Facile one-step fabrication of carboxymethyl cellulose based hydrogel for highly efficient removal of Cr(VI) under mild acidic condition

Carboxymethyl cellulose/polyethylenimine hydrogel (CMC/PEI) was firstly prepared with a facile one-step method to enhance Cr(VI) removal. The sufficient hydrogen ions in double-network structure contributed to a high adsorption capacity for Cr(VI) (6.01 mmol g−1) especially under mild acidic condition (pH 5). Attenuated total reflection-Fourier-transform infrared (ATR-FTIR) spectroscopy in combination with X-ray photoelectron spectroscopy (XPS) confirmed that Cr(VI) was firstly removed by protonated imine groups through electrostatic attraction, and subsequently reduced to Cr(III) by oxidizing hydroxyl groups. Moreover, in situ generated Cr(III) was well immobilized through coordination with nitrogen and oxygen and precipitation. Furthermore, CMC/PEI could be successfully regenerated and reused, because the adsorption capacity for Cr(VI) was still higher than 2.0 mmol g−1 even after four cycles. Additionally, the highly efficient removal of Cr(VI) was hardly affected by coexisting substances, so CMC/PEI has great potential in practical applications.