Regular Article Hairy cationic nanocrystalline cellulose as a novel flocculant of clay Cristina Campano a,1 , Patricio Lopez-Exposito b , Angeles Blanco b , Carlos Negro b , Theo G.M. van de Ven a,⇑ a Department of Chemistry, Pulp and Paper Research Centre, and Quebec Centre for Advances Materials, McGill University, 3420 University Street, Montreal, Quebec H3A 2A7, Canada b Department of Chemical Engineering, Complutense University of Madrid, Avda. Complutense s/n, 28040 Madrid, Spain graphical abstract + + + + + - - - - - - - - - - - - - - - - - - - - - - - + + + + + + + + + + + + + + + + + + + + + + + + + + + + + Clay CNCC Increasing CNCC dosage Df = 2 Negative ZP Size < 120 μm Efficacy < 60% Df = 1.6 ZP ~ 0 mV Size > 200 μm Efficacy ~ 100% Df = 1.9 Positive ZP Size < 200 μm Efficacy > 80% article info Article history: Received 11 December 2018 Revised 27 February 2019 Accepted 28 February 2019 Available online 1 March 2019 Keywords: Hairy nanocellulose Cationic nanocrystals Flocculation Clay Fractal dimension Conformation abstract Hypothesis: The present paper investigates, for the first time, the potential of cationic hairy cellulose nanocrystals (CNCC) to induce the flocculation of a model suspension of kaolinite. CNCC belong to a brand new family of nanocelluloses characterized for presenting a crystalline rod-like body and functionalized amorphous chains at both ends. Given that these chains can be easily tuned, these nanocelluloses present a high potential as fit-to-purpose flocculants. Experiments: CNCC were produced through periodate oxidation, cationization and thermal treatment of cellulose. Flocculation was monitored by both photometric dispersion analysis and laser reflectance. Flocs were characterized by the determination of zeta potential, supernatant turbidity removal and optical microscopy. A recently developed machine learning random forest regression model was used to esti- mate fractal dimension (D f ) from chord length distribution data. Findings: Although a high efficiency was achieved for CNCC dosages between 7.5 and 75 mg/g, the max- imum floc size and the fastest flocculation were found near the isoelectric point (10–30 mg/g). Thus, CNCC acted through charge neutralization mechanism. The model used to estimate flocs D f was found very successful to describe the flocculation process. The clay/CNCC flocs D f values suggest a relation between floc conformation and CNCC dosage, presenting an opener structure when closer to the isoelec- tric point. Ó 2019 Elsevier Inc. All rights reserved. 1. Introduction Cationic hairy cellulose nanocrystals (CNCC) have been recently developed by Yang and van de Ven [1]. These nanoparticles have the exceptional properties of other nanocelluloses while also pre- senting areas with a high density of positive charge that can poten- tially induce the aggregation of colloidal materials. https://doi.org/10.1016/j.jcis.2019.02.097 0021-9797/Ó 2019 Elsevier Inc. All rights reserved. ⇑ Corresponding author. E-mail addresses: ccampano@ucm.es (C. Campano), plopezex@ucm.es (P. Lopez-Exposito), ablanco@ucm.es (A. Blanco), cnegro@ucm.es (C. Negro), theo.vandeven@mcgill.ca (T.G.M. van de Ven). 1 Permanent address: Department of Chemical Engineering, Complutense Univer- sity of Madrid, Avda. Complutense s/n, 28040 Madrid, Spain. Journal of Colloid and Interface Science 545 (2019) 153–161 Contents lists available at ScienceDirect Journal of Colloid and Interface Science journal homepage: www.elsevier.com/locate/jcis