Eco-friendly polymer nanocomposite hydrogel enhanced by cellulose nanocrystal and graphitic-like carbon nitride nanosheet

The eco-friendly sodium carboxymethylcellulose (CMC-Na)/polyvinyl alcohol (PVA) hydrogel reinforced with cellulose nanocrystal (CNC) and graphitic-like carbon nitride (g-C3N4) was firstly prepared as smart adsorption hydrogel with mechanical, thermal and swelling response. Encouragingly, the mechanical properties of the g-C3N4/CNCs-H hydrogel were enhanced with simply changing the content of g-C3N4. The 1.0% g-C3N4/CNCs-H hydrogel had outstanding tensile strength (up to 648 KPa), excellent elongation (1169%) and satisfactory toughness (340 KJ/m3). These enhancements were due to the inherently superior properties of the prepared CMC-Na/PVA and the synergistic effect of strong hydrogen bonding interactions between g-C3N4, CNCs and CMC-Na/PVA chains. The as-prepared g-C3N4/CNCs-H hydrogel has high equilibrium swelling capacity (90.47–117.3 g/g), which greatly improved the adsorption capacity of methylene blue (MB, qe > 198.6 mg/g). The adsorption properties of MB on the as-prepared hydrogel fitted well with the pseudo-second-order kinetic model and the Langmuir isotherm model. It was showed that the interaction of π-π stacking and hydrogen bonds resulted in the high adsorption capacity of the hydrogels. This study presented a basis and demonstration for the application of hydrogels in contaminants removal in poisonous waterbodies.