Defence of doctoral thesis: Huisi Li – Lignin-Rich Microfibrillated Cellulose Films: From Production to Application

Lignocellulosic biomass, particularly wood-derived cellulose, offers an abundant and renewable resource for producing advanced bio-based materials. This thesis explores the development and application of lignin-rich microfibrillated cellulose (LMFC) films produced from high-kappa number kraft pulp, highlighting their potential as sustainable alternatives to petrochemical-based materials. The research focuses on understanding the influence of residual lignin and raw fiber characteristics on the properties of LMFC films. The effects of drying conditions on the physicochemical and mechanical properties of these films were also investigated.

The study demonstrates that residual lignin enhances the thermal stability and hydrophobicity of the films while also improving their mechanical properties under optimized processing conditions. Furthermore, hardwood and softwood pulps exhibit distinct fibrillation behaviors, with softwood-derived LMFC films showing superior tensile strength due to the formation of more fiber joints within the fiber networks. The exceptional mechanical performance of LMFC films, comparable to chemically modified cellulose nanofibers, demonstrates their potential for industrial applications. These lignin-rich films show promise in high-value fields such as battery, organic dye adsorption, and proton exchange application. Notably, LMFC films are ideal candidates as separators in aqueous zinc-ion batteries, where their enhanced wet tensile strength, superior electrolyte uptake, and good ionic conductivity enable stable cycling performance. Additionally, the films’ enhanced affinity for cationic organic dyes positions them as effective and eco-friendly adsorbents for water treatment. The findings of this thesis contribute to the sustainable development of bio-based cellulose materials by optimizing lignocellulosic resources for a wide range of applications. 

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