Fast adsorption of methyl blue on zeolitic imidazolate framework-8 and its adsorption mechanism

Abstract

Zeolitic imidazolate framework-8 (ZIF-8) is synthesized and the adsorption behavior and mechanism of methyl blue (MB) are studied in detail. Results show that ZIF-8 has a higher MB adsorption capacity than most of adsorbents reported so far (the maximum adsorption capacity of ZIF-8 is 2500 mg g⁻¹) and a fast adsorption rate (sorption saturation can be achieved within 30 min). The adsorption kinetics and isotherms were studied in detail. The mechanism study shows that the existence of Zn²⁺ exposed on the surface of ZIF-8 nanoparticles plays an important role in the high adsorption of MB and the ionic bonding between Zn²⁺ in ZIF and –SO₃⁻ in MB is formed. ZIF-8 nanoparticles also show high adsorption selectivity with negligible adsorption for other dyes such as rhodamine B, methylene blue and methyl orange.