A highly porous metal-organic framework (MOF) material based on chromium-benzenedicarboxylates
(MIL-101) was applied to the adsorption of xylenol orange (XO) from aqueous solution. Adsorption
kinetics and isotherms were determined from the experimental data, and the results showed that pseudosecond-order
kinetic model and Langmuir adsorption isotherm matched well for the adsorption of XO
onto MIL-101. Thermodynamic parameters including free energy, enthalpy, and entropy of adsorption
were obtained, and all the results were in favor of the adsorption. It was found that the adsorbed amounts
decreased with increasing pH value of the XO solution, which indicates that the mechanism may be the
charge interactions between the dye stuffs and the adsorbents. The used MIL-101 could be regenerated by
washing with a dilute concentration of NaOH solution. Compared with other adsorbents like active carbon
and MCM-41, especially in high concentrations of XO, MIL-101 demonstrated a superior dye adsorption
capability.