Effect of chitosan molecular weight on the performance of chitosan-silica nanoparticle system in recycled pulp

Abstract

The application of chitosan biopolymer with and without nanoparticles in the papermaking process was investigated. The effect of the chitosan’s molecular weight on its interaction with silica nanoparticles in recycled old corrugated container pulp was studied. Initially, the nanosilica particles were analyzed via atomic force microscopy and scanning electron microscopy, which confirmed the spherical shape of the silica nanoparticles with diameter less than 5 nm. Dynamic light scattering method was used to determine the zeta potential and the hydrodynamic radius of the chitosan with different molecular weights. Infrared spectroscopy was used to show the possibility of hydrogen bonding between the chitosan and the nanosilica. The results showed that the chitosan with low and medium molecular weights in alkaline and in some neutral suspensions had better process performances. Increasing the molecular weights of the chitosan improved the mechanical properties. The influence of chitosan on the process parameters was dependent on different factors such as its configuration in the aqueous media before and after adsorption, its ability to penetrate the fiber pores, and its charge density. In contrast, the effect of chitosan on the strength of paper was influenced by its performance following adsorption and retention within the fibrous mat.