Renewable 4-HIF/NaOH aerogel for efficient methylene blue removal via cation-π interaction induced electrostatic interaction.

A novel porous organic material 4-hydroxyindole-formaldehyde/NaOH (4-HIF/NaOH) aerogel was prepared via a facile polymerization, soaking in NaOH aqueous solution and ambient drying method. 4-HIF/NaOH aerogel porous polymer networks with high surface area have been applied as efficient adsorbents to remove methylene blue from wastewater via synergistic effects of cation-π interaction induced electrostatic interaction, electrostatic interaction and π-π interaction. The adsorption capacity calculated by adsorption isotherms at 303 K was 1016.9 mg g-1 which is higher than those observed for methylene blue on other aerogels and most other materials. Furthermore, the methylene blue loaded 4-HIF aerogel can easily be regenerated with 0.1 M HCl solution and ethanol wash, retaining over 75% of the adsorption capacity after recycling five times.