David Reckhow CEE 680 #32 1 - UMass AmherstCEE 680 Lecture #32 3/25/2020 5 Cu‐NTA III Specific...
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CEE 680 Lecture #32 3/25/2020 1 Lecture #32 Coordination Chemistry: Case Studies: NTA (cont.) (Stumm & Morgan, Chapt.6: pg.317‐319) Benjamin; Chapter 8.1‐8.6 David Reckhow CEE 680 #32 1 Updated: 25 March 2020 Print version Biotic ligand model of the acute toxicity of metals. 2. Application to acute copper toxicity in freshwater fish and Daphnia Environmental Toxicology and Chemistry, Volume: 20, Issue: 10, Pages: 2397-2402
Transcript of David Reckhow CEE 680 #32 1 - UMass AmherstCEE 680 Lecture #32 3/25/2020 5 Cu‐NTA III Specific...
CEE 680 Lecture #32 3/25/2020
1
Lecture #32Coordination Chemistry: Case Studies: NTA
(cont.)
(Stumm & Morgan, Chapt.6: pg.317‐319)
Benjamin; Chapter 8.1‐8.6
David Reckhow CEE 680 #32 1
Updated: 25 March 2020 Print version
Biotic ligand model of the acute toxicity of metals. 2. Application to acute copper toxicity in freshwater fish and Daphnia
Environmental Toxicology and Chemistry, Volume: 20, Issue: 10, Pages: 2397-2402
CEE 680 Lecture #32 3/25/2020
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Algae and Copper
McKnight et al., 1983; Environmental Management 7(4)311-320
%𝜇
𝜇
Fresh and salt water algae
Depends on Cu+2 ion: 10‐7M seems to work for most
Add CuSO4
Smith et al., 2015, Applied Geochemistry 57:55
CEE 680 Lecture #32 3/25/2020
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Modeling the Fate of Metal Concentrates in Surface Water
Environmental Toxicology and Chemistry, Volume: 38, Issue: 6, Pages: 1256-1272, First published: 23 March 2019, DOI: (10.1002/etc.4417)
Copper – NTA problem
NTA: nitrilotriacetate Used as a substitute “builder” in place of phosphate
Good example of moderately strong ligand
Research interests: 70’s & 80’s General Review
Perry et al., 1984 [Wat. Res., 18(3)255] Other Aspects
Photochemistry: e.g., Langford et al., 1973 [ES&T 7(9)820] Biodegradation: e.g., Kuhn et al., 1987 [Wat. Res. 21(10)1237], Vanbriesen
et al., 2000 [ES&T 34(16)3346]
Bioavailability of bound metals: e.g., Bressan & Brunetti, 1988 [Wat. Res. 22(5)553]
David Reckhow CEE 680 #32 6
N
CH2COOH
CH2COOH
CH2COOH
See: Knud-Hansen Paper
CEE 680 Lecture #32 3/25/2020
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Cu‐NTA II
Thermodynamics (20ºC)
Acid/Base
H3NTA = H+ + H2NTA‐ pK1 = 1.6
H2NTA‐ = H+ + HNTA‐2 pK2 = 3.0
HNTA‐2 = H+ + NTA‐3 pK3 = 10.3
Cu complex
Cu+2 + NTA‐3 = CuNTA‐ p1 = ‐13.0
Others are rather weak
CuHNTA
David Reckhow CEE 680 #32 7
David Reckhow CEE 680 #32 8
From: Snoeyink & Jenkins, 1980
CEE 680 Lecture #32 3/25/2020
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Cu‐NTA III Specific problem
CuT = 10‐4 M 6.35 mg/L
NTAT = 10‐4 M 19.1 mg/L
Notes: this is a much higher concentration of NTA than is generally found, but it can be used to represent background natural organic matter
Copper concentrations may sometimes be this high when used as an algicide
We are ignoring other complexes such as copper hydroxides or carbonates
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Cu‐NTA IV Mass Balance Equations
CuT = [Cu+2] + [ CuNTA‐]
NTAT = [CuNTA‐] + [H3NTA] + [H2NTA‐] + [HNTA‐2] + [NTA‐3]
Definition: total free concentration (TF) is that which is unbound to any metal except H+
NTAT = [CuNTA‐] +NTATF
David Reckhow CEE 680 #32 10
CEE 680 Lecture #32 3/25/2020
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Cu‐NTA V Equilibria
Acid/base
Complexation
David Reckhow CEE 680 #32 11
1
321
3
32
2
3
3
3
][][][1
][
KKK
H
KK
H
K
H
NTA
NTA
TF
]][[
][321
NTACu
CuNTA
Cu‐NTA VI Substitute mass balance and alpha equations into the beta equation
David Reckhow CEE 680 #32 12
])[(][
][
][][
][
][
][
]][[
][
23
2
2
32
2
32
2
321
CuCuNTACu
CuCu
CuNTANTACu
CuCu
NTACu
CuCu
NTACu
CuNTA
TT
T
T
T
TF
T
CEE 680 Lecture #32 3/25/2020
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Cu‐NTA VII
Now solve, noting that CuT = NTAT
Which gives us a quadratic which can be solved for a given pH
David Reckhow CEE 680 #32 13
][][
][
])[(][
][
23
2
2
23
2
2
1
CuCu
CuCu
CuCuNTACu
CuCu
T
TT
T
0][][ 22213
TCuCuCu
Cu‐NTA VIIIThen determine other species from the free copper
Can use a spreadsheet to calculate 3 versus pH, and then calculate the other species
David Reckhow CEE 680 #32 14
][][ 2 CuCuCuNTA T
][ CuNTANTANTA TTF
TFNTANTA 33][
CEE 680 Lecture #32 3/25/2020
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Cu‐NTA IX
Figure shows impact of ligand speciation on extent of complexation
Same thing happens with fulvic acid
David Reckhow CEE 680 #32 15pH
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Con
cent
ratio
n (m
oles
/L)
1e-19
1e-18
1e-17
1e-16
1e-15
1e-14
1e-13
1e-12
1e-11
1e-10
1e-9
1e-8
1e-7
1e-6
1e-5
1e-4
1e-3
Cu+2
NTA-3
CuNTA-
CuNTA X
David Reckhow CEE 680 #32 16pH
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Log
Con
cent
ratio
n (m
oles
/L)
-19
-18
-17
-16
-15
-14
-13
-12
-11
-10
-9
-8
-7
-6
-5
-4
-3
Cu+2
NTA-3
CuNTA-
CEE 680 Lecture #32 3/25/2020
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CuNTA XI
David Reckhow CEE 680 #32 17pH
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Log
Con
cent
ratio
n (m
oles
/L)
-19
-18
-17
-16
-15
-14
-13
-12
-11
-10
-9
-8
-7
-6
-5
-4
-3Cu+2
NTA-3
CuNTA-
CuOH+
Cu(OH)2(aq)
Cu(OH)3-
Cu(OH)4-2
CuOHNTA-2
Cu(NTA)2-4
Cu2(OH)2+2
To next lecture
David Reckhow CEE 680 #32 18
