From Waste Paper to Regenerated Nanocellulose: Purification Strategy Controls the Residual Chemical Fingerprint

Waste paper is a promising secondary cellulose resource for nanocellulose production, but residual constituents originating from its previous manufacturing and recycling history may affect the chemical quality of the final material. This study evaluated purification strategies for regenerated nanocellulose (RNC) produced from waste office paper using X-ray diffraction (XRD), attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR), and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), with commercial cellulose nanocrystals (CNCs) as a reference. Direct dissolution-regeneration retained substantial concentrations of residual non-cellulosic organic compounds (542.2 mg·kg^-1). It generated a membrane-associated fraction representing 18% of the recovered dry mass but containing 53% of the quantified residual organic load. Post-regeneration hexane-ethanol purification reduced the organic residuum to 11.9 mg·kg^-1, whereas acetic acid pretreatment followed by dissolution-regeneration resulted in 20.0 mg·kg^-1 and prevented formation of the membrane-associated fraction. Both values were substantially below that of commercial CNCs (229.1 mg·kg^-1). The results demonstrate that the purification strategy controls both residual chemical composition and fractionation behaviour during processing, supporting an application-oriented purification concept in which purification intensity is matched to the requirements of the intended nanocellulose application.