Microcrystalline cellulose modified by phytic acid and condensed tannins exhibits excellent flame retardant and cationic dye adsorption properties

Functionalized microcrystalline cellulose (MCC) and its composites have a wide range of applications. In this research, bio-based phytic acid (PA) rich in phosphorus and condensed tannins (CT) were incorporated into MCC, and a product PA/CT/MCC with excellent flame retardant and cationic dye adsorption properties was prepared. The FT-IR and ICP-MS analyses confirmed the phosphorylation of MCC. The thermal stability, charring ability, heat release capability, and combustibility of PA/CT/MCC were investigated. PA/CT/MCC was susceptible to degradation and charring at low temperature primarily resulting from the pyrolysis products of PA, and yielded char layers at high temperature. Furthermore, PA/CT/MCC had a very low heat release capability in the microscale combustion, and displayed excellent flame retardancy in the vertical combustion, thereby being a potential FR material. Additionally, PA/CT/MCC exhibited a strong capability of adsorbing cationic dye from water, thereby being a potential adsorbent for removing cationic dye. The adsorption of cationic dye on PA/CT/MCC followed the pseudo-second-order kinetic model and the Langmuir–Nernst dual isotherm model. The Langmuir adsorption played a major role in total adsorption. This research suggests the novel approaches of constructing flame retardant and adsorptive MCC materials, which have potential application prospects in the fire protection and water treatment fields, respectively.