Simultaneous uptake of anionic surfactants and micellar-solubilized contaminants using anion-exchange resins

Abstract

This research studied simultaneous uptake of anionic surfactants and micellar-solubilized organic contaminants by anion-exchange resins. Anionic surfactant molecules adsorbed onto the positively charged resin mainly through electrostatic attraction, while the micellar-solubilized contaminants were excluded from aqueous solutions once the remaining micelles could no longer solubilize them. Data suggest that the excess contaminants adsorbed onto the resin skeleton and admicelle layer formed on the resin surface through hydrophobic interactions and eventually partitioned into the resin gel phase matrix. In batch adsorption, the contaminant solubilization capacity did not decrease linearly with respect to surfactant concentration decrease due to the increased solution counterion activity during anion exchange, and caused “delayed” contaminant uptake relative to that of the surfactant. No such effect occurred in continuous column adsorption, where the surfactant and contaminant breakthrough occurred simultaneously. Surfactant head and tail group properties, along with resin structure and particle size significantly affected surfactant and contaminant uptake rates. Relative to recovering the surfactant, the high exchange potential of the anionic surfactant prevented effective surfactant desorption, even at high electrolyte concentration and in the presence of a cosolvent. The resin matrix also had high affinity for the partitioned contaminant, and the contaminant elution from the resin seemed to be controlled by equilibrium partitioning.