Direct Ink Writing of Hierarchically Porous Cellulose/Alginate Monolithic Hydrogel as a Highly Effective Adsorbent for Environmental Applications

Cellulose has been extensively studied for environmental applications owing to its biocompatible, nontoxic, and cost-effective properties. Herein, a simple method for the design of printable cellulose-based inks was proposed, which is achieved by adding sodium alginate (SA) to the formulation. Combined with this method, hierarchically porous cellulose/alginate monolithic hydrogel (CAH) as a highly effective adsorbent for methylene blue (MB) removal was manufactured by direct ink writing. The composite hydrogel was characterized by SEM, FTIR, XRD, TGA, and XPS, which confirmed the successful preparation of CAH. Meanwhile, characterization by XPS and zeta potential suggested that hydrogen bond interaction and electrostatic interaction dominated the adsorption mechanism of MB removal onto CAH. In batch adsorption, the kinetic data were well fitted to the pseudo-second-order model, indicating that chemical sorption dominated the adsorption process. Equilibrium adsorption data were well fitted to the Langmuir adsorption isotherm with maximum adsorption capacity of 66.31 mg g–1. After eight adsorption–desorption cycles, the removal efficiency of MB remained at 95%. The results indicated that mixing cellulose solution with SA is a practicable method to obtain the printable cellulose ink, and the 3D-printed hierarchically porous structural CAH could be one of the high-potential materials used in environmental applications.