Separation of oil and water represents one of the key environmental challenges, particularly in the remediation of oil spills and the treatment of industrial wastewater. The development of efficient, sustainable, and biodegradable materials for such applications is therefore extremely important. Nanocellulose, due to its availability, high specific surface area, and potential for functionalization, is a very promising material for the development of filtration and absorption systems.
In this master’s thesis, we studied the possibility of hydrophobization of films and aerogels made from cellulose nanofibrils (CNF) by treatment with nitrogen plasma, and analyzed the influence of preparation parameters on the properties of the materials. CNF films have already been successfully hydrophobized using nitrogen plasma, whereby the presence of siloxanes proved to be important for hydrophobization. Short-chain siloxanes can leach from silicone baking molds and trays into water, fats, and air. Since CNF films are prepared on silicone substrates, some siloxanes are released into the CNF matrix. After nitrogen plasma treatment, they bind to cellulose and cause increased hydrophobicity. We wanted to test whether the process of preparing hydrophobic CNF films could also be adapted for the preparation of hydrophobic CNF aerogels. CNF aerogels could not be successfully hydrophobized, which we attribute to the too low concentration of siloxane groups in the material after lyophilization. ATR-FT-IR spectra did not show clear peaks indicating the presence of siloxanes, while the effect of plasma was limited due to the thermal sensitivity of aerogels.
We also tested whether drying temperature and film thickness influence the hydrophobicity of the treated CNF films. No differences in hydrophobicity were observed between CNF films of different thicknesses or between those dried at different temperatures. However, after plasma treatment, CNF films transitioned from a hydrophilic to a hydrophobic state, independent of the orientation during preparation, which was further confirmed by contact angle analysis. AFM analysis confirmed changes in surface morphology, indicating the influence of plasma on roughness as an additional factor in the development of hydrophobicity. Finally, we tested selective oil absorption from an oil–water mixture with a simple experiment. The hydrophobized films showed clearly improved phase separation ability, confirming their potential for environmental applications such as filtration or oil spill remediation.
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