Enhanced removal of selected ionizable micro-pollutants from drinking water by adsorption on activated carbon fiber filters under electrochemical assistance

Abstract

Micro-pollutants have raised serious concerns for drinking water safety because of their great harm to the ecological environment and public health. Traditional water purification technologies, including coagulation and sand filtration, are commonly insufficient to treat micro-pollutants. Adsorption process through carbon-based material has the potential to remove micro-pollutants from aqueous solution. However, the adsorption efficiency is restrained by insufficient adsorption capacity of the adsorbent. Ionization is a common character of most micro-pollutants in aquatic environment, which enables the possibility to improve adsorption capacity by enhance the electrostatic interaction through electrochemical ways. In this work, the activated carbon fiber (ACF) filter possessing high inherent adsorption capacity was prepared and the electrochemical assistance was adopted to improve the adsorption capacity by enhancing the electrostatic attraction between ionizable micro-pollutant and the adsorbent. The adsorption behavior under electrochemical assistance was well fitted by the pseudo-second-order kinetic model. The initial adsorption rates v0 for dichloroacetic acid (DCAA), levofloxacin (LVFX) and ciprofloxacin (CIP) reached 10.8 mg·g−1·h−1 (2.0 V), 48.3 mg·g−1·h−1 (−2.0 V) and 39.4 mg·g−1·h−1 (−2.0 V), respectively, which were 1.1–2.0 times higher than those without electrochemical assistance. The Langmuir model well fitted the adsorption isotherms of the three pollutants under electrochemical assistance. The calculated adsorption capacities (qm) of DCAA, LVFX and CIP under electrochemical assistance were 1.9, 1.3 and 1.1 times higher than those without electrochemical assistance. Furthermore, the adsorption of DCAA of 100 μg·L−1 by ACF filters under continuous flow-through mode was further investigated. The DCAA concentration in effluent maintained lower than the World Health Organization (WHO) limitation of 50 μg·L−1 for 3150 bed volumes under electrochemical assistance, which was 2.4 times higher than that without electrochemical assistance. This work provided a new approach for the efficient removal of ionizable micro-pollutants during drinking water treatment.