Selective and effective adsorption of methyl blue by barium phosphate nano-flake

We report the synthesis of barium phosphate (BP) nano-flake and its adsorption behavior to methyl blue (MB) in aqueous solution. The as-obtained BP nano-flake revealed pure rhombohedral crystal structure. The adsorption capacity of MB onto BP reached 1500 mg g−1. The adsorption equilibrium results fitted well with the Freundlich isotherm model. The adsorption process took less than 30 min to reach equilibrium. The adsorption kinetics was elucidated by the pseudo-second-order kinetic equation. It followed 2-stage and 3-stage intra-particle diffusion models for the low and high concentration of dye solutions, respectively. The adsorption of MB using the BP nano-flake was highly selective, compared with the adsorption of other dyes. The interactions between MB and BP were mainly the ionic interaction and hydrogen bonds, which were confirmed by the X-ray photoelectron spectroscopic results and the density functional theory calculations. The BP nano-flake revealed less than 5% decrease in adsorption amount when it was recycled and reused five times. The present work shows that the BP nano-flake is promising for practical applications in MB removal from aqueous solutions.

Figure optionsDownload high-quality image (263 K)Download as PowerPoint slideHighlights
► Fine-structured barium phosphate (BP) nano-flake has been studied as adsorbent.
► High adsorption capacity of methyl blue (MB) onto BP was about 1500 mg/g.
► The adsorption for MB was highly selective.
► Ionic and hydrogen bonds existed between BP and MB by XPS and calculation analysis.