Hexavalent chromium (Cr(VI)) is a highly toxic pollutant that is widespread and hazardous. Since Cr(VI) mainly exists in the form of anions in natural water, adsorption shows great advantages in the removal of Cr(VI), but the method is greatly affected by pH, and the development of adsorbent materials with excellent adsorption properties in a wide pH range is still expected. In this study, a novel strategy for the universal surface functionalization of poly-quaternary ammonium via in situ covalent cross-linking was proposed by combining mussel-inspired adhesion and macromolecular grafting, which enhanced the functional group density and adsorption capacity on the surface of adsorbent materials effectively. Amino groups were selected as the reaction sites, and glutaraldehyde as the cross-linking agent to covalently cross-link and graft amine-capped poly(quaternary ammonium salts) (PDDA-NH2) onto the surface of mussel-inspired coatings in situ, and the widely criticized instability of mussel-inspired coatings was improved at the same time. The functional modification of the surfaces of 10 different substrates confirmed the universality of this strategy. The modified nonwoven fabrics were characterized by SEM, FTIR, XPS, zeta potential, and water contact angle, and the adsorption behaviors of the adsorbent for Cr(VI) ions were systematically investigated. It was proved that the functionalized nonwoven fabrics exhibited good adsorption performance in the range of pH 1-12, with the maximum adsorption amount up to 74.90 mg/g, and that the maximum adsorption amount was 38.68 mg/g for natural water. The adsorption mechanism was well demonstrated based on the experiments and DFT simulations.
Zhao et al. (Wed,) studied this question.