Poly(acrylic acid)-modified poly(glycidylmethacrylate)-grafted nanocellulose as matrices for the adsorption of lysozyme from aqueous solutions

Abstract

In this study, a cellulose based hydrogel, poly(acrylic acid)-modified poly(glycidylmethacrylate)-grafted nanocellulose (PAPGNC) was synthesized by graft copolymerization reaction of glycidylmethacrylate onto nanocellulose (NC) in the presence of ethyleneglycoldimethacrylate as cross-linker followed by immobilization of poly(acrylic acid). The hydrogel was characterized using thermogravimetric (TG) analysis, X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) analyses. The efficiency of PAPGNC to adsorb chicken egg white lysozyme (LYZ) from aqueous solutions was studied. LYZ exhibited a decrease in α-helix and increase in β-structure, upon immobilization onto PAPGNC. The maximum adsorption was found to be at pH 6.0 and adsorption capacity attained saturation within 2h. The kinetic data were found to follow pseudo-second-order model which is based on chemisorption. The well agreement of equilibrium data with Langmuir and Jovanovic isotherm models confirm the monolayer coverage of LYZ onto PAPGNC surface. The maximum adsorption capacity based on Langmuir isotherm model was found to be 148.42mg/g at 30°C. Thermodynamic study revealed an endothermic adsorption process. Spent adsorbent was effectively degenerated with 0.1M NaSCN. The present investigation shows that PAPGNC is a promising material for the recovery of LYZ from aqueous solutions.