Integrated mechanochemistry and filtrate recycling for sustainable production of phosphorylated cellulose nanofibers

The commercial application of phosphorylated cellulose nanofibrils (PCNFs) is restricted by the high environmental burdens and production costs. In this study, we developed an integrated process incorporating solvent-free phosphorylation and recycled filtrate-based phosphorylation for sustainable production of PCNFs. The phosphorylation process consisting of solvent-free ball milling and heat curing was optimized, and the obtained PCNFs showed high charge content (3.78 mmol/g) and ultrafine diameter (~2.2 nm). The washing filtrates were recycled as the aqueous solutions used in heat soaking-based phosphorylation, which could be regarded as the substitute of pure urea and phosphates. Moreover, this integrated phosphorylation process exhibited enhanced environmental friendliness with an average reduction ratio of 14.7% across all impact categories, and the production cost decreased by 31.7% compared with the traditional production route, as the life cycle assessment and techno-economic analysis results revealed. This integrated process offers valuable guidance for the sustainable industrial-scale production and efficient commercialization of PCNFs.