광산폐수 내 시안 제거를 위한 TiO2와 UV-LED를 이용한 광촉매 산화

김성희 ( Seong Hee Kim ),이상우 ( Sang Woo Lee ),조현구 ( Hyen Goo Cho ),김영호 ( Young Ho Kim ),김순오 ( Soon Oh Kim ) 한국광물학회 2014 광물과 암석 (J.Miner.Soc.Korea) Vol.27 No.4

광산에서 순도 높은 금은을 추출하기 위해 청화법을 이용해 왔다. 이러한 광산 활동에서 많은 양의 시안이 사용되어 왔으며 이에 따라 고농도의 시안을 함유한 광산폐수가 발생되어 광산 주변 지역의 수계를 오염시킬 수 있다. 본 연구에서는 이러한 시안함유 광산폐수 및 침출수로부터 시안을 제거하기 위하여 TiO2 광촉매와 UV-LED 광원을 이용한 광산화 공정에 대하여 연구하였다. 기존 광산화 공정에서는 주로 UV 램프가 광원으로 많이 사용되었지만 여러 가지 단점으로 인하여 본 연구에서는 그 대체 광원으로 UV-LED의 적용 가능성을 평가하였다. 세 종류의 TiO2의 광산화 효율을 평가한 결과, 아나타제와 루틸이 혼합된 Degussa P25가 광산화 효율이 가장 좋은 것으로 확인되었다. 또한 형태와 파장이 다른 네 종류의 UV-LED를 비교 평가한 결과, 365 nm 램프형 > 365 nm 캔형 > 280nm 캔형 > 420 nm 램프형 순으로 제거효율이 좋은 것으로 나타났다. 본 연구는 UV-LED는 기존의UV 램프의 단점을 극복할 수 있는 대체광원으로서 광산화 공정에 적용 가능하다는 것을 입증하였으며, 시안의 광산화 효율은 TiO2 광촉매의 종류에도 영향을 받는다는 것을 확인하였다. Cyanidation method has been used to extract high-purity gold and silver in mining industry. Such mining activities have used a large amount of cyanide, and the mine wastewater contained a high level of cyanide has brought about pollution of surrounding aqueous environments. This research was initiated to study TiO2-catalytic UV-LED photo-oxidation to remove cyanide from the mine wastewater. UV lamp has been generally used as a light source in conventional photo-oxidation so far, but it shows numerous drawbacks. For this reason, this study focused on the evaluation of applicability of UV-LED as an alternative light source in cyanide photo-oxidation process. Three types of TiO2 photo-catalyst were compared in terms of performance of photo-oxidation of cyanide, and the results show that Degussa P25 was the most efficient. In addition, four types of UV-LED were tested to compare their efficiencies of cyanide photo-oxidation, and their efficacy was increased in the order of 365 nm lamp-type > 365 nm can-type > 280 nm can-type > 420 nm lamp-type. Not only did this study demonstrate that UV-LED can be used in the photo-oxidation of cyanide as an alternative light source of UV lamp, but also confirmed that the performance of photo-oxidation was significantly influenced by the type of TiO2 catalysts.

Enhanced photo-catalytic activity of TiO₂ films by removal of surface carbon impurities; the role of water vapor

Seo, Hyun Ook,Woo, Tae Gyun,Park, Eun Ji,Cha, Byeong Jun,Kim, Il Hee,Han, Sang Wook,Kim, Young Dok Elsevier 2017 APPLIED SURFACE SCIENCE - Vol.420 No.-

<P><B>Abstract</B></P> <P>We have studied the photo-catalytic degradation of acetaldehyde over the surface of TiO<SUB>2</SUB> films under UV light (365nm) irradiation both at dry and humid air conditions using a high vacuum chamber equipped with on-line gas-chromatography as a batch-type reactor. Changes of TiO<SUB>2</SUB> surfaces upon the photo-catalysis experiments were studied by X-ray photoelectron spectroscopy. The competitive adsorption of water and acetaldehyde resulted in the reduction of reaction rate of photo-catalytic degradation of acetaldehyde under the UV light irradiation. The photo-catalytic reaction rate of TiO<SUB>2</SUB> films towards acetaldehyde mineralization increased when the photo-catalysis experiments were performed repeatedly and it was much more pronounced under humid conditions. Our XPS analysis revealed that carbon impurities on the surface of TiO<SUB>2</SUB> films were removed by UV-light driven photo-catalytic mineralization under humid conditions. Water vapor facilitated the photo-catalytic removal of carbon impurities from TiO<SUB>2</SUB> surface generating additional active sites of TiO<SUB>2</SUB> which resulted in the enhanced photo-catalytic activity of TiO<SUB>2</SUB> films.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Changes of TiO<SUB>2</SUB> surfaces during photo-catalysis were studied by XPS. </LI> <LI> Role of humidity for photo-catalytic decomposition of acetaldehyde was studied. </LI> <LI> Competitive adsorption of water and acetaldehyde resulted in the reduction of reaction rate. </LI> <LI> Water vapor facilitated the photo-catalytic removal of carbon impurities from TiO<SUB>2</SUB>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Molecular weight changes during photo-oxidation of polyethylene nanocomposites

T.O. Kumnayaka,R. Parthasarathay,M. Jollands,I. Ivanov 한국유변학회 2010 Korea-Australia rheology journal Vol.22 No.3

The environmental degradation of synthetic polymers is enhanced by blending them with biopolymers such as starch, pro-oxidants (metal complexes, such as cobalt stearate and manganese stearate) and inorganic fillers. Recent studies have shown that nano-clay used to enhance the mechanical properties of polymers such as polyethylene also helps in polymer degradation (Lee et al., 2005; Qin et al., 2003). The present work aims to investigate the effect of montmorillonite nano-clay (MMT) on the photo-oxidation of polyethylene. The molecular weight changes of polyethylene in MMT/polyethylene nanocomposites upon UV irradiation were evaluated using rheological measurement and gel permeation chromatography. The molecular weight decrease for nanocomposites is found to be greater than that for the pure polyethylene. Furthermore, the increase in clay concentration also enhances the rate of photo-oxidation of the polymer. These results show that clay is acting as a self pro-oxidant during the photo-oxidation. The dynamic shear measurements show that both cross-liking and chain scission occur during the photo-oxidation but the latter seems to be dominant.

Photochemical Reaction in Monolayer MoS₂ <i>via</i> Correlated Photoluminescence, Raman Spectroscopy, and Atomic Force Microscopy

Oh, Hye Min,Han, Gang Hee,Kim, Hyun,Bae, Jung Jun,Jeong, Mun Seok,Lee, Young Hee American Chemical Society 2016 ACS NANO Vol.10 No.5

<P>Photoluminescence (PL) from monolayer MoS2 has been modulated using plasma treatment or thermal annealing. However, a systematic way of understanding the underlying PL modulation mechanism has not yet been achieved. By introducing PL and Raman spectroscopy, we analyze that the PL modulation by laser irradiation is associated with structural damage and associated oxygen adsorption on the sample in ambient conditions. Three distinct behaviors were observed according to the laser irradiation time: (i) slow photo-oxidation at the initial stage, where the physisorption of ambient gases gradually increases the PL intensity; (ii) fast photo-oxidation at a later stage, where chemisorption increases the PL intensity abruptly; and (iii) photoquenching, with complete reduction of PL intensity. The correlated confocal Raman spectroscopy confirms that no structural deformation is involved in slow photo-oxidation stage; however, the structural disorder is invoked during the fast photo-oxidation stage, and severe structural degradation is generated during the photoquenching stage. The effect of oxidation is further verified by repeating experiments in vacuum, where the PL intensity is simply degraded with laser irradiation in a vacuum due to a simple structural degradation without involving oxygen functional groups. The charge scattering by oxidation is further explained by the emergence/disappearance of neutral excitons and multiexcitons during each stage.</P>

TiO2 광촉매 산화 반응에서 생성된 수산기 라디칼 분석 방법

김성희 ( Seong Hee Kim ),이상우 ( Sang Woo Lee ),김정진 ( Jeong Jin Kim ),김순오 ( Soon Oh Kim ) 한국광물학회 2015 광물과 암석 (J.Miner.Soc.Korea) Vol.28 No.3

TiO2 광촉매 산화 공정의 효율은 수산기 라디칼의 생성량에 따라 크게 의존한다. 따라서 생성되는 수산기 라디칼의 정확한 정량이 공정을 평가하는데 필수적이다. 하지만 아직까지 이러한 수산기라디칼 정량법이 마련되지 못했다. 이에 본 연구는 TiO2 광촉매 산화 반응에서 생성되는 수산기 라디칼을 정량화하기 위한 기존 분석법들을 비교하고, 기존 분석법들의 단점을 극복할 수 있는 새로운 방법을 제안하고자 수행되었다. TiO2 광촉매 산화 반응을 모사하기 위하여, 표준 TiO2 광촉매로서 널리이용되고 있는 Degussa P25를 사용하였으며, 투여량은 0.05 g/L이었다. 그리고 UVC 수은 저압램프(11 W, 2,975 mW/cm2)를 광원으로 이용하였다. 연구결과, 기존에 많이 활용되고 있는 요오드화칼륨(KI)/UV-vis 분광분석법과 테레프탈산(TPA)/형광 분광분석법은 각각 요오드이온(I-)과 테레프탈산을 공정 중 생성된 수산기 라디칼과 반응시켜 발생하는 삼중요오드이온(I3-)과 2-하이드록시 테레프탈산을 검출하여 수산기 라디칼의 생성여부만을 확인할 수 있는 정성적인 분석법들이었다. 하지만 본 연구에서 테레프탈산 방법을 고성능 액체 크로마토그래프(HPLC) 분석법과 연계하였을 때 수산기 라디칼의 정량화가 가능하였다. 이렇게 새롭게 개발된 TPA/HPLC 분석법을 이용하여 측정한 결과, 본 연구의 실험 조건에서 8시간의 광촉매 산화 공정에 의해서 0.013 M의 수산기 라디칼이 생성되는 것을 확인하였다. 본 연구에서 제안하는 수산기 라디칼 정량법은 광촉매 산화 공정의 성능을 평가하는데 기여할 것으로 기대된다. The performance of TiO2 photo-catalytic oxidation process is significantly dependent on the amount of hydroxyl radicals produced during the process, and it is an essential prerequisite to quantify its production. However, precise and accurate methods for quantification of hydroxyl radicals have not been developed so far. For this reason, this study was initiated to compare existing methods for analysis of hydroxyl radicals produced by TiO2 photo-catalytic oxidation and to propose a new method to overcome the limitation of established methods. To simulate TiO2 photo-catalytic oxidation process, Degussa P25 which has been widely used as a standard TiO2 photo-catalyst was used with the dose of 0.05 g/L. The light source of process was UVC mercury low-pressure lamp (11 W, 2,975 mW/cm2). The results indicate that both potassium iodide (KI)/UV-vis spectrometer and terephthalic acid (TPA)/fluorescence spectrometer methods could be applied to qualitatively measure hydroxyl radicals via detection of triiodide ion (I3 -) and 2-hydroxyterephthalic acid which are produced by reactions of iodine ion (I-) and TPA with hydroxyl radicals, respectively. However, it was possible to quantitatively measure hydroxyl radicals using TPA method coupled with high-performance liquid chromatograph (HPLC). The analytical results using TPA/HPLC method show that hydroxyl radical of 0.013 M was produced after 8 hours operation of photo-catalytic oxidation under specific experimental conditions of this study. The proposed method is expected to contribute to precise the evaluation of the performance of photo-catalytic oxidation process.

양친매성 덴드리머의 광산화적 분해 반응

장동욱 ( Dong Wook Chang ) 대구가톨릭대학교 자연과학연구소 2012 자연과학연구논문집 Vol.10 No.1

We have studied the singlet oxygen meditated photo-oxidative degradation of amphiphilic dendrimers with oligo(phenylenevinylene) core branches and oligo(ethylene oxide) terminal chains. Due to the unique micellar aggregate structures of amphiphilic dendrimers in aqueous medium and their optimized structural features, they are highly susceptible to singlet oxygen meditated photo-oxidative degradation. Interestingly, their photo-oxidative degradation process is highly dependent on the types of additional photosensitizers. As a result, the degradation processes of amphiphilic dendrimers in aqueous medium were monitored by the UV-vis spectra as a function of the elapsed irradiation time. Furthermore the chemical and morphological changes of amphiphilic dendrimers during degradation process were also investigated by FT-IR and AFM studies

TiO₂ 광-촉매 반응에 의한 Cu(II)-EDTA의 산화(I) - TiO₂ 량과 pH의 영향 -

정흥호,박은희,노재성,성기웅,조영현,Chung, Hung-Ho,Park, Eun-Hee,Rho, Jae-Seong,Sung, Ki-Woung,Cho, Young-Hyun 한국공업화학회 1999 공업화학 Vol.10 No.1

수중 금속이온 착화용 공업세정제를 비롯하여 산업적으로 다양한 용도로 폭넓게 사용되고 있는 EDTA (ethylenediaminetetraacetic acid)는 수처리시 금속이온들을 제거할 경우에 방해요인으로 작용하므로, EDTA를 우선적으로 분해하여 착화결합을 끊어야 금속이온들의 제거가 용이해진다. 본 연구에서는, $TiO_2$ (Degussa P-25)를 사용하여 1.79 mM의 초기 Cu(II)-EDTA 수용액 농도와 $20^{\circ}C$의 호기성 분위기 하에서, 촉매의 양과 초기의 수용액 pH가 Cu(II)-EDTA 착물의 산화에 미치는 영향을 고찰하였다. $TiO_2$량이 2.0 g/L일 경우에 EDTA, Cu와 TOC 감소율이 최대로 나타났고, DETA의 촉매표면 흡착은 $TiO_2$ 표면전하에 의해 영향을 받으며 광-촉매 반응에 의한 EDTA의 분해는 광-조사전의 촉매표면 흡착에 의존하는 것으로 보였다. EDTA (ethylenediaminetetraacetic acid), a chelating agent is most widely used in industrial applications, especially for cleaning of metals in water, frequently prohibits metal removal from water in conventional water treatment technologies. It could be easier to remove aqueous metal ions by the breakdown of DETA complexed bonds first. This study investigated the availability of $TiO_2$ photo-catalysis for the aqueous phase oxidation of Cu(II)-EDTA, under an aerobic condition at $20^{\circ}C$ with $TiO_2$ (Degussa P-25) and 1.79mM of Cu(II)-EDTA. When $TiO_2$ loading was 2.0 g/L, the photo-catalytic oxidation of Cu(II)-EDTA was maximal. The tendency of EDTA adsorption onto the catalyst surface was affected by $TiO_2$ surface charge, and the oxidation rate of Cu(II)-EDTA by photo-catalysis was shown to be dependent upon the tendency of EDTA adsorption before photo-irradiation.

Analysis on the photo-carrier generation and photo-decay in metal-oxide semiconductors

김영훈 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.0

Solution-processed metal-oxide semiconductors such as zinc oxide are now widely used in various energy harvesting devices such as organic solar cells and perovskite solar cells. However, since the oxide semiconductors can also show a high response to light illumination and possess persistent photoconductivity (PPC), it is important understand the photo carrier generation and decaying properties of oxide semiconductors. Here, we investigate the photoconductivity and photo-decaying porperties of various oxide semiconductor materials and structures such as indium gallium zinc oxide (IGZO), and a double-layered IZO/IGZO structure to identify the influence of channel materials and structures on the photocurrent and relaxation time of the device.

금강밀과 dark northern spring밀의 기울과 배아에서 추출한 기름의 광산화 과정 중 천연산화방지성분의 변화

최현기(Hyunki Choi),최은옥(Eunok Choe) 한국식품과학회 2010 한국식품과학회지 Vol.42 No.1

금강밀과 Dark Northern Spring(DNS)밀의 제분 중 발생하는 기울과 배아로부터 추출한 기름(WBG oil)을 5℃, 1700 Lux로 12일 동안 광산화시킬때 토코페롤, 카로티노이드, 인지질 함량 변화를 측정하고 이들과 WBG oil의 광산화 관련성을 평가하였다. 토코페롤, 카로티노이드, 인지질은 WBG oil의 광산화 중 분해되었으며 DNS밀 WBG oil이 금강밀 WBG oil에서보다 토코페롤의 분해가 빨랐으나, 카로티노이드와 인지질 분해 속도는 느렸다. WBG oil의 광산화 정도와 산화방지성분의 상관관계는 매우 높았으며 인지질이 WBG oil의 광산화에 가장 큰 영향을 나타내었다. 금강밀 WBG oil에 비해 리놀레산 함량이 낮고 올레산 함량이 높았던 DNS밀 WBG oil은 지방산 조성은 물론 인지질의 높은 함량과 낮은 분해 속도에 기인하여 높은 광산화안정성을 나타내었다. 본 결과는 빛의 존재하에서 DNS밀 WBG oil보다는 금강밀 WBG oil이 토코페롤 source로 사용될 수 있는 가능성을 보여주었다. Naturally present antioxidants, tocopherols, carotenoids, and phospholipids in the bran and germ oils from Keumkang (K-WBG oil) and Dark Northern Spring wheats (DNS-WBG oil) were determined during storage under 1700lux light at 5℃ by HPLC. Oil oxidation was monitored by peroxide values (POV) and conjugated dienoic acid content. The results showed that antioxidants were degraded during storage of the WBG oils under light, with higher degradation rates for carotenoids and phospholipids in the K-WBG oil compared to the DNS-WBG oil. Light increased oil oxidation and the rate of oxidation was higher in K-WBG oil than in the DNS-WBG oil. There was a high correlation between POV and residual amounts of antioxidants during photo-oxidation, with phospholipids showing the greatest effects on POV. This study suggests that a higher amount and lower degradation rate of phospholipids in the DNS-WBG oil contributed to its higher photo-oxidative stability compared to the K-WBG oil.

자외선 LED와 백금으로 박막된 TiO2 광촉매를 이용한 중금속과 결합한 시안화합물의 광촉매 산화

설정우 ( Jeong Woo Seol ),김성희 ( Seong Hee Kim ),이우춘 ( Woo Chun Lee ),조현구 ( Hyen Goo Cho ),김순오 ( Soon Oh Kim ) 한국광물학회 2015 광물과 암석 (J.Miner.Soc.Korea) Vol.28 No.1

광석에서 순도 높은 금은을 추출하기 위해 사용된 청화법으로부터 시안이 유출되어 광석 내 존재하는 중금속들과 결합하여 다양한 형태의 시안화합물이 생성된다. 이러한 시안화합물은 난분해성 오염물질로서 인간을 포함한 생태계에 악영향을 끼친다. 결합력에 따라서 중금속과 결합한 시안화합물은 공유결합성 화합물(weak acid dissociable, WAD)과 착화합물(strong acid dissociable, SAD) 등으로 분류할 수 있다. 본 연구에서는 시안화합물의 존재 형태별 광촉매 산화 효율을 비교 평가하였다. 특히 자외선 LED 광원의 파장과 광촉매 표면 개질이 시안화합물의 분해에 미치는 영향을 살펴보았다. 실험 결과, 동일한 광촉매 산화 조건에서 자유 시안보다는 중금속과 결합한 시안화합물의 광산화분해 효율이 떨어짐을 알 수 있었다. 그리고 자유 시안의 경우에는 짧은 파장에서 광촉매 산화가 효과적이었지만 중금속과 결합한 시안화합물의 경우에는 긴 파장에서 광산화 분해능이 더 높게 나타났다. 그리고 광촉매 표면 개질에 의하여 광촉매 산화 공정의 성능을 향상시킬 수 있음을 확인하였다. Cyanide can be leached out from the cyanidation method which has been used to extract high-purity gold and silver from ores, and it becomes a variety of cyanide complexes associated with heavy metals contained in ores. Such cyanide complexes are considered as persistent and non-degradable pollutants which cause adverse effects on humans and surrounding environments. Based on binding force between heavy metals and cyanide, cyanide complexes can be categorized weak acid dissociable (WAD) and strong acid dissociable (SAD). This study comparatively evaluated the performance of photo-catalytic process with regard to forms of cyanide complexes. In particular, both effects of UV LED wavelength and surface modification of photo-catalyst on the removal efficiency of cyanide complexes were investigated in detail. The results indicate that the performance of photo-catalytic oxidation is significantly affected by the form of cyanide complexes. In addition, the effect of UV LED wavelength on the removal efficiency was quite different between free cyanide and cyanide complexes associated with heavy metals. The results support that the surface modification of photo-catalyst, such as doping can improve overall performance of photo-catalytic oxidation of cyanide complexes.