Agricultural residue-based adsorbents with anisotropic cross-linked structures for simultaneous instantaneous capture of heavy metal ions

Converting agricultural residues into environmentally friendly adsorbents to address the problem of low removal efficiency of low-concentration heavy metal ions is an effective strategy for high-value utilization of agricultural residues. Herein, a simple general strategy is proposed for constructing amphoteric agricultural residues-based porous adsorbents by forming anisotropic cross-linked structures at the heterogeneous interface of agricultural residue, coconut shell carbon, and polyethyleneimine. This green preparation strategy can be widely adapted to agricultural residues with hydroxyl structures, such as bagasse fiber, corn cob, and peanut shell, to prepare high-performance adsorbents with high densities of amphoteric adsorption sites (The density of amino and carboxyl groups was 3.44 mmol·g−1 and 3.64 mmol·g−1) while maintaining a developed microporous structure (BET specific surface area of 760.68 m2·g−1), the reactant conversion rate was higher than 99 %. Interestingly, the synergistic effect of abundant amphoteric functional groups and developed microporous structures enabled the adsorbents to completely remove Cr(VI), Cu(II), Pb(II), and Cd(II) from water within 10 min, which exhibited a promising synchronous removal efficiency for multiple heavy metal ions. It provides a reference for the remediation of heavy metals contaminated groundwater and soil by agricultural residues-based adsorbent.