연세대학교 화학공학과 이 태 규 제 4 회 광촉매 연구회 2004 년 2 월 26 일 Comparison of Mercury Removal Efficiency from a Simulated Exhaust Gas by Several Types of TiO 2 under Various Light Sources

Mercury Toxic properties High volatility Tendency to bio-accumulate IntroductionIntroduction Emission resources 80% of the total emission from the combustors (Coal Combustors, Waste Incinerators, etc.)

Hg Emissions Control Methods IntroductionIntroduction Oxidized mercury can be captured relatively easily because of its high solubility in weak acidic solution Elemental mercury is difficult to capture Unusual non-reactivity compared to other metals –5d 10 6s 2 closed shell electronic structure for Hg atom –extremely slow or no oxidation at high temperatures –possible oxidation by strong oxidants (NO 2, Cl 2 )

=> most widely used Activated Carbon Hg removal by adsorbents IntroductionIntroduction Photocatalyst TiO 2  high removal efficiency for low concentrations of toxic compounds disadvantage Low applicable temperature range Low regeneration rate & slow adsorption rate Hg removal under UV light

IntroductionIntroduction - high energy strength - harmful - development of improved photocatalysts activating under the visible light!!! UV light Hg removal using a TiO 2 under the fluorescent light Intermediate step

Hg capture by TiO 2 TheoryTheory HgTiO 2 HgO OH H 2 O O 2 O 2 - HgHgO Light e H + TiO 2 (s) + light → TiO 2 ·OH + Hg(g) → TiO 2 ·HgO(complex)

Apparatus ExperimentalExperimental

UV black light UV sterilizing light fluorescent light blue light blue light UV black light UV sterilizing light fluorescent light blue light blue light pure anatase (Ishihara co.) pure anatase (Ishihara co.) P25 (Degussa co.) P25 (Degussa co.) anatase : rutile = 80 : 20 anatase : rutile = 80 : 20 pure rutile (Junsei co.) pure rutile (Junsei co.) pure anatase (Ishihara co.) pure anatase (Ishihara co.) P25 (Degussa co.) P25 (Degussa co.) anatase : rutile = 80 : 20 anatase : rutile = 80 : 20 pure rutile (Junsei co.) pure rutile (Junsei co.) Light SourcesTiO 2 PowderExperimentalExperimental

Wave length ExperimentalExperimental UV-CUV-BUV-AVisible LightInfrared Ray

[a] UV black light ResultsResults

[b] UV sterilizing light ResultsResults

[c] fluorescent light ResultsResults

[d] blue light ResultsResults

Breakthrough Experiment ResultsResults TiO 2 activated carbon average time to reach 80% of the initial Hg conc. ~ 570 hrs~ 40 hrs amount of Hg per gram of adsorbent ~ 48.0 mg~ 2.5 mg cost per gram of adsorbent 3~5 원 2~4 원 estimated cost per gram of Hg ~ 원 ~ 1600 원

XRD pattern of (TiO 2 -Hg) Complex ResultsResults

ConclusionConclusion The removal efficiency was close to 100% under most light sources tested. More than 99% of initial Hg was removed under all the light sources tested except for the blue light still achieving a Hg removal efficiency close to 80%. High efficiency was achieved even under the low concentration. Easily maintainable and cost-effective fluorescent light can be used.

Hg removal by sunlight Future Works Verification of Hg removal efficiency with crystallinity, surface area, and particle size Verification of Hg adsorption mechanism under the visible light Hg removal by TiO 2 directly coated on beads Application of TiO 2 coated ferro-powder to water treatment

Furnace 온도가 증가함에 따라 크기가 커지지만 open structure 를 가진 입자를 생성 입자의 크기가 증가할수록 수은의 제거효율 증가 NH 3 를 이용하여 TiO x -N y 를 제조, 가시광선에의 반응성 측정 및 촉매 특성 분석 Structural Effect of In Situ Generated TiO 2 on Hg 0 Removal in a Simulated Combustion Flue Gas

Ti(OC 3 H 7 ) O 2 → TiO 2 +12CO 2 +14H 2 O Structural Effect of In Situ Generated TiO 2 on Hg 0 Removal in a Simulated Combustion Flue Gas

Preparation of Column Shape TiO 2 Fiber by a Diffusion Flame Reactor H eight above burner (HAB) 에 따른 particle shape / crystallinity ; fibrous / anatase Raman Spectroscopy

Apparatus

SEM I

SEM II

The End