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Cadmium Batteries & electroplating Very high ratio of abundance - - PDF document

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CEE 680 Lecture #29 3/11/2020 Print version Updated: 11 March 2020 Lecture #29 Complexation: Speciation in Fresh Waters (Stumm & Morgan, Chapt.6: pg.289 305) Benjamin; Chapter 8.1 8.6 David Reckhow CEE 680 #29 1 Cadmium

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SLIDE 1

CEE 680 Lecture #29 3/11/2020 1

Lecture #29 Complexation: Speciation in Fresh Waters

(Stumm & Morgan, Chapt.6: pg.289‐305)

Benjamin; Chapter 8.1‐8.6

David Reckhow CEE 680 #29 1

Updated: 11 March 2020

Print version

Cadmium

David Reckhow CEE 680 #29 2

Cadmium is of no use to the human body and is toxic even at low levels. The negative effects of cadmium on the body are numerous and can impact nearly all systems in the body, including cardiovascular, reproductive, the kidneys, eyes, and even the brain.

  • Cadmium affects blood pressure.
  • Cadmium affects prostate function and testosterone levels.
  • Cadmium induces bone damage (Itai-ltai).
  • Exposure to cadmium can affect renal and dopaminergic systems in children.

 Batteries & electroplating  Very high ratio of abundance to toxicity

 Like Pb, Hg, As

 EPA Standards

 0.005 g/L in drinking water

 Concern over kidney damage

Click here for more on Cd

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SLIDE 2

CEE 680 Lecture #29 3/11/2020 2

David Reckhow CEE 680 #29 3

 Flux in 107

M/yr

David Reckhow CEE 680 #29 4

From: Morel & Malcolm, “The Biogeochemistry of Cadmium”, Chapt 8 in Metal Ions in Biological Systems, Vol 43 Sigel, Sigel & Sigel, eds.

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SLIDE 3

CEE 680 Lecture #29 3/11/2020 3

CdCl Example

 Consider the speciation of cadmium

and chloride

 First the four beta’s

 Cd+2 + Cl‐ = CdCl+  Cd+2 + 2Cl‐ = CdCl2  Cd+2 + 3Cl‐ = CdCl3 ‐  Cd+2 + 4Cl‐ = CdCl4 ‐2

 Now plot the alpha curves

David Reckhow CEE 680 #29 5

-value

21 166 204 71.5

Cadmium Chloride

David Reckhow CEE 680 #29 6

From: Butler, 1964; pg.268

Reproduced in Langmuir, 1997; pg.96 Similar to: Butler, 1998; pg.241

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SLIDE 4

CEE 680 Lecture #29 3/11/2020 4

CdCl Example

 Calculate the concentration of all species for the

following solution

 0.01 M Cd(NO3)2 + 1 M HCl

 Use the equilibrium equations

 But what do you use for [L]?

David Reckhow CEE 680 #29 7

 

1 2 2 1

] [ ] [ ] [ 1 ] [

     

n n M

L L L C M     

n n M n n

L C ML ] [ ] [

0

   

Cadmium Chloride

David Reckhow CEE 680 #29 8

From: Butler, 1964; pg.268

Reproduced in Langmuir, 1997; pg.96 Similar to: Butler, 1998; pg.241

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SLIDE 5

CEE 680 Lecture #29 3/11/2020 5

Cadmium Chloride (cont.)

David Reckhow CEE 680 #29 9

Butler, 1964; pg.269

David Reckhow CEE 680 #29 10

Pankow, 1991; pg.375

Cadmium Chloride (cont.)

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SLIDE 6

CEE 680 Lecture #29 3/11/2020 6

Ligand Number

 Definition

 The average number of bound ligands per atom of

metal

 Significance

 Defines Mixture  Can be analytically determined

 Used to evaluate ’s

 Can be calculated via 2 independent ways and used to

solve problems, if you know the free ligand concentration

 Mass balance equations  Equilibrium equations

 Thus, we have 2 independent equations and two

unknowns (free L, and n‐bar), so we can solve

David Reckhow CEE 680 #29 11

Determination of Ligand #

Equilibrium constant approach

And substituting in for the apha’s

David Reckhow CEE 680 #29 12

n M n M M M M n

n C ML n C ML C ML C ML C ML n ML ML ML n                      

3 2 1 3 2 3 2

3 2 ] [ ] [ 3 ] [ 2 ] [ ] [ ] [ 3 ] [ 2 ] [

 

n n n n

L n L L L L n L L L n ] [ ] [ 3 ] [ 2 ] [ ] [ ] [ 3 ] [ 2 ] [

3 3 2 2 1 3 3 2 2 1

                        

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SLIDE 7

CEE 680 Lecture #29 3/11/2020 7

Determination of ligand #

Mass balance approach

 CM = [M]+[ML]+[ML2]+[ML3]+ +[MLn]  CL = [L]+[ML]+2[ML2]+3[ML3]+ +n[MLn]

David Reckhow CEE 680 #29 13

M L M n

C L C C ML n ML ML ML n ] [ ] [ ] [ 3 ] [ 2 ] [

3 2

       

Take alpha diagram

 For CdClx  Next add n‐bar

curves

 One based on

equilibria

 Other based on

mass balances

David Reckhow CEE 680 #29 14

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SLIDE 8

CEE 680 Lecture #29 3/11/2020 8

David Reckhow CEE 680 #29 15

Log [L]

  • 4.0
  • 3.5
  • 3.0
  • 2.5
  • 2.0
  • 1.5
  • 1.0
  • 0.5

0.0 0.5 1.0

Alpha

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2

n-bar

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0

n-bar (equ)

    

Cadmium Chloride alpha diagram

In‐Class Problems

 Class problems with CdClx

 Sea Water: CL=5 x 10‐1, CM=1 x 10‐9  Contaminated Sea Water: CL=5 x 10‐1, CM=1 x 10‐1  Desal Brine: CL=15 x 10‐1, CM=3 x 10‐9  RO conc. of Cont. Sea Water: CL=15 x 10‐1, CM=3 x 10‐1

David Reckhow CEE 680 #29 16

𝑜 𝐷 𝑀 𝐷

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SLIDE 9

CEE 680 Lecture #29 3/11/2020 9

David Reckhow CEE 680 #29 17

Log [L]

  • 4.0
  • 3.5
  • 3.0
  • 2.5
  • 2.0
  • 1.5
  • 1.0
  • 0.5

0.0 0.5 1.0

Alpha

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2

n-bar

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0

n-bar (equ)

    

Cadmium Chloride problem

𝑜 𝐷 𝑀 𝐷

Sea Water: CL=5 x 10-1, CM=1 x 10-9

David Reckhow CEE 680 #29 18

Log [L]

  • 4.0
  • 3.5
  • 3.0
  • 2.5
  • 2.0
  • 1.5
  • 1.0
  • 0.5

0.0 0.5 1.0

Alpha

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2

n-bar

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0

n-bar (equ)

    

Cadmium Chloride problem 2

𝑜 𝐷 𝑀 𝐷

Contaminated Sea Water: CL=5 x 10-1, CM=1 x 10-1

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SLIDE 10

CEE 680 Lecture #29 3/11/2020 10

David Reckhow CEE 680 #29 19

Log [L]

  • 4.0
  • 3.5
  • 3.0
  • 2.5
  • 2.0
  • 1.5
  • 1.0
  • 0.5

0.0 0.5 1.0

Alpha

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2

n-bar

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0

n-bar (equ)

    

Cadmium Chloride problem 3

𝑜 𝐷 𝑀 𝐷

Desal Brine: CL=15 x 10-1, CM=3 x 10-9

David Reckhow CEE 680 #29 20

Log [L]

  • 4.0
  • 3.5
  • 3.0
  • 2.5
  • 2.0
  • 1.5
  • 1.0
  • 0.5

0.0 0.5 1.0

Alpha

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2

n-bar

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0

n-bar (equ)

    

Cadmium Chloride problem 4

𝑜 𝐷 𝑀 𝐷

RO conc. of Cont. Sea Water: CL=15 x 10-1, CM=3 x 10-1

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SLIDE 11

CEE 680 Lecture #29 3/11/2020 11

Speciation in Natural Waters

 Mostly Cl complexes in

sea water

David Reckhow CEE 680 #29 21

From: Morel & Malcolm, “The Biogeochemistry of Cadmium”, Chapt 8 in Metal Ions in Biological Systems, Vol 43 Sigel, Sigel & Sigel, eds.

Cellular metabolism of Cd

 gg

David Reckhow CEE 680 #29 22

From: Morel & Malcolm, “The Biogeochemistry of Cadmium”, Chapt 8 in Metal Ions in Biological Systems, Vol 43 Sigel, Sigel & Sigel, eds.

PCs are phytochelatins; metal binding proteins that help regulate Cd concentrations

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SLIDE 12

CEE 680 Lecture #29 3/11/2020 12

 K1=106,

K2=102

 K1=104.5,

K2=103.5

David Reckhow CEE 680 #29 23 Log [L]

  • 8
  • 6
  • 4
  • 2

Alpha

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2

n-bar

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

n-bar (equ)

  

Log [L]

  • 8
  • 6
  • 4
  • 2

Alpha

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2

n-bar

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

n-bar (equ)

  

Note: as K’s get closer, so do the intersections, and the middle alpha’s get compressed with diminished height  K1=104, K2=104  K1=103.5,

K2=104.5

David Reckhow CEE 680 #29 24 Log [L]

  • 8
  • 6
  • 4
  • 2

Alpha

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2

n-bar

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

n-bar (equ)

  

Log [L]

  • 8
  • 6
  • 4
  • 2

Alpha

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2

n-bar

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

n-bar (equ)

  

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SLIDE 13

CEE 680 Lecture #29 3/11/2020 13

Features of alpha diagrams

 Intersection point for adjacent curves

 Occur at: log [L] = pK’s

 E.g., first intersection occurs where: 0 =1 which is where:

[M]=[ML]

 And in general, intersection of adjacent curves will occur where:

[ML(i‐1)]=[ML(i)]  So at these intersection points, the metal terms in the

equations for K will cancel each other out and:

David Reckhow CEE 680 #29 25

] ][ [ ] [

1

L M ML K 

] ][ [ ] [

) 1 (

L ML ML K

i i i 

1 1

] log[ 1 ] [ pK L K L  

i i

pK L K L   ] log[ 1 ] [

  • r

Features (cont.)

 An alpha curve will reach its maximum at the point

where the preceding alpha and the following alpha intersect (i.e., i‐1 and i+1 ),

 Consider the intersection of i‐1 and i+1

 The two K equations are:  And their product gives us:  Once again, we can cancel

metal concentrations to get:

David Reckhow CEE 680 #29 26

] ][ [ ] [

) 1 (

L ML ML K

i i i 

 ] ][ [ ] [

) ( 1 1

L ML ML K

i i i    2 ) 1 ( 1 1

] ][ [ ] [ L ML ML K K

i i i i    

) ( 5 . ] log[ 1 ] [

1 1  

  

i i i i

pK pK L K K L

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SLIDE 14

CEE 680 Lecture #29 3/11/2020 14

Height of alpha maximum

 Dependent on difference between K1 and K2

David Reckhow CEE 680 #29 27

LogKx-LogKx+1

  • 1

1 2

-max value

0.0 0.2 0.4 0.6 0.8 1.0

To next lecture

David Reckhow CEE 680 #29 28