Investigation of the adsorption behaviour of different types of dyes on MIL-100(Fe) and their removal from natural water

Metal-organic framework MIL-100(Fe) has high surface area, mesoporous cages, metal active sites and excellent water stability. These fascinating properties endow MIL-100(Fe) with the potential to extract organic dyes from environmental water samples. In the present work, MIL-100(Fe) is synthesized and applied as an adsorbent to remove three different types of dyes from aqueous solution in view of assessing the adsorption isotherms, kinetics and thermodynamics, desorption, and adsorbent regeneration. The adsorption for methylene blue and methyl blue follows a pseudo-second-order kinetics and fits the Freundlich model. The adsorption is a spontaneous process, but is controlled by different thermodynamic parameter changes. Moreover, MIL-100(Fe) could hardly adsorb isatin. Variables influencing the adsorption efficiency, such as adsorption time, temperature, solution pH, adsorbent dosage and salt concentration, are investigated. No remarkable effects of pH and ionic strength are observed for the adsorption of methylene blue and methyl blue on MIL-100(Fe). The used MIL-100(Fe) could be regenerated effectively and recycled without a significant loss of adsorption ability. The adsorption efficiency is about 100% for methylene blue and 52.1% for methyl blue, and the developed method is applied to remove two types of dyes in local water samples.