Use of carboxylated cellulose nanofibrils-filled magnetic chitosan hydrogel beads as adsorbents for Pb(II)

Abstract

Novel magnetic hydrogel beads (m-CS/PVA/CCNFs), consisting of carboxylated cellulose nanofibrils (CCNFs), amine-functionalized magnetite nanoparticles and poly(vinyl alcohol) (PVA) blended chitosan (CS), were prepared by an instantaneous gelation method. SEM, XRD, and TGA techniques were applied to investigate the structure of the hydrogel materials. The magnetic hydrogels were employed as absorbents for removal of Pb(II) ions from aqueous solutions and the fundamental adsorption behavior was studied. Experimental results revealed that the m-CS/PVA/CCNFs hydrogels exhibit higher adsorption capacity with the value of 171.0mg/g, and the carboxylate groups on the CCNFs surface play an important role in Pb(II) adsorption. Moreover, adsorption isotherm data were reliably described by the Langmuir model and the adsorption kinetics closely followed pseudo-second order model. Additionally, the Pb(II)-loaded m-CS/PVA/CCNFs hydrogels could be easily regenerated in weak acid solution and the adsorption effectiveness of 90% can be maintained after the 4 cycles.

Keywords: 2,2,6,6-tetramethylpiperidine-1-oxyl radical; Adsorption; CCNFs; CNFs; CNWs; CS; CS/PVA; Carboxylated cellulose nanofibrils; Heavy metals; MCC; Magnetic chitosan hydrogel; SEM; TEMPO; TGA; X-ray diffraction; XRD; carboxylated cellulose nanofibrils; cellulose nanofibrils; cellulose nanowiskers; chitosan; chitosan/poly(vinyl alcohol) hydrogel beads; m-CS/PVA; m-CS/PVA/CCNFs; magnetic-chitosan/poly(vinyl alcohol) hydrogel beads; magnetic-chitosan/poly(vinyl alcohol)/CCNFs hydrogel beads; microcrystalline cellulose; scanning electron microscopy; thermogravimetric analysis.