Sorption Behaviour of Enzymatically and Chemically Formed Beechwood (Fagus sylvatica) Xylan Hydrogels onto Cellulosic Materials Under Different Sorption Conditions

Abstract

Interaction between xylan and cellulose is important in surface modification and production of novel composites because different surface properties and functionalities can be introduced. Such interactions are enhanced when xylan is less soluble (hydrogel form). The study investigated how production and sorption conditions influence sorption behaviour of xylan hydrogels onto pure and less pure cellulosic materials. Xylan hydrogels were produced from beechwood (Fagus sylvatica) xylan by selective removal of 4-O-methyl-glucuronic acid substituents using recombinant α-d-glucuronidase and by coacervation using NaOH and CH3COOH, for sorption either ex-situ or in-situ onto bleached pulp and filter paper (both containing less pure cellulose) and cotton wool (pure cellulose). The interaction between the xylan hydrogel production method and the type of cellulosic material significantly (p < 0.5) influenced xylan sorption behaviour onto cellulosic materials. In-situ sorption of enzymatic xylan hydrogels increased the weight of cellulosic materials the highest when compared to sorption of xylan hydrogel ex-situ. However, among the cellulosic materials, the highest weight gain upon xylan hydrogels sorption was of bleached pulp. Therefore, the in-situ enzymatic method offered a biobased method that can facilitate xylan sorption onto different cellulosic materials. On the other hand, coacervation method produced spherical xylan hydrogels that maintained spherical morphology upon assembling onto cotton wool in ex-situ sorption; a behaviour not evident on bleached pulp and filter paper. Furthermore, temperature significantly influenced the sorption process compared to xylan hydrogel concentration. Therefore, varying xylan hydrogel production and sorption conditions can customize the sorption capacity and assembling of xylan hydrogels onto different cellulosic materials.