Polyethylenimine-functionalized cellulose aerogel beads for efficient dynamic removal of chromium(vi) from aqueous solution

Abstract

For the highly effective removal of hexavalent chromium from aqueous solutions, a new polyethylenimine (PEI) grafted porous adsorbent, a cellulose@PEI aerogel (CPA-2) composite, was synthesized through a glutaraldehyde crosslinking reaction between the amine groups of PEI and the hydroxyl groups of cellulose. The physicochemical properties of this new adsorbent were characterized by FT-IR, SEM, EDX, XPS, etc., and the modification of grafting with PEI was demonstrated by FT-IR, EDX and XPS analyses. The effects of pH, contact time, initial concentration and PEI content on Cr(VI) sorption were systematically investigated. Experimental data were well described by the Freundlich isotherm and the pseudo-second-order model in a batch system, demonstrating that chemisorption was the rate-controlling factor for Cr(VI) removal with CPA-2. Furthermore, the experimental maximum adsorption capacity of CPA-2 was 229.1 mg g⁻¹, which was around 12 times higher than that of cellulose aerogel (CA) (18.7 mg g⁻¹). The Thomas model was well fitted to the breakthrough curves of adsorption processes under different fixed-bed conditions. Above all, the exhausted bead-like adsorbent could be easily separated and regenerated without significant loss of adsorption capacity. Accordingly, this new composite material should be a promising sorbent for sewage disposal, with advantages of high performance, low-cost, biodegradability and excellent reusability.