PEI-functionized cellulose foam for the visual recognition and removal of Cr(VI)

In this work, a novel PEI-functionized cellulose foam (PEI-CF) was prepared by crosslinking polyethyleneimine and cellulose with epichlorohydrin followed freeze drying. The resultant foam not only possessed a three-dimensional network structure but also emitted strong blue fluorescence. It can efficiently remove Cr(VI) from aqueous solution and reduce its concentration below 0.05 mg/L. Other competing anions including NO3−, Cl− and H2PO4− had no remarkable influence on Cr(VI) removal except SO42−. Moreover, the PEI-CF demonstrated good regeneration performance. In addition, a reversible fluorescence "on–off-on" phenomenon was found for the PEI-CF before and after the Cr(VI) loaded under 365 nm UV light. By using the PEI-CF, the visual recognition of Cr(VI) was achieved in a wide pH range of 2–8 and low Cr(VI) concentration of 0.05 mg/L. Coexisting ions (Cu2+, Pb2+, Fe3+, Zn2+, Cr3+, SO42−, Cl−, NO3−, H2PO4− and S2−) had no significant influence on the visual recognition of Cr(VI), exhibiting good selectivity. The PEI-CF showed great promise for the emergency monitoring and Cr(VI) removal in environmental water.