• Polymer(Korea)
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• v.26 no.4
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• pp.431-438
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• 2002

We studied the orientation behavior and thermal stability of polyimide (PI) molecules under irradiation of polarized UV (PUV) using polarized fourier transform infrared (FTIR) spectroscopy. In the case of PUV-exposed PI films, the remaining PI molecules after photo-degradation showed molecular orientation perpendicular to the irradiated PUV polarization direction predominantly, due to the preferential degradation of PI molecules parallel to the irradiated PUV Polarization direction. On the other hand, the rubbing of PI films induced reorientation of the PI molecules parallel to the rubbing direction. We also investigated the thermal stability of the alignment layers furled by rubbing and PUV irradiation on the PI films using Polarized FTIR. The thermal stability of the PUV irradiated PI alignment layer is lower than that of the rubbed PI layer due to the fragmentation reaction of the PI by PUV.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.11
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• pp.1087-1094
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• 2008

Diazinon is a phosphorothiate insecticide widely used in the world including Korea. This study investigates the feasibility of photolysis and photocatalysis processes for the degradation of diazinon in water. Both photolysis and photocatalysis reactiosn were effective in degrdading diazinon, however lower TOC removals were achieved. In case of photocatalysis, approximately 40% of nitrogen from diazinon was recovered as NO$_3^-$, and less than 5% of phosphorus as PO$_4{^{3-}}$. However, the sulfur in diazinon molecule was completely recovered to SO$_4{^{2-}}$ from photocatalysis reaction, and the recovery from photolysis was 50%, indicating that P=S bond easily breaks first during photolysis and photocatalysis. The poor recoveries of ionic byproducts and TOC from photolysis and photocatalysis indicate the presence of other organic intermediates during reactions. The formation of organic intermediates were identified during reactions using GC/MS and LC/MS/MS, and the main degradation products were diazoxon, and 2-isopropyl-4-methyl-6-hydroxypyrimidine (IMP), respectively. Finally, the acute 48-hr toxicity test using Daphnia magna were employed to measure the toxicity reduction during photocatalysis of degradation. The results showed that the toxicity increased until 180 min of the photocatalysis reaction (from EC$_{50}$ (%) of 69.6 to 13.2%), however, acute toxicity completely disappeared (>100%) after 360 min. The toxicity results showed that the intermediates from photocatalysis such as diazoxon were more toxic than diazinon itself, however these intermediates can be degraded or mineralized with further reaction.

• Applied Chemistry for Engineering
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• v.27 no.3
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• pp.307-312
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• 2016

Lead molybdate ($PbMoO_4$) was successfully synthesized using a facile surfactant-assisted hydrothermal process and characterized by XRD, Raman, TEM, PL, BET and DRS. We also investigated the photocatalytic activity of these materials for the decomposition of Rhodamine B under UV-light irradiation. From XRD and Raman results, well-crystallized $PbMoO_4$ crystals were successfully synthesized with the particle size of 52-69 nm. $PbMoO_4$ catalysts prepared in the presence of cetyltrimethyl ammonium bromide (CTAB) enhanced the photocatalytic activity compared to that of using P-25 and pure $PbMoO_4$ catalysts. The maximum photocatalytic activity of $PbMoO_4$ catalyst were observed when preparing it in pH 9 solution. The The PL peak at about 540 nm were observed for all catalysts and the excitonic PL signal increased proportionally with respect to the photocatalytic activity of Rhodamine B.

• Korean Chemical Engineering Research
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• v.58 no.2
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• pp.313-318
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• 2020

Bi₂WO₆ were successfully synthesized using EGME, GL, EG and water as solvents by a conventional hydrothermal method. They were characterized by XRD, DRS, BET and SEM and we also investigated the photocatalytic activity of these materials for the decomposition of Rhodamin B under visible light irradiation. The XRD results revealed the successful synthesis well-crystallized Bi₂WO₆ crystals with Aurivillius structure when EGME and EG are used as solvents. In addition, the well-crystallized Bi₂WO₆ crystals showed the flower-like structure. The Bi₂WO₆ catalysts prepared at 180 ℃ using EGME as a solvent showed the highest photocatalytic activity. The Bi₂WO₆ catalysts prepared at mole ratio of H₂O/EGME more than 50% showed high photocatalytic activity.

• Polymer(Korea)
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• v.36 no.2
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• pp.145-148
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• 2012

The effects of the linearly polarized UV (LPUV) irradiation and thermal treatment of a photo-degradable polyimide (CBDA-ODA) alignment layer (AL) on its AL properties, liquid crystal (LC) alignment, and LCD characteristics have been investigated. The best quality of LC photo-alignment have been induced by the LPUV-irradiation with much (about 5~10 times) less dosage than that generating the maximum anisotropy of the AL. A thermal treatment of the LPUV-irradiated AL has effectively removed the undesirable, low-M.W. fragments of the AL generated during the photo-decomposition and increased the stability of the AL, which has resulted in improvement of the LC alignment and the LCD property.

• Journal of the Korean Society of Clothing and Textiles
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• v.18 no.1
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• pp.15-22
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• 1994

The formation of carbonyl group was dominant to other functional groups. Concentrations of both carboxyl and peroxide groups were found to rapidly reach low steady state values that increased slightly with increa-sing temperature and relatice humidity. Since the deg-radation of cellulose samples was in the initial stage and the conversion of glycosidic bonds and hydroxyl groups were very small, it was found that changes in the physical and chemical properties could be fitted to a first-order reaction model.

• Journal of Environmental Science International
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• v.11 no.6
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• pp.589-596
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• 2002

Photocatalytic degradation of chlorpyrifos and diazinon, which are extensively used as an organophosphorous pesticide in the agriculture field, has been investigated with UV-radiated TiO$_2$ in aqueous phase. Photodegradation rate was increased with increasing pH of the solution. The removal efficiencies of chlorpyrifos and diazinon were 100% after 200 min in pH 9. Photodegradation followed a pseudo-first-order reaction. The rate constants of chlorpyrifos and diazinon were 0.0160min$\^$-1/ and 0.0180min$\^$-1/, respectively. NO$_3$$\^$-/, PO$_4$$\^$3-/, SO$_4$$\^$2-/ and Cl$\^$-/ were found as end products on the photocatalytic degradation of chlorpyrifos and diazinon with TiO$_2$/UV.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2005.05a
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• pp.340-343
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• 2005

광촉매 효율을 높이기 위해 WO$_{3}$를 첨가하여 제주에 산재해 있는 스코리아를 지지체로 하여 TiO$_{2}$ 및 WO$_{3}$/TiO$_{2}$ 광촉매를 이용하여 humic acid를 분해시킬 경우 반응영향인자에 따른 분해효율을 구한 결과 다음과 같은 결론을 얻었다. Humic acid의 분해시 Ca$^{2+}$를 첨가하였을 때가 첨가하지 않았을 때 보다 효율이 증대한 것은 이온강도가 증가하여 반발력을 감소하여 분해효율이 증대된 것이다. HCO$_{3}\;^-$를 첨가시 분해효율이 감소하는 것은 HCO$_{3}\;^-$이온이 OH radical scavenger로 작용했기 때문이다.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2001.11a
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• pp.365-366
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• 2001

자동차 제조공장, 화학 및 제약 공장 등 각종 산업체 뿐만 아니라 가정생활에서 배출되는 휘발성유기화합물들 (Volatile Organic Compounds)을 처리하기 위하여 지난 수년간 많은 공정들이 개발되어 왔으며, 이러한 공정들 중 광촉매에 의한 유기화합물의 광분해에 관한 연구는 일본 등 선진국을 비롯하여 우리나라에서도 각광을 받고 있다. TiO$_2$광촉매는 항균, 탈취 등의 기능을 가지고 있어 산업계 및 생활환경에서 많은 적용 가능성을 가지고 있으며, 특히 일상에 존재하는 태양광이나 형광등에 의해서도 광촉매 반응을 일으킬 뿐만 아니라 내마모성이 우수하며, 화학적으로 안정적이다는 장점을 가지고 있다. (중략)

• Proceedings of the KAIS Fall Conference
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• 2000.10a
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• pp.233-236
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• 2000

산업화에 따라 발생하는 산업폐수에는 많은 종류의 유해한 유기물들이 함유되어 있으며, 이러한 유독성 유기물을 제거하기 위하여 많은 연구가 진행되어 왔으나. 기존의 처리 방법들은 2차 환경오염을 유발한다는 문제점을 갖고 있다. 최근 폐수처리에 광촉매를 이용한 광분해 반응이 기존의 처리방법들에서 나타날 수 있는 문제점과 폐수중의 유독성 유기물을 제거할 수 있는 환경친화적 공정이라는 보고가 있은 후 광촉매에 대한 연구가 활발히 진행되고 있다. 본 연구에서는 광촉매 TiO₂의 표면특성을 XRD, SEM 및 BET를 사용하여 자세히 고찰하였다. XRD 결과 Degussa P25는 anatase 구조와 rutile 구조가 섞인 형태였으며, Aldrich Degissa TiO₂는 100% anatase 구조, KIER TiO₂는 100% rutile 구조를 가졌고 SEM 결과 Aldrich와 Degussa TiO₂의 입자형태는 작은 입자들이 뭉쳐있는 형태였으나 KIER TiO₂는 작은 입자들이 독립적으로 분리된 타원형으로 입자크기가 가장 컸다. 반면 BET 결과 Degussa TiO₂의 비표면적이 59㎡/g으로 Aldrich TiO₂(6㎡/g)나 KIER TiO₂(14 ㎡/g)에 비하여 매우 큼을 알 수 있었다.