Simultaneous production and functionalization of cellulose nanofibrils (CNFs) for heavy metal ion removal is an economical and promising solution to expedite their use in water treatment. In this work, carboxymethylated CNFs (CMCNFs) with a carboxylate content up to 2.7 mmol/g are prepared by a combination of carboxymethylation and homogenization, which show diameters of 3.40–3.53 nm and lengths of 1210.6–383.3 nm. The effect of experimental conditions (including pH, carboxylate content, contact time, initial Cu2+ concentration) on the removal performance of CMCNFs for Cu2+ is investigated in detail. Adsorption performances of CMCNFs present a record high equilibrium Cu2+ removal capacity of 115.3 mg/g at pH 5.0. Additionally, the underlying mechanism for the removal of Cu2+ ions was uncovered by coupling the fitting results based on pseudo-second-order kinetic and Langmuir isotherm models with various characterizations such as scanning electron microscopy, energy dispersive spectroscopy (EDS), EDS mapping, X-ray photoelectron spectroscopy, atomic force microscopy, and powder X-ray diffraction. Finally, the potential application of CMCNF-2.7 with high carboxylate content in converting copper-contaminated water into drinking water was demonstrated. CMCNFs provide a new selection for the design of novel nanocellulose-based materials for water treatments.

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To obtain high performance of nanocomposite lms made of cellulose nano brils (CNFs) and montmorillonites (MMTs), highly ordered nanostructures and abundant interfacial interactions are of extreme importance, especially for CNF lm with high MMT content. Here, we tend to unveil the in uence of exfoliation degree of MMTs and their interfacial interactions with CNFs on the properties of ensuing nanocomposite lms. Monolayer MMTs prefer to form highly ordered nanostructure during water evaporation induced self-assembly. The obtained nanocomposite lm with 30 wt% monolayer MMTs exhibits a tensile strength of 132 MPa, a total light transmittance of 90.2% (550nm), and water vapor transmission rate (WVTR) of 41.5 g•mm/m2•day, better than the lm made of original bulk MMTs and CNFs (30 MPa strength, 60% transparency, and 78.7 g•mm/m2•day WVTR). Moreover, the physical properties (153 MPa strength and 20.9 g•mm/m2•day WVTR) of nanocomposite lm can be further enhanced by constructing ionic interactions between the monolayer MMT and CNF using 0.5 wt% cationic polyethylenimine (PEI). However, as the amount of PEI continues to increase, its performance will be deteriorated dramatically because of the disordered orientation of monolayer MMTs. This work could provide an insight into the fabrication of high performance MMT/CNF nanocomposite lm for advanced applications.