Nanofibrous aerogel based on cross-linked chitin / partially deacetylated chitin for efficient adsorption of organic pollutant from aqueous solutions.

The demand for a highly efficient bio-based adsorbent is increasing expeditiously. Chitin, an abundant, inexpensive, polysaccharide in the form of aerogels offers high surface area and low density. The low content of amino groups and brittleness limits application for dye adsorption. This can be mitigated by combining with partially deacetylated chitin. In this study, chitin and partially deacetylated chitin (C/dC-A) nanofibres (90/10, 80/20, 70/30, 60/40, 50/50) was converted to cross-linked aerogels via freeze-drying technique for sequestration of azo type dye, methyl orange (MO). The bulk density decreased with increasing dC content while the accessible porosity decreased. The aerogels as revealed by FESEM images are macroporous and exhibited high compressive strength and modulus of 0.72 MPa and 1.8 MPa, respectively, for C/dC-A(50/50). All aerogels exhibited an equilibrium adsorption by 10 min. Moreover, in 30 mg/L of MO, the adsorption capacity of C/dC-A (70/30) enhanced from 20.1 mg/g (pH 7) to 33 mg/g (pH 4). The pseudo-second order kinetics and both the Langmuir, Freundlich isotherm models agreed well with the experimental data reflecting chemisorption and mono/multilayer adsorption. Thus C/dC-A cross-linked aerogel developed by a simple economic method could be a promising reusable adsorbent for the sequestration of anionic dyes from waste water.