Cellulose-based amphoteric adsorbent for the complete removal of low-level heavy metal ions via a specialization and cooperation mechanism.

• A cellulose-based amphoteric adsorbent was obtained by crosslinking. • The simultaneous complete removal of low-concentration heavy metal was achieved. • The specialization and cooperation mechanism were proposed. • The remaining concentrations still met the US EPA standards after 5 regenerations. A novel cellulose-based amphoteric adsorbent (MCC/DTPA-PEIA) with a high density of amino and carboxyl groups for the simultaneous complete removal of anionic and cationic heavy metal ions was designed and prepared by using cross-linking with microcrystalline cellulose (MCC) and DTPA-PEI, which was synthesized by the modification of diethylenetriaminepentaacetic acid (DTPA) with polyethylenimine (PEI). The MCC/DTPA-PEIA could completely remove Cr(VI), Cd(II), Cu(II), Zn(II) and Pb(II), and the remaining concentrations of low-level heavy metal ions after adsorption (2000 ppb) could reach the safe drinking level standards (US EPA). In addition, the cellulose-based amphoteric adsorbent exhibited good regeneration. It is interesting to note that the MCC provided by the MCC/DTPA-PEIA skeleton improved the adsorption rate of heavy metal ions. The competitive adsorption behaviors for anionic and cationic heavy metal ions on cellulose-based amphoteric adsorbents depend on the affinities of heavy metal ions for the amino and carboxyl groups of the adsorbents, and the simultaneous complete removal of MCC/DTPA-PEIA for low-level Cr(VI), Cd(II), Cu(II), Zn(II) and Pb(II) was attributed to the specialization and cooperation mechanism between amino and carboxyl groups of MCC/DTPA-PEIA. [ABSTRACT FROM AUTHOR]