• Title, Summary, Keyword: photocatalytic reaction

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Surface Modification Reaction of Photocatalytic Titanium Dioxide with Triethoxysilane for Improving Dispersibility

  • Lee, Myung-Jin;Kim, Ji-Ho;Park, Young-Tae
    • Bulletin of the Korean Chemical Society
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    • v.31 no.5
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    • pp.1275-1279
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    • 2010
  • We have carried out the surface modification of photocatalytic $TiO_2$ with triethoxysilane through dehydrogenation reaction and characterized the modified photocatalyst by spectroscopic methods, such as FT-IR, solid-state $^{29}Si$ MAS NMR, XPS, and XRF, etc. We also examined photocatalytic activity of the immobilized photocatalytic titanium dioxide with triethoxysilane by decolorization reaction of dyes such as cong red and methylene blue under visible light. Dispersion test showed that the photocatalytic titanium dioxide immobilized with triethoxysilane group has kept higher dispersibility than titanium dioxide itself. No appreciable precipitation takes place even after standing for 24 h in the 4:6 mixture ratio of ethanol and water.

Effects of Water Vapor, Molecular Oxygen and Temperature on the Photocatalytic Degradation of Gas-Phase VOCs using $TiO_2$Photocatalyst: TCE and Acetone

  • Kim, Sang-Bum;Jo, Young-Min;Cha, Wang-Seong
    • Journal of Korean Society for Atmospheric Environment
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    • v.17 no.E2
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    • pp.35-42
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    • 2001
  • Recent development of photocatalytic degradation method that is mediated by TiO$_2$ is of interest in the treatment of volatile organic compounds(VOCs). In this study, trichloroethylene(TCE) and acetone were closely examined in a batch scale of photo-reactor as a function of water vapor, oxygen, and temperature. Water vapor inhibited the photocatalytic degradation of acetone, while there was an optimum concentration in TCE. A lower efficiency was found in nitrogen atmosphere than air, and the effect of oxygen on photocatalytic degradation of acetone was greater than on that of TCE. The optimum reaction temperature on photocatalytic degradation was about 45$^{\circ}C$ for both compounds. NO organic byproducts were detected for both compounds under the present experimental conditions. It was ascertained that the photocatalytic reaction in a batch scale of photo-reactor was very effective in removing VOCs such as TCE and acetone in the gaseous phase.

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Photocatalytic Degradation Mechanism of Methyl Mercaptan using $TiO_2$ (TiO$_2$를 이용한 메틸메르캅탄의 광촉매 분해메커니즘)

  • Lee, Byung-Dae;Lee, Jin-Shik;Kim, Yeoung-Chan
    • Journal of the Korean Applied Science and Technology
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    • v.24 no.3
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    • pp.296-300
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    • 2007
  • This paper presents applicability of photocatalytic decomposition of methyl mercaptan using $TiO_2$. A quartz reactor was used in order to elucidate reaction pathway in photocatalytic decomposition of methyl mercaptan. Experimental results showed that more than 99.9% of methyl mercaptan was decomposed within 30 minutes. It was found that the photocatalytic decomposition of methyl mercaptan followed pseudo first order and its reaction coefficient was $0.05min^{-1}$ During 30 minutes in the photocatalytic reaction, the concentration of methyl mercaptan, dimethyl disulfide, $SO_2$, $H_2SO_4$, COS, $H_2S$ were determined. These results showed that 64% of methyl mercaptan were compensated for the increase in sulfur after 30 minutes through the mineralization. The proposed main photocatalytic decomposition pathway of methyl mercaptan was methyl $mercaptan{\rightarrow}dimethyl$ $disulfide{\rightarrow}SO_2{\rightarrow}H_2SO_4$.

Fulvic Acid Removal Using Ag-TiO2 Photocatalytic Process (Ag-TiO2 광촉매 공정을 이용한 Fulvic acid의 제거)

  • Lee, Byung-Hun;Kim, Min-Gyeong
    • Journal of Korean Society of Water Science and Technology
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    • v.25 no.1
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    • pp.23-35
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    • 2017
  • This study is to remove fulvic acid of natural organic matters(NOMs) that existed in water and polluted in the water system. Fulvic acids show a high reactivity towards chlorine and make trihalomethanes in water treatment. The optimum conditions for the removal of natural organic matters were investigated using photocatalytic oxidation, which is and advanced oxidation process. For the more effective photocatalytic reaction than the conventional photocatalytic reaction, Ag was added and the experiment was conducted. Response surface methodology (RSM) was used to find the appropriate amount of Ag injection. Fulvic acid was selected as Natural Organic Matter(NOM). $TiO_2$ was fixed to the reactor at 300 g/L and a UV lamp with a wavelength of 254 + 185 nm was used in the experiment. Experiments were conducted under the conditions of Ag of 0.15 - 5.8 g / L, reaction time of 10 - 70 min, and irradiation density of 9.5 - 13.7 W / L. Experimental results showed that the optimum removal rate was Ag 3.5 g/L, irradiation density 13 W/L and reaction time 50 min.

A Study of Non-thermal Plasma Generation on a Photocatalytic Reactor Using a Ceramic Honeycomb Monolith Substrate (세라믹 벌집형 담체를 사용한 광촉매 반응기의 플라즈마 생성에 관한 연구)

  • 손건석;윤승원;고성혁;김대중;송재원;이귀영
    • Transactions of the Korean Society of Automotive Engineers
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    • v.10 no.2
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    • pp.48-54
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    • 2002
  • Since photocatalysts are activated by lights of UV wavelengths, plasma is alternatively used as a light source for a photocatalytic reactor. Light intensity generated by plasma is proportional to the surface area of catalytic material, and this, in many practical applications, is prescribed by the geometry of a plasma generator. Thus, it is crucial to increase the surface area far sufficient light intensity for photocatalytic reaction. For example, in a pack-bed type reactor, multitudes of beads are used as a substrate in order to increase the surface area. Honeycomb monolith type substrate, which has very good surface area to volume ratio, has been difficult to apply plasma as a light source due to the fact that light penetration depth through the honeycomb monolith was too short to cover sufficient area, thus resulting in poor intensity for photocatalytic reaction. In this study, nonthermal plasma generation through a photocatalytic reactor of honeycomb monolith substrate is investigated to lengthen this short penetration depth. The ceramic honeycomb monolith substrate used in this study has the same length as a three way catalyst used fur automotive applications, and it is shown that sufficient light intensity for photocatalytic reaction can also be obtained with honeycomb monolith type reactor.

Investigation of Photocatalytic Process on Removal of Natural Organic Matter in Nanofiltration Process (광촉매 공정에 의한 유기물 제거가 나노여과 공정에 미치는 영향)

  • Lee, Kew-Ho;Choi, In-Hwan;Kim, In-Chul;Min, Byoung-Ryul
    • Membrane Journal
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    • v.17 no.3
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    • pp.244-253
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    • 2007
  • This research investigated the effect of a photocatalytic reaction on nanofiltration(NF) membrane fouling by natural organic matter(NOM). The photocatalytic degradation was very effective for destruction and transformation of NOM and was carried out by titanium dioxide($TiO_2$) and $TiO_2$-immobilized bead as a photocatalyst. In order to compare their phtocatalytic properties, the photocatalytic degradation of humic acid in the presence of calcium ion was used as a model reaction. After the photocatalytic degradation the membrane fouling was dramatically decreased.

Preparation of the Titanium Dioxide-Phosphor Composite and its Photocatalytic Reaction under Visible Light (이산화티타늄-발광체 복합소재 제조 및 가시광선 광촉매 반응)

  • Park, Jin-Woo;Kim, Jung-Sik
    • Journal of the Korean Ceramic Society
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    • v.45 no.11
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    • pp.688-693
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    • 2008
  • This paper presents a study on the photocatalytic reaction about the composite particles of $TiO_2$-coated phosphors under visible light irradiation. Nanocrystalline titanium dioxide layers were directly coated on the alkaline earth aluminate phosphor, $CaAl_2O_4:Eu^{2+},\;Nd^{3+}$ particles by an sol-gel processing method. The photocatalytic reaction was analyzed with the degradation of methylene blue (MB) aqueous solution under UV and visible light irradiations. $TiO_2$-coated phosphor powders showed different photocatalytic mechanism, compared with pure $TiO_2$ (P-25, Degussa). Under UV-irradiation, $TiO_2$-coated phosphor powders showed slow photocatalytic reactivity in the early stage and fast in the latter, compared with that of pure $TiO_2$. However, $TiO_2$-coated phosphor powders showed much faster photocatalytic reactivity than that of pure $TiO_2$ under visible irradiation. In addition, the characterizations of the $TiO_2$-coated phosphor powders were conducted by a X-ray diffractometer (XRD), transmission electron microscope (TEM), and energy dispersive spectroscopy (EDS).

Photocatalytic Properties of the Ag-Doped TiO2 Prepared by Sol-Gel Process/Photodeposition (졸-겔공정/광증착법을 이용한 Ag-Doped TiO2 합성 및 광촉매 특성)

  • Kim, Byeong-Min;Kim, Jung-Sik
    • Korean Journal of Materials Research
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    • v.26 no.2
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    • pp.73-78
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    • 2016
  • $TiO_2$ nanoparticles were synthesized by a sol-gel process using titanium tetra isopropoxide as a precursor at room temperature. Ag-doped $TiO_2$ nanoparticles were prepared by photoreduction of $AgNO_3$ on $TiO_2$ under UV light irradiation and calcinated at $400^{\circ}C$. Ag-doped $TiO_2$ nanoparticles were characterized for their structural and morphological properties by X-ray diffractometry (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and transmission electron microscopy (TEM). The photocatalytic properties of the $TiO_2$ and Ag-doped $TiO_2$ nanoparticles were evaluated according to the degree of photocatalytic degradation of gaseous benzene under UV and visible light irradiation. To estimate the rate of photolysis under UV (${\lambda}=365nm$) and visible (${\lambda}{\geq}410nm$) light, the residual concentration of benzene was monitored by gas chromatography (GC). Both undoped/doped nanoparticles showed about 80 % of photolysis of benzene under UV light. However, under visible light irradiation Ag-doped $TiO_2$ nanoparticles exhibited a photocatalytic reaction toward the photodegradation of benzene more efficient than that of bare $TiO_2$. The enhanced photocatalytic reaction of Ag-doped $TiO_2$ nanoparticles is attributed to the decrease in the activation energy and to the existence of Ag in the $TiO_2$ host lattice, which increases the absorption capacity in the visible region by acting as an electron trapper and promotes charge separation of the photoinduced electrons ($e^-$) and holes ($h^+$). The use of Ag-doped $TiO_2$ nanoparticles preserved the option of an environmentally benign photocatalytic reaction using visible light; These particles can be applicable to environmental cleaning applications.

Effect of Inorganic Salts on Photocatalytic Degradation of Rhodamine B Using Sulfide Photocatalysts under Visible Light Irradiation (가시광선하에서 황화물계 광촉매를 이용한 로다민 B의 광분해 반응에 대한 무기염의 영향)

  • Lee, Gun Dae;Jin, Youngeup;Park, Seong Soo;Hong, Seong Soo
    • Applied Chemistry for Engineering
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    • v.28 no.6
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    • pp.655-662
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    • 2017
  • Sulfide photocatalysts, CdS and CdZnS, were synthesized using a simple precipitation method and their photocatalytic activities were evaluated by the degradation of rhodamine B under visible light irradiation. The effects of four inorganic salt additives, KCl, NaCl, $K_3PO_4$, and $Na_3PO_4$, on the photocatalytic reaction were examined and the role of $K^+$, $Na^+$, $Cl^-$ and $PO_4{^{3-}}$ ions during photocatalytic reaction was discussed. The added inorganic salts were shown to have a remarkable effect on the photocatalytic reaction. It was also found that the anions in inorganic salts have a much more profound effect on the reaction rate, as compared to the cations. Under the present experimental conditions, $PO_4{^{3-}}$ revealed a significant inhibitory effect on the degradation rate whereas $Cl^-$ enhanced the rate slightly. This work pointed out that the consideration of additive effects is needed in the photocatalytic reaction for wastewater treatment.

Enhanced sunlight photocatalytic activity of silver nanoparticles decorated on reduced graphene oxide sheet

  • Baskey, Moni (Sen);Ghosh, Sanjukta
    • The Korean Journal of Chemical Engineering
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    • v.34 no.7
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    • pp.2079-2085
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    • 2017
  • A facile and straightforward method has been developed to synthesize silver nanoparticles decorated on reduced graphene oxide (RGO) nanosheets through hydrothermal reaction. The composite was characterized by XRD, UV-Visible spectroscopy, SEM and TEM techniques. In this synthesized RGO-Ag nanocomposite, the Ag nanoparticles size ranges 30-50 nm. Moreover, the RGO-Ag composites exhibited excellent photocatalytic activity towards the degradation of methylene blue (MB) in presence of sunlight. This photocatalytic reaction is completed within 20 min and the rate of reaction depends on the amount of RGO present in the nanocomposites.