Print version Updated: 13 April 2020 Lecture #43 Precipitation and - PowerPoint PPT Presentation

Print version Updated: 13 April 2020 Lecture #43 Precipitation and Dissolution: Cadmium Case Study (Stumm & Morgan, Chapt.7) Benjamin; Chapter 8 David Reckhow CEE 680 #43 1

Hydroxo complexes  10 -4 M Cd T  Figure 8.2, pg.369 in Benjamin -9 -8 -7 -4 -3 -2 -1 0 -6 -5 -10 David Reckhow CEE 680 #43 2 Log {OH - }

Chloride Complexes  10 -4 M Cd T  Low pH (no OH complexes)  Figure 8.5, pg.376 in Benjamin David Reckhow CEE 680 #43 3

Mixed OH, Cl complexes  10 -4 M Cd T ; {Cl - }=0.5M  Figure 8.6, pg.379 in Benjamin -9 -8 -7 -4 -3 -2 -1 0 -6 -5 -10 David Reckhow CEE 680 #43 4 Log {OH - }

3D Surface: Cl, OH complexes  Fig 8.7 in Benjamin Slice shown in Fig. 8.6 David Reckhow CEE 680 #43 5

Cd(OH) 2 Precipitate  no {Cl - }  Figure 8.12, pg.401 in Benjamin -3 -2 -9 -8 -7 -6 -5 -4 -1 0 -10 David Reckhow CEE 680 #43 6 Log {OH - }

Cd(OH) 2 (s) with Cl -  {Cl - }=0.5M  Figure 8.13, pg.403 in Benjamin -3 -2 -9 -8 -7 -6 -5 -4 -1 0 -10 David Reckhow CEE 680 #43 7 Log {OH - }

Cd limited; no Carbonate  10 -4 M Cd T  Cd(OH) 2 (s) allowed  Figure 8.19, pg.421 in Benjamin Not really “concentration”, more accurately the mass of precipitate per L solution David Reckhow CEE 680 #43 8

CdCO 3 (s) low C T  C T =10 -3 M  Figure 8.15, pg.406 in Benjamin -3 -2 -9 -8 -7 -6 -5 -4 -1 0 -10 David Reckhow CEE 680 #43 9 Log {OH - }

CdCO 3 (s) High C T  C T =10 -1 M  Figure 8.17, pg.409 in Benjamin -3 -2 -9 -8 -7 -6 -5 -4 -1 0 -10 David Reckhow CEE 680 #43 10 Log {OH - }

CdCO 3 (s) Open  pCO 2 =10 -3.5  Figure 8.18, pg.410 in Benjamin -3 -2 -9 -8 -7 -6 -5 -4 -1 0 -10 David Reckhow CEE 680 #43 11 Log {OH - }

Solid formation  Open system a b c d David Reckhow CEE 680 #43 12

Open System Dual Solids  Figs 8.21 & 8.22 Closed System; C T = 10 -3 M David Reckhow CEE 680 #43 13

Cd limited; no Carbonate  10 -4 M Cd T  Cd(OH) 2 (s) allowed  Figure 8.19, pg.421 in Benjamin Not really “concentration”, more accurately the mass of precipitate per L solution David Reckhow CEE 680 #43 14

Cd limited; Closed System  10 -4 M Cd T  10 -3 CO3 T  Cd(OH) 2 (s) & CdCO 3 (s) allowed  Figure 8.23, pg.428 in Benjamin Not really “concentration”, more accurately the mass of precipitate per L solution David Reckhow CEE 680 #43 15

3D, 4D, 5D?  Fig 8.7 in Benjamin David Reckhow CEE 680 #43 16

With S -2 , low pH Stumm & Morgan, 1996, Figure 7.19a, pg. 405 Stumm & Morgan, 1996, Figure 7.19b, pg. 405 David Reckhow CEE 680 #43 17

With S -2 , high pH Stumm & Morgan, 1996, Figure 7.19c, pg. 406 Stumm & Morgan, 1996, Figure 7.19d, pg. 406 David Reckhow CEE 680 #43 18

0 Fe +2 -1 Fe Total -2 H + Fe(OH) 2 Fe(OH) 2 -3 Fe(OH) +  No C T -4 -5 OH - -6 Log C -7 -8 -9 - Fe(OH) 3 -10 -11 -12 -13 -14 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 pH David Reckhow CEE 680 #42 19

0 Fe Total -1 Fe(OH) 2 FeCO 3 -2 H + Fe(OH) 2 -3 -4 Mid-range C T Fe(OH) + -5 -6 Log C -7 OH - -8 Fe +2 -9 - Fe(OH) 3 -10 -11 -12 C T = 10 -3 -13 -14 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 pH David Reckhow CEE 680 #42 20

0 Fe Total -1 Fe(OH) 2 FeCO 3 -2 H + Mid C T -3 -4 Combined II Fe(OH) + -5 -6 Log C -7 OH - -8 Fe +2 -9 - Fe(OH) 3 -10 -11 -12 C T = 10 -3 -13 -14 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 pH David Reckhow CEE 680 #42 21

 To next lecture David Reckhow CEE 680 #43 22