Advanced Membrane Distillation and Pervaporation

Membrane distillation (MD) is a membrane-based separation and concentration process driven by a vapor pressure (temperature) gradient between the feed and permeate sides of a hydrophobic membrane. In other words, membrane distillation is a thermally driven separation process in which separation occurs due to a phase change.

A hydrophobic membrane acts as a barrier to the liquid phase while allowing the vapor phase (e.g., water vapor) to pass through its pores. In a typical process, heated saline water (feed) flows along one side of the membrane, while chilled, salt-free water (permeate) flows along the opposite side. The operating pressure is maintained below the membrane’s breakthrough pressure, ensuring that liquid water does not penetrate the membrane pores.

Since the vapor pressure of saline water is lower than that of pure water, this vapor pressure difference drives evaporation from the feed side. The generated water vapor diffuses through the membrane pores and condenses on the permeate side, producing purified water.

The PMI Membrane Distillation System is capable of measuring the rate of permeate volume increase under a wide range of experimental conditions, including variations in pressure, circulation flow rate, and temperature. The quality of feed and permeate streams can be evaluated using conductivity measurements. Clean permeate can be collected in flowing water, flowing gas, or under vacuum conditions.

Feed Characteristics:

• Temperature Range: 5–90 °C
• Recirculation Flow Rate: 0.1–1 gallon/min (up to 10 gallons/min optional)
• Pressure Range: 1–120 psi
• Maximum Concentration: Up to 200,000 ppm (NaCl equivalent)
• pH Range: 1.5–13 (depending on membrane type)
• Feed Tank Volume: 5 liters (standard), up to 50 liters (optional)