Cr(VI) removal by cellulose-based composite adsorbent with a double-network structure

A cellulose-based composite adsorbent (PEI-PAM-CF) was fabricated via a facile cross-linking of polyethyleneimine/polyacrylamide (PEI/PAM) and cellulose using epichlorohydrin as the cross-linker. It possessed a double-network structure and emitted blue fluorescence. Compared with the control samples (PEI-CF and PAMCF), the PEI-PAM-CF showed a synergy effect for the Cr(VI) removal. It can effectively remove Cr(VI) at low concentration with no structure destroyed for the adsorbent. Other coexisting anions (NO3- , Cl-, H2PO4- and CH3COO-) and cations (Na+, K+, Mg2+, Ca2+ and Cr3+) had no significant effect on Cr(VI) removal except SO42-. After five adsorption/desorption cycles, the Cr(VI) removal only decreased with a loss of 7%, suggesting that the PEI-PAM-CF had good regeneration performance. Most importantly, the electrostatic adsorption mechanism between Cr(VI) and the PEI-PAM-CF was revealed by a reversible fluorescence on-off-on phenomenon and the DFT calculation. The adsorption sites on the PEI-PAM-CF were attributed to the amino groups of the PEI and PAM. Hence, the PEI-PAM-CF was potential for the treatment of Cr(VI)-containing wastewater at low concentration.

Automated summary

The cellulose-based composite adsorbent PEI-PAM-CF, featuring a double-network structure and blue fluorescence, demonstrated synergistic effects in removing low concentrations of Cr(VI) and exhibited good regeneration performance. The electrostatic adsorption mechanism between Cr(VI) and PEI-PAM-CF was revealed through reversible fluorescence phenomenon and DFT calculation, showing potential for treating Cr(VI)-containing wastewater at low concentrations.