Ultra-low-pressure water softening with pore-filled membranes

The design parameters for high-performance, ultra-low-pressure water soften ing membranes based on a construct involving pore-filling microporous subst rates with polyelectrolyte gels are presented. The design parameters were t hen used to make a series of gel-filled membranes by in situ crosslinking o f poly(vinylbenzyl chloride) with diamines (piperazine and 1,4-diazabicyclo [2.2.2]octane) or poly(4-vinylpyridine) with dihalides such as alpha,alpha' -dichloro-p-xylene in DMF solutions in the pores of either a TIPS poly(prop ylene) or non-woven ultra-high molecular weight poly(ethylene) support. The separation properties of these membranes were tested under ultra-low press ure (100 kPa) using untreated municipal tap water. These membranes exhibit excellent separation properties, comparable to those of a commercial thin-f ilm nanofiltration membrane (Desal-51, Osmonics), and productivity (flux) m arkedly higher than that of the thin-film membrane. The results of this stu dy clearly show the importance of the mechanical strength (rigidity) of the microporous supports in designing high-performance pore-filled membranes.