Efficient adsorption of perfluoroalkyl acids by the quaternized hierarchically porous polystyrene-divinylbenzene

Abstract

Perfluoroalkyl acids (PFAAs) are persistent organic pollutants and it should be removed from the environment before they reach public for water consumption. Herein, the quaternized hierarchically porous polystyrene-divinylbenzene (PS-DVB-N+) was designed as the adsorbent to remove PFAAs. PS-DVB-N+ provided multiple interactions with PFAAs, i.e. hydrophobic, electrostatic and hydrogen interactions, beneficial to enhance the adsorption capacity. Additionally, the multiple interactions could compensate for each other so that relatively stable adsorption performance was expected under different adsorption conditions. Moreover, thanks to hierarchically porous structure of the adsorbent, blockage of adsorbent’s pores by aggregates which were formed at certain PFAAs’ concentrations was inhibited or at least lessened, thus promoting mass transfer and enhancing adsorption efficiency. For the individual four studied PFAAs, adsorption kinetics all well fitted pseudo-second-order model, reaching adsorption equilibrium quickly within 200 min. Particularly, the four studied PFAAs were competitively adsorbed. Perfluorooctane sulfonic acid and perfluorodecanoic acid were fast adsorbed at the beginning until completely adsorbed; adsorption of perfluorooctanoic acid and perfluoroheptanoic acid then took place if the enough adsorbent was available. Besides, PS-DVB-N+ was conveniently regenerated for repetitive usages. This study proposed an efficient adsorbent towards PFAAs with large adsorption capacity, fast adsorption rate and good resistance to the adsorption condition, which was potential for real applications.