Selective adsorption and separation of methylene blue by facily preparable xanthan gum/amantadine composites.

In this work, xanthan gum-based composites were successfully graft-modified by amantadine (XG-Fe3+/AM) with higher adsorption capacity and selectivity on recycling cationic dye (methylene blue, MB) from aqueous solution. The adsorption equilibrium of MB could be achieved approximately within 5 min when the initial concentration was 100 mg/L, and the maximum adsorption capacity was up to 565 mg/g. After 5 desorption-regeneration cycles, the removal rate of XG-Fe3+/AM for MB could still be as high as 95 % with slight decrement. Additionally, the effects of pH, contact time, temperature and initial dye concentration on the adsorption performance of MB were systematically examined. Furthermore, the adsorbent was characterized by FT-IR, BET and XPS analysis. In mixed anionic and cationic dyes, the adsorption selectivity of XG-Fe3+/AM on MB in the mixture of MB and methyl orange (MO) reached up to 99.69 %. Molecular dynamics simulation revealed that the trend of adsorption energy for dyes was in good agreement of the experimental order of adsorption capacities and molecular sizes among seven anionic and cationic dyes based on molecular matching effect and electrostatic interaction. Therefore, XG-Fe3+/AM is an eco-friendly, facile-synthesis and high-selectivity adsorbent, which remove cationic dyes in multi-component systems through electrostatic interaction and molecular matching effect. [Display omitted] • A facile-preparation xanthan gum adsorbent was studied to recover MB selectively. • The adsorption equilibrium of MB could be achieved within 5 min. • The adsorption selectivity on MB in the mixture of MB and MO can reach up to 99.69 %. • The adsorption capacity on MB could be up to 565 mg/g. • The selective mechanism has been well studied by molecular dynamics. [ABSTRACT FROM AUTHOR]