Oscillatory and rotational rheological characterization of jackfruit peel cellulose suspension: Effect of concentration, pH and ionic strength

Abstract

Jackfruit peel (JP) is considered as an agro-industrial lignocellulosic waste which can be utilized for cellulose isolation. In this work, a yield of 25.6% cellulose was obtained from JP powder through alkali (NaOH) and bleaching (NaClO2) treatment along with the elimination of lignin, hemicellulose and other non-cellulosic constituents. The IR spectroscopy confirmed the existence of cellulose content in the final extracted product. The SEM images and EDX spectra demonstrated the microstructure of cellulose fibrils and their major elemental components as carbon and oxygen, respectively. The XRD data validated the crystalline (69.42%) nature of the cellulose. The various rheological attributes of cellulose suspension like the flow properties and dynamic rheological characteristics were examined at different pH, ionic strength and cellulose concentration. The cellulose suspensions exhibited shear thinning nature for all the pH, ionic concentration and cellulose concentrations. The change in viscoelastic behaviour of the cellulose suspension was noticed with the rise in storage modulus (G′) value with ionic concentration. The pH of the cellulose suspension had a significant impact on its viscoelastic properties due to the modifications in interfibrillar interactions of cellulose fibrils. The temperature ramp test showed that the G’ is independent of the heating of cellulose suspension from 20 °C to 80 °C. The creep and thixotropic recovery test revealed that upon removal of stress, there is the recovery of strain and viscosity up to a certain extent, which is a characteristic property of viscoelastic material.