Oxford OH USA wwwnovachemlabscom Sponsored by Powell Fabrication Understanding Bleach Degradation NovaChem Laboratories Inc Testing bleach since 1989 1990s AWWA Bleach Decomposition Study ID: 674607
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Slide1
Bernard
Bubnis
NovaCem
Laboratories, Inc.Oxford, OH USAwww.novachemlabs.comSponsored by: Powell Fabrication
Understanding Bleach DegradationSlide2
NovaChem Laboratories, Inc.Testing bleach since 19891990’s - AWWA Bleach Decomposition StudyCollaboration with Powell Fabrication & ManufacturingDecomposition Model StudiesChemistry Validation Measurement Protocols forInorganic disinfection by-products
Transition metal ionsSlide3
Bleach DegradationParameters That Influence Decomposition
ConcentrationTemperatureIonic StrengthTransition Metal IonsSlide4
What is the chemistrythat controls decompositionand the formation of
disinfection by-products ? Slide5
Bleach Decomposition2nd
Order Rate = k2 [OCl-]
2Primary Pathway OCl- + OCl
- → ClO2- + Cl- OCl- + ClO2- → ClO3- + Cl-Stoichiometry 3OCl- → ClO3
-
+ 2Cl
-
Secondary Pathway
OCl
-
+
OCl
-
→ O
2
+ 2Cl
-
“
uncatalyzed
” and “catalyzed”Slide6
OCl- Lost …ClO3- FormedSlide7
Decomposition Comparison (90°F) Concentration EffectSlide8
2nd Order Plot vs. TemperatureSlide9
Decomposition Comparison (13%) Temperature EffectSlide10
Rate Constant as a Function of Ionic StrengthSlide11
Decomposition Comparison (90°F) HSLS vs. Typical 13%Slide12
HSLS Bleach “High Strength Low Salt”30 Wt% NaOCl385 GPL Available Chlorine≈1 Wt%
NaOH8.5 Wt% NaCl13 Wt% NaOCl (traditional)10.4 Wt% NaClSlide13
HSLS Bleach “High Strength Low Salt”13% Wt NaOCl (traditional)10.4% Wt NaCl13% Wt HSLS - 3.7% Wt NaCl6% Wt HSLS - 1.7% Wt NaClSlide14
It is not obvious that ionic strength might affect oxygen formation … but it does (30% less) Less oxygen ….more bleachSlide15
Decomposition Comparison (90°F) Transition Metal IonsSlide16
OCl- Lost … Catalyzed ReactionSlide17
Oxygen Comparison (90°F)0.5 mg/L Ni vs.
Typical 13%Slide18
Decomposition as a Function of pHSlide19
Chlorate Formation as a Function of pH Slide20
What Happens in UV-light ?Slide21
Unwanted By-ProductsWhat are they ?Bromate BrO3-Chlorate ClO3-Perchlorate ClO4-How do they get into the bleach?Raw materials and decompositionSlide22
Bromate Ion, BrO3-Bromide ion in salt used to make Cl2Forms Br2Reacts with caustic to form BrO3-Impurity in causticSlide23
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 StrengthRate 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)Slide24
Perchlorate Ion, ClO4-Slide25
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)Slide26
Decomposition Software Modeling What can you model ?Bleach LossChlorate Ion FormationOxygen FormationPerchlorate Ion FormationWhat factors can you manipulate?Concentration
TemperatureCaustic strengthIonic strengthMetal ion concentrationTime parametersSlide27
Powell SoftwareSlide28
Powell SoftwareSlide29
Powell SoftwareSlide30
Powell SoftwareSlide31
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 Solids Suspended SolidsSlide32
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 128Normalization 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 acceptableSlide33
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 Slide34
Suggested Bleach QAManage the DecompositionConcentrationTemperatureTransition Metal IonsIonic StrengthManage the Storage and DeliveryModel the Bleach and VerifyMake Measurements
Tier I analysis (minimum)