Anisotropic Nanocellulose Aerogel Loaded with Modified UiO-66 as Efficient Adsorbent for Heavy Metal Ions Removal

Currently, the preparation of outstanding adsorbents has attracted public concern in environmentally friendly and sustainable pollutant redress. Herein, we report a directional freeze-drying method to prepare a strong and reusable adsorbent by introducing metal-organic framework which modified by ethylene diamine tetraacetic acid (named UiO-66-EDTA) into cellulose nanofiber (CNF) aerogel. Compared to traditional aerogels, the fabricated adsorbent showed a good flexibility and reusability by forming a homogeneous three-dimensional structure. By controlling the concentration of a crosslinkable carboxymethyl cellulose (CMC) solution, we produced aerogels with different pore structures and fibrillar, columnar, and lamellar morphologies. The obtained UiO-66-EDTA/CNF/CMC aerogel (U(-EDTA)CCA) showed an excellent adsorption performance for a total of nine types of heavy metal ions, as the removal efficiency could reach 91%. Moreover, the aerogels could retain 88% of their original shape after five cycles. The aerogel may be an appropriate material for the adsorption of heavy metal ions.