• Title, Summary, Keyword: UV-catalytic treatment

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The Influence of Surface Modification of Gold Nanoparticles Supported on TiO2 in the Catalytic Activity of CO Oxidation

  • Park, Da-Hee;Reddy, A.S.;Eah, Sang-Kee;Park, Jeong-Young
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.213-213
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    • 2011
  • Gold catalysts supported on TiO2 have shown a unique catalytic behavior on CO oxidation, depending on surface effects. Particle size has an influence on the surface activity. To make monodisperse Au nanoparticles, organic capping ligands, such as alkylthiols, were used by a "greener" synthesis method [1,2] and Au nanoparticles were deposited on TiO2. However, organic capping ligands must be removed for high catalytic activities by the Au nanoparticles without changing the Au size [3]. We used UV ozone treatment to decompose thiol ligands. The samples have been characterized by X-ray photoelectron spectroscopy to examine the surface modification by UV ozone treatment. We show the size distribution of the gold nanoparticles by light scattering analysis and transmission electron microscopy. Au/TiO2 have been prepared using the wetness impregnation method. The catalytic performance of CO oxidation over Au supported on TiO2 under oxidizing reaction conditions (40 Torr CO and 100 Torr O2) were tested. The results show that the catalytic activity depends on particle size and the time of UV ozone exposure, which suggests the role of sulfur bonding in determining the catalytic activity of Au/TiO2 catalysts.

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Advanced Oxidation Processes of Secondary Effluent for Reuse (재사용을 위한 하수처리장 방류수의 고급산화처리)

  • 조일형;송경석;성기석;정문호;이홍근;조경덕
    • Journal of Environmental Health Sciences
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    • v.26 no.3
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    • pp.61-68
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    • 2000
  • The use of photo-catalytic processes in pollution abatement and resource has a significant economic importance. Therefore, the applications of photochemical oxidation of secondary effluent driven by UV, TiO2, TiO2/UV, H2O2/UV and TiO2/H2O2/UV, have been investigated in order to treat the secondary effluent from municipal sewage. Various experimental parameters such as BOD, CODcr, Nurbidity, total P, and SPC were examined in each photo-catalytic reaction system. The results showed that the application of single oxidant such as UV, TiO2 only has a minor effect on parameters reduction (CODcr, BOD, etc) to treat the secondary effluent, whereas the combinations of oxidants increase the removal efficiency. The best removal efficiency in every parameters was achieved by the combination of TiO2, H2O2 and UV. It was also found that the optimum amount of TiO2 for the treatment was 1g/ι to achieve water reuse standard. From the results, the photocatalytic reaction system can be an alternative as a post-treatment to treat the secondary effluent from municipal sewage.

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UV-OXIDATIVE TREATMENT OF BIO-REFRACTORY ORGANIC HALOGENS IN LEACHATE: Comparison Between UV/O3, UV/H2O2, and UV/H2O2/O3 Processes

  • Qureshi, Tahir Imran;Kim, Young-Ju
    • Environmental Engineering Research
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    • v.11 no.2
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    • pp.84-90
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    • 2006
  • UV-catalytic oxidation technique was applied for the treatment of bio-refractory character of the leachate, which is generally present in the form of adsorbable organic halogens (AOX). Destruction of AOX was likely to be governed by pH adjustment, quantitative measurement of oxidants, and the selection of oxidation model type. Peroxide induced degradation ($UV/H_2O_2$) facilitated the chemical oxidation of organic halides in acidic medium, however, the system showed least AOX removal efficiency than the other two systems. Increased dosage of hydrogen peroxide (from 0.5 time to 1.0 time concentration) even did not contribute to a significant increase in the removal rate of AOX. In ozone induced degradation system ($UV/O_3$), alkaline medium (pH 10) favored the removal of AOX and the removal rate was found 11% higher than the rate at pH 3. Since efficiency of the $UV/O_3$ increases with the increase of pH, therefore, more OH-radicals were available for the destruction of organic halides. UV-light with the combination of both ozone and hydrogen peroxide ($UV/H_2O_2$ 0.5 time/$O_3$ 25 mg/min) showed the highest removal rate of AOX and the removal efficiency was found 26% higher than the removal efficiency of $UV/O_3$. The system $UV/H2O_2/O_3$ got the economic preference over the other two systems since lower dose of hydrogen peroxide and relatively shorter reaction time were found enough to get the highest AOX removal rate.

Comparative treatment of textile wastewater by adsorption, Fenton, UV-Fenton and US-Fenton using magnetic nanoparticles-functionalized carbon (MNPs@C)

  • Babaei, Ali Akbar;Kakavandi, Babak;Rafiee, Mohammad;Kalantarhormizi, Fariba;Purkaram, Ilnaz;Ahmadi, Ehsan;Esmaeili, Shirin
    • Journal of Industrial and Engineering Chemistry
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    • v.56
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    • pp.163-174
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    • 2017
  • Textile wastewater was treated using an enhanced simultaneous adsorption/oxidation process with magnetic nanoparticles-functionalized carbon (MNPs@C) and $H_2O_2$, UV and ultrasonic (US). Both film- and pore-diffusion affect adsorption mechanisms were included in the adsorption process. The dye adsorption was enhanced by oxidative degradation in the present of $H_2O_2$ with the suitability in order of UV-Fenton > US-Fenton > Fenton. Catalytic potential of 47% was observed for $MNPs@C/H_2O_2/UV$ system. For UV-Fenton system 94.8% removal of dye with minimal iron leaching was observed after 5 times of recycle. Increasing catalytic activity of MNPs@C on direct red 16 (DR16) degradation follows the order of PMS > PS > $H_2O_2$.

The Role of the Surface Oxide Layer on Ru Nanoparticles in Catalytic Activity of CO Oxidation

  • Kim, Sun-Mi;Qadir, Kamran;Jin, Sook-Young;Jung, Kyeong-Min;Reddy, A. Satyanarayana;Joo, Sang-Hoon;Park, Jeong-Young
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.304-304
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    • 2010
  • The study on the catalytic oxidation of carbon monoxide (CO) to carbon dioxide ($CO_2$) using the noble metals has long been the interest subject and the recent progress in nanoscience provides the opportunity to develop new model systems of catalysts in this field. Of the noble metal catalysts, we selected ruthenium (Ru) as metal catalyst due to its unusual catalytic behavior. The size of colloid Ru NPs was controlled by the concentration of Ru precursor and the final reduction temperatures. For catalytic activity of CO oxidation, it was found that the trend is dependent on the size of Ru NPs. In order to explain this trend, the surface oxide layer surrounding the metal core has been suggested as the catalytically active species through several studies. In this poster, we show the influence of surface oxide on Ru NPs on the catalytic activity of CO oxidation using chemical treatments including oxidation, reduction and UV-Ozone surface treatment. The changes occurring to UV-Ozone surface treatment will be characterized with XPS and SEM. The catalytic activity before and after the chemical modification were measured. We discuss the trend of catalytic activity in light of the formation of core-shell type oxide on nanoparticles surfaces.

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A Comparative Study of Catalytic Ozone processes for Removal of Refractory Organics (난분해성 유기물질 제거를 위한 오존/촉매 공정의 비교에 관한 연구)

  • Lee, Gyu-Hwan;Lee, Yu-Mi;Rhee, Dong-Seok
    • Journal of Industrial Technology
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    • v.26 no.A
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    • pp.199-205
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    • 2006
  • Ozone alone and catalytic ozone processes were introduced for treatment of humic acid, which is representative refractory organic compound. The treatment efficiencies of humic acid in each process were analyzed in pH variation, DOC removal, and $UV_{254}$ decrease. Mn loaded GAC catalyst was prepared by loading potassium permanganate onto the granular activated carbon surface. BCM-GAC and BCM-Silica gel catalyst were prepared by BCM. $UV_{254}$ decrease in all processes was comparatively high with efficiency over 87%. DOC removal in ozone/GAC process was the highest with 78%, and removal rates for other processes followed the order ozone/BCM-GAC(62%) > ozone/BCM-silica gel(45%) > ozone/silica gel(43%) > ozone/Mn Loaded GAC(42%) > ozone alone(37%).

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Catalytic combustion type hydrogen gas sensor using TiO2 and UV LED (TiO2 광촉매와 UV LED를 이용한 접촉연소식 수소센서)

  • Hong, Dae-Ung;Han, Chi-Hwan;Han, Sang-Do;Gwak, Ji-Hye;Lee, Sang-Yeol
    • Journal of Sensor Science and Technology
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    • v.16 no.1
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    • pp.7-10
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    • 2007
  • A thick film catalytic gas sensors which can be operated at $142^{\circ}C$ in presence of ultra violet-light emitting diode has been developed to measure hydrogen concentration in 0-5 % range. The sensing material as a combustion catalyst consists of $TiO_{2}$ (5 wt%) and Pd/Pt (20 wt%) supported on $Al_{2}O_{3}$ powder and the reference material to compensate the heat capacity of it in a bridge circuit was an catalyst free $Al_{2}O_{3}$ powder. Platinum heater and sensor materials were formed on the alumina plate by screen printing method and heat treatment. The effect of UV radiation in the presence of photo catalyst $TiO_{2}$ on the sensor sensitivity, response and recovery time has been investigated. The reduction of operating temperature from $192^{\circ}C$ to $142^{\circ}C$ for hydrogen gas sensing property in presence of UV radiation is attributed to the hydroxy radical and superoxide which was formed at the surface of $TiO_{2}$ under UV radiation.

The Role of Surface Oxide of Metal Nanoparticles on Catalytic Activity of CO Oxidation Unraveled with Ambient Pressure X-ray Photoelectron Spectroscopy

  • Park, Jeong Young
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.132-132
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    • 2013
  • Colloidal synthesis of nanoparticles with well-controlled size, shape, and composition, together with development of in situ surface science characterization tools, such as ambient pressure X-ray photoelectron spectroscopy (APXPS), has brought new opportunities to unravel the surface structure of working catalysts. Recent studies suggest that surface oxides on transition metal nanoparticles play an important role in determining the catalytic activity of CO oxidation. In this talk, I will outline the recent studies on the influence of surface oxides on Rh, Pt, Ru and Co nanoparticles on the catalytic activity of CO oxidation [1-3]. Transition metal nanoparticle model catalysts were synthesized in the presence of poly(vinyl pyrrolidone) polymer capping agent and deposited onto a flat Si support as two-dimensional arrays using the Langmuir-Blodgett deposition technique. APXPS studies exhibited the reversible formation of surface oxides during oxidizing, reducing, and CO oxidation reaction [4]. General trend is that the smaller nanoparticles exhibit the thicker surface oxides, while the bigger ones have the thin oxide layers. Combined with the nature of surface oxides, this trend leads to the different size dependences of catalytic activity. Such in situ observations of metal nanoparticles are useful in identifying the active state of the catalysts during use and, hence, may allow for rational catalyst designs for practical applications. I will also show that the surface oxide can be engineered by using the simple surface treatment such as UV-ozone techniques, which results in changing the catalytic activity [5]. The results suggest an intriguing way to tune catalytic activity via engineering of the nanoscale surface oxide.

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Characterization of Nickel Composite Plating with TiO2 Particles for Photolysis of Organic Compound (유기물 광분해용 니켈-TiO2 복합도금 전극 특성에 관한 연구)

  • Choi, Chul-Young;Cho, Seung-Chan;Ryu, Young-Bok;Kim, Young-Seok;Kim, Hyoung-Chan;Kim, Yang-Do
    • Journal of the Korean institute of surface engineering
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    • v.40 no.3
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    • pp.125-130
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    • 2007
  • Many fundamental studies have been carried out regarding waste water and hazardous gas treatment technology using the photolysis effect of $TiO_2$. However, photolysis of both organic and organic-inorganic binders immobilizing $TiO_2$ makes permanent use impossible. In this study we manufactured a catalytic electrode by nickel-$TiO_2$ composite plating in order to immobilize $TiO_2$. The surface properties according to the current density changes of cathode and concentration changes of $TiO_2$ powder in nickel plating bath has been analysed with EDX, XRF, SEM, Raman spectrometer etc. The characterization of the catalytic electrode in decomposition of organic compound has been obtained by using UV-Visible spectrophotometer through analysing concentration changes of methyl orange solution containing the catalytic electrode vs. time with projecting UV-light in the solution. The study shows that a catalytic electrode of nickel-$TiO_2$ composite plating with high-efficiency in decompostion of organic compound has been formed under high concentration of $TiO_2$ powder and low current density of cathode.

Catalytic Ozonation of Phenol (페놀의 촉매오존산화 반응에 관한 연구)

  • Lee, Cheal-Gyu;Woo, Jeong-Hun
    • Journal of Korean Society of Environmental Engineers
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    • v.33 no.10
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    • pp.731-738
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    • 2011
  • In this study AOPs of $O_3/UV$ radiation, $O_3/Mg(OH)_2/UV$ radiation and $O_3/MgO/UV$ radiation system for phenol treatment in aqueous solution was performed in a laboratory scale circulating batch reacter. Flow rate of ozone 1.0 L/min, ozone concentrations $150{\pm}10mg/L$ was maintained constantly at the above-mentioned oxidation processes. During the oxidation processes the $COD_{Cr}$ and TOC was measured in the composition. The pseudo first-order rate constants of the processes was $5.12{\times}10^{-5}$, $1.19{\times}10^{-4}$ and $1.79{\times}10^{-4}sec^{-1}$, and the activation energy was 3.03, 1.79 and $2.32kcal{\cdot}mol^{-1}$ at $20^{\circ}C$, respectively. It was found that both $Mg(OH)_2$ and MgO had remarkable accelerations on degradation of phenol and removal of COD in water. On this basis, $O_3/MgO/UV$ system is an effective and feasible routes for catalytic ozonation of phenol in water.