uv/h2o2 process modeling for design and mechanistic...

UV/H2O2 Process Modeling for Design and Mechanistic Studies

Presented at

Developments in Drinking Water

Treatment Modeling

Delft TU

June 22-23, 2006

John C. Crittenden, Ke LiArizona State University Main Campus

Ira A. Fulton School of Engineering

Department of Civil and Environmental Engineering

David HandMichigan Technological University

Department of Civil and Environmental Engineering

“All models are wrong but

some are useful.”-- George E.P. Box

“Let’s develop some useful models

and make good use of them.”

-- How models can help

-- an optimistic modeler

Environmental Technologies Design Option Tool

(ETDOT)

•A compilation of self-contained simulation software for

use in assessing and implementing effective treatment

strategies for gaseous, aqueous, organic, and solid

waste by-product streams. ETDOT provides simulation

software necessary in determining whether prevention

or treatment is preferred during the design phase.

•May be used to evaluate source reduction versus

end-of-pipe treatment, integrate treatment into the

manufacturing process, evaluate waste segregation

versus central treatment, and select and size the

most effective environmental technologies.

Environmental Technologies Design Option Tool(> 100 man years invested)

ETDOT TM

(available)

http://www.cpas.mtu.edu/etdot

AdDesignSTM

Fixed bed adsorber performance; contains extensive adsorber, adsorbent, and isotherm databases

AdOx TMAdvanced oxidation processes (AOPs); contains second order rate constant database

ASAP TM Packed tower, surface, and bubble aeration systems

StEPP TM Provides physical property data for chemicals

Biofilter TM Biofiltration including gas, liquid and biofilm phases

ETDOT TM

http://www.cpas.mtu.edu/etdot

MC-DIST TM Distillation columns

AdRecover TMFixed-bed adsorber performance for the recovery of organic compounds from gaseous by-product streams

FaVOr TM Fate of VOCs in wastewater treatment facilities

IonX TM Ion exchange separation systems

CatReac TM Catalytic and separative reactor systems

MPS TM Membrane process performance

Environmental Technologies Design Option Tool

AdOxTM

UV/H2O2 Process Design Aid

Photolysis of H2O2:

•Initiation: H2O2 / HO2- + hv 2HO =0.5 @254nm

•Propagation:

H2O2 / HO2- + HO H2O / OH- + HO2

H2O2 + HO2 / O2

- HO + H2O / OH- + O2

•Termination:

HO + HO H2O2

HO + HO2 / O2

- H2O / OH- + O2

HO2 + HO2

/ O2- H2O2 / HO2

- + O2

Design Aid -- chemistry

• Reactions of organic compound R:

R + hv Products

R+ HO Products

• Inorganic Scavengers:HO + CO3

2- / HCO3- CO3

-+OH- / H2O

HO + HPO42- HPO4

- + OH-

Reduced Metal ions + HO

• NOM

NOM + hv

HO + NOM

Design Aid -- chemistry

Rate laws can be written for all the elementarysteps to describe the kinetics of the system.

Electrical Energy per Order (EE/O)

The electrical energy (in kilowatt hours)

required to reduce the concentration of a

pollutant by one order of magnitude for 1000

U.S. gallons of water.

i

f

LampSize(kW) x 1000EE/O(flow)

CFlowRate(gpm) 60(min/hr) log

C

i

f

LampSize(kW) Time(min) 3785(L / gal)EE /O(Batch)

CVolume(L) 60(min/hr) log

C

UV/H2O2 Process – process efficiency

i

f

UVDoseEE/O

Clog

C

UV/H2O2 Process – process efficiency

For a plug flow reactor or batch reactor! In general, a larger

EEO will be required for commericial reactors because plug

flow connect be achieved for large removals (> 99%).

HOCg1) Carbonate/bicarbonate species2) NOM3) pH4) Reduced metal ions (iron and manganese)5) Background light absorbance6) Reactivity of the parent compound with HO•

Many factors affect UV/H2O2 by either interfering UV light and scavenging the hydroxyl radical.

UV/ H2O2 Process -- Factors affect performance

HOCg

Carbonate Species

HO + CO32- CO3

-+OH- K =3.9 x 108 M-1S-1

HO + HCO3- CO3

-+ H2O K = 8.5 x 106 M-1S-1

2 2

3 3 3 3

R RR

R R HCO HCO CO CO

k CQ

k C k C k C

QR = target organics (R) reaction rate with hydroxyl radical

divided by the total reaction rate of hydroxyl radical with both

R and carbonate/bicarbonate, (equals the reduction in

reaction due to the presence of alkalinity), dimensionless


NOM

R RR

NOM DOC R R

k CQ

k C k C

2) Absorption of UV light

1) Quenching HO•

k 3~5 x 108 L/s-mole NOM carbon

2 2 2 2

H O H O2 2 2 2

H O H O

NOM NOM

ε CFraction

ε C +ε C

NOM = 0.013 to 0.107 L/mg DOC-cm

L cmSUVA 254 100

mg cm m


HOCg

Reduced metal ions (iron and manganese)

kFe(II) = 2.3 x10 8 M-1s-1

kMn(II) 1.4 x 10 8 M-1s-1

R RR

R R Fe Fe(II) Mn Mn(II)

k CQ

k C k C k C

pH affect

1) the concentration of HCO3- and CO3

2- as discussed above.

2) the concentration of HO2- (e.g., H2O2 has a pKa of 11.6,

absorbs 10X UV light as compared to H2O2), which is important

in the UV/ H2O2 processes.

3) the charge on the organic compounds if they are weak acids or

bases.


HOCg

Relative rates of 0.100 mg/L TCE destruction (QTCE) for

various pH values and alkalinities

Relative

rate QTCE

(%)

pH CT,CO3

(mM)

HCO3-

(mM)

CO32-

(mM)

10.9 7.0 1 0.997 0.003

5.78 7.0 2 1.994 0.006

2.98 7.0 4 3.988 0.012

2.00 7.0 6 5.982 0.018

1.51 7.0 8 7.976 0.024

5.55 8.0 2 1.990 0.010

3.04 9.0 2 1.904 0.096

0.754 10.0 2 1.333 0.667


To assess the feasibility of UV/H2O2 processes,

the following parameters should be measured :

(1)alkalinity,

(2) pH,

(3) COD,

(4) TOC,

(5)Fe(II),

(6)Mn(II), and

(7) light transmission.

Design Aid

• Once these parameters are known, models can be used to help planning pilot study to answer the questions:

– Is UV/H2O2 a feasible technology

– How to evaluate the effect of pretreatment options

– How much energy is required

– What is the optimum H2O2 dosage

– What are the optimum hydraulic parameters

– How the efficiency would change if raw water quality changes

Governing equations for different reactors

Design Aid – reactor type

VR

Ce

Q,

Cin V

R

Ce

Q, Ce

Q,

Cin VR

Cn

VR

C1

Q,

C1

Q,

Cn-1

Q,

CnVR

Cn-1

Q, Cn-

2

Q, Cn-

1

n-CMFR:

Completely Mixed Flow Reactor(CMFR)

Completely Mixed Batch Reactor(CMBR)

dCa

dt(C

aoC

ara

1

) (Governing Equation)

d Ca

d tra

(Governing Equation)

VR

Ce

Q,

Cin V

R

Ce

Q, Ce

Q,

Cin VR

Cn

VR

C1

Q,

C1

Q,

Cn-1

Q,

CnVR

Cn-1

Q, Cn-

2

Q, Cn-

1

n-CMFR:



dCa

dt(C

aoC

ara

1


d Ca

d tra


VR

Ce

Q,

Cin V

R

Ce

Q, Ce

Q,

Cin VR

Cn

VR

C1

Q,

C1

Q,

Cn-1

Q,

CnVR

Cn-1

Q, Cn-

2

Q, Cn-

1

n-CMFR:



dCa

dt(C

aoC

ara

1


d Ca

d tra


CMBR

Light Sources

Design Aid – Light Source

Low Pressure UV

Photolysis of a single chromophore system

Design Aid – photolysis

dI = 2.303 IC

dx

Quantum yield denoted as , is the number of reactions divided by the number of photons absorbed by the molecule.

R

a

r Reaction Rate =

Excitation Rate(photon absorption)I

2.303 Cx

R a R or I 2.303 C I e

For a single wavelength, single chromophore system at a point in space

For a multi-wavelengths, multi-chromophores system over the entire reactor.

n

i,j i

i=1

k -2.303 C b

i,j j 0,j j

j 1

r = - I f 1 e

• Modeling Different Reactor Configurations

Design Aid Model

• Modeling Multi-wavelengths (up to 100) Light Sources

Design Aid Model

• Dye Study Analysis for Actual Mixing Conditions

Design Aid Model

Database of Hydroxyl-Radical Rate Constants (650 of commonly encountered contaminants)

Design Aid Model

Case Study -- Removal of MtBE and tBA

from Drinking Water Source

(Note HiPOx is not feasible because of

bromate formation and we will have to

remove residual hydrogen peroxide)

Treatment Objectives

State Regulation

Primary MCL for MtBE: 13 µg/L

Secondary MCL for MtBE: 5 µg/L

Public Acceptance

Effluent MtBE Goal < 1 µg/L (with a target of 0.2 µg/L)

Effluent tBA Goal < 1 µg/L

MtBE and tBA levels:

a combined Influent MtBE = 500 µg/L, tBA = 50 µg/L

Raw Water Quality

Parameter

units value Parameter units Value

Conductivity mmho/cm 1435 Aluminum mg/L 0.005

TDS mg/L 940 Potassium mg/L 11.4

Alkalinity mg/L

CaCO3

313 Iron mg/L 0.44

Calcium mg/L 138 Manganese mg/L 0.089

Hardness mg/L 533 Fluoride mg/L 0.29

Chloride mg/L 138 Bromide mg/L 0.9

Nitrate mg/L NO3- 0.9 pH unitless 7.56

Sulfate mg/L 272 MTBE μg/L 300

Sodium mg/L 107 TOC mg/L 1.35

Magnesium mg/L 54 TBA μg/L 30

Raw Water Quality

Diagram of Pretreatment ProcessIo

n E

xch

an

ge w

ith

Sea W

ate

r

(+D

ea

lka

lizati

on

)

Courtesy of R.

Trussell

Diagram of Pretreatment ProcessP

elle

t S

oft

en

ing

( N

o D

ea

lka

lizati

on

)

Courtesy of R.

Trussell

Diagram of Pretreatment ProcessL

ime S

oft

en

ing

+

Rev

ers

e O

sm

os

is

Courtesy of R.

Trussell

Water Quality after Pretreatment

AlternativeTOC

(mg/L)

Alkalinity

(mg/L as CaCO3)pH

Ferrous Iron

(mg/L)

Raw Water 1.4 318 7.6 0.44

Ion Exchange with Sea

Water

(+dealkalization)

1.4 0 4.75 0

Pellet Softening 1.4 203 9.1 0

Reverse Osmosis

(no dealk)0.07 54.1 7.0 0

Low Pressure UV/H2O2 System (LPUV)

Lamp ConfigurationLPUV System


0

0.2

0.4

0.6

0.8

1

1.2

0 0.5 1 1.5 2 2.5 3 3.5 4

Theta

F(T

he

ta)

experimental

NTIS=24

Cumulative Exit Age Distribution, F(), versus Normalized Time for tracer

study data of 3 LPUV chambers in series and the fitting with 24 Tanks-In-

Series model. 8 Tanks-In-Series was decided to be appropriate for

modeling each LPUV Chamber.

Fth

eta


The AOP modeling approach

involved determining the

appropriate number of chambers

in a single train (Q=1,750 gpm) to

meet the treatment objective for

both MtBE and tBA. The following

design parameters are evaluated:

1. The number of chambers required

at a H2O2 dosage that does not

result in chlorate problem.

2. Optimum H2O2 dosage.

3. The number of chambers required

for each pretreatment option.

4. H2O2 residual with the above

designs.

7000

gpm

Medium Pressure UV/H2O2 System (MPUV)

Lamp ConfigurationMPUV System

Four tanks-in-series was estimated to be appropriate to simulate

the mixing conditions in the MPUV system based on the geometry

of the reactor.

Medium Pressure UV/H2O2 System (MPUV)

The AOP modeling approach

involved determining the

appropriate number of parallel

trains consisting of one or two

reactors in each train (that is,

determine Q for each parallel train)

to meet the treatment objective for

both MtBE and tBA. The following

design parameters are evaluated:

1. The number of trains and the

number of reactors in each train

required at a H2O2 dosage that

does not result in chlorate problem

for each pretreatment option.

2. Optimum H2O2 dosage.

3. H2O2 residual with the above

designs.

7000

gpm

Design of LPUV System with

Different Pretreatment Options

Pretreatment

Process

H2O2

(mg/L)

EE/O

(kWh-

kgal/order)

Effluent

Concentrati

on (µg/L)

No. of

reactors

per

train

No. of

parallel

trains

In outMtBE tBA

MtBE tBA

Low Pressure UV System

None (raw) 25 13 1.1 4.4 0.5 5.7 9 4

Ion Exchange

with Sea Water

(+dealkalization)

Pellet+Dealk,

10 6.9 0.77 3.0 0.6 5.8 6 4

Pellet 70 35 1.4 5.3 0.4 5.4 11 4

RO 7.0 4.9 0.15 0.49 1.3 5.7 1 4

Design of MPUV System with

Different Pretreatment Options

Medium Pressure UV System

None (Raw) 30 15 7.3 23 1.3 5.2 2 8

Ion Exchange

with Sea Water

(+dealkalization)

Pellet+Dealk,

10 6.6 4.6 15 1.4 5.8 2 5

Pellet 50 19 8.3 27 1.4 5.9 2 9

RO 4 1.9 0.99 2.8 2.1 5.0 1 2

Pretreatment

Process

H2O2

(mg/L)

EE/O

(kWh-

kgal/order)

Effluent

Concentrati

on (µg/L)

No. of

reactors

per train

No.

of

Paral

lel

trains

In outMtBE tBA

MtBE tBA

The effluent concentration for the treatment of raw water

using different number of LPUV chambers with H2O2

dosage of 16 mg/L

Note: The unit for the H2O2 residual is mg/L, while the units for the MtBE and

tBA effluent concentration are ug/L.

0

2

4

6

8

10

12

24 26 28 30 32 34 36 38

number of chambers

Eff

lue

nt

Co

nc

en

tra

tio

n

H2O2 Residual (mg/L)

MTBE (ug/L)

TBA (ug/L)

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

5 25 45 65 85 105

H2O2 Dosage (mg/L)

H2

O2

Re

sid

ua

l c

on

ce

ntr

ati

on

(mg

/L)

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

Eff

lue

nt

Co

nc

en

tra

tio

n (

ug

/L)

H2O2 Residual

MTBE

TBA

Optimum H2O2 dosage using 36 LPUV chambers

with Pellet pretreatment

Impact of dosage on treatment effect and residual using 28

LPUV chambers for ion exchange/ or pellet treatment and

dealkalization pretreatment

4.00

5.00

6.00

7.00

8.00

9.00

10.00

11.00

12.00

13.00

14.00

9 10 11 12 13 14 15H2O2 Dosage (mg/L)

H2

O2

Re

sid

ua

l (m

g/L

)

0.00

0.50

1.00

1.50

2.00

2.50

3.00

EE

O (

kW

h/k

ga

l-o

rde

r)

H2O2 residual

EE/O (MTBE)

EE/O (TBA)

Impact of dosage on treatment effect and residual using 5 trains

of 2 MPUV reactor in series for ion exchange and dealkalization

pretreatment

2.00

4.00

6.00

8.00

10.00

12.00

14.00

5 10 15

H2O2 Dosage (mg/L)

H2

O2

Re

sid

ua

l (m

g/L

)

0.00

5.00

10.00

15.00

20.00

25.00

30.00

EE

O (

kW

h/k

ga

l-o

rde

r)

residual

EE/O (MTBE)

EE/O (TBA)

UV/H2O2 Process Mechanism Study

Compound Observed by-products

Acetonea 1. acetic, pyruvic, and oxalic acids, pyruvaldehyde

2. formic and glyoxylic acids, hydroxyacetone, formaldehyde

Methyl

tertiary

butyl etherb

1. acetone, acetic acid, formaldehyde, tert-butyl formate

(TBF), pyruvic acid, tert-butyl alcohol (TBA), 2-methoxy-2-

methyl propionaldehyde (MMP), formic, methyl acetate

2. hydroxy- iso-butyraldehyde, hydroxyacetone,

pyruvaldehyde and hydroxy- iso-butyric, oxalic acid

Dioxanec 1. 1,2-ethanediol diformate, formic acid, oxalic acid, glycolic

acid formaldehyde1,2-ethanediol monoformate

2. methoxyacetic acid glyoxal,

3. Acetaldehyde

TCEd 1. formic acid, oxalic acid

2. dichloroacetic acid, mono-chloroacetic acid.

1.Major by-products (yield 10 to 30 mole %) ; 2.Minor by-products (yield 2

to 5 mole %); 3.Very Minor By-product (yield <1 mole %).

UV/H2O2 Process – byproducts

Models for Mechanism Study-- Conventional Modeling Approach

collect kinetic data from experiments

propose hypotheses of a set of pathways

construct kinetic law models that contain a set

of ordinary differential equations with

corresponding kinetic parameters

adjust the parameters and model to

interpret the experiments

Byproducts in TCE Destructionby courtesy of Dr. Mihaela Stefan

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0 5 10 15 20 25 30 35

Time / min

[Ch

lori

de

Io

n]

/ m

M

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

[In

term

ed

iate

s]

/ m

M

Chloride

Oxalic Acid

DCA

Formic Acid

MCA

Proposed Mechanism

ClHC=CCl2

ClCH(OH)-CCl2

HO

hv *Cl

Cl2HC-CCl2

ClH2CCOOH

ClHC-COOH

HO

O2

HC(O)Cl

CO2

OHC-COOH

HCl +CO

O2

OHC-CCl2+HCl

O2

OHC-CCl2+HCl

OHC-CCl2+HCl C(O)Cl2

CHO HCOOH

CO2+HCl

HCOOHOHC-CClO+Cl

OHC-COOH

H2O

HO

CO2+H++H2O

H2O2

HCOOH

CO2

H2O

HO

HOOC-COOH

HO

CO2+CO2+H+

Cl2HCCOOH

Cl2C-COOH

HO

O2

C(O)Cl2

CO2

HOOC-C(O)Cl

HOOC-COOHHOOC-COOH

Cl2CHCHO

HCCCl

ClCCCl

H2O

HO

HO

Cl2CHCOOH

CO2 + Cl

CO2 + Cl

• the complex radical reactions between hydrogen peroxide, hydroxyl radical, superoxide radical and formyl radical

• TCE direct photolysis and reactions with OH • and Cl•

• the formation and destruction of main byproducts and intermediates, such as di-chloroacetic acid (DCA), mono-chloroacetic acid (MCA), oxalic acid and formic acid

• Intermediate byproducts those are not detected: glyoxylic acid and phosgene

• scavenging of hydroxyl radical by bicarbonate species

The model contains 34 differential equations for 8 molecules and 6 radicals, including:

TCE UV/H2O2 Modeling

• the UV irradiation ranging from 200nm to 300nmin an interval of 1nm

• the molar extinction coefficients of TCE, H2O2 and4 types of main byproducts are measured andsimulated in an interval of 1nm from 200 to 300nm

• the pH change of the system

• the dissociation of 8 orgainc/inorganic acids

• 22 literature reported rate constants are used in the model

The model is a kinetic model and considers:


0.E+00

2.E-03

4.E-03

6.E-03

8.E-03

1.E-02

1.E-02

0 5 10 15 20 25 30 35

Time (min)

Co

nc

en

tra

tio

n (

mo

l/L

)

exp

mod

0.E+00

2.E-04

4.E-04

6.E-04

8.E-04

1.E-03

1.E-03

0 10 20 30 40

Time (min)

Co

nc

en

tra

tio

n (

mo

l/L

)mod

exp

0.E+00

1.E-06

2.E-06

3.E-06

4.E-06

5.E-06

6.E-06

7.E-06

8.E-06

9.E-06

0 10 20 30 40

Time (min)

Co

nc

en

tra

tio

n (

mo

l/L

)

exp

mod

0.E+00

2.E-06

4.E-06

6.E-06

8.E-06

1.E-05

1.E-05

0 10 20 30 40

Time (min)

Co

nc

en

tra

tio

n (

mo

l/L

)

mod

exp

Comparison of Modeled and Experimental Concentration Profile of

(a) TCE (b) H2O2 (c) DCA (d) MCA

(a)

(d)(c)

(b)


Comparison of Modeled and Experimental Concentration Profile of

(a) Formic Acid (b) Oxalic Acid (c) pH

0.E+00

1.E-05

2.E-05

3.E-05

4.E-05

5.E-05

6.E-05

7.E-05

8.E-05

9.E-05

1.E-04

0 5 10 15 20 25 30 35

Time (min)

Co

nc

en

tra

tio

n (

mo

l/L

)

exp

mod

(b)

0.E+00

5.E-05

1.E-04

2.E-04

2.E-04

3.E-04

3.E-04

4.E-04

4.E-04

5.E-04

0 10 20 30

Time (min)

Co

nc

en

tra

tio

n (

mo

l/L

)

exp

mod

(a)

0

1

2

3

4

5

6

7

0 10 20 30 40

Time (min)

pH

exp

mod

(c)


Models for Mechanism Study-- Complexity Modeling Approach

H

H

H

H

H

H

HH

H

F

FF

FF

F

F

Patterns

Reaction to emergent

patterns

Interaction between

agents

Emerging patterns

MACRO

MICRO

Graph Theory Approach (Euclid 1735) –Mathematic Abstraction

HCHC

HCCH

CH2 +

O

S

CCl2 HCCH

C

SHCCH

H2C

O

Cl

ClC

C

CC

S

C

C

CC

C

SC

G1

Patterns

G2

G3 G4

Transformation

Reaction rule

Diels-Alder reaction

Representation of an Atom• graph: A graph consists of two sets: a set of

nodes or vertices), and a set of edges that connect those nodes. Figure below is an example of graph.

• Chemical structures are intrinsically

graphs.

node

edge

Name ID Valence Weight

Array of Bond Types

Pointer to the Parent

Pointer Array to the

Children

A Tree

Sub-tree

or Pattern

Representation of a Molecule

Root

A Chemical Tree

Leaf

Cl H

CH

H

OCl

H

C

H

H

CH

HClC

Cl HO

H

C

C

H

H

Abstraction:OH + R-H R + H2O

Reaction Rules Included

Double Bond Addition:OH + R1=R2 R1(OH)-R2

O2 Addition:

R + O2 R-OO

Peroxyl Radical Reaction: HO2/O2

- Elimination,

Bimolecular Decay

Oxyl Radical Reaction: b-scission, 1,2-H shift

Hydrolysis: Carbonyl-chloride, b-Halogen

Others: HCl elimination of germinal chlorohydrin radical,Chlorine radical reaction

Reactant Graph

Reaction Rules

Products Graph

Take Unique Products as New Reactants

Computer

Pathway

Generator

Linear Notation

Logic

Match Patterns

Products Analysis

Reactant/Product relationships

Complexity Setting

Complexity Reaction Rules Application

0 Major elementary

reactions and strict

exclusion rules

Direct Kinetic

Modeling

1 Minor elementary

reactions

More complex

kinetic modeling

2 No exclusion and bi-

radical reactions

All possible

reactions

Generated Results at Different Complexity

Complexity 1 2 3

species reaction species reaction species reaction

TCE 35 49 41 76 87 384

Methane 11 16 24 63 57 180

Ethane 25 78 136 3367 827 35641

Example: Generated Pathways for TCE

• 49 reactions illustrate the destruction pathways for TCE and the formation and decay of byproducts including: DCA, Formic acid, Oxalic acid, phosgene, etc.

• 15 more byproducts/intermediates than proposed which forms reasonable elementary routes.

• MCA was not predicted since it was produced via photolysis mechanism

With the lowest complexity, the generated pathways for TCE destruction in H2O2/UV process contains:

Details of TCE pathway accounts for the formation and decay of

formic, glyoxylic, oxalic acids and phosgene. Cl2C=CHCl

Cl2CCH(OH)Cl Cl2C

CHCl2

Cl2C-CHO

-HCl

HO

Cl

OO-Cl2C-CHO

OCl2C-CHO

O2

Cl(O)C-CHO

+ Cl

HOOCCHOCO2 + HCl

H2OH2O

CHO +C(O)Cl2

H2O

HC(OH)2

O2

OOCH(OH)2

HCOOH + HO2

HCOOH

H2O2

O2

OOCCl2CHCl2

OCCl2CHCl2

O2

+OCHCl2

Cl2CHC(O)Cl C(O)Cl2 + CHCl2

- Cl

Cl2CHCOOH

O2

OOCHCl2

C(O)Cl2

+(OH)CHCl2

C(O)Cl2

+H2O2

C(OH)Cl2HC(O)Cl

CO + HCl OOC(OH)Cl2

CCl2COOH

OOCCl2COOH

C(O)Cl2 +HO2

OCCl2COOH

C(O)Cl2+ COOH ClC(O)COOH

HOOCCOOHO2

OOCOOH

CO2 + HO2

H2O

HOOCCOOH

HO

CO2 + CO2

HO

CO2 H2O2O2

CO2 + O2

CO2 + HO

Li, K., M. I. Stefan, J. C. Crittenden, “UV Photolysis of

Trichloroethylene (TCE): Product Study and Kinetic

Modeling”, ES&T, 2004, 38, 6685-6693.

Crittenden, J.C.; Hu, S.; Hand, W. D.; Green, A. S. A kinetic

model for H2O2/UV process in a completely mixed match

reactor. Wat. Res. 1999, 33(10), 2315-2328.

Li, K., M. I. Stefan, J. C. Crittenden, “Trichloroethylene

(TCE) Degradation by UV/H2O2 Advanced Oxidation

Process: Product Study and Kinetic Modeling”, ES&T, 2006,

in revision.Li, K., J. C. Crittenden, T. N. Rogers, Zh. Zhang “Pathway

Elucidation for Hydroxyl Radical Induced Chain Reaction

Mechanisms in Aqueous Phase Advanced Oxidation

Processes ”, ES&T, in preparation.

Water Treatment Book -Theory Reduced to Practice

Montgomery-Watson-Harza invested $ 1 million, 1948 Pages

Water Treatment Book -Theory

Reduced to Practice

Montgomery-Watson-Harza

invested $ 1 million, 1948

Pages

CONCLUSIONS

• With known mechanism and basic water chemistry information, models at different levels can be built to help interpret and plan treatability studies for AOPs and investigate pretreatment options that my be needed.

• Complexity modeling can use the current understanding on the basic elementary reactions to generate reaction pathways for different contaminants.

• It can provide information about the important pathways leading to toxic byproducts. However, good strategy is required to reduce the redundancy and screen the pathways for the purpose of kinetic modeling.

• More experimental study is necessary before the complexity model is able to include the UV photolysis mechanism.

Thank you so much for your

attention!

uv/h2o2 process modeling for design and mechanistic...

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