Real-time adsorption of optical brightening agents on cellulose thin films

Publication year: 2021
Authors: C. Sampl a,b, S.Eyley c, W. Thielemans c, U.Hirn a,b,1, S.Spirk a,b

a - Graz University of Technology, Institute of Bioproducts and Paper Technology (BPTI), Inffeldgasse 23, 8010 Graz, Austria
b - CD-Laboratory for Fibre Swelling and Paper Performance, Inffeldgasse 23, 8010 Graz, Austria
c - Sustainable Materials Lab, Department of Chemical Engineering, KU Leuven, Campus Kulak Kortrijk, Etienne Sabbelaan 53, 8500 Kortrijk, Belgium

Published in: Carbohydrate Polymers, Vol. 261 (2021), 117826
doi: 10.1016/j.carbpol.2021.117826

Optical brightening agents (OBAs) are commonly used in textile and paper industry to adjust product brightness and color appearence. Continuous production processes lead to short residence time of the dyes in the fiber suspension, making it necessary to understand the kinetics of adsorption. The interaction mechanisms of OBAs with cellulose are challenging to establish as the fibrous nature of cellulosic substrates complicates acquisition of real-time data. Here, we explore the real-time adsorption of different OBAs (di, tetra- and hexasulfonated compounds) onto different cellulose surfaces using surface plasmon resonance spectroscopy. Ionic strength, surface topography and polarity were varied and yielded 0.76–11.35 mg m−2 OBA on cellulose. We identified four independent mechanisms governing OBA-cellulose interactions. These involve the polarity of the cellulose surface, the solubility of the OBA, the ionic strength during adsorption and presence of bivalent cations such as Ca2+. These results can be exploited for process optimization in related industries as they allow for a simple adjustment and experimental testing procedures including performance assessment of novel OBAs.

MP-SPR keywords: adsorption, Au sensor slide, mechanism of interaction, protein-small molecule interaction