Bernard BubnisNovaCem Laboratories, Inc.

Oxford, OH USAwww.novachemlabs.com

Sponsored by: Powell Fabrication

Understanding Bleach Degradation

NovaChem Laboratories, Inc.Testing bleach since 19891990’s - AWWA Bleach Decomposition

StudyCollaboration with Powell Fabrication &

ManufacturingDecomposition Model StudiesChemistry Validation Measurement Protocols for

◦Inorganic disinfection by-products◦Transition metal ions

Bleach Degradation

Parameters That Influence Decomposition◦Concentration◦Temperature◦Ionic Strength◦Transition Metal Ions

What is the chemistrythat controls decomposition

and the formation of disinfection by-products ?

Bleach Decomposition2nd Order Rate = k2 [OCl-]2

Primary Pathway OCl- + OCl- → ClO2- + Cl-

OCl- + ClO2- → ClO3

- + Cl-

Stoichiometry 3OCl- → ClO3- + 2Cl-

Secondary Pathway OCl- + OCl- → O2 + 2Cl-

“uncatalyzed” and “catalyzed”

OCl- Lost …ClO3- Formed

Decomposition Comparison (90°F) Concentration Effect

0 10 20 30 40 50 605.000

6.000

7.000

8.000

9.000

10.000

11.000

12.000

13.000

14.000

13%10%

Days

Wt%

NaO

Cl

Half-life = 48.5 dayst=60 days, 43% original concentration

Half-life = 94.7 dayst=60 days, 60% original concentration

2nd Order Plot vs. Temperature

Decomposition Comparison (13%) Temperature Effect

0 10 20 30 40 50 604.000

5.000

6.000

7.000

8.000

9.000

10.000

11.000

12.000

13.000

14.000

68 F90 F

Days

Wt%

NaO

Cl

Rate Constant as a Function of Ionic Strength

Decomposition Comparison (90°F) HSLS vs. Typical 13%

0 10 20 30 40 50 605.000

6.000

7.000

8.000

9.000

10.000

11.000

12.000

13.000

14.000

HSLSTypical 13%

Days

Wt%

NaO

Cl

t = 60 days, 59% original concentration

t = 60 days, 43% original concen-tration

HSLS Bleach “High Strength Low Salt”

30 Wt% NaOCl◦385 GPL Available Chlorine◦≈1 Wt% NaOH◦8.5 Wt% NaCl

13 Wt% NaOCl (traditional)◦10.4 Wt% NaCl

HSLS Bleach “High Strength Low Salt”

13% Wt NaOCl (traditional)◦10.4% Wt NaCl

13% Wt HSLS - 3.7% Wt NaCl6% Wt HSLS - 1.7% Wt NaCl

It is not obvious that ionic strength might affect oxygen formation … but it does (30% less) Less oxygen ….more bleach

0 10 20 30 40 50 600

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Oxygen Comparison (90°F)HSLS vs Typical 13%

HSLSTypical 13%

Days

Oxy

gen

(L g

as/L

OCl

-)

Decomposition Comparison (90°F) Transition Metal Ions

0 10 20 30 40 50 600.000

2.000

4.000

6.000

8.000

10.000

12.000

14.000

13% NaOCl0.5 mg/L Ni

Days

Wt%

NaO

Cl t = 60 days, 43% original concentration

t = 60 days, 24% original concentration

OCl- Lost … Catalyzed Reaction

Oxygen Comparison (90°F)0.5 mg/L Ni vs. Typical 13%

0 10 20 30 40 50 600

2

4

6

8

10

12

0.5 mg/L NiTypical 13%

Days

Oxy

gen

(L g

as/L

OC

l-)

t = 60 days, 11x more oxy-gen

“uncatalyzed” reaction

“catalyzed” reaction

Decomposition as a Function of pH

Chlorate Formation as a Function of pH

What Happens in UV-light ?

Unwanted By-ProductsWhat are they ?

◦Bromate BrO3-◦Chlorate ClO3-◦Perchlorate ClO4-

How do they get into the bleach?Raw materials and decomposition

Bromate Ion, BrO3-Bromide ion in salt used to make Cl2

◦Forms Br2◦Reacts with caustic to form BrO3-

Impurity in caustic

Perchlorate Ion, ClO4-

Source: Water Research Foundation, 2009, An Assessment of the Factors that Influence the Formation of Perchlorate and

Other Contaminants

ReactionOCl- + ClO3

- → ClO4- + Cl-

Strongly dependent on Temperature and Ionic Strength

Rate Lawd[ClO4

-]/dt = kClO4- [OCl-] [ClO3-]

Rate Constantlog (kClO4- ) = 0.0788(I) + log (2.084 x 1016 x T x e -1.01x10^5/RT x e -10^6/R)

Perchlorate Ion, ClO4-

0 10 20 30 40 50 600.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

45.00

50.00

Perchlorate Ion Comparison (90°F)HSLS vs Typical 13%

HSLSTypical

Days

Perc

hlor

ate

Ion

(mg/

L)

Basis of a Chemical Model

Chlorate and Oxygen Formation(3kCl + 2kox)t = 1/[OCl-]t – 1/[OCl-]0

Perchlorate Ion Formationd[ClO4

-]/dt = kClO4- [OCl-] [ClO3-]

log (kClO4- ) = 0.0788(I) + log (2.084 x 1016 x T x e -1.01x10^5/RT x e -10^6/R)

Decomposition Software Modeling What can you model ?

◦ Bleach Loss◦ Chlorate Ion Formation◦ Oxygen Formation◦ Perchlorate Ion Formation

What factors can you manipulate?◦ Concentration◦ Temperature◦ Caustic strength◦ Ionic strength◦ Metal ion concentration◦ Time parameters

Powell Software

Powell Software

0 5 10 15 20 25 300.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

0.0

5.0

10.0

15.0

20.0

25.0

30.0

Diluted HSLS Hypo vs. Traditional Hypo @ 90°F

Traditional Hypo Dilute HSLS HypoDilute HSLS Hypo GPL NaClO3 Trad. Hypo GPL NaClO3

Days

Stre

ngth

, wt.

% N

aOCl

Sodi

um C

hlor

ate,

GPL

Powell Software

0 5 10 15 20 25 300.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Diluted HSLS Hypo vs. Traditional Hypo @ 90°F

Traditional Hypo Dilute HSLS HypoDilute HSLS Hypo Oxygen Trad. Hypo Oxygen

Days

Stre

ngth

, wt.

% N

aOCl

Oxy

gen,

LO

2/LO

Cl

Powell Software

0 5 10 15 20 25 300.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

0.0

2.0

4.0

6.0

8.0

10.0

12.0

Diluted HSLS Hypo vs. Traditional Hypo @ 90°F

Traditional Hypo Dilute HSLS HypoDilute HSLS Hypo mg/L NaClO4 Trad. Hypo mg/L NaClO4

Days

Stre

ngth

, wt.

% N

aOCl

Sodi

um P

erch

lora

te, m

g/L

Bleach TestingEssential Analyses: (Tier 1)Wt% NaOCl g/L Available Cl2 Specific gravityWt% NaOH Wt% Na2CO3 mg/L chlorate

Optional Analyses I: (Tier 2)mg/L bromate mg/L perchlorate mg/L Fe, Cu, Ni

Optional Analysis II: (Tier 3)Filter test Dissolved SolidsSuspended Solids

ClO3- Normalized Result Calculation

INPUTS

Maximum Use Level (MUL), mg/L 80Trade % Bleach 13.475 Vol of Hypo Rec'd, mL 156.5 Vol of Peroxide, mL 31.5 Vol of Hypo Sample, mL 125 Peroxide Dilution Correction 1.25 Hypo Density, g/mL 1.2 Chlorate analysis value, mg/L 128

Normalization Factor (NF)NF = (MUL) (Peroxide Dil Correction) (1/Hypo Density) ( 1/10^3) (1/10^3) NF = 8.3475E-05

Normalized Result (NR)NR = Test Result * NF * 10^3 ug/LNR = 10.7 ug/L <200 ug/L is acceptable

Filter TestOperations ToolParticulate matter causes problemsIn-field testing determined the parametersAt 20 inches of Hg, 1 liter of bleach should

filter through 0.8 micron filter paper in < 3 minutes

Suggested Bleach QAManage the Decomposition

◦ConcentrationTemperatureTransition Metal Ions

◦Ionic StrengthManage the Storage and DeliveryModel the Bleach and VerifyMake MeasurementsTier I analysis (minimum)