Mechanochemical processing of date fronds and seeds: Chemistry-dependent nano-fibrillation and dispersion properties

Date seed and frond are the principal by-products of date palm trees. Despite their abundance, their potential as feedstocks for high-value fibrillated materials remains underexplored. This study provides the first systematic comparison of the sub-cellular fibrillation behavior of date palm waste, specifically date fronds (DF) and date seeds (DS) as a function of alkaline, oxidative, or combined chemical pre-treatments followed by ball milling. By exploring how the distinct chemistries influence fibrillation efficiency, gel formation, and sedimentation, the work establishes a detailed structure-processing-property relationship. The obtained dispersions were examined for their physico-chemical properties, such as gelling and sedimentation behavior. DF samples generally exhibited superior fibrillation, particularly following oxidative and alkaline-oxidative treatments, whereas sulfite-oxidative routes generated aggregated clusters rather than uniform nanofibers. DS-derived biomass showed pronounced aggregation and shorter fibrillar or particulate structures, reflecting intrinsic differences in composition and microstructure. The combination of oxidative and alkaline-oxidative treatments was the most effective approach for obtaining high-quality nanocellulose from DF. Interestingly, for both samples after chemical treatments and thorough removal of residuals, mechanical fibrillation led to large amounts of non-fibrous leachates in the dispersion. Overall, this study outlines the key chemical factors governing nanofibrillation of date palm residues and provides guidance for optimizing their conversion into biomass-based micro- and nanomaterials.