Gas Separation Mechanisms of Gas Separation Membrane Separation Types of Membranes Types of Membrane Separation Mechanism of Membrane Separation Technology Science

1. SUBMITTED BY
HAMYAL AWAIS
MPHIL CHEMICAL ENGINEERING
SCME, NUST

2. GAS SEPARATION
MECHANISM

3. INTRODUCTION
 Gas separation refers to the process of isolating or
extracting specific gases from a mixture using
various methods and technologies.
 Gas separation is crucial across industries for
purifying gases, enhancing air quality, and refining
products.
 Membranes play a pivotal role by selectively
allowing specific gases to pass through while
retaining others.

4. TECHNIQUES FOR
GAS SEPARATION
Membrane
Separation
• Utilizes
membranes with
specific pore
sizes or materials
that allow
selective passage
of gases based
on their
molecular size,
shape, or affinity
for the
membrane
material
Adsorption
• Involves the
adherence of
gases onto
surfaces or
adsorbents,
where certain
gases are
preferentially
retained while
others pass
through
Absorption
• Relies on the
solubility of
gases in liquids
or solid
absorbents,
where specific
gases dissolve
more readily
than others,
allowing their
separation
Pressure Swing
Adsorption
• Cycles between
high and low
pressures to
adsorb and
desorb gases
onto adsorbents,
allowing
selective
separation
Cryogenic
Distillation
• Uses low
temperatures to
condense gases
into liquids,
separating
different
components
based on their
boiling points

5. MEMBRANE SEPARATION

6.  Save Large Amount Of Energy
 Long Life Membrane
 Defect Free
 More Contact
 More Easily Operated, Controlled And Maintained
WHY MEMBRANE SEPARATION ?

7. FUNDAMENTALS OF
MEMBRANE SEPARATION
Selective
Permeability
Affinity
Molecular Size

8. TYPES OF MEMBRANES

9. MECHANISMS OF
MEMBRANE SEPARATION
MECHANISMS IN
POROUS
MEMBRANES
MECHANISMS IN
DENSE POLYMER
MEMBRANES

10. MECHANISMS IN
POROUS MEMBRANES
MACROPOROUS MEMBRANES
ConvectiveFlowMechanism
• Larger pores allow gases to pass without selective separation
• Limited efficiency for gas separation due to pore size

11. MESOPOROUS MEMBRANES
Molecular DiffusionandKnudsenMechanism
• Predominant molecular diffusion due to interactions with pore walls
• Knudsen mechanism governs gas transport
MECHANISMS IN
POROUS MEMBRANES

12. MOLECULAR SIEVING
SelectiveSeparationMechanisms
• Extremely small pores (<2nm) enable molecular-size-based separation
• Complex transport mechanisms involving adsorption and diffusion
MECHANISMS IN
POROUS MEMBRANES

13. MECHANISMS IN
DENSE POLYMER MEMBRANES
Solution-DiffusionMechanism
Permeation Overview
• Gas absorption, diffusion through the polymer matrix, and desorption
• Dependent on chemical structure and nature of the gas

14. PERMEABILITY COEFFICIENT (P)
• Represents the flux of a specific gas through the membrane
• Formula: P = Q⋅δ / A⋅Δp, where Q is the gas permeation rate, δ is membrane thickness, A is
membrane surface area, and Δp is the pressure difference
SELECTIVITY (α)
• Ratio of permeability coefficients of different gases
• Formula: α = Pi​​ / Pj for single gas permeation
RELATIONSHIP BETWEEN P, D, AND S
• P = D × S defines the relationship between permeability, diffusivity, and solubility coefficients
• Diffusivity reflects molecule mobility; solubility increases with molecular weight
KEY PARAMETERS AFFECTING
MEMBRANE PERFORMANCE

15. SORPTION MECHANISMS IN RUBBERY MEMBRANES
Henry’s LawandSolution-Diffusion
• Describes sorption of low molecular weight gases in rubbery polymers.
• Solution-diffusion mechanism akin to penetrant sorption in low molecular weight liquids.
Temperature-DependentSorptionBehavior
• Describes the behavior of rubbery membranes at varying temperatures and gas concentrations.
SORPTION PROCESSES IN GLASSY MEMBRANES
Dual-ModeModelandLangmuir Adsorption
• Differentiates between gas molecules absorbed in the polymer matrix and those adsorbed in microscopic
voids.
• Dual sorption components influence overall sorption behavior.
DIFFERENCES BETWEEN
RUBBERY AND GLASSY
MEMBRANES

16. Dialysis
Gas
Permeation
Osmosis
Reverse
Osmosis
Pervaporation
INDUSTRIAL APPLICATIONS

17. THANK YOU