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Reinforced Membranes for Producing Osmotic Power in Pressure Retarded Osmosis

Technology Overview

The Pressure Retarded Osmosis (PRO) membrane is the key factor affecting the PRO performance (both water flux and power density). However, the most apparent drawback of the current membranes used for PRO is severe membrane deformation at high applied pressures which enhance the internal concentration polarization (ICP) and hence decrease the water flux and power density under PRO operation.

The optimal PRO membrane should incorporate the characteristics of both RO membranes and FO membranes. In this invention, a PRO membrane was fabricated based on the above principle. A hydrophilic tricot mesh fabric with strong mechanical strength and high porosity was embedded into the middle substrate layer to support the whole membrane. A selective thin rejection layer was formed on the top of the middle substrate layer.

 

Technology Features & Specifications

To date, there is no commercial membrane specially designed for PRO application. The reported membranes used for PRO testing either have low performance or lack mechanical stability. This invention developed a robust thin film composite (TFC) membrane with reinforced mechanical strength and high power density specifically for PRO application.

 

Potential Applications

The reinforced PRO membranes can be competitively used for producing osmotic power in PRO processes when operated under a variety of conditions especially at high applied pressures. These include the following,

• Osmotic power plant for producing electricity.
• Desalination industry for diluting the seawater and waste brine as well as harvesting the osmotic power from the waste brine.
• Hybrid single or dual PRO and RO system for reduced energy consumption and easy disposal of brine to the ocean through simple mixing and without capital intensive brine dispersal outfalls.

Customer Benefits

  • Strong mechanical strength to avoid severe membrane deformation at high applied pressure
  • Dense rejection layer with high water permeability and low solute permeability to improve the water transport and reduce the reverse solute diffusion
  • Small structure parameter of support layer to minimize the ICP
  • Able to withstand a hydraulic pressure above 400 psi (∽28 bar) and achieve a peak power density of 7.1 W/m2 when tested with 1 M NaCl draw solution and 10 mM NaCl feed solution.

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