Superhigh adsorption of perfluorooctane sulfonate on aminated polyacrylonitrile fibers with the assistance of air bubbles

Abstract

The role of air bubbles in the adsorption of perfluorooctane sulfonate (PFOS) is normally overlooked, and particularly the influence of air bubbles on PFOS adsorption onto hydrophilic adsorbents remains unclear. In this study, for the first time we propose that air bubbles originally existing in solution or being formed during shaking play an important role in the adsorption of PFOS on the aminated polyacrylonitrile fibers (APANFs). The APANFs possess a superhigh adsorption capacity of 15.0mmol/g for PFOS at pH 3 with the assistance of air bubbles. The contribution of air bubbles to PFOS adsorption increases with the decrease of initial PFOS concentrations and the increase of solution pH. The adsorbed amount of PFOS on the APANFs deceases by 79% when 0.026mmol/L PFOS solution at pH 6 is degassed at 0.01atm for 24h. By contrast, degassing the APANFs shows no influence on PFOS adsorption, suggesting the dominant contribution of air bubbles in solution rather than on the APANFs. PFOS is adsorbed on the APANFs via not only the electrostatic attraction and micelles, but also the adsorbed air bubbles with accumulated PFOS at gas-liquid interfaces. A new schematic sorption model of PFOS on the APANFs with the assistance of air bubbles is proposed, and this finding is helpful for developing PFOS removal strategy and understanding PFOS transport and fate in aquatic environments.