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