Updated: 24 March 2020 Print versionBenjamin; Chapter 8.1- 8.6 David Reckhow CEE 680 #32 1 Updated:...

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: 24 March 2020 Print version

http://www.ecs.umass.edu/cee/reckhow/courses/680/slides/680l32p.pdf

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

Presenter

Presentation Notes

Conceptual diagram of the biotic ligand model (BLM) showing inorganic and organic complexation in the water and interaction of metals and cations on the biotic ligand. DOC = dissolved organic carbon. IF THIS IMAGE HAS BEEN PROVIDED BY OR IS OWNED BY A THIRD PARTY, AS INDICATED IN THE CAPTION LINE, THEN FURTHER PERMISSION MAY BE NEEDED BEFORE ANY FURTHER USE. PLEASE CONTACT WILEY'S PERMISSIONS DEPARTMENT ON [email protected] OR USE THE RIGHTSLINK SERVICE BY CLICKING ON THE 'REQUEST PERMISSIONS' LINK ACCOMPANYING THIS ARTICLE. WILEY OR AUTHOR OWNED IMAGES MAY BE USED FOR NON-COMMERCIAL PURPOSES, SUBJECT TO PROPER CITATION OF THE ARTICLE, AUTHOR, AND PUBLISHER.

Algae and Copper

McKnight et al., 1983; Environmental Management 7(4)311-320

%𝜇𝜇

𝜇𝜇𝑚𝑚𝑚𝑚𝑚𝑚

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

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)

Presenter

Presentation Notes

Conceptual description of the processes affecting fate of metals during release of a metal concentrate to a lake. Arrows represent transport processes modeled by tableau input coupled kinetics equilibrium transport‐unit world model (TICKET‐UWM). Dashed line represents speciation calculations performed in the water column and sediment. DOC = dissolved organic carbon; POC = particulate organic carbon. IF THIS IMAGE HAS BEEN PROVIDED BY OR IS OWNED BY A THIRD PARTY, AS INDICATED IN THE CAPTION LINE, THEN FURTHER PERMISSION MAY BE NEEDED BEFORE ANY FURTHER USE. PLEASE CONTACT WILEY'S PERMISSIONS DEPARTMENT ON [email protected] OR USE THE RIGHTSLINK SERVICE BY CLICKING ON THE 'REQUEST PERMISSIONS' LINK ACCOMPANYING THIS ARTICLE. WILEY OR AUTHOR OWNED IMAGES MAY BE USED FOR NON-COMMERCIAL PURPOSES, SUBJECT TO PROPER CITATION OF THE ARTICLE, AUTHOR, AND PUBLISHER.

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]


N

CH2COOH

CH2COOH

CH2COOH

See: Knud-Hansen Paper

http://www.colorado.edu/conflict/full_text_search/AllCRCDocs/94-54.htm/

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- pβ1 = -13.0 Others are rather weak

CuHNTA



From: Snoeyink & Jenkins, 1980

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


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


Cu-NTA V Equilibria

Acid/base

Complexation


1

321

3

32

2

3

3

3

][][][1

][

−+++

−

+++=

≡

KKKH

KKH

KH

NTANTA

TF

α

]][[][

321 −+

−

=NTACu

CuNTAβ

Cu-NTA VI Substitute mass balance and alpha equations into the

beta equation


( )

( )])[(][][

][][][

][][

]][[][

23

2

23

2

23

2

2

321

++

+

−+

+

+

+

−+

−

−−−

=

−−

=

−==

CuCuNTACuCuCu

CuNTANTACuCuCu

NTACuCuCu

NTACuCuNTA

TT

T

T

T

TF

T

α

α

αβ

Cu-NTA VII Now solve, noting that CuT = NTAT

Which gives us a quadratic which can be solved for a given pH


( )

][][][

])[(][][

23

2

2

23

2

2

1

++

+

++

+

−=

−−−

=

CuCuCuCu

CuCuNTACuCuCu

T

TT

T

α

αβ

0][][ 22213 =−+ ++

TCuCuCuβα

Cu-NTA VIIIThen determine other species from the free

copper

Can use a spreadsheet to calculate α3 versus pH, and then calculate the other species


][][ 2+− −= CuCuCuNTA T

][ −−= CuNTANTANTA TTF

TFNTANTA 33 ][ α=−

Cu-NTA IX

Figure shows impact of ligand speciation on extent of complexation

Same thing happens with fulvic acid


pH

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


pH

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-

CuNTA XI


pH

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


http://www.ecs.umass.edu/cee/reckhow/courses/680/slides/680l33.pdf

Updated: 24 March 2020 Print versionBenjamin; Chapter 8.1- 8.6 David Reckhow CEE 680 #32 1 Updated:...

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