Accelerated Sonochemical Extraction of Cellulose Nanowhiskers.

Studies on sonochemical hydrolysis of cellulose have been suggested as an alternative route to obtaining cellulose nanoparticles. In this work, the potential use of acid hydrolysis assisted by sonication to obtain cellulose whiskers was studied. Parameters such as acid concentration, hydrolysis time and temperature were investigated to evaluate their effect on the morphological properties of the nanowhiskers, as compared to the conventional extraction process by acid hydrolysis with mechanical stirring. Morphology and degree of crystallinity of the nanowhiskers were studied by atomic force microscopy (AFM) and X-ray diffraction (XRD). Results indicated that the extraction time was reduced from about 45 min to less than 3 min using the same acid concentration and temperature used in conventional acid hydrolysis treatment. Likewise, it was possible, within the range of 30 min, to extract whiskers at room temperature or using half the concentration of acid by raising the temperature to about 80 degrees C. These are promising results towards a more economically viable and ecologically friendly extraction procedure used to obtain cellulose nanowhiskers, since both extraction time and acid concentration, used in nanowhisker extraction, were significantly reduced by replacing mechanical with sonochemical stirring.

Evaluation of sub-critical water as an extraction fluid for model contaminants from recycled PET for reuse as food packaging material.

Recycling of plastics for food-contact packaging is an important issue and research into meaningful and cost-effective solutions is in progress. In this paper, the use of sub-critical water was evaluated as an alternative way of purifying poly(ethylene terephthalate) (PET) flakes for direct food contact applications. The effects of temperature, pressure and flow rate were assessed on the extraction efficiency of two of the most challenging classes of contaminants (toluene and benzophenone) from PET by sub-critical water using a first-order fractional experimental design. Extraction yield was quantified using GC/FID. The most important parameter was flow rate, indicating that the decrease in sub-critical water polarity with temperature was insufficient to eliminate partition effects. Temperature was also important, but only for the optimization of toluene extraction. These results may be explained by the poor solubility of higher molar mass compounds in sub-critical water compared to lower molar mass compounds under the same conditions, and the small decrease in dielectric constant with temperature under the experimental conditions evaluated. As cleaning efficiency is low and PET is very susceptible to hydrolysis, which limits the use of higher temperatures vis-à-vis physical recycling, the proposed extraction is unsuitable for a standalone super-clean process but may be a step in the process.