Sacrificial polyelectrolyte multilayer coatings as an approach to membrane fouling control: Disassembly and regeneration mechanisms

This study evaluates polyelectrolyte multilayers (PEMs) as sacrificial separation layers on polysulfone ultrafiltration (OF) membranes. Exposure to surfactants and a swing in pH can disassemble PEMs by disrupting non-ionic and electrostatic bonds within the PEM and between the PEM and the support. Trends in frequency and dissipation in quartz crystal microbalance studies confirm layer-by-layer (LbL) adsorption of PEMs on the quartz crystal and subsequent PEM removal in response to acid/base treatment. After disassembly of PEMs on OF membranes, water permeability increases and methylene blue rejection decreases, in some cases reaching values close to those for pristine ultrafilters. PEM removal occurs even with fouled membranes. After fouling by aqueous solutions of bovine serum albumin and alginate, the PEM disassembly via exposure to acid, base and surfactant results in a 99% decrease in the hydraulic resistance of the PEM (compared to the unfouled PEM) and, on average, more than 80% recovery of pure water permeability (compared to an uncoated UP membrane). Repeated cycles of PEM disassembly and readsorption give stable water permeabilities and methylene blue rejections for the coated membranes. (C) 2015 Elsevier B.V. All rights reserved,