Application of the central composite design to study the flocculation of an anionic azo dye using quaternized cellulose nanofibrils

- Quaternized cellulose nanofibrils were prepared for use as sustainable flocculants.
- The degree of quaternization could be easily tuned by varying the reactant ratio.
- Reactive Orange 16 was used as a model anionic azo dye.
- Central composite design was used to model flocculation behaviour.
- Dye removal efficiencies of up to 295.1 mg g−1 were observed.