Preparation of ultra-lightweight and surface-tailored cellulose nanofibril composite cryogels derived from Date palm waste as powerful and low-cost heavy metals adsorbent to treat aqueous medium

Abstract

In this study, new bio-based crogels as adsorbents were prepared from date palm tree waste (Phoenix dactylifera L). Cellulose nanofibrills (CNFs) and cellulose nanofibrills cryogels modified with 10 % GO and Fe3O4 nanoparticle as filler (CNFs/GO/Fe3O4) were prepared by facile freeze drying methodology. The unmodified and modified cryogels were characterized by fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), X-ray diffraction analysis (XRD), energy-dispersive X-ray spectroscopy (EDAX), specific surface area (BET), thermogravimetric analysis (TGA) and mechanical test. In the following, CNFs/GO/Fe3O4 cryogels were achieved with low density (0.0139 (g/cm3)), ultra-porosity (99.46 %), appropriate specific surface area (SBET = 55 (m2/g)) with more significant thermal and mechanical properties than unmodified cryogel. Furthermore, the adsorptive removal of chromium (VI), lead (II) and mercury (II) ions was investigated by response surface methodology (RSM) with central composite design (CCD), on to CNFs/GO/Fe3O4 cryogels. Optimal conditions resulting from the effective parameters such as pH, adsorbent dosage and contact time were assessed via RSM for this novel adsorbent. The adsorption kinetics were fitted well with pseudo-second-order model and the adsorption capacity of Pb(II), Hg(II) and Cr(VI) on CNFs/GO/Fe3O4 cryogels by Langmuir model concluded 126.58, 36.70 and 73.52 mg/g, respectively at 298 ±1°K. In addition, CNFs/GO/Fe3O4 cryogels could be successfully reused even after four cycles.