교대로 운전되는 두 개의 UV/광촉매반응기로 구성된 폐가스 처리시스템에서의 광촉매의 비활성화 및 재생 특성 = Characterization of Repeated Deactivation and Subsequent Re-activation of Photocatalyst Used in Two Alternatively-operating UV/photocatalytic Reactors of Waste-air Treating System

국문 초록 (Abstract)

본 연구에서는 교대로 운전되는 두 개의 UV/광촉매 반응기로 구성된 폐가스 처리시스템의 운전단계와 단계별 광촉매의 비활성화의 상관관계를 사용된 광촉매에 대한 기기분석을 통하여 규명하였다. 선행연구[Lee와 Lim, Korean Chem. Eng. Research, 59(4), 574-583 (2021)]의 광촉매 반응기 시스템 운전에 사용되지 않은 광촉매를 담지한 다공성 SiO₂ 담체(A4), 1회 운전하는 동안 사용되고 재생을 경험하지 않은 광촉매를 담지한 다공성 SiO₂ 담체(A1), 2회 운전에 사용되고 1회 재생된 광촉매를 담지한 다공성 SiO₂ 담체(A2) 및 3회 운전에 사용되고 2회 재생된 광촉매를 담지한 다공성SiO₂ 담체(A3)와, 1차 재생(AD1) 또는 3차 재생(AD3)된 광촉매를 담지한 다공성 SiO₂ 담체에 대한 BET 분석, SEM, XPS, SEM-EDS 및 FTIR 분석 등을 수행하여, 광촉매를 담지한 다공성 SiO₂ 담체의 비활성화 및 재생 특성을 포함하는 특성 분석을 수행하였다. 그 결과로서, 3회 이상의 여러 번 재생을 수행하는 광촉매의 적정 재생 온도를 200℃ 미만으로 도출하였다. 이러한 광촉매의 적정 재생 온도는 BET 분석결과에서 도출된 기공에 흡착된 에탄올 산화분해 중간생성물의 대부분이 완전 분해가 되어 기공이 재생되는 재생 온도와 거의 일치하였다. 특히, XPS 분석 결과는, 선행 연구[Lee와 Lim, Korean Chem. Eng. Research, 59(4), 574-583 (2021)]에서 광촉매 반응기의 첫 번째 운전 후에 광촉매의 미세한 비활성화가 발생하였음을 나타내었다. 또한, XPS 분석 결과는, 선행연구[Lee와 Lim, Korean Chem. Eng. Research, 59(4), 574-583 (2021)]에서 광촉매 반응기의 두 번째 운전에서 비교적 큰 광촉매의 비활성화가 발생하여 첫번째 운전성능보다 약 5%만큼 못 미치는 에탄올과 황화수소 각각의 제거효율을 초래하였으나, 세 번째 운전에서의 에탄올과 황화수소의 제거효율은 두 번째 운전에서의 에탄올과 황화수소의 제거효율 실험 결과와 거의 비슷하였다는 연구 결과와 일치하였다. 한편, AD3를 사용하여 선행연구[Lee와 Lim, Korean Chem. Eng. Research, 59(4), 574-583 (2021)]에서와 같은 광촉매 반응기의 네 번째 운전을 수행할 것을 가정하면, 두 번째 운전에서보다 더 큰 광촉매의 비가역적 비활성화의 발생으로 인하여 에탄올과 황화수소 제거효율이 가장 크게 저하되리라 예상되었다.

다국어 초록 (Multilingual Abstract)

In this study, the correlation between operating stages of waste air-treating system composed of two alternatively-operating UV/photocatalytic reactors, and the deactivation of photocatalyst used in each operating stage, was investigated by instrumental analysis thereon. The repeated deactivation and subsequent re-generation of photocatalyst used in the waste air treating system of previous investigation performed by Lee and Lim (Korean Chem. Eng. Research, 59(4), 574-583(2021)), were characterized on virgin photocatalyst-carrying porous SiO₂ media (A4), used photocatalystcarrying porous SiO₂ media (A1, A2 and A3) collected from the corresponding photocatalytic reactor upon 1^st, 2^nd, and 3^rd run, respectively, regenerated photocatalyst-carrying porous SiO₂ media upon 1 time-run (AD1) and 3 times regenerated photocatalyst-carrying porous SiO₂ media upon 3 time-runs (AD3) by instrumental analysis including BET analysis, SEM, XPS, SEM-EDS and FT-IR. As a result, the proper regeneration-temperature for deactivated photocatalyst to be regenerated several times (more than 3 times), was suggested below 200℃. Such temperature of deactivated photocatalystregeneration was almost consistent to the one, according to BET analysis, at which tiny nano-pores blocked by adsorbed ethanol-oxidative and degraded intermediates (AEODI), were regenerated to be reopened through almost complete mineralization of AEODI. In particular, the results of XPS analysis indicated an incurrence of insignificant deactivation of photocatalysis upon 1^st run of UV/photocatalytic reactor (A or C) of the previous investigation. In addition, the results of XPS analysis were consistent with the experimental results of the previous investigation in that 1) deactivation of photocatalyst incurred during 2^nd run of the UV/photocatalytic reactor (A or C) resulted in decreased removal efficiency, by ca. 5% and 5%, of ethanol and hydrogen sulfide, respectively, compared with its 1^st run; 2) there was insignificant difference between the removal efficiencies of its 2^nd run and 3^rd run. Furthermore, the removal efficiencies of ethanol and hydrogen sulfide for hypothetical 4^th run of photocatalytic reactor in the previous investigation, using AD3, were expected to decrease, compared with its 3^rd run, by much more than those for 2^nd run in the previous investigation did, compared with its 1^st run.

참고문헌 (Reference)

1 이은주, "교대로 운전되는 두 개의 UV/광촉매반응기로 구성된 폐가스 처리시스템의 성능 및 특성 평가" 한국화학공학회 59 (59): 574-583, 2021

2 Hao, L., "Visible-light-driven Oxygen Vacancies and Ti3+ co-doped TiO2Coatings Prepared by Mechanical Coating and Carbon Reduction" 97 : 13-18, 2018

3 Vorontsov, A. V., "TiO2 Reactivation in Photocatalytic Destruction of Gaseous Diethyl Sulfide in a Coil Reactor" 44 : 25-40, 2003

4 Ingo, G. M., "Thermal and Microchemical Characterisation of Sol-Gel SiO2, TiO2 and xSiO2-(1-x)TiO2 Ceramic Materials" 66 : 37-46, 2001

5 Medina-Valtierra, J., "The Photocatalytic Application and Regeneration of Anatase Thin Films with Embeded Commercial TiO2 Particles Deposited on Glass Microrods" 252 : 3600-3608, 2006

6 Chen, X. F., "The Effect of Postnitridation Annealing on the Surface Property and Photocatalytic Performance of N-doped TiO2Under Visible Light Irradiation" 255 : 59-67, 2008

7 Dupin, J. -C., "Systematic XPS Studies of Metal Oxides, Hydroxides and Peroxides" 2 : 1319-1324, 2000

8 Saoud, W. A., "Study of Synergetic Effect, Catalytic Poisoning and Regeneration Using Dielectric Barrier Discharge and Photocatalysis in a Continuous Reactor: Abatement of Pollutants in Air Mixture System" 213 : 53-61, 2017

9 Vorontsov, A. V., "Selectivity of Photocatalytic Oxidation of Gaseous Ethanol over Pure and Modified TiO2" 221 : 102-109, 2004

10 Wang, Z, "Role of Oxygen Vacancy in Metal Oxide Based Photoelectrochemical Water Splitting" 3 : e12075-, 2021

11 Cao, L., "Photocatalytic Oxidation of Toluene on Nanoscale TiO2 Catalysis: Studies of Deactivation and Regeneration" 196 : 253-261, 2000

12 Chang, C. P., "Photocatalytic Oxidation of Gaseous DMF Using Thin Film TiO2 Photocatalyst" 58 : 1071-1078, 2005

13 Vikrant, K., "Photocatalytic Mineralization of Hydrogen Sulfide as a Dual-phase Technique for Hydrogen Production and Environmental Remediation" 259 : 118025-, 2019

14 Praserthdam, S., "Performance Controlled Via Surface Oxygen-vacancy in Ti-based Oxide Catalyst During Methyl Oleate Epoxidation" 10 : 18952-, 2020

15 Arana, J., "Gas Phase Ethanol Photocatalytic Degradation Study with TiO2Doped with Fe, Pd and Cu" 215 : 153-160, 2004

16 Mamaghani, A. H., "Gas Phase Adsorption of Volatile Organic Compounds Onto Titanium Dioxide Photocatalysts" 337 : 60-73, 2018

17 Corby, S., "Determining the Role of Oxygen Vacancies in the Photoelectrocatalytic Performance of WO3 for Water Oxidation" 11 : 2907-2914, 2020

18 Liqiang, J., "Deactivation and Regeneration of ZnO and TiO2 Nanoparticles in the Gas Phase Photocatalytic Oxidation of n-C7H16 or SO2" 275 : 49-54, 2004

19 Zhang, Z., "Controlling the Synergistic Effect of Oxygen Vacancies and N Dopants to Enhance Photocatalytic Activity of N-doped TiO2 by H2 Reduction" 425 (425): 117-124, 2012

20 Yang, W., "Comparative Study of α-, β-, γ- and δ-MnO2 on Toluene Oxidation: Oxygen Vacancies and Reaction Intermediates" 260 : 118150-, 2020