Charge reversal system with cationized cellulose nanocrystals to promote dewatering of a cellulosic fiber suspension

A surface-modified form of cellulose nanocrystals (CNC) was employed to explore mechanisms related to the release of water from cellulosic fiber suspensions during papermaking. The CNC surface was rendered partly cationic (forming CCNC) by adsorption of poly-(diallyldimethylammonium chloride) (poly-DADMAC), a high charge density cationic polymer. Meanwhile, a suspension of cellulosic fibers and calcium carbonate particles was prepared from recycled copy paper, which was treated sequentially with poly-DADMAC and a very-high-mass anionic acrylamide copolymer (aPAM). Subsequent addition of CCNC strongly promoted water release, whereas ordinary CNC had the opposite effect. The effect of the CCNC was achieved with ten times less poly-DADMAC, as the final additive, compared to when adding the polymer alone. Results were consistent with a model of nanoparticle-enabled bridging, based on an assumption of non-equilibrium or slowly equilibrating processes of adsorption.