Directed selective transport and enrichment of micropollutants by gradient hydrogels

Selective autonomous enrichment of micropollutants in the aquatic media has attracted increasing attention because of their low concentration characteristics and diverse coexisting species. Herein, the gradient hydrogels were prepared via free redical polymerization of AA and NH₂-β-CD under the induction of unilateral UV illumination (P(AA-NH₂-β-CD)). The gradient hydrogels present autonomous enrichment towards Sb(III) with a higher selectivity both in single and binary solutions. The simulation calculations proved that the electrostatic potential of the gradient hydrogel is almost identical before and after enrichment of Sb(III), suggesting that the formed hydrogen bonds between carboxyl and hydroxyl groups with gradient distribution play vital voles on its higher selectivity by gradient hydrogels. Moreover, the gradient P(AA-NH₂-β-CD) hydrogels showed selective self-driven enrichment performance for identically charged organic dyes based on host-guest and electrostatic interactions. For the positively charged model pollutants, the gradient hydrogels exhibited a superior selective enrichment performance for MG than X-GRL with a lower K value. The as-prepared gradient hdyrogel may have potential applications for the self-driven and selective removal of micropollutants.