slides share the idea about forward osmosis

1. FORWARD OSMOSIS
Presented By:
MOHIT KUMAR (18FET208)
NISHANK WAGHMARE (18FET211)
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2.  Osmosis is defined as the net movement of solvent molecules
across a selectively permeable membrane driven by a difference
in osmotic pressure across the semipermeable membrane.
 Osmotic pressure is the minimum pressure which needs to be
applied to a solution to prevent the inward flow of its pure
solvent across a semipermeable membrane.
Π = iMRT
where, i is van 't Hoff factor,
M is molar concentration,
R is the ideal gas constant,
T is the temperature in kelvin.
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3. 3
OSMOTIC PROCESSES

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There are 3 types of osmotic solutions:

5. The FO process results in concentration of a feed stream and dilution
of a highly concentrated stream (referred to as the draw solution).
Forward osmosis membranes are of the asymmetric composite
type-
• active layer (typically 100-200nm in thickness)
• support layer (typically 100-200μm in thickness)
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Forward osmosis process

6.  The general equation describing water transport in FO, RO, and
PRO is Jw = A(σ π − ∆P)
where Jw is the water flux,
A the water permeability constant of the membrane,
σ the reflection coefficient
∆P is the applied pressure. In FO ∆P = 0
The reflection coefficient describes the ability of a membrane active
layer to preferentially allow solvent permeation over solute
permeation
σ = 𝒋 𝒘,𝒆𝒙𝒑 / 𝒋 𝒘,𝒑𝒓𝒆𝒅
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7. Concentration polarization is the build-up of concentration gradients
both inside and around forward osmosis membranes during
operation.
4 types of concentration polarization
two main categories :
 External concentration polarization (ECP)
 Internal concentration polarization (ICP)
And two sub-categories;
 Dilutive
 Concentrative
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CONCENTRATION POLARIZATION

8. Modules Packing density Advantages disadvantages
Plate and frame below 100
m2/m3
ease of operation in case of
high amounts of fouling agents
large footprint
Spiral wound up to 600 m2/m3 suitable for large volume
applications due to high
packing density
membrane fouling
Tubular up to 500 m2/m3 ease of cleaning, replacement
and ease of operation
tube wall thickness
might limit the water
flux performance
Hollow up to 1600
m2/m3
Ideally suitable for high
volume applications
prone to fouling with
high solid loadings
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9. MODERN APPLICATIONS OF FORWARD OSMOSIS
 Waste water treatment and water purification
 Seawater desalination
 Food processing
 Pharmaceutical industry
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10.  Achilli, A., Cath, T.Y., Childress, A.E. (2010). Selection of inorganic-based draw
solutions for forward osmosis applications, Journal of Membrane Science, 364, 233-
241.
 Cath, T.Y., Childress, A.E., Elimelech, M. (2006). Forward osmosis: principles,
applications and recent developments. Journal of Membrane Science , 281, 70-87.
 Tang, C.Y., She, Q., Lay, W.C.L., Wang, R., Fane AG. (2010). Coupled effects of
internal concentration polarization and fouling on flux behavior of forward osmosis
membranes during humic acid filtration. Journal of Membrane Science, 354, 123-
133.
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