Experimental analysis of cellulose behavior in aqueous streams

The rising environmental awareness is leading scientists to find more sustainable technologies and materials to substitute the ones that have negative impacts on the ecosystems. Particularly, natural and sustainable polymers, such as cellulose, are under investigation to find out whether they can be substitutes for petroleum based polymers in numerous applications (e.g. packaging, cosmetics industry) In this work, the behaviors of nano fibrils and nanocrystalline cellulose materials, derived from plant and food grade, were analyzed in test media mimicking many environmental waters’ conditions. Size and stability of NC particles, which were extracted from primary source using chemical and physical pre-treatment, were determined by Dynamic Light Scattering (DLS) and Nanoparticle Tracking Analysis (NTA). Particles’ size was found to be ranging from 100 to 150 nanometers; NC pre-treated with chemical methods were found to be more stable than those pre-treated with mechanical fibrillation. Nanoparticles’ characterization was followed by an experiment aimed to determine the colloidal stability of the materials. The Organization for Economic Co-operation and Development (OECD) test n°318 guidelines were followed; and for a better mimic of European natural waters some modifications of the test mediums were performed. Test media containing fixed amount of particles and two different sources of carbon (Sodium bicarbonate and Natural Organic Matter (NOM)) were prepared. Also varying concentrations of electrolytes were added. Different methods, such as Total Organic Carbon (TOC) and Pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) were chosen to monitor the variations of NC particles along the experimental time. However, many issues were faced due to low carbon concentration in the samples and due to the difficulty to separate the carbon coming from the nanocellulose and the one derived from the test mediums. Alternatively, the attachment or collision efficiency was determined for these materials, which were prepared with the same method described by the OECD guidelines but with a higher NC concentration. The DLS was used to monitor the variation of nanoparticles’ size along the experimental time span. NC particles were found to have low attachment efficiency, that got lower when particles were dispersed in test mediums which contained natural organic matter, this was due to biofilm formation and particles’ surface modification. So, particles were found to be stable in natural water. The fate and transport of NC particles in a generic natural river was modeled using the Full Multi framework, developed by Domercq et al. (2022). The mechanisms that had bigger impacts on the fate of these particles were advection, settling and degradation, which are able to half the NC’s concentration in very short time. Despite NC samples being characterized by particles of different shapes, sizes and surface functional groups, their behaviors and potential fate in natural waterbodies resulted similar. In general, nanocellulose particles were mainly found in two states, namely aggregated and free. Mostly, the behavior of nanoparticles was influenced by the presence of NOM. Due to its properties and high degradation rate, nanocellulose can be an optimal substitute to microplastic and petroleum-based polymers, and its use in different fields (e.g. in cosmetic industry as rheological regulator in face masks and creams) can be promoted to develop more sustainable technologies and products.