• Proceedings of the Korea Air Pollution Research Association Conference
• /
• 2003.11a
• /
• pp.71-72
• /
• 2003

고도산화방식(AOPs: Advanced Oxidation Processes)을 이용한 수질 및 공기오염물질 처리 관련 연구가 국내에서 지난 수년간 다수 진행되었으며 현재도 진행되고 있다. 특히 근래에는 공기오염물질 처리에 관한 연구가 활발하게 진행되고 있는데, 이는 향후 시행될 실내공기질 규제에 많은 관심이 집중되고 있기 때문인 것으로 보인다. 공기처리, 특히 실내공기 처리에 적용될 가능성이 있는 기존의 방법들 중에서 플라즈마와 광촉매반응(Ollis, 1993)이 가장 적용 타당성이 높은 것으로 판단된다. (중략)

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2009.05a
• /
• pp.191-191
• /
• 2009

최근 많은 환경오염물질을 제거하기 위한 방법으로 광촉매를 이용한 기술들이 다양하게 활용되고 있다. 본 연구에서는 높은 비표면적을 갖는 관촉매를 제조하기 위해, 전기화학적인 방법인 양극 산화법을 사용하여 기지 Ti 금속 표면에 pore 형태의 광촉매용 $TiO_2$를 제조하고, 염료분해 반응을 통해 광촉매의 효율을 조사하였다. 또한 염료분해 효율을 높이기 위해 $Eu(NO_3)_3$를 첨가하여 염료분해 반응에 미치는 영향에 대해 조사하였다.

• Proceedings of the Korea Air Pollution Research Association Conference
• /
• 1999.10a
• /
• pp.453-454
• /
• 1999

최근 대기 환경오염이 심각한 문제로 부각됨에 따라 독성 유기물질 분해 및 제독에 반도체 광촉매를 이용한 광산화기술(Advanced Oxidation Process, AOP)을 적용한 연구가 활발히 진행되고 있다. 1972년 Fujishima와 Honda가 전압을 걸어준 TiO$_2$ 단결정 전극상에 자외선을 쪼이면 물이 수소와 산소로 광분해되는 것을 발견한 이후 분균일 광촉매반응(Heterogeneous Photocatalysis)에 관한 연구가 시작되었다.(중략)

• Journal of the Korean Chemical Society
• /
• v.65 no.6
• /
• pp.415-418
• /
• 2021

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.246-246
• /
• 2016

Tungsten-nitrogen (W-N) co-doping has been known to enhance the photocatalytic activity of anatase titania nanoparticles by utilizing visible light. The doping effects are, however, largely dependent on calcination or annealing conditions, and thus, the massive production of quality-controlled photocatalysts still remains a challenge. Using density functional theory (DFT) thermodynamics and time-dependent DFT (TDDFT) computations, we investigate the atomic structures of N doping and W-N co-doping in anatase titania, as well as the effect of the thermal processing conditions. We find that W and N dopants predominantly constitute two complex structures: an N interstitial site near a Ti vacancy in the triple charge state and the simultaneous substitutions of Ti by W and the nearest O by N. The latter case induces highly localized shallow in-gap levels near the conduction band minimum (CBM) and the valence band maximum (VBM), whereas the defect complex yielded deep levels (1.9 eV above the VBM). Electronic structures suggest that substitutions of Ti by W and the nearest O by N improves the photocatalytic activity of anatase by band gap narrowing, while defective structure degrades the activity by an in-gap state-assisted electron-hole recombination, which explains the experimentally observed deep level-related photon absorption. Through the real-time propagation of TDDFT (rtp-TDDFT), we demonstrate that the presence of defective structure attracts excited electrons from the conduction band to a localized in-gap state within a much shorter time than the flat band lifetime of titania. Based on these results, we suggest that calcination under N-rich and O-poor conditions is desirable to eliminate the deep-level states to improve photocatalysis.

• Journal of Environmental Science International
• /
• v.15 no.6
• /
• pp.533-538
• /
• 2006

Removal of $NO_x$ on $CaO/TiO_2$ photocatalyst manufactured by the addition of $Ca(OH)_2$ was measured in relation with the amount of $Ca(OH)_2$ and calcination temperature. In case of pure $TiO_2$, the $NO_x$ removal decreased greatly with the increase of calcination temperature from $500^{\circ}C\;to\;700^{\circ}C$, whereas in the photocatalyst added with $Ca(OH)_2$, the removed amount of $NO_x$ was high and constant regardless of calcination temperature. Considering $NO_x$ removal patterns depending on the amount of $Ca(OH)_2$ added(50, 30, 10wt%), high removal rate showed at the photocatalysts containing less than 30wt% of $Ca(OH)_2$, and it was about 30% higher than that of pure $TiO_2$. From the XRD patterns, it is seen that the addition of $Ca(OH)_2$ contributes to maintaining the anatase structure that is favourable to photocatalysis. It also indicates that the possibility of the formation of calcium titanate($CaTiO_3$) by reacting with $TiO_2$ above $700^{\circ}C$. Apart from the favourable crystalline structure, the addition of $Ca(OH)_2$ helped increase the alkalinity of photocatalyst surface, thus promoting the photooxidation reaction of $NO_x$.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.6 no.2
• /
• pp.108-114
• /
• 2018

Degradations of durability and aesthetic performance in concrete happen during service life due to surface deterioration and dirt stains. Recently, many researches have been performed on self-cleaning and surface enhancement through surface impregnant using photocatalytic reaction with VOCs(Volatile Organic Compounds) removal. This paper is for preliminary study on surface impregnation with silicate and photocatalysis - $TiO_2$. For the work, two types of silicate based impregnants(CS - Coloidal Silica and SC - Sodium Alumina Silicate) are considered. Several tests for viscosity and surface tension are performed, and pull-off test on impregnated concrete is performed. For the surface impregnated concrete, $TiO_2$ is absorbed through submerging and spraying conditions. Through compressive strength test and SEM analysis, it is evaluated that spraying $TiO_2$ on surface impregnated concrete after 30min. of drying period is very effective both for strength enhancement and surface densification.

• Journal of Environmental Science International
• /
• v.17 no.11
• /
• pp.1195-1201
• /
• 2008

Enhancing with non-metallic elemental nitrogen(N) is one of several methods that have been proposed to modify the electronic properties of bulk titanium dioxide($TiO_2$), in order to make $TiO_2$ effective under visible-light irradiation. Accordingly, current study evaluated the feasibility of applying visible-light-induced $TiO_2$ enhanced with N element to cleanse aromatic compounds, focusing on xylene isomers at indoor air quality(IAQ) levels. The N-enhanced $TiO_2$ was prepared by applying two popular processes, and they were coated by applying two well-known methods. For three o-, m-, and p-xylene, the two coating methods exhibited different photocatalytic oxidation(PCO) efficiencies. Similarly, the two N-doping processes showed different PCO efficiencies. For all three stream flow rates(SFRs), the degradation efficiencies were similar between o-xylene and m,p-xylene. The degradation efficiencies of all target compounds increased as the SFR decreased. The degradation efficiencies determined via a PCO system with N-enhanced visible-light induced $TiO_2$ was somewhat lower than that with ultraviolet(UV)-light induced unmodified $TiO_2$, which was reported by previous studies. Nevertheless, it is noteworthy that PCO efficiencies increased up to 94% for o-xylene and 97% for the m,p-xylene under lower SFR(0.5 L $min^{-1}$). Consequently, it is suggested that with appropriate SFR conditions, the visible-light-assisted photocatalytic systems could also become important tools for improving IAQ.

• Bulletin of the Korean Chemical Society
• /
• v.35 no.12
• /
• pp.3521-3526
• /
• 2014

A magnetic sonophotocatalyst $Fe_3O_4@SiO_2@TiO_2$ is synthesized for the enhanced biodegradability of organophosphate pesticide. The as-prepared catalysts were characterized using different techniques, such as X-ray diffraction (XRD) and transmission electron microscopy (TEM). The radial sonophotocatalytic activity of $Fe_3O_4@SiO_2@TiO_2$ nanocomposite was investigated, in which commercial dichlorvos (DDVP) was chosen as an object. The degradation efficiency was evaluated in terms of chemical oxygen demand (COD) and enhancement of biodegradability. The effect of different factors, such as reaction time, pH, the added amount of catalyst on $COD_{Cr}$ removal efficiency were investigated. The average $COD_{Cr}$ removal efficiency reached 63.13% after 240 min in 12 L sonophotocatalytic reactor (catalyst $0.2gL^{-1}$, pH 7.3). The synergistic effect occurs in the combined sonolysis and photocatalysis which is proved by the significant improvement in $COD_{Cr}$ removal efficiency compared with that of solo photocatalysis. Under this experimental condition, the $BOD_5/COD_{Cr}$ ratio rose from 0.131 to 0.411, showing a remarkable improvement in biodegradability. These results showed that sonophotocatalysis may be applied as pre-treatment of pesticide wastewater, and then for biological treatment. The synthesized magnetic nanocomposite had good photocatalytic performance and stability, as when it was used for the fifth time, the $COD_{Cr}$ removal efficiency was still about 62.38%.

• Ecology and Resilient Infrastructure
• /
• v.5 no.3
• /
• pp.174-179
• /
• 2018

$TiO_2$-embedded expanded polystyrene (TiEPS) balls with powdered $TiO_2$ particles embedded on the surface of EPS were developed, and the growth inhibition of Chlorella ellipsoidea, a green algae, was evaluated. The experiment was conducted using four reactors with various conditions of (A) natural sunlight, (B) natural sunlight + TiEPS balls, (C) dark, and (D) dark + TiEPS balls on the roof of the building during five days. Based on the analysis of cell number, cell morphology, concentrations of chlorophyll-a and phaeopigments, both surface reactions in heterogeneous photocatalysis and light shielding could inhibit the growth of C. ellipsoidea. The highly reactive hydroxyl radicals ($OH{\cdot}$) from TiEPS balls degraded the lipid cell membrane through the peroxidation reaction with the light shielding, eventually resulting in cell inactivation. Although dominant inhibitory effects on the growth of C. ellipsoidea were ambiguous, TiEPS balls were feasible to prevent and inhibit the excessive growth of algae in eutrophic water body.