Microwave-Assisted Recycling of Waste Paper to Green Platform Chemicals and Carbon Nanospheres

Effective high-yield recycling of waste paper to well-defined future platform chemicals and carbon nanospheres was demonstrated. The developed process utilized the exceptional combined effect of microwave irradiation and dilute acid catalyst to hydrothermally degrade cellulose in waste paper. The process was evaluated for three different waste papers, brown and white paper tissues and white printing paper. Different pretreatment processes were investigated to further increase the cellulose liquefaction efficiency. By utilizing soda pretreatment, liquefaction efficiencies as high as 88% were achieved. The obtained liquefaction products were fingerprinted by NMR and LDI-MS, while the solid residues were analyzed by XRD, SEM, TGA, and FTIR. As industrial-scale microwave reactors are currently under development, the developed method displays significant potential for recycling waste paper to green platform chemicals at the industrial scale

Zero-Dimensional and Highly Oxygenated Graphene Oxide for Multifunctional Poly(lactic acid) Bionanocomposites

The unique strengths of 2D graphene oxide nanosheets (GONSs) in polymer composites are thwarted by nanosheet agglomeration due to strong intersheet attractions. Here, we reveal that shrinking the planar size to 0D graphene oxide quantum dots (GOQDs), together with the intercalation of rich oxygen functional groups, reduces filler aggregation and enhances interfacial interactions with the host polymer. With poly­(lactic acid) (PLA) as a model matrix, atomic force microscopy colloidal probe measurements illustrated that a triple increase in adhesion force to PLA was achieved for GOQDs (234.8 nN) compared to GONSs (80.4 nN), accounting for the excellent exfoliation and dispersion of GOQDs in PLA, in contrast to the notable agglomeration of GONSs. Although present at trace amount (0.05 wt %), GOQDs made a significant contribution to nucleation activity, mechanical strength and ductility, and gas barrier properties of PLA, which contrasted the inferior efficacy of GONSs, accompanied by clear distinction in film transparency (91% and 50%, respectively). Moreover, the GOQDs with higher hydrophilicity accelerated the degradation of PLA by enhancing water erosion, while the GONSs with large sheet surfaces gave a higher hydrolytic resistance. Our findings provide conceptual insights into the importance of the dimensionality and surface chemistry of GO nanostructures in the promising field of bionanocomposites integrating high strength and multifunction (e.g., enhanced transparency, degradation and gas barrier)