Sorption Behaviour of Enzymatically and Chemically Formed Beechwood (Fagus sylvatica) Xylan Hydrogels onto Cellulosic Materials Under Different Sorption Conditions
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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.
KeywordsXylan nano-hydrogels Cellulose Sorption α-d-glucuronidase Coacervation
Ms Katiana Gomes and Mr Tinus van Rooyen of Department of Process Engineering, Stellenbosch University for their contribution in data collection and analysis, Ms Manda Rossouw of Department of Process Engineering and Ms Lize Engelbrecht and Ms Madelaine Franzenburg of the Central Analytical Facility, Stellenbosch University for their contribution in providing analytical services. Prof. Emile van Zyl of Microbiology Department and Prof. JF Görgens of Process Engineering Department, Stellenbosch for providing facilities to produce α-d-glucuronidase used in this study. Funding for the project was provided by Process Engineering Department and NRF CSUR Grant No. 93723.
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