Magnetic poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol) nanotubes modified with glacial acetic acid for removing methylene blue: Adsorption performance and mechanism

Developing excellent dye adsorbent with high adsorption capability and good reusability and clarifying the interaction mechanism between adsorbent and adsorbate are highly desired for eliminating water pollution. Herein, we present a novel magnetic adsorbent Fe3O4/poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol) nanotube modified by glacial acetic acid (defined as Gl-PZSNTs-Fe3O4) to remove cationic dye methylene blue (MB) from aqueous solution. Compared with the unmodified magnetic PZSNTs-Fe3O4, the Gl-PZSNTs-Fe3O4 exhibits rapid adsorption rate and high adsorption capacity. The adsorption equilibrium data was fitted well with Langmuir model, and the adsorption kinetics obeyed the pseudo-second-order kinetics model and Elovich model. Thermodynamic analysis showed that the MB adsorption onto the Gl-PZSNTs-Fe3O4 was endothermic and spontaneous. Especially, through contrasting the adsorption behavior of Gl-PZSNTs-Fe3O4 and PZSNTs-Fe3O4 towards MB dye, we highlighted the importance of glacial acetic acid modification for enhancing the adsorption capacity of the Gl-PZSNTs-Fe3O4. Meanwhile, we also proposed the adsorption mechanism of the Gl-PZSNTs-Fe3O4 towards MB dye.