Ethoxylated nonionic surfactants in hydrophobic solvents: Separation using membrane immobilized poly-acrylic acid

Certain polyelectrolytes, poly-acrylic acid (PAA) and ethoxylated nonionic surfactants, form complex in aqueous solution due to hydrogen bonding between carboxyl group of PAA and ethylene oxide group of the surfactants. Pure ethoxylated surfactant solution in a hydrophobic solvent is permeated through a partially cross-linked PAA composite membrane to quantify the extent of separation of the surfactants in the heterogeneous system. The permeation properties of the PAA functionalized membrane were studied to establish certain characteristics of the membrane. Role of ethylene oxide group variation in surfactant separation for the heterogeneous system was established by performing experiments with pure surfactants having same alkyl chain length but varying ethoxylate chain lengths. The surfactants with higher number of ethylene oxide groups per molecule exhibit higher extent of separation from the hydrophobic solvents. The pH sensitivity of the PAA-surfactant complex is established by verifying its reversibility under varying pH conditions. The successful regeneration and reuse of the membrane can be exploited to develop a process for separation of nonionic surfactants from hydrophobic solvents and also for purification of surfactant mixture. This is an abstract of a paper presented at the AIChE Annual Meeting and Fall Showcase (Cincinnati, OH 10/30/2005-11/4/2005).