Efficient adsorption of fluorescent whitening agent 351 from high salinity environmental water by polymer supported hydroxyl functional ionic liquid

Abstract

Fluorescent whitening agent 351 (FWA351) is an emerging highly persistent pollutant with potentially harmful effects on human health and aquatic ecosystem. However, developing highly effective adsorbents for the pre-treatment of environmental water samples containing FWA351 remains a problem. In this study, a novel polymer supported hydroxyl-functionalized ionic liquid (PS-[HMMim][Cl]) was prepared via a simple one-step method and used for the removal of FWA351 from water. It was found that the PS-[HMMim][Cl] exhibited an ultrahigh adsorption capacity of 1203.6 mg/g for FWA351 and maintained high removal efficiency in a wide pH range (2.0–9.0). Notably, even the concentration of FWA351 was as low as 0.005 mg/L (5 ppb), FWA351 could be effectively removed by the adsorbent, achieving an enrichment factor as high as 447.8. Various inorganic salts (such as KCl, NaCl and MgCl2) at the concentration up to 1.0 mol/L had no obvious effect on the removal efficiency. The PS-[HMMim][Cl] also displayed outstanding adsorption performance towards fluorescent whitening agents (FWAs) with similar structure to FWA351 and could be regenerated and reused for at least 8 cycles. Finally, the adsorbent was applied for the pre-treatment and then detection of FWA351 in six kinds of environmental water samples. Mechanism studies suggest that the synergistic driving forces of electrostatic attraction, hydrogen bonding, π-π interaction and ion exchange are responsible for the efficient adsorption of FWA351. This work provides a new strategy for efficient adsorption and analysis of FWA351.