Advanced Membrane Distillation and Pervaporation

Membrane distillation is a membrane separation/concentration
process which has vapor pressure (temperature) gradient/
difference between the feed and the permeate side of a
hydrophobic membrane as the driving force for the process, in
other words, Membrane distillation is a thermally driven
separation process in which separation is enabled due to phase
change. A hydrophobic membrane acts as a barrier for the liquid
phase, letting the vapor phase (e.g. water vapor) pass through the
membrane’s pores.
In simple terms, heated salt water (feed) flows across one side and
chilled salt free water (permeate) flows across the other side of a
hydrophobic membrane at pressures less than the breakthrough
pressure of the membrane. Liquid Water does not penetrate the
pores of the membrane since it is hydrophobic. The vapor
pressure of salt water is lower than the vapor pressure of salt free
water. This vapor pressure differential encourages salt water to
vaporize. Pure water vapor diffuses across the hydrophobic
membrane from the feed to the permeate side and condenses
into the chilled permeate stream.
The PMI Membrane distillation machine is capable of measuring
rate of increase in volume of the permeate stream under a wide
variety of experimental conditions including pressure, circulation
flow rate and temperature. Quality of feed and permeate can be
compared using conductivity measurements of both streams.
Clean permeate may be collected in flowing water, in flowing gas
or under vacuum.

Application

The major advantage of MD in desalination is the ability to achieve
high rejection factors which cannot be accomplished by RO at high
permeate fluxes. Production of high purity water is well established
with rejection factors of almost 100% of non-volatile compounds
Food industry
• Fruit Juice concentration (Orange, Blackcurrant, pineapple, kiwi,
sugarcane, camu-camu and cherry)
• Removing ethanol from fermentation broth
• Concentration of food colorants
• Dealcoholization of wine
• Concentration of herbal and plant extracts
Chemical Industry
• Concentration of nonvolatile acids
• Recovery of volatile compounds from aqueous solutions
Water industry applications
• Semiconductor grade water (100% rejection)
• Pharmaceutical grade water
• Pure Drinking water
• Treatment of water with nanoparticles
• Purification of High Salinity water
• Nuclear Membrane distillation (waste heat from reactor is used)
Environmental applications
• Landfill leachate treatment
• Heavy metal concentration