Defence of doctoral thesis: Billy Hoogendoorn – Exploring cellulose as a biomacromolecule for enhanced battery metal ion recovery/recycling

The research focused on the effects of integrating nanocellulose in the solidification of metal ions into metal oxide particles or metallic electrodeposits.  Firstly, the cellulose was isolated as highly crystalline ca. 15-25 nm thick and 500 nm long fibers from bacterial cellulose using acid hydrolysis and had a negative surface charge. Positively charged nanocellulose was also explored using cationic functional groups substituted onto the nanofiber surface.  The effect of the isolated nanocellulose when preparing metal oxides via enforced precipitation of zinc metal ions into zinc oxide particles was investigated at ultra-low nanocellulose content ≤0.01 %. The result indicated that increased reaction yields of ~15 % and a reduction of particle sizes by up to 50 % could occur at nanocellulose concentrations of 0.01 %. The kinetics was studied and showed that the presence of cellulose consistently increased the consumption rates of zinc ions. If the reaction consumed a large fraction of the zinc-ions (>80%) within the first 15 min, continued growth of ZnO was also suppressed by the presence of nanocellulose. This was observed during the synthesis of sheet-like ZnO-particles, where an increase in reaction yield from 81 to 95 % hindered the growth of additional nanorods, which otherwise had formed after 15 min of the reaction. Further, nanocellulose was then evaluated for metal recovery reactions of Zn, Cd, and Ni using electrodeposition. Zinc and cadmium, which generally form separate, faceted metal particles during electrodeposition, grew large dendrites when nanocellulose was present in the electrolyte. In the case of cadmium, the formation of dendrites was correlated with increases in yield by up to 15 %. For nickel, which always deposited as uniform and non-faceted layers, the presence of nanocellulose did not result in dendritic deposits. While the presence of 0.05 % of nanocellulose did not affect the yield for negatively charged nanocellulose, positively charged nanocellulose decreased the deposited amount by up to ca. 20 %. The temperature was also used to tune the dendritic formation during the zinc deposition. The major finding was that while the zinc electrodeposition in the presence of nanocellulose at 20 or 40°C induced dendritic growth, a similar deposition at 60 °C did not, reverting the deposition towards promoting dense and faceted zinc particles. The research on integrating nanocellulose in metal oxide particle solidification and metal recovery using electrodeposition aligns with the United Nations’ Sustainable Development Goals (SDGs), particularly Goal 12: Responsible Consumption and Production, and Goal 1: End poverty in all its forms everywhere, but also Goal 13: Climate Action. The use of nanocellulose as an additive can contribute to sustainable consumption and production practices, reducing waste and conserving natural resources. This approach can help to address the challenge of meeting growing demands for metals used in various industrial applications, particularly those associated with battery manufacturing. Recycling valuable metals using nanocellulose can reduce the environmental impact of mining and processing ores, contributing to sustainable resource management and contribute to poverty reduction for creating job opportunities. Furthermore, the use of nanocellulose in electrodeposition reactions will help to combat climate change by promoting more efficient and environmentally friendly metal recovery methods, potentially reducing the carbon footprint associated with traditional metal recovery and mitigate the environmental impacts of metal extraction and mining. Overall, the research on integrating nanocellulose in metal oxide particle solidification and metal recovery using electrodeposition demonstrates innovative and sustainable solutions for resource management, contributing to the UN’s SDGs.

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