A simple and green method to construct cyclodextrin polymer for the effective and simultaneous estrogen pollutant and metal removal

Abstract

The contamination of the surface and groundwaters by estrogens and metals poses considerable threat to environment and public health. Herein, we reported a Zr(IV)-cross-linked carboxymethyl-β-cyclodextrin (Zr/CM-β-CD) bifunctional adsorbent, which was constructed by a simple, versatile, and green method through the chelation reaction between CD carboxyl and Zr(IV), to simultaneously remove estrogens and metals from aqueous solution. In this system, the CD cavities encapsulated estrogen micropollutants through the host/guest interactions, and the residual carboxyl groups were expected to act as chelating sites for metal ions. In the monocomponent system, the maximum adsorption capacities of Zr/CM-β-CD adsorbent toward the estrogens estradiol and bisphenol A and metals Cd(II) and Cu(II) were 210.53, 182.15, 118.34, and 78.80 mg/g, respectively. Langmuir isothermal model was suitable to describe the adsorption process, and the adsorption mechanism was further verified through solid-state 13C NMR, FT-IR, and EDS. The adsorption capacities of the adsorbent were maintained at high levels after five cycles. Most importantly, the Zr/CM-β-CD adsorbent was highly efficient in the simultaneous uptake of estrogen and metal pollutants. Thus, the advantages of simple and green fabrication, excellent adsorption capacity, and perfect regenerate ability demonstrated that the Zr/CM-β-CD adsorbent possessed potential for application in the treatment of environmental pollution. This study also provides a new insight into the preparation of the advanced trifunctional CD polymer absorbent under simple and green conditions for water purification.