"Membrane contactors are devices that allow a gaseous phase and a liquid phase to come into direct contact with each other, for the purpose of mass transfer between the phases, without dispersing one phase into the other.
Membrane contactor technology has been demonstrated
in a range of liquid/liquid along with gas/liquid software in
wastewater therapy, fermentation, drugs, chiral
separations, and semiconductor creation, material ion
removal, and protein removal.
These are functionally similar to continuous contact mass
transfer devices like forced draft aerators or vacuum
Even some kind of long-term human missions in space
require a continuous and self-sufficient supply of fresh
water for consumption, hygiene and maintenance. In
these type of missions the sources of wastewater is
hygiene wastewater, urine and humidity condensates.
To satisfy these concerns and other
requirements there should be one equipment
or technology or process required. Similarly the
process is needed to be cost effective,
efficient and lightweight. There is one
equipment or process called membrane
contactors which usually satisfy almost all
above needs can be acquired.
This Article will describe about this equipment
or process used for this purpose and also
explains which are the techniques, procedure
and applications in different fields.
Membrane contactors are devices that allow a
gaseous phase and a liquid phase to come into
direct contact with each other, for the purpose of
mass transfer between the phases, without dispersing
one phase into the other.
Membrane contactors are manufactured with
hydrophobic hollow-fiber microporous membranes.
The hollow fiber wall is very thin (25-100 micron) and
highly porous. Hydrophobic nature of membrane will
hold the water, and the force required for water to
enter into membrane pores is calculated through
Young-Lapace equation explains capillary pressure
difference sustained across the interface between
two static fluids, such as water and air.
δP1 = σ(1/R1 + 1/R2)
δP1 - pressure drop
σ - Surface tension
By watchful control of the pressure difference relating to the fluids, one
of the fluids is usually immobilized inside pores of the membrane in order
that the fluid/fluid interface is found at the particular mouth of each one
This approach offers quite a few important benefits over typical
dispersed phase contactors, including absence of emulsions, zero
flooding from high stream rates, unloading from low stream rates,
density distinction between body fluids required.
Indeed, membrane contactors typically offer thirty times additional area
than what's achievable in gas absorbers in addition to 500 times what's
obtainable in liquid/liquid removal columns, leading to remarkably
reduced height of a transfer unit (HTU) values.
Membrane contactor’s primary function is recovery of potable water
from wastewater and secondary functions include oxygen reconstitution
and humidity control systems.
f hollow fiber membranes are pressurized from the
outside by a liquid and membrane prevents the
liquid from entering from pores. The pressure utilized
for this purpose is called critical entry pressure. Critical
entry pressure is dependent on the water surface
tension, membrane pore size and the contact angle
of water on membrane surface.
The membrane prevents any water flow across the
hollow fiber wall as long as the water pressure is less
than this critical pressure. The pores remain dry and
allow all volatile species dissolved in water to pass
unhindered through the pores if a proper driving
force is applied and maintained.
First reverse osmosis (RO) of wastewater
Second Direct osmosis process
In Direct/ Forward osmosis process two membrane
contactors are used for the pretreatment of two streams
of wastewater before treatment with RO. The stream of
hygiene wastewater mixed with humidity condensate then
followed by mixing with urine and treated with a unique
dual membranes process direct osmosis and osmotic
distillation. Then RO subsystem is used to produce two
It is a novel and prospective water treatment process that
emerges as a result of water scarcity and energy crisis. In
the FO process, a solution of considerably high
concentration is utilized to generate a hydrostatic osmotic
pressure gradient across a semi-permeable membrane to
extract freshwater from feed solution such as seawater or
brine, which is on the other side of the membrane.
Osmotic distillation (OD) is an evaporative membrane contactor
process. OD technique can be used to extract selectively the
water from aqueous solutions under atmospheric pressure and
at room temperature, thus avoiding thermal degradation of the
solutions. This process involves the contact of two streams of
liquid with a hydrophobic microporous membrane. If the
operating pressure is kept below the capillary penetration
pressure of liquid into the pores, the membrane cannot be
wetted by the solutions.
The difference in solute concentrations, and consequently in
water activity of both solutions, generates, at the vapor–liquid
interface, a vapor pressure difference causing a vapor transfer
from the dilute solution towards the stripping solution.
Removal of dissolved oxygen from
microelectronics industry, food industry,
Removal of carbon dioxide from water in
Removal of dissolved nitrogen from water
from blanketed storage tanks
Removal of volatile organic compounds from water
Humidification of air and other gases
Removal of ammonia content from wastewater
Removal of dissolved carbon dioxide from water
Carbon dioxide (CO2) is one of major impurities in water.
Generally CO2 present in water as inorganic form of carbon.
There are several ways to remove CO2 from water includes
By Anion exchange columns
By lowering water ph