Shape recovery aerogels from wheat straw-based cellulose nanofibrils for dynamic removal of Cr (VI)

Wheat straw-based cellulose nanofibrils (CNFs) were used to synthesize aerogel adsorbents for efficient removal of Cr (VI) from contaminated wastewater. Polyethylenimine (PEI) was introduced onto the surface of CNFs by a combined physical and chemical crosslinking strategy to produce CNF@PEI aerogels (CPAs). The resultant CPAs exhibited superior properties, including highly porous structure, good wet strength, and outstanding shape recovery performance in water, which are conducive to fix-bed column operation. The optimal CPA11 exhibited outstanding Cr (VI) adsorption performance, and the theoretical maximum uptake capacity was 710.10 mg/g aerogel. This higher adsorption efficiency was achieved by the combined action of electrostatic attractions, chemical reduction and chelation reaction. CPA11 maintained 90% of its initial uptake capacity after five cycles of adsorption–desorption. The results of fixed-bed column experiments showed the breakthrough curves of adsorption process under different conditions fit well with the Thomas model. Lower flow rate, lower influent concentration, and higher column height can facilitate the dynamic adsorption process of Cr (VI) on the CPA11. This research demonstrates a green and sustainable approach to fabricate high efficiency biosorbents from agricultural waste and has great potential applications for large-scale Cr (VI) contaminated wastewater treatment.