10/8/2013
Updated: 8 October 2013 CEE690K Lecture #09 1
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CEE 690K ENVIRONMENTAL REACTION KINETICS
Lecture #9
Reaction Mechanisms: Acid Catalysis Brezonik, Chapter 4
David A. Reckhow Introduction
Mechanisms: Haloform Reaction
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Chlorine + acetone Morris & Baum, 1978 Brezonik, 1994 Pg 240-241
CEE690K Lecture #09 David A. Reckhow
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Haloform reaction: initial step
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Three potential pathways to enolate
Reaction with water (KO), hydroxide (KOH), and proton (KH) - + kf=KO+KOH[OH ]+KH[H ] For acetone, the OH pathway dominates above pH 5.5
k f [H ][A ] Ka What is kr? kr [HA]
CEE690K Lecture #09 David A. Reckhow
Haloform: Doré’s diagram
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Doré (1989)
RLS is the first one
CEE690K Lecture #09 David A. Reckhow
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Loss of intermediates in lab water
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21C, ultrapure water (Nikolaou et al., 2001)
CEE690K Lecture #09 David A. Reckhow
Profile of TCP in water systems
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1,1,1-Trichloropropanone concentrations compared to the corresponding TTHM concentration for all samples
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San Francisco Jan(Cl2/NH4Cl)
Charleston(ClO2/ NH4Cl) San Francisco Apr (Cl /NH Cl) 4 Monroe 2 4
g/L) Ann Arbor(O3/NH4Cl) East Bay( Cl2/NH4Cl)
Cincinnati(Cl2) 3 Minneapolis (NH4Cl/NH4Cl)
Monroe(O3/Cl2)
Wyoming( Cl2/Cl2)
2 Pinellas Co. Pinellas County(Cl2/Cl2) Pinellas County(Cl /NH Cl) Knoxville 2 4
Knoxville(ClO2/Cl2) 1 1,1,1- trichloropropanone ( trichloropropanone 1,1,1-
0 0 20 40 60 80 100 120 140 ChloroformCEE690K (g/L) Lecture #09 David A. Reckhow
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Loss in water heaters
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0.6 3.0 a No heating b Liu et al., 6 hrs incubation+heating 0.5 2.5 24 hrs incubation+heating 48 hrs incubation+heating 2013 0.4 2.0 72 hrs incubation+heating 96 hrs incubation+heating g/L) g/L)
0.3 1.5
In review CP ( No heating 1,1-DCP ( 0.2 1.0 6 hrs incubation+heating 24 hrs incubation+heating 0.1 48 hrs incubation+heating 0.5 72 hrs incubation+heating 96 hrs incubation+heating 0.0 0.0 0 20406080100120 0 20406080100120 Reaction Time (hr) Reaction Time (hr) 8.0 2.5 c No heating No heating d 6 hrs incubation+heating 6 hrs incubation+heating 24 hrs incubation+heating 2.0 24 hrs incubation+heating 6.0 48 hrs incubation+heating 48 hrs incubation+heating 72 hrs incubation+heating 72 hrs incubation+heating 96 hrs incubation+heating 1.5 96 hrs incubation+heating g/L) g/L) 4.0
TCP ( 1.0 DCAN (
2.0 0.5
0.0 0.0 0 20 40CEE690K 60 Lecture 80 100 #09 120 0 20406080100120David A. Reckhow Reaction Time (hr) Reaction Time (hr)
Case Study: TCP Note: both TCP and TCAC refer to the 1,1,1-trichloropropanone 8
Observed loss of 1,1,1- trichloropropanone in distribution systems Lab studies show that chloroform is the product Logically presumed to be a simple hydrolysis
Reckhow & Singer, 1985 “Mechanisms of Organic Halide Formation During Fulvic Acid Chlorination and Implications with Respect to Preozonation”, In Jolley et al., Water Chlorination; Chemistry, Environmental Impact and Health Effect, CEE690K Lecture #09 David A. Reckhow Volume 5, Lewis.
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TCP (cont.)
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Ionic strength effects
ln kH 4.811.4 I
log kH 2.08 0.6 I
Rate with chlorine Increases greatly High intercept
kT 0.024 32HOCl T
CEE690K Lecture #09 David A. Reckhow
Disagreement with prior study
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Gurol & Suffet showed 10x higher rate constants
Phosphate?
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Putting it together
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CEE690K Lecture #09 David A. Reckhow
Catalysis
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Homogeneous Catalysis Definition Liquid-phase substances which react with the main reactants or intermediates thereby providing an alternative pathway to products with a lower activation energy or a higher frequency factor. Catalysts are often regenerated over the course of the reaction.
2A2 B 2A B3 termolecular reaction? – be skeptical
2 2 What A C A C 2 2 3 “C” serves as a sort of charge- really A C A C transfer facilitator, since “B” does happens: C 3 B C B3 not exist in a divalent state 2A2 B 2A B3
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Summary
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To next lecture
CEE690K Lecture #09 David A. Reckhow
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