DECONTAMINATION OF LAND USING ELECTROCHEMICAL TREATMENT

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BINARY VAPOR-LIQUID EQUILIBRIUM

• Nonideal Liquid Solutions

• If a molecule contains a hydrogen atom attached
  to a donor atom (O, N, F, and in certain cases
  C), the active hydrogen atom can form a bond with
  another molecule containing a donor atom.

two water molecules coming close together

• Table 2.7 shows qualitative estimates of
  deviations from Raoults law for binary pairs
  when used in conjunction with Table 2.8.

• Positive deviations correspond to values of ?iL gt
  1. Nonideality results in a variety of variations
  of (?iL) with composition, as shown in Figure
  2.15 (Seader Henely) for several binary
  systems, where the Roman numerals refer to
  classification groups in Tables 2.7 and 2.8.

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BINARY VAPOR-LIQUID EQUILIBRIUM
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BINARY VAPOR-LIQUID EQUILIBRIUM
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BINARY VAPOR-LIQUID EQUILIBRIUM

• Figure 2.15a Normal heptane (V) breaks ethanol
  (II) hydrogen bonds, causing strong positive
  deviations.

n-heptane(v)-Ethanol (II) system (Semi-log
paper)
Note Ethanol molecules form H-bonds between each
other and n-heptane breaks these bond causing
strong () deviation.
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BINARY VAPOR-LIQUID EQUILIBRIUM

• In Figure 2.15b,
• Similar Figure 2.15a but less positive
  deviations occur when acetone (III) is added to
  formamide (I).

?iLgt1

• In Figure 2.15c,
• Hydrogen bonds are broken and formed with
  chloroform (IV) and methanol (II) resulting in an
  unusual positive deviation curve for chloroform
  that passes through a maximum.

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BINARY VAPOR-LIQUID EQUILIBRIUM
In Figure 2.15d, Chloroform (IV) provides
active hydrogen atoms that can form hydrogen
bonds with oxygen atoms of acetone (III), thus
causing negative deviations

• Non-ideal solution effects can be incorporate
  into K-value formation into different ways.

Non-ideal liquid solution at near ambient
pressure
1.
Non-ideal liquid solution at moderate pressure
and TC.
2.
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BINARY VAPOR-LIQUID EQUILIBRIUM

• Repulsion
• Molecules that are dissimilar enough from each
  other will exert repulsive forces

Component(1) x1

e. g polar H2O molecules organic hydrocarbon
molecules. ?i gt 1
Component(2) x2
When dissimilar molecules are mixed together due
to the repulsion effects, a greater partial
pressure is exerted, resulting in positive
deviation from ideality.

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BINARY VAPOR-LIQUID EQUILIBRIUM

• Fore the last two figures, as the mole fraction
  x1 increases its ?1 ?1, as its mole fraction x1
  decreases ?1 increases till it reaches to ?1?
  (activity coefficient at infinite dilution)

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BINARY VAPOR-LIQUID EQUILIBRIUM

• Attraction
• When dissimilar molecules are mixed together,
  due to the attraction effects, a lower partial
  pressure is exerted, resulting in negative
  deviation from ideality.

?i lt 1 are called negative deviation from
ideality.
Component(1) x1
Component(2) x2
-
-
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BINARY VAPOR-LIQUID EQUILIBRIUM

• Example
• calculate ?ij of methanol water system for the
  following data 760 mmHg

Vapor phase ym 0.665 yw 0.33
Liquid phase xm 0.3 xw 0.7
Vapor Pressure Data at 78 oC (172.1F) Methanol
Pmsat 1.64 atm Water Pwsat 0.43 atm
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BINARY VAPOR-LIQUID EQUILIBRIUM
solution
For methanol
For water
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BINARY VAPOR-LIQUID EQUILIBRIUM

• How to calculate ?iL of Binary Pairs

Many empirical and semi-theoritical equations
exists for estimating activity coefficients of
binary mixtures containing polar and/ or
non-polar species. These equations contain
binary interaction parameters, which are back
calculated from experimental data. Table (2.9)
show the different equations used to calculate
?iL.
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BINARY VAPOR-LIQUID EQUILIBRIUM
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THERMODYNAMICS OF SEPARATION OPERATIONS
Table (2.10) shows the equations used to
calculate excess volume, excess enthalpy and
excess energy.
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THERMODYNAMICS OF SEPARATION OPERATIONS
Example. (problem 2.23 (
Benzene can be used to break the ethanol/water
azeotrope so as to produce nearly pure ethanol.
The Wilson constants for the ethanol(1)/benzene(2)
system at 45C are A12 0.124 and A21 0.523.
Use these constants with the Wilson equation to
predict the liquid-phase activity coefficients
for this system over the entire range of
composition and compare them, in a plot like
Figure 2.16, with the following experimental
results Austral. J. Chem., 7, 264 (1954)
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THERMODYNAMICS OF SEPARATION OPERATIONS
Let 1 ethanol and 2 benzene The Wilson
constants are A12 0.124 and A21 0.523 From
Eqs. (4), Table 2.9,
Using a spreadsheet and noting that ? exp(ln
?), the following values are obtained,
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THERMODYNAMICS OF SEPARATION OPERATIONS
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THERMODYNAMICS OF SEPARATION OPERATIONS
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THERMODYNAMICS OF SEPARATION OPERATIONS

• Activity coefficient at infinite dilution

Modern experimental techniques are available for
accurately and rapidly determining activity
coefficient at infinite dilution (?iL? )
Appling equaion(3) in table (2.9) (van Laar
(two-constant)) to conditions
Xi 0 and then xj 0
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THERMODYNAMICS OF SEPARATION OPERATIONS
Component(1) x1
Component(2) x2


Repulsive ? gt 1.0
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ChE 334 Separation Processes