UVUV--based technologies for waterbased technologies for waterand air purificationand air purification
张彭义张彭义PengyiPengyi ZhangZhang
Department of Environmental Science andDepartment of Environmental Science andEngineering, Tsinghua UniversityEngineering, Tsinghua University
OutlinesOutlines
1.1. Enhanced photocatalytic process forEnhanced photocatalytic process forwater purificationwater purification
2.2. Vacuum UV technology for indoorVacuum UV technology for indoorair purificationair purification
3.3. PhotochemicalPhotochemical decompostiondecompostion ofofPFOAPFOA
Adsorp
Adsorp
Red
Ox
Desorp
Desorp
Eg
Photocatalysis PrinciplePhotocatalysis Principle
hν
heat
e
h
Conduction Band
Valence Band
Drawback
Low efficiency
Photocatalyst deactivation
Deactivation of TiODeactivation of TiO22 filmfilm
Change ofphotocatalytic
activity
0
20
40
60
80
100
0 10 20 30 40Time/d
Deg
rada
tion
rate
% TiO2/TiTiO2/glassTiO2/Al
Kept in tape water
0
20
40
60
80
0 5 10 20 30 40 55 65
time/d
Deg
rada
tion
rate
%TiO2/TiTiO2/glassTiO2/Al
Kept in deionized water
Change of photocatalyst morphology —AFM
Fresh film Aged in water for 20d
AFM results of TiO2-CB films coated on Al sheet
Pretreatment of thePretreatment of thesubstratesubstrate
0 10 20 30 40 50 600.0000
0.0005
0.0010
0.0015
0.0020
0.0025
0.0030
0.0035
0.0040
0.0045
0.0050
0.0055
0.0060
0.0065
0.0070
Des
orpt
ion
surf
ace
Ds
/m
2 .g-1
Pore Width/Ao
untreated Ti basetreated Ti base
20μm
20μm
a)
b)
未乙二酸活化预处理的试样表面浅孔数量较少且分布不均匀( a)而经乙二酸进行1h活化预处理的Ti基底试样表面均匀分布大量新增浅孔( b),且孔径为1~3nm的微孔数量剧增,表面积比未经乙二酸预处理的Ti基底比表面增大近2倍。
不同基底表面积及孔径分布分析图
TiO2薄膜体系的阻抗谱
Without pretreatmentWithout pretreatment界面电荷传递法拉第界面电荷传递法拉第阻抗(阻抗(RctRct))值增大幅度值增大幅度明显,明显,6060天后其天后其RctRct值已经增大至新制备样值已经增大至新制备样品品RctRct值的值的55倍之多倍之多
PretreatedPretreatedRctRct值增幅缓慢,值增幅缓慢,浸泡浸泡365365天后的天后的RctRct值仅比新值仅比新制备样品增大了约制备样品增大了约11倍倍
0 5000 10000 15000
-15000
-10000
-5000
0
Z'
Z''
60d
5d
10d
0d
45d
30d
5000
15000
25000
35000
45000
0 100 200 300 400time/day
Rcp(ohm)
未预处理
预处理基底
a)
0 2500 5000 7500
-7500
-5000
-2500
0
Z'
Z''
60d120d
0d
15d
365d
180d
300d
b)
c)
TiO2/Ti sample after 60 days
TiO2/Ti-new sample after 365 days
0
20
40
60
80
100
0 100 200 300 400Test days
Rel
ativ
eac
tivity
(%)
reference photocatalyst
our photocatalyst
0
500
1000
1500
2000
2500
0 4 8 12 16
Reaction time (min)
C(m
g/L
)
VUV TiO2/VUV
UV TiO2/UV0.0
0.5
1.0
1.5
2.0
2.5
0 20 40 60 80
Reaction time (min)
TO
C(m
g/L
)
UVTiO2/UVVUVTiO2/VUV
VUV photocatalytic degradation of4-chlorobenzoic acid
((22))Vacuum UV photocatalytic technologyVacuum UV photocatalytic technology
W Y Han, P Y Zhang*, et al. WaterResearch, 2004, 38(19): 4197-4203
0.0
0.2
0.4
0.6
0.8
1.0
0 5 10 15 20
t (min)
C/C
0
TiO2/UV
TiO2/VUV
4-nitrophenol
0
0.2
0.4
0.6
0.8
1
0 5 10 15 20t (min)
C/C
0
UV
TiO2/UV
TiO2/VUV
4-chlorophenol
VUV photocatalyticdegradation of
phenols
0.0
0.2
0.4
0.6
0.8
1.0
0 5 10 15 20t (min)
C/C
0
TiO2/UV
TiO2/VUV
catechol
((33))Combination of ozone or hydrogen peroxide and VUVCombination of ozone or hydrogen peroxide and VUVphotocatalysisphotocatalysis
0
0.2
0.4
0.6
0.8
1
0 40 80 120t/s
[NB]
/[NB
]0
O3
O3/UV
O3/TiO2/UV
O3/TiO2/VUV
Removal of low concentrationnitrobenzene in water
0.0
0.2
0.4
0.6
0.8
1.0
0 50 100
反应时间 /s
[NB
]/[N
B]0
VUV/TiO2
VUV/TiO2/H2O2
UV/TiO2/H2O2
(4)UV based equipment for water treatment
微污染水处理设备
设备参数设备参数设计流量设计流量0.5t/h0.5t/h66根根150W150W低压汞灯低压汞灯配制配制10g/h10g/h臭氧发生器臭氧发生器停留时间停留时间12min12min
OzoneOzone--photocatalysis equipmentphotocatalysis equipment
((55))AOPsAOPs--BACBAC
0
10
20
30
40
50
60
O3/TiO2/UV O3/TiO2/UV-BAC
TO
C去除
率(
%) 5min
15min
二级出水
原水
高级氧化出水
生物活性碳出水
repulsion
TiO2 film PVAAu(Pd,Pt) NPs
Noble nanoparticlesdeposited on TiO2 film
Pt NPsAu/TiO2
Au/TiO2
OutlinesOutlines
1. Enhanced photocatalytic process forwater purification
2.2. Vacuum UV technology for indoorVacuum UV technology for indoorair purificationair purification
3. Photochemical decompostion ofPFOA
Principle of VUV photocatalysis for airpurification
Zhang P Y, Liu J.Chemistry Letters 2004, 33(10): 1242-1243
1852
185 12
12
1 32 2
32 3
2
3 3
13 2
2 ( )
( ) 2
( ) ( or ) ( )
( )
( 290 ) ( )
nm
nm
H O H OH
O O D
O D H O OH
O D M O N O P
O P O O
TiO hv h e
h OH OH
O e O
O hv nm O D O
TolueneToluene
C0=0.8-1ppmRH=35%
0
5
10
15
20
25
0 5 10 15 20
流量 (L/min)
Rea
ctio
nra
te(m
g/m
3.m
in) TiO2/VUV
VUVTiO2/UV
0
10
20
30
40
50
60
0 5 10 15 20
Flow rate (L/min)
Rea
ctio
nra
te(m
g/m
3 .min
)
TiO2/VUVVUVTiO2/UV
hexaneC0=2.9-3.2ppm
RH=35%
VUV photocatalytic degradation of VOCs
VUV photocatalytic degradation ofVUV photocatalytic degradation of VOCsVOCs
50
60
70
80
90
100
0 2 4 6 8 10
甲醛初始浓度(mg/m3)
去除
率(
%)
VUVTiO2/UVTiO2/VUV
Q=8L/min;RH=33-36%
60
70
80
90
100
5 6 7 8 9 10
流量(L/min)
去除
率(
%)
VUVTiO2/VUV
C0=4.3-4.8mg/m3;RH=33-36%
Formaldehyde
High efficiency catalyst for ozoneHigh efficiency catalyst for ozonedecompositiondecomposition
0102030405060708090
100
0 1000 2000 3000 4000 5000
时间(min)臭
氧去
除率
(%
)
接触时间0.03s,RH 45%
O3浓度50mg/m3
碳载催化剂
活性碳
Pd/AC
Au/AC
Developed Air purifierDeveloped Air purifier
OutlinesOutlines
1. Enhanced photocatalytic process forwater purification
2. Vacuum UV technology for indoorair purification
3.3. PhotochemicalPhotochemical decompostiondecompostion ofofPFOAPFOA
PFOA and its precursors widelyPFOA and its precursors widelyused and detectedused and detected
EST, 2006, 40, 32-44EST, 2006, 40, 5647-5652
PFOA concentrations in human serumPFOA concentrations in human serum
Occupational worker: 0.84-6.4 mg/LGeneral public: 3-17 g/L
Mean half-life 4.37 years in human’s serum
EST, 2009,43:5565-5575
PFOA is very stable, persistent and accumulatesPFOA is very stable, persistent and accumulatesin the environmentin the environment
Conventional treatment methods are not effectiveConventional treatment methods are not effectiveto decompose PFOAto decompose PFOA
Only at highly acidic contion, PFOAdecomposed by TiO2 photocatalysis
60 μM PFOA, 0.15 M HClO4 (pH<1) and 0.66g/L TiO2, t1/2 = 58 min
DillertDillert R et al.R et al. ChemosphereChemosphere 2007, 67: 7852007, 67: 785--792792
PanchangamPanchangam C S et al.C S et al. ChemosphereChemosphere 2009, 77: 2422009, 77: 242--248248
gas
UV lamp254nm, 23 W
Reaction volume: 400 mL
Initial PFOA con.: 100μmol/L
(40 mg/L)
Catalyst dosage: 0.5 g/L
AnalysisUPLC-MS/MS: PFCAs
IC: F-
Comparison of commercialphotocatalysts for PFOA decomposition
0 1 2 3 40
20
40
60
80
100
PF
OA
dec
om
po
siti
on
/%
Time / ( hour )
O2 blank experiment
TiO2
Ga2O
3
In2O
3
Under oxygen atmosphere
Fluorine balance
In2O3 , O2 gas
1:solvothermal route to prepare precursorsIn(OH)3 or InOOH
2:calcining precursors at 500 oC to obtain In2O3
Synthesis of nano-In2O3 bysolvothermal method
In(OH)3→ In2O3InOOH → In2O3
washing
ethylenediamine/ethanol=1/1140 oC ethylenediamine/ethanol=1/1
200 oC
solvothermal synthesized In2O3
ethylenediamine/water=1/1,180 oC
nanosphereFlower-like
1,3-propanediamine/ethanol=1/1180 ℃nanocube nanorod
Decomposition of PFOA
Reuse of In2O3 nanosphere for PFOAdecomposition
ESR analysis(1) In pure water, TiO2 has stronger OH signalthan In2O3(2) TiO2 signal decreases with irradiation time
ESR
333.0 333.1 333.2 333.3-2000
-1000
0
1000
2000
3000TiO
2+ PFOA + DMPO (pH=2) - dark
TiO2
+ PFOA + DMPO (pH=2) - UV 4 minTiO
2+ PFOA + DMPO (pH=2) - UV 8 min
Inte
nsi
ty
mT333.0 333.1 333.2 333.3
In2O
3+ PFOA + DMPO (pH=2) - dark
In2O
3+ PFOA + DMPO (pH=2) - UV 4 min
In2O
3+ PFOA + DMPO (pH=2) - UV 8 min
mT
OH signal when PFOA (pH=2) is present
PFOA addition greatly enhances OH signalof TiO2
TiO2 In2O3
FT-IR analysis
4000 3500 3000 2500 2000 1500
OO
C
OOC
O-H
O-H
C-F(1300-1000)
C=O1766KBr
TiO2
In2O
3
Wavenumber (cm-1)
In2O3/PFOA
TiO2/PFOA
KBr/PFOA
CF3(CF2)6C
O
OH
CF3 - CF2 - CF2 - CF2 - CF2 - CF2 - CF2 - COOHPFOA :(1)(2)(3)(4)(5)(6)(7)(8)
F chemical shift (ppm) -80.087 -124.583 -120.552 -120.045 -119.584 -120.857 -116.905
19F Solid State NMR results
-60 -80 -100 -120 -140
C(3-6)F2
C(7)F2C(2)F
2
CF3
In2O
3
TiO2
KBr
F chemical shift ( ppm )
In2O3 & TiO2
1. C(2)F2 : δ , line widths broad
2. CF3 and C(7)F2 : δ
TiO2
C(3-6)F2 signals coalesce
/PFOA
/PFOA
/PFOA
CF3(CF2)6C
O
OH
TiO2-PFOAIn2O3-PFOA
Coordination of PFOA withIn2O3 and TiO2
TiO O
TiO
TiO
Ti Ti
F
C C
F F
C
F
C
F
C
OO
O
InO O
InO
In InO O
C
C
FF
C
FF
C O
Adsorp
Adsorp
Red
Ox
Desorp
Desorp
Eghν
heat
e
h
Conduction Band
Valence Band
h+ + OH-/H2O OH
e- + O2 O2-
h+ + PFOA PFOA+
e- + PFOA PFOA-
Direct charge transfer to PFOAIn the case of In2O3
Proposed PFOA decomposition mechanismby In2O3
Holes prefer to react withwater in the case of TiO2