Switching surface charge properties of hybrid nano-SiO2 for the flexible removal of cationic or/and anionic pollutants in water

Dual-alkylamino-doped silica AP-SiO 2 -DEAP was synthesized with a higher content. • Surface charge property of AP-SiO 2 -DEAP can be flexibly switched with wetting. • Efficient removal of cationic or anionic pollutant species with one adsorbent. Electrostatic attraction is one of the main interactions during the adsorption. Seldom an adsorbent can simultaneously remove the cationic and anionic pollutant due to owning a single surface charge property. In this manuscript, a two-alkylamino-doped silica material AP-SiO 2 -DEAP was synthesized with one-step condensation method. Due to the protonation of a higher content of alkylamino groups in water, the surface of this material initially presented to be very positively-charged (+31.3 mV), which showed excellent adsorption performance for the recently emerging anionic pollutant of perfluoroalkylated substances (PFASs) such as sodium p -perfluorous nonenoxybenzene sulfonate (OBS) with a maximum adsorption capacity of 2821 mg g −1 . Being prewetted in water, however, the surface of this material could be switched to be more negatively-charged (−33.9 mV) due to the generation of large amounts of Si-O − accompanying the generation of obvious mesoporous structure. The obtained material turned to be more efficient for the adsorption of the cationic pollutant such as the heavy metal ion Pb 2+ with a maximum adsorption capacity of 712 mg g −1 . More attractively, synergetic adsorption was obtained for the simultaneous adsorption of anionic OBS and cationic Pb 2+ . The removal efficiency for OBS and Pb 2+ both reached above 99% for the complex wastewater. Download: Download high-res image (259KB) Download: Download full-size image