Highly Efficient Adsorption of Cr(VI) by Mechanically Enhanced Chitosan Oligosaccharide Aerogel with Hierarchical Porosity

A three-dimensional porous aerogel was synthesized by combining soft chitosan oligosaccharide to hard multi-walled carbon nanotubes (MWCNTs) under mild conditions. Owing to the support of MWCNTs, mesopores can be detected on the inner surfaces of the aerogel. The cross-linking by tetraethylenepentamine forms a macropore structure after freeze drying, using water as the template. The hydrogel can bear 30% recoverable compression with the aid of hydrogen bonds between the amide groups. The aerogel exhibits excellent adsorption capabilities for Cr(VI) in water. The adsorption capacity can reach 367.6 mg/g within 100 min. Notably, the aerogel demonstrated an extremely high efficiency in removal for trace Cr(VI). Soluble Cr(VI) of 1 mg/L can be completely removed by the aerogel at a dosage of 0.2 g/L. This work provides a new strategy to synthesize adsorbents with hierarchical pores that exhibit high porosity and a fast mass transfer rate.