Synthesis and Characterization of a Composite Reverse Osmosis Membrane With Improved Chlorine Tolerance

Polyamide composite reverse osmosis (RO) membranes cannot withstand continuous chlorine exposure without intolerable loss of salt rejection. Significant research effort has been expended over the past 40-50 years to create more chlorine-tolerant RO membrane materials, but to date none have proved effective in practical applications. This is largely because most chlorine tolerant polymers cannot be made with commercially viable water permeability and salt rejection. However, the implication of more chlorine tolerant membrane materials would be virtual elimination of biofouling, which plagues many RO desalination plants and has been referred to as “the Achilles’ heel of RO membranes.”

Here, we present a new interfacial composite membrane formulation that exhibits significantly improved tolerance to continuous hypochlorite exposure. The use of a new diamine monomer reduces the sensitivity of the polymer to Orton-rearrangement while introducing additional hydrophilicity to the film. In preliminary tests, the novel membrane surface is significantly more hydrophilic (as hypothesized) and smoother than hand-cast MPD-TMC and commercial polyamide RO membranes. While early performance testing is promising, ongoing research focuses on tailoring the film structure and thickness along with support membrane chemistry and morphology to optimize the composite membrane for specific water treatment applications.