Integrating direct reuse and extraction recovery of TEMPO for production of cellulose nanofibrils

TEMPO-oxidized cellulose nanofibrils (CNFs) possess lots of attractive properties. However, recycling of TEMPO is desirable because of ecological and economic demands. In this study, a novel strategy integrating direct reuse and extraction recovery of TEMPO was developed. 50 % of filtrates after TEMPO oxidation were directly reused and half of the fresh TEMPO was added to maintain a constant dosage, the obtained CNFs within 2 cycles shared similar carboxylate contents, crystallinity, and homogeneous width compared to the original ones. Furthermore, TEMPO in another 50 % of filtrates was extracted by ethyl acetate followed by distillation. The CNFs produced using the extracted TEMPO had almost the same properties compared to those of original ones, suggesting a negligible loss of activity of the recovered catalyst. Compared to the traditional route, the combined strategy exhibited a 31.3 % reduction in production costs, which enables clean and cost-effective production of CNFs and shows a promising industrial feasibility. [Display omitted] •A strategy integrating direct reuse and extraction recovery of TEMPO is proposed•CNFs produced by the recovered TEMPO is similar to the original product•The extraction recovery process exhibits no adverse impacts on the TEMPO activity•The combined recycling strategy has both environmental and economic advantages•This production route shows promising industrial feasibility