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

Cellulose nanofibrils (CNF) grafted with glycidyltrimethylammonium chloride (GTMAC), containing quaternary ammonium contents of 0.44 (QCNF-1), 1.47 (QCNF-2), and 2.28 (QCNF-3) meq g(-1), were evaluated as flocculants for the removal of Reactive Orange 16, an anionic azo dye, from aqueous solution. A rotatable and orthogonal central composite design was used to examine the performance of QCNFs under a range of experimental conditions. Removal efficiencies at the centre point of the design space were found to be 236.9 +/- 7.8, 254.2 +/- 3.8, and 264.6 +/- 2.8 mg g(-1) for QCNF-1, QCNF-2 and QCNF-3, respectively. The highest removal efficiency, 295.1 mg g(-1), was observed when using QCNF-3 at a low monovalent salt concentration. The QCNF reported herein provides a sustainable and biodegradable alternative to traditional synthetic flocculants for the decolorization of dye-containing effluents. (C) 2015 Elsevier Ltd. All rights reserved.