Valorization of industrial paper waste by isolating cellulose nanostructures with different pretreatment methods

Industrial paper wastes are an underestimated source of lignocellulosic materials. In this work cellulose nanostructures (CNS) were produced from this residue by acid hydrolysis and two chemical pretreatments consisting of an alkaline (CNS-I) or an acid (CNS-II) treatment. These pretreatments and the obtained CNSs were characterized using compositional analysis, Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), dynamic light scattering (DLS), zeta potential, atomic force microscopy (AFM), and X-ray diffraction (XRD), Results reveal a reduction in the non-cellulosic compounds in pre-treated samples, with different levels of components removal and lower lignin values for alkali treatment. TGA reveals that CNSs present lower thermal stability than the residue. The SEM images revealed that pretreatment led to fiber breakage. The XDR diffractions show the co-existence of cellulose I and cellulose II, with different crystallinity index for CNSs. The DLS and AFM revealed that the production of spherical nanoparticles was following the dimensions of (similar to)195 for CNS-I and (similar to)350 nm for CNS-II. All the analysis allowed a more comprehensive understanding of the CNS properties and their possible applications. Finally, it is possible to conclude that the conversion of paper wastes into CNS is an excellent opportunity to recovery this residue and aggregate value to them.