Fast dewatering of high nanocellulose content papers with in-situ generated cationic micro-nano bubbles

Herein, an innovative method to improve the dewatering of micro- and nanofibrillated cellulose (MNFC) containing furnishes is proposed. This method is based on fiber flotation in which cationic bubbles are injected into the furnish to separate fibers from liquid medium and accumulate them on the surface of the furnish. These cationic bubbles are generated by pressurizing a solution of Hexadecyltrimethylammonium chloride in deionized water in a dissolved air flotation (DAF) tank. The drainage properties of the furnishes with MNFC content from 0% to 25% were studied. With the help of the cationic bubbles, drainage rate of 0% and 15% MNFC furnish increased from 183 ml/s to 210 ml/s and 38 ml/s to 113 ml/s, respectively. The final couch solids content of these furnishes also increased from 16 wt% to 23 wt% and from 21 wt% to 24 wt%, respectively. Cationic bubbles flocculate MNFC fibers and increase retention. Sheets characteristics including morphology, permeability, mass distribution and surface profilometry were investigated. Cationic bubbles help structure fiber elements and improve the sheet formation.