Poly(vinyl alcohol) (PVA) composites with various graphite oxide (GO) contents (0 to 10 wt%) were prepared by sonicating the mixture of PVA and GO, followed by crosslinking with glutaraldehyde. GO was pre-treated with oxyfluorination (O2:F2 = 8:2) in order to modify the surface of GO to allow it to carry hydrophilic functional groups. PVA/GO composite hydrogels were characterized by scanning electron microscopy and Fourier-transform infrared spectrometer (FT-IR). The morphology of the PVA/GO composite hydrogels and the variations in soluble gel portion were investigated under various GO contents and UV irradiation doses. The variation in the chemical structure of photo degraded PVA/GO composite hydrogels was studied by FT-IR. The photochemical stability of PVA/GO composite hydrogels under UV irradiation was found to improve noticeably with increasing content of uniformly dispersed GO.

The photodegradation of the model compounds Quinol, an aromatic organic compound and Acid blue FFS, an acid dye of chemical class Triphenylmethane was studied by using illumination with UV lamp of light intensity 250W. TiO2 and TiO2 doped with Boron and Nitrogen was used as catalyst. The sol-gel method was followed with titanium isopropoxide as precursor and doping was done using Boron and Nitrogen. In photocatalytic degradation, TiO2 and doped TiO2 dosage, UV illumination time and initial concentration of the compounds were changed and examined in order to determine the optimal experimental conditions. Operational time was optimized for 360 min. The optimum dosage of TiO2 and BN doped TiO2 was obtained to be 2 mgL-1 and 2.5 mgL-1 respectively. Maximum degradation % for quinol and Blue FFS acid dye was 78 and 95 respectively, at the optimum dosage of BN-doped TiO2 catalyst. It was 10 and 4% higher than when undoped TiO2 catalyst was used.

For the present paper, we prepared MgO/MWCNT/TiO2 photocatalyst by using multi-walled carbon nanotubes(MWCNTs) pre-oxidized by m-chlorperbenzoic acid (MCPBA) with magnesium acetate tetrahydrate (Mg(CH2COO)2·4H2O)and titanium n-butoxide (TiOC(CH3)34) as magnesium and titanium precursors. The prepared photocatalyst was analyzed byX-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis. The decompositionof methylene blue (MB) solution was determined under irradiation of ultraviolet (UV) light. The XRD results show that theMgO/MWCNT/TiO2 photocatalyst have cubic MgO structure and anatase TiO2 structure. The porous structure and the TiO2agglomerate coated on the MgO/MWCNT composite can be observed in SEM images. The Mg, O, Ti and C elements can bealso observed in MgO/MWCNT/TiO2 photocatalyst from EDX results. The results of photodegradation of MB solution under UVlight show that the concentration of MB solution decreased with an increase of UV irradiation time for all of the samples. Also,the MgO/MWCNT/TiO2 photocatalyst has the best photocatalytic activity among these samples. It can be considered that theMgO/MWCNT/TiO2 photocatalyst had a combined effect, the effect of MWCNT, which could absorb UV light to create photo-induced electrons (e−), and the electron trapping effect of MgO, which resulted in an increase of the photocatalytic activity of TiO2.

The composite photocatalysts of a Fe-modified carbon nanotube (CNT)-TiO2 were synthesized by a two-step sol-gel method at high temperature. Its chemical composition and surface properties were investigated by BET surface area, scanning electron microscope (SEM), Transmission Electron Microscope (TEM), X-ray diffraction (XRD) and ultraviolet-visible (UV-Vis) spectroscopy. The results showed that the BET surface area was improved by modification of Fe, which was related to the adsorption capacity for each composite. Interesting thin layer aggregates of nanosized TiO2 were observed from TEM images, probably stabilized by the presence of CNT, and the surface and structural characterization of the samples was carried out. The XRD results showed that the Fe/CNT-TiO2 composites contained a mix of anatase and rutile forms of TiO2 particles when the precursor is TiOSO4·xH2O (TOS). An excellent photocatalytic activity of Fe/CNT-TiO2 was obtained for the degradation of methylene blue (MB) under visible light irradiation. It was considered that Fe cation could be doped into the matrix of TiO2, which could hinder the recombination rate of the excited electrons/holes. The photocatalytic activity of the composites was also found to depend on the presence of CNT. The synergistic effects among the Fe, CNT and TiO2 components were responsible for improving the visible light photocatalytic activity.

Activated carbon fiber (ACF) filters are widely used to remove volatile organic compounds (VOCs) in air cleaning devices. The performance of ACF filters could be enhanced combining adsorption process with photodegradation process. In this study, to investigate this enhancement effect, a duct-type reactor was made and TiO2 was i㎜obilized on a co㎜ercialized ACF filter. Benzene, toluene, and m-xylene (BTX) were chosen as target compounds. Removal experiments for BTX were done under different air velocity and upstream concentration conditions. The range of inlet concentration was 200～1,400 ppb and the air velocities were 0.4, 0.7 and 1.0 m/s. Adsorption by an ACF filter alone showed high removal efficiency of BTX, depending on the BTX species, the upstream concentration, and the air velocity. The combination of TiO2 and ACF filter significantly increased removal of benzene which was less removed than other pollutants by an ACF filter alone. It was found that the combination effect was small in removal test of toluene and m-xylene. Removal efficiency in the tested experimental conditions was decreased in order of toluene > m-xylene > benzene.

Piperophos에 대한 광분해 실험을 수행하여 속도상수와 분해생성물을 측정하였다. 햇빛을 이용한 광분해 실험은 2003년 10월 3일부터 10월 22일 까지 하였으며 상당기간 동안 농약이 햇빛에 안정함을 확인할 수 있었고, humic acid 의 광관여 효과가 없음을 알 수 있었다. 자외선을 이용한 광분해 실험에서 piperophos는 자외선을 단독조사하였을 때 자외선의 세기가 클수록 상대적으로 빠르게 분해되었으며, 광분해 촉매제인 TiO₂의 양을 증가시켜도 별 차이가 없었다. 광분해에 의한 분해산물을 확인하고자 GC/MS분석을 한 결과 piperophos의 분해생성물은 m/z=166의 0.0-dipropyl phosphorodithioate로 추정된다.

수산 시설물의 내구성을 평가하기 위한 기초 단계로 부력재 또는 프레임용 재질로 많이 사용되고 있는 국산 고밀도 PE 및 고강도 PVC와 노루웨이 고밀도 PE에 대하여 인공 광원을 조사한 후 시간의 경과에 따른 시료의 물성과 그 표면 및 파면의 형태적 변화를 비교·분석하였다. 실험에서 얻어진 결과를 요약하면 다음과 같다. 1) 자외선 조사 시간이 경과됨에 따라 세 시료 모두 인장 응력과 탄성률은 미처리된 초기의 그것보다 크게 감소하였으나, 파단 신장률의 경우 처음에는 증가하다가 다시 감소하는 불규칙적인 경향을 나타내었다. 2) 잔여 응력 RS(kg/mm 상(2))와 자외선 폭로 기간 Y(Year)와의 상관 관계는 다음과 같이 나타났다. KHDPE : RS=2.6769-0.0003Y(r 상(2)=0.63) Hi-PVC : RS=5.3470-0.0003Y(r 상(2)=0.91) NHDPE : RS=2.4929-0.0004Y(r 상(2)=0.97) 3) 전자 현미경 촬영 결과, 자외선의 영향으로 시료의 표면에 물방울 형상이 나타났으며, 자외선 조사 시간이 경과됨에 따라 분자 구조의 분해로 인하여 작은 구멍이 확인되었다.

수산시설용 그물감 재료로 많이 사용되고 있는 PE 및 나일론과 신소재섬유로 구성된 Hi-PE 그물실의 내후성 기구를 파악하기 위하여 그물실에 인공광원을 조사한 후 시간의 경과에 따른 그물실 표면의 형태적 변화와 밀도 및 광각X선 회절 측정을 실시하였으며, 이들 결과를 인장시험에 의한 기계적 물성 특성과 비교「고찰하였다. 실험의 결과를 요약하면 다음과 같다. 1. 그물실 표면의 형태적 변화는 염색 처리된 PE와 나일론 그물실의 경우에는 표면에 안료가 석출되었을 뿐 균열은 나타나지 않았으나, 미처리된 Hi-PE 그물실의 경우 자외선 etching에 따른 균열의 현저한 증가를 확인할 수 있었다. 2. 그물실의 분자 충진 밀도의 경우, 염색된 PE 및 나일론 그물실의 경우에는 노출시간이 증가함에 따라 큰 변화는 없었으나, Hi-PE 그물실의 경우에는 분자사슬의 재배열과 chain scission 등의 영향에 의해 밀도가 증가하였다. 3. 세 그물실 모두 회절 피크의 2θ에는 큰 변화가 없는 것으로 보아 결정구조의 근본적인 변화는 없다고 생각할 수 있다. 4. 잔여 강도는 염색처리된 PE 및 나일론 그물실에서 각각 90.8%와 75.3%로 높게 나타났으나, 미처리된 Hi-PE 그물실에서는 68.3%로 가장 작았으며, 이는 전자현미경에 의해 촬영된 그물실 표면의 형태적 변화와도 잘 일치하고 있다.

The present study was performed to investigate photodegradation rate constants and degradation products of dichlorvos and methidathion by the USEPA method. The two pesticides were very stable in sunlight for 16 days from September 2 to 18, 1998 and humic acid had no sensitizing effect on the photolysis of each pesticide in sunlight. The photolysis rate was fastest for methidathion, followed by dichlorvos in the presence of UV irradiation. Photodegradation rate constant and half-life of dichlorvos were 0.0208 and 33.3 min, respectively. Photodegradation rate constant and half-life of methidathion were 0.6789 and 1.0min, respectively. The two pesticides were degraded completely in the presence of UV irradiation and UV irradiation with TiO₂ in about 3 hours. Therefore, it is suggested that UV treatment will be effective for the degradation of pesticides in the process of drinking water purification. In case of dichlorvos and methidathion, UV irradiation with TiO₂ was more effective for degradation than UV irradiation. In order to identify photolysis products, the extracts of degradation products were analyzed by GC/ MS. The mass spectrum of photolysis products of dichlorvos was at m/z 153, those of the photolysis of methidathion were at m/z 198 and 214, respectively. Photolysis products of dichlorvos was O, O-dimethyl phosphate(DMP), those of methidathion were O, O-dimethyl phosphorothioate(DMTP) and O, O-dimethyl phosphorodithioate (DMDTP).

본 연구에서는 금 나노입자 콜로이드를 이용하여 safranin-O의 광촉매적 분해를 관찰하였다. 금 나노입자는 용액상에서 safranin-O의 분해 속도를 빠르게 하기 위해서 사용되었다. 금 나노입자 콜로이드는 수용액상에서 Na₂CO₃ 와 PVP 고분자(poly(vinyl pyrrolidone))를 이용하는 환원방법에 의하여 제조하였다. Safranin-O의 분해현상은 자외선(UV light)와 과산화수소(H₂O₂)의 존재 하에서 금 나노입자 콜로이드와 염화금의 농도, 반응계의 산도(pH), 반응시간과 같은 실험조건들의 조절을 통해 연구되었다. 분해반응에 사용된 금 나노입자 콜로이드의 농도가 증가함에 따라서 염료가 분해되는 속도가 증가하였다. Safranin-O의 광산화 반응은 광학적으로 측정되었고, 금 나노입자의 기본적인 물성과 촉매 특성은 UV-Vis 광학계를 이용하여 측정되었다.

The photodegradation and by-products of the gaseous toluene with TiO2 (P25) and short-wavelength UV (UV254+185nm) radiation were studied. The toluene was decomposed and mineralized efficiently owed to the synergistic effect of photochemical oxidation in the gas phase and photocatalytic oxidation on the TiO2 surface. The toluene by the UV254+185nm photoirradiated TiO2 were mainly mineralized CO2 and CO, but some water-soluble organic intermediates were also formed under severe reaction conditions. The ozone and secondary organic aerosol were produced as undesirable by-products. It was found that wet scrubber was useful as post-treatment to remove water-soluble organic intermediates. Excess ozone could be easily removed by means of a MnO2 ozone-decomposition catalyst. It was also observed that the MnO2 catalyst could decompose organic compounds by using oxygen reactive species formed in process of ozone decomposition.

Photodegradation of endosulfan alpha, beta, and sulfate known as the most toxic substance among organochlorine pesticides by UV irradiation was studied at experimental conditions such as different pH aqueous solution and reaction time. The initial concentration of endosulfan alpha, beta, and sulfate in aqueous solution was 500 ppb, respectively. The experiment of photodegradation was conducted in a quartz reactor equipped with a low pressure mercury lamp (100 W, 240 nm). The samples were withdrawn from the photo reactor at intervals of 0, 10 min, 30 min, 1 hr, 2 hr, and 4 hr. Endosulfan sulfate was never hydrolyzed and photodegraded in wide range of pH. At pH 5 and reaction time (240 min), endosulfan alpha was photodegraded up to 67%. Both endosulfan alpha and beta were started to photodegrade at pH 6.5 with the lapse of time, resulting in approximately 99.9% and 87.2% of photodegradation efficiency, respectively. Furthermore, at pH 9, endosulfan alpha and beta was partially hydrolyzed and photodegraded to 99.5% at 120 min of reaction time. During the photolysis, any photo-products of endosulfan alpha, beta, and sulfate were not observed.

We investigated the relationship between the TiO2 photocatalytic decomposition of bisphenol A in water and biological toxicity to zebrafish (Danio rerio) during 1～28 weeks post development stage. The bisphenol A in water was completely degraded by the TiO2 photocatalysis in 50 hours. After the photocatalysis, no toxic effects on the morphogenesis of the zebrafish were observed during the development, growth, and maturate stages. Catalase activity of control group was not different from 1～5 week post fertilized group. However, toxic effect on the catalase activity of adult stage(28 weeks) decreased 50% than control group.

The objective of this study is to delineate removal efficiency of the MTBE in solution by TiO2 photocatalytic degradation as a function of the following different experimental conditions : Initial concentration of MTBE, air flow rate in solution, H2O2 dosage and pH of the solution. hotodegradation rate was increased with decreasing initial concentration of MTBE. The removal efficiency was 82% after 180 min in the case of MTBE concentration of 100 mg/L but 100% after 180 min in the case of 20 mg/L. Removal efficiency was increased with increasing pH, H2O2 dosage and air flow rate in solution.

The photodegradations of pyrene, chrysene and benzo[a]pyrene that were similar in structure among polycyclic aromatic hydrocarbons (PAHs) were investigated with a low-pressure mercury lamp(the wavelength of 253.7 nm and UV output of 1.35x10-3 J/s). The optimum concentrations of TiO2 and H2O2 on the photodegradation of pyrene, chrysene and benzo[a]pyrene were 1 g/L and 1.5 x 10-3 M, respectively. By these optimum concentrations, their rates increased with increasing the concentration of TiO2 and H2O2 because the amounts of OH radical formed increased, but for the higher concentrations than the optimum, their rates decreased with increasing those concentrations because the white turbidity phenomena occurs in case of TiO2 and H2O2 acts as an OH radical inhibitor. The photodegradation rates among the photodegradation processes such as UV, UV/TiO2, UV/H2O2, and UV/H2O2/TiO2 decreased in the following sequences: UV/H2O2/TiO2> UV/H2O2> UV/TiO2> UV.

The photodegradation of pyrene, chrysene and benzo[a]pyrene, that were similar in structure among polycyclic aromatic hydrocarbons (PAHs), were investigated in water irradiated with a low-pressure mercury lamp (wavelength of 253.7nm and UV output of 1.35×10-3J/s). The effects of several factors (t-BuOH, HCO3- and pH) on photodegradation of above three PAHs were also examined. The photodegradation rates of PAHs decreased with increasing the concentration of t-BuOH, but decreased little with increasing the concentration of HCO3- under the concentrations used in this study. The photodegradation rates of PAHs decreased with increasing pH, but their change were greater in case of pH increase from acid to neutral and were little in case of pH increase from neutral to base. The photodegradation rates of PAHs fitted a first-order kinetic model and their photodegradation rates decreased in the following sequences: pyrene>chrysene>benzo[a]pyrene among the PAHs used.

Photocatalytic degradation of phenol was carried out with UV-illuminated TiO2- SiO2 in aqueous suspension. TiO2-SiO2 catalysts were prepared by sol-gel method from the titanium isopropoxide and tetraethylorthosilicate at different Ti/Si ratio and some commercial TiO2 catalysts were used as purchased. All catalysts were characterized by X-ray Diffraction(XRD) and BET surface area analyzer. The effect of reaction conditions, such as initial concentration of phenol, reaction temperature and catalyst weight on the photocatalytic activity was studied. In addition, TiO2-SiO2(49:1) prepared by sol-gel method showed higher activity than commercial TiO2 catalysts on the photocatalytic degradation of phenol. The addition of SiO2 into TiO2 hepled to increase the thermal stability of titania which suppressed the formation of anatase into rutile. The photocatalytic degradation of phenol showed pseudo-1st order reaction and the degradation rate increases with decreasing initial phenol concentration.

Photocatalytic degradation of chlorpyrifos and diazinon, which are extensively used as an organophosphorous pesticide in the agriculture field, has been investigated with UV-radiated TiO2 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. NO3-, PO43-, SO42- and Cl- were found as end products on the photocatalytic degradation of chlorpyrifos and diazinon with TiO2/UV.

Considerable interest has been shown in recent years towards utilizing TiO2 particles as a photocatalyst in the degradation of harmful organic contaminants. In this study, photocatalytic degradation of diazinon which is extensively used as a pesticide in the agriculture field, has been investigated with UV-illuminated TiO2 in aqueous suspension as a function of the following different experimental parameters : initial concentration of diazinon, TiO2 weight, UV wavelength, pH of the solution. Photodegradation rate increased with decreasing initial concentration of diazinon and with increasing pH of the solution. Photodegradation rate increased with increasing TiO2 weight, but was nearly the same at TiO2 weight of 1 g/ℓ , 2 g/ℓ , i.e., for initial diazinon concentration of 5 ㎎/ℓ . UV wavelength affecting on the degradation rate of diazinon decreased in the order of 254 nm > 312 nm > 365 nm. For TiO2 weight of 1 g/ℓ and initial diazinon concentration of 5 ㎎/ℓ , the photodegradation removal of diazinon was 100% after 130 min in the case of 254 nm, but 95% in the case of 312 nm, and 84% in the case of 365 nm, after 180 min. The photodegradation of diazinon followed a first order or a pseudo-first order reaction rate. For initial diazinon concentration of 5 ㎎/ℓ , the rate constants(k) in UV and TiO2(1g/ℓ )/UV system were 0.006 min-1 and 0.0252 min-1 at 254 nm, 0.0055 min-1 and 0.0104 min-1 at 312 nm, and 0.004 min-1 and 0.0092 min-1 at 365 nm respectively.

The rates of photodegradation, reactivities, and mechanisms of photooxidation for the aqueous solution containing with halogen derivatives of aliphatic hydrocarbons have been discussed with respect to the kinds of photocatalysts, concentration of photocatalytic suspensions, strength of radiant power , time of illumination, changes of pH of substrate solution, wavelength of radiation, and pressure of oxygen gas saturated in the solution. These aqueous solutions suspended with 0.5 gL^-1 TiO_2 powder have been photodecomposed in the range of 100 and 93.8% per 1 hour if it is illuminated with wavelength (λ≥ 300nm) produced from Xe-lamp(450W). The photocatalytic abilities have been increased in the order of Fe_2O_3 < CdS < CeO_2 < Y_O2_3 < TiO_2, and rates of photodegradation for the solution have maximum values in the condition of pH 6∼8 and 3 psi-O_2 gL^-1. These rates for the photooxidation per 1 hour were dependent on the size of molecular weight and chemical bonding for organic halogen compounds and the rates of photodegradation were increased in the order of C_2H_5Br < CH_2Br_2 < C_5H_11Cl C_2H_4Cl_2 < trans-C_2H_2Cl_2 < cis-C_2H_2Cl_2 The t_1/2 and t_99% for these solutions were 5∼21 and 40∼90 minutes, respectively, and these values were coincided with initial reaction kinetics(r_0). It was found that reaction of photodegradation has the pseudo first-order kinetics controlled by the amount of h^+_VB diffused from a surface of photocatalysts.