Effect of hydrolysis time, pH and surfactant type on stability of hydrochloric acid hydrolyzed nanocellulose.

Nanocelluloses are the subject of much interest on the account of their mechanical properties, high surface area, porosity, etc. Typically, sulfuric acid is used to produce cellulose nanocrystals with high aspect ratio and dispersibility in water suspensions. However, hydrolysis in sulfuric acid leads to cellulose esterification, which has some drawbacks such as lower thermal stability of nanocellulose. Hydrochloric acid does not cause functionalization of the nanocellulose surface, yet yields in poor colloidal stability in aqueous solutions due to the lack of ionic interactions between CNC/CNF and water molecules. Therefore, it should be possible to tune the colloidal stability of nanocellulose aqueous suspensions by modifying the properties of the solution (such as pH and/or the presence of surfactants). In this work, we attempted to obtain stable aqueous CNF suspensions via hydrochloric acid hydrolysis. Hydrolysis was performed at three time intervals, at 60 °C temperature and 6 mol/dm3 of hydrochloric acid. To find the optimum stabilizing conditions, the effect of different pH values and various surfactants on CNF stability was explored. The best stabilizing effect was observed at pH range 5-9 and in nonionic surfactant. The obtained products were characterized by using spectroscopic (FTIR), microscopic (AFM), thermogravimetric and X-ray diffraction techniques.

Microbes of XVI century Arrases of Krakow Royal Castle.

Sixteenth-century Arrases from the Krakow Royal Castle constitute a Polish national cultural heritage; hence, they should be under special protection. The storage of historic objects at strict temperature and humidity conditions is fundamental for their protection against microorganisms. However, sometimes active preservation must be applied to disinfect bio-contaminated objects. In this study, 39 strains of microorganisms, both fungi and bacteria, isolated from Arrases deposited in the Wawel warehouse were isolated and then identified using molecular tools. Fungal ability to colonize and degrade silk and wool laboratory samples was studied. Selected microbial strains were compared concerning their ability to affect silk fibroin using size-exclusion chromatography (SEC). The effectiveness of low-temperature helium-generated plasma in disinfecting the model wool and silk samples inoculated with selected strains was tested. The results showed that plasma, despite its high biocidal activity in the case of paper, was not effective on porous textile materials. The alternative protection mechanism, involving active packaging in the form of textiles impregnated with silver-exchanged zeolites, could be used to separate layers of rolled tapestries in the warehouse. Nevertheless, optimal temperature and humidity conditions should be strictly maintained and controlled.

Recognizing ancient papyri by a combination of spectroscopic, diffractional and chromatographic analytical tools.

Ancient papyri are a written heritage of culture that flourished more than 3000 years ago in Egypt. One of the most significant collections in the world is housed in the Egyptian Museum and Papyrus Collection in Berlin, from where the samples for our investigation come. The papyrologists, curators and conservators of such collections search intensely for the analytical detail that would allow ancient papyri to be distinguished from modern fabrications, in order to detect possible forgeries, assess papyrus deterioration state, and improve the design of storage conditions and conservation methods. This has become the aim of our investigation. The samples were studied by a number of methods, including spectroscopic (FTIR, fluorescent-FS, Raman) diffractional (XRD) and chromatographic (size exclusion chromatography-SEC), selected in order to determine degradation parameters: overall oxidation of lignocellulosic material, degree of polymerization and crystallinity of cellulose. The results were correlated with those obtained from carefully selected model samples including modern papyri and paper of different composition aged at elevated temperature in humid air. The methods were classified in the order SEC > FS > FTIR > XRD, based on their effectiveness in discriminating the state of papyri degradation. However, the most trustworthy evaluation of the age of papyri samples should rely on several methods.