ coatings were prepared by dip-coating method. Sol solutions for coating were prepared by mixing the gel, which can be produced by the reaction of $TiOCl_2$ and $NH_4OH$ solution, and hydrogen peroxide solution, and hydrolysis of titanium tetraisopropoxide (TTIP). It was shown from XRD that coatings from sol aged at $100^{\circ}C$ for 18h with titanium peroxo solution were crystallized to anatase in the range of temperatures of $25^{\circ}C$ to $500^{\circ}C$. In contrast, those coated from TTIP were crystallized to anatase at temperature above $400^{\circ}C$. So the sols originated from $TiCl_4$ can be applied for not only on the heat-resistance substrates but on the plastic substrates. Thickness and the quality of the films were dependent on the withdrawing speed, the concentration of sol, and the number of coating. The films showed various interference colors depending on the thickness of them. In the case that the films coated 2 times at withdrawing speed of 2.5cm per minute by 0.2M sol, the films had a transparent light blue color with thickness of around 50nm. It was known from the result of photo-degradation by $TiO_2$ coatings using humic acid that the removal efficiency of $COD_{cr}$ was over 85% after illumination of $UV/H_2O_2$ for 40min. and that of UV/VIS absorbable materials was over 95%.

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