Invited Paper TF-ThA1
Enhancing Water Desalination Membranes by Initiated Chemical Vapor Deposition (iCVD)

Thursday, November 13, 2014, 2:20 pm, Room 307

The process of iCVD (initiated Chemical Vapor Deposition) is compatible with the fragile polymeric membranes utilized in seawater desalination, since no solvents or high surfaces temperatures are employed. The iCVD method is scaleable over large areas (commercial reactors >1 m across) and to roll-to-roll processing. Over 70 different monomers have been successfully surface polymerized with iCVD.

Two applications of iCVD to water desalination membranes will be discussed. First, iCVD layers have been directly applied to reverse osmosis (RO) membranes for prevention of fouling by molecules and microbes. Second, iCVD enables the deposition of conformal hydrophobic fluoropolymers which are desired for fabricating high performance membranes for desalination by membrane distillation (MD).

The motivation for the antifouling layers is that with the build-up of scale and/or biofilms, system performance declines, resulting in increased operating costs. Fouling also necessitates periodic shutdown for cleaning and replacement of system components and expensive membranes, resulting in higher maintenance costs. Antifouling surface chemistries synthesized by iCVD include amphiphilic and zwitterionic copolymers. Ultrathin (~20 nm) iCVD coatings have been proved to significantly reduce fouling on commercial reverse osmosis (RO) membranes retaining their water permeation and salt rejection performance. The synthesis of iCVD polymer films starts from the membrane surface allowing chemical design strategies for forming grafted interfaces. These grafted interfaces greatly enhance the durability of iCVD surface modification layer which is essential for real-world implementation that would help ensure reliable and economical clean water production.