1. Ch. 2 Basic concepts of separations
Goal
(a) preparative work: to purify (or partial purify) component (drugs, fuel, metals, chemical feedstocks)
特徵: continuous operation; large in scale, etc.
(b) analytical goals: to generate information about the mixture; to eliminate the interference component for measurement.
Giddings, J.C.; Unified Separation Science, John Wiley & Sons, Inc, 1991.

2. (a+b+c+d)→(a+b)+(b+a) 熱力學上的限制：
Complete separation
(a+b+c+d)→(a)+(b)+(c)+(d)
Partial separation
(a+b+c+d)→(a+b)+(b+a)
熱力學上的限制：
(a) + (b) + (c) + (d)  (a+b+c+d) (mixing)
(a)  (a) (diffusion)

3. Bulk flow displacement
分離須進行搬運的動作(包含兩部分)
Bulk flow displacement
無分離作用
(壓力、重力、離心力、電力)
Relative displacement
具分離作用

4. Driving force of relative displacement: Eq.`
Molecular equilibrium in a closed system
1st law：
2nd law：
Gibbs free energy：

5. (2) Molecular equilibrium in open system
μ：chemical potential

6. Two open system α,β
(α,β)：a closed system
at eq. , T , P constant

7. (K：partition coefficient)
at eq.

8. Intermolecular force Ionic force Non-ion molecular interaction
(1) dipole - dipole
(2) dipole - induced dipole
(3) induced dipole - induced dipole
(4) H – bonding

9. Solvent extraction Tech. phase 1 phase 2 Chromatography stationary
mobile
LLE
raffinate
extractant
Dialysis
retentate
diffusate
← extractant
← raffinate
(sample was dissolvent in)
q：fraction of solute extracted
1-q：fraction of solute unextracted

10. is the ratio of total amount (weight) of A in one phase to that in the 2nd phase
partition ratio ： (capacity factor)
phase ratio：

11. (1) Partition coefficient
(2)
(3)
(4)

12. 操作模式 Single contact (2) Multiple contact (crosscurrent extraction)
(3) Multiple contact (countercurrent extraction)

13. Multiple extraction ....... extracted left 1st extract q 1-q 2nd
1st extract q
1-q
2nd
q(1-q)
1-q-q(1-q)=(1-q)2 N
q(1-q)n-1
(1-q)n

14. A solute with a partition coefficient of 4
A solute with a partition coefficient of 4.0 is extracted from 10 mL of phase 1 into phase 2. (a) What volume of phase 2 is needed to extract 99% of solution in one extraction? (b) What volume of phase 2 is needed to remove 99% of solution in three equal extractions instead?

15. Effect of pH value on extraction
KD ─→ D ( distribution coeff. )
HAo
org.
aq.
HAaq + H2O
H3O+ + A-

16. very acid [H+] >>Ka
D=KD
(b) at pH
(c) [H+] <<Ka
D >>KD

17. Effect of pH value on extraction
KD ─→ D ( distribution coeff. ) Bo
org.
aq.
BH+aq H+ + B

18. very acid [H+] >>Ka
D >> KD
(b) at pH
(c) [H+] <<Ka

19. Suppose that the partition coefficient for an amine, B, is 0
Suppose that the partition coefficient for an amine, B, is 0.33 and the acid dissociation constant of BH+ is Ka=1.0x If 50 mL of 0.010M aqueous amine is extracted with 100 mL of solvent. What will be the formal concentration remaining in the aqueous phase (a) at pH 10.0? (b) 8.0?

20. Application
Extraction of metal ions

21. 加入chelator (HL) HL (aq) HL (o) (1) HL (aq)+ H2O H3O+(aq) +L-(aq) (2)
Mn+(aq)+ nL-(aq)
MLn(aq)
(3)
MLn(o)
MLn(aq)
(4)

22. → excess chelator CL≈[HL(o)] (6)
→ HL, MLn在有機相中溶解度大
>>1
→ [L-] is pH dependent
CL：orignal molar conc. of HL in organic phase mass balance
(5)
→ excess chelator CL≈[HL(o)]
(6)

23. (3)
(4)
代入(5)
(6)
(7)