Efficient selective recycle of acid blue 93 by NaOH activated acrolein/chitosan adsorbent via size-matching effect.

Here we report an efficient strategy to separate and recycle acid blue 93 (AB93) from mixed anionic dyes selectively within sodium hydroxide activated A/CS adsorbent (N-A/CS). This work broke the common sense that the larger the specific surface area, the better the adsorption property is, which provided an alternative strategy to separate dyes. The adsorption equilibrium of AB93 could be achieved approximately within 1-2 min, and the maximum adsorption capacity was up to 2500 mg/g. Besides, it can be activated continuously and reused at least 15 times. In mixed anionic dyes, the adsorption selectivity of N-A/CS on AB93 in the mixture of AB93 and acid fuschin (AF) reached up to 99.7 %. Molecular dynamics simulation revealed that the trend of adsorption energy for dyes qualifies well with the experimental order of adsorption capacities and molecular sizes among five anionic dyes based on molecular matching effect. Thus, N-A/CS is a low-cost, easily-preparable, significantly-effective-and-reusable adsorbent, providing a promising "size-matching" strategy to adsorb multi-component dye systems.