A pillar[5]arene-based hydrogel adsorbent in aqueous environments for organic micropollutants

Adsorption and removal of organic micropollutants from aqueous environments has attracted lots of attention in global water treatment. As a kind of smart adsorbent, hydrogel is widely used in the field of wastewater treatment due to its convenient operability. In this study, we successfully utilized hydrazide-functionalized pillar[5]arene P5-1 and 4-aldehydephenyl-functionalized pillar[5]arene P5-2 to prepare a hydrogel, P5P5G, for the adsorption and removal of organic micropollutants from aqueous media. P5P5G is sturdy enough to exhibit robust operability in the adsorption experiment and can adsorb a variety of organic micropollutants from water with high removal efficiency. Kinetic and thermodynamic studies and NMR experiments imply that the adsorption is mainly driven by the host-guest interactions between the pillar[5]arene macrocycle and pollutant molecules. The guest recognition nature thus endows the pillararene with the ability to capture multiple types of pollutants, including cationic, anionic, and neutral molecules. As a result, our pillararene-based hydrogel can adsorb various kinds of pollutants with diverse characteristics and be easily regenerated by the decomposition of the host-guest complexation.