For the purpose of manufacturing a high efficiency TiO2 photocatalyst, B-doped TiO2 photocatalysts are synthesized using a plasma electrolytic oxidation method in 0.5 M H2SO4 electrolyte with different concentrations of H3BO3 as additive. For the B doped TiO2 layer fabricated from sulfuric electrolyte having a higher concentration of H3BO3 additive, the main XRD peaks of (101) and (200) anatase phase shift gradually toward the lower angle direction, indicating volume expansion of the TiO2 anatase lattice by incorporation of boron, when compared with TiO2 layers formed in sulfuric acid with lower concentration of additive. Moreover, XPS results indicate that the center of the binding energy peak of B1s increases from 191.45 eV to 191.98 eV, which suggests that most of boron atoms are doped interstitially in the TiO2 layer rather than substitutionally. The B doped TiO2 catalyst fabricated in sulfuric electrolyte with 1.0 M H3BO3 exhibits enhanced photocurrent response, and high efficiency and rate constant for dye degradation, which is ascribed to the synergistic effect of the new impurity energy band induced by introducing boron to the interstitial site and the improvement of charge transfer reaction.

The potential use of UV-TiO2 photocatalytic oxidation absorbent reactor in the removal of gaseous formaldehyde was studied. This study was conducted inside a bench-type circulation reactor chamber at ambient air conditions. PCO (Photocatalytic Oxidaion) degradation test for formaldehyde was done repeatedly and the average was reported. It was evident that photocatalytic oxidation was proven to be an effective method to control indoor air pollutants, like formaldehyde in indoor air. However, by-products are produced in the case of formaldehyde degradation also CO2, CO, H2O and formic acid are produced. These by-products can inhibit the active site of the photocatalyst. Thus, addition of adsorbent succeeding the PCO-TiO2, acts as a secondary treatment wherein produced by-products from the degradation and unreacted HCHO will adhere to the surface of the adsorbent. In this study, synthetic zeolite and activated carbon pellets were used to control of by-products of formaldehyde. PCOTiO2 degradation alone achieves 86% for a period of 60 minutes. Addition of adsorbent improves the removal efficiency achieving 90% and 96% using activated carbon pellet and zeolite, respectively.

This paper presented experimental results for circulation type UV-TiO₂ photocatalytic oxidation process. We have developed UV-TiO₂ photocatalytic oxidation process with activated carbon to control odor and VOCs in indoor and industrial applications. In this study, common indoor air pollutants, namely ammonia, formaldehyde, hydrogen disulfide, toluene were selected to investigate their efficiencies for UV-TiO₂ photocatalytic oxidation. In high concentration test, the decomposition efficiency was high in order as ammonia, toluene, formaldehyde, hydrogen disulfide. Three type of individual processes are tested for ability to increase decomposition efficiency. UV-TiO₂ photocatalytic oxidation combined process with activated carbon was excellent among the three type processes without reference to gas species. It was considered that this circulation type process will overcome short retention time for treatment for UV-TiO₂ photocatalytic oxidation. It will promise that this circulation type UV-TiO₂ photocatalytic oxidation combined process can apply indoor and industrial applications to remove odor and VOCs quickly.

양극산화법을 이용하여 광촉매 특성을 나타내는 TiO2 피막을 제조하고 염료의 분해반응을 통하여 광분해 효율을 조사하였다 양극산화법에 의해 제조된 산화피막은 모두 광촉매 분해특성이 있었으며 양극산화의 조건에 따라서 TiO2 피막의 성장거동과 피막 형태에 차이가 나타났다. 황산용액에서 양극산화된 TiO2 피막은 불규칙적 인 입자모양으로 anatase와 rutile이 혼합된 조직이었으며, 인산이 첨가된 혼합용액에서 형성된 TiO2는 anatase로 셀 모양의 피막형태로 생성되었다. 광촉매 특성에 적합한 양극산화의 인가 전압은 180V인 것으로 나타났다.

반도성 세라믹 광촉매 막 반응기(membrane reactor)에 의한 난분해성 유독 유기물질의 효율적인 분해공정을 개발하기 위한 기초 연구로서 TiO2 광촉매 막의 전기화학 반응에 의한 개미산(formic acid)의 산화/분해 효율성에 대해 연구하였다. 막 반응기는 용액의 여과(filtration)와 광전기화학 반응에 의한 유기물의 광분해를 동시에 수행할 수 있도록 제작되었다. 복합막의 담체임과 동시에 전극의 역할을 할 수 있는 전기 전도성 SnO2 또는 stainless steel 다공성 튜브상에 pH가 1.45인 TiO2 졸을 졸-겔 침지 코팅하여 광촉매 복합막을 제조하였으며 광원으로는 365 nm 파장을 갖는 UV를 사용하였다. TiO2 광촉매 막의 전기화학 반응에 의한 개미산의 산화효율은 전극에 걸어주는 전압과 반응시간에 따라 증가하였으나 투과량(flux)에는 거의 무관하였다. TiO2/SnO2 복합막을 사용한 경우 외부 전압을 27V 걸어주었을때 77% 정도의 산화효율을 얻을 수 있었으며 TiO2 /stainless steel 복합막에서는 90% 이상이었다. 광촉매 전기화학 반응을 이용함으로써 높은 투과량하에서도 개미산의 산화효율을 단순한 TiO2 광촉매 반응에서 보다 6~7배 가량 증진시킬 수 있었다.

The Electron/Hole Pair is generated when the activation energy produced by ultraviolet ray illuminates to the semiconductor and OH- ion produced by water photocleavage reacts with positive Hole. As a results, OH radical acting as strong oxidant is generated and then Photocatalytic oxidation reaction occurs. The photocatalytic oxidation can oxidate the non-degradable and hazardous organic substances such as pesticides and aromatic materials easier, safer and shorter than conventional water treatment process. So in this study, many factors influencing the oxidation of chlorophenols, such as inorganic electrolytes addition, change of oxygen and nitrogen atmosphere, temperature, pH, oxygen concentration, chlorophenol concentration, were throughly examined. According to the experiments observations, it is founded that the rate of chlorophenol oxidation follows a first-order reaction and the modified Langmuir-Hinshelwood relationship. And the photocatalytic oxidation occurs only when activation energy acting as Electron/Hole generation, oxygen acting as electron acceptor to prevent Electron/Hole recombination, $TiO_2$ powder acting as photocatalyst are present. The effects of variation of dissolved oxygen concentration, temperature and inorganic electrolytes concentration on 2-chlorophenol oxidation are negligible. And the lower the organic concentration, the higher the oxidation efficiency becomes. Therefore, the photocatalytic oxidation is much effective to oxidation of hazardous substances at very low concentration. The oxidation is effective in the range of 0.1 g/L-10 g/L of $TiO_2$. Finally when the ultra-violet ray is illuminated to $TiO_2$, the surface characteristics of $TiO_2$ change and Adsorption/Desorption reaction on $TiO_2$ surface occurs.

광촉매 TiO2 막에 의한 formic acid의 광분해 효율이 연구되었다. 막반응기는 용액의 정밀여과(micro-filtration)는 물론 유기물의 광분해를 동시에 수행할 수 있도록 다공성 TiO2 튜브 (평균기공: 0.2μm)를 이용한 새로운 타입으로 개발되었으며 광원으로는 365 nm 파장을 갖는 UV를 사용하였다. 또한 반응기의 광분해 효율을 증진시키기 위하여 슬립케스팅법으로 제조한 TiO2 튜브표면을 TiO2 졸로 코팅하였다. TiO2 막 반응기의 분해효율은 용액의 투과량(flux), 막의 미세구조(졸의 pH), 공급산소량, H2O2와 같은 1차 산화제(primary oxidants)의 첨가 그리고 Nb2O5와 같은 물질의 도핑(doping)에 매우 민감함을 알 수 있었다. 최적의 광분해 반응조건에서 formic acid의 산화효율은 pH가 1.45인 TiO2 졸로 코팅한 막 반응기를 사용했을때 80% 이상이었다. Formic acid 용액에 1차 산화제 H2O2를 첨가하거나 막을 Fe2O3로 도핑함으로써 산화효율은 최고 20%까지 증가시킬 수 있었다.

This study introduces a method to eliminate formaldehyde and benzene, toluene from indoor air by means of a photocatalytic oxidation reaction. In the method introduced, for the good performance of the reaction, the effect and interactions of the TiO2 catalyst and ultraviolet in photocatalytic degradation on the reaction area, dosages of catalysts, humidity and light should be precisely examined and controled. Experiments has been carried out under various intensities of UV light and initial concentrations of formaldehyde, benzene and toluene to investigate the removal efficiency of the pollutants. Reactors in the experiments consist of an annular type Pyrex glass flow reactor and an 11W germicidal lamp. Results of the experiments showed reduction of formaldehyde, benzene and toluene in ultraviolet /TiO2/ activated carbon processes (photooxidation-photocatalytic oxidation-adsorption processes), from 98% to 90%, from 98% to 93% and from 99% to 97% respectively. Form the results we can get a conclusion that a ultraviolet/Tio2/activated carbon system used in the method introduced is a powerful one for th treatment of formaldehyde, benzene and toluene of indoor spaces.

Removal of NOx on CaO/TiO2 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 TiO2, the NOx removal decreased greatly with the increase of calcination temperature from 500oC to 700oC, whereas in the photocatalyst added with Ca(OH)2, the removed amount of NOx was high and constant regardless of calcination temperature. Considering NOx 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 TiO2. 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(CaTiO3) by reacting with TiO2 above 700oC. 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 NOx.

The aim of this study is, firstly, to find out what kinds of inorganic species are produced in the photocatalytic oxidation of ammonium-nitrogen containing water and, secondly, to seek the influence of anion for the photocatalytic oxidation of ammonium contained compounds. The photoenergy above 3 eV(λ＜415 nm) was effectively absorbed by TiO2 and TiO2/polymer was used to be oxidized NH4-N in wastewater to NO3-N. Existing the anion as Cl-, the rate of photocatalytic oxidation decreased regardless of other condition. This result showed that the chloride ions reduced the rate of oxidation by scavenging oxidizing radical species as OH- and OCl-. Some of the added ion might have blocked the active sites of the catalyst surface, thus deactivated the catalyst.