Effect of mineralizing agents on the adsorption performance of metal–organic framework MIL-100(Fe) towards chromium(VI)

Four microporous MIL-100(Fe) metal–organic frameworks (MOFs) synthesized with or without mineralizing agents by hydrothermal method were evaluated for their characteristics, water stability and adsorption performance towards Cr(VI). In the study, we compared two traditional mineralizing agents (i.e. hydrofluoric acid (HF) and tetramethyl ammonium hydroxide (TMAOH)) and an environmental-friendly mineralizing agent sodium carbonate (Na2CO3) for the likelihood of quality improvement of MIL-100(Fe). Results showed that MIL-100(Fe) prepared using Na2CO3 mineralizing agent exhibited excellent physicochemical property and higher adsorption capacity for Cr(VI) than the others. The adsorption of Cr(VI) on MIL-100(Fe)_Na2CO3 fitted better with Langmuir isotherm model and pseudo first-order kinetics model. Desorption and regeneration of used MIL-100(Fe)_Na2CO3 were achieved using NaOH (0.01 M) with a high desorption efficiency of 73% in four hours. Based on the improved structural characteristics and excellent adsorption performance of MIL-100(Fe)_Na2CO3, using the environmental friendly and low-cost Na2CO3 as mineralizing agent could be an alternative and preferred pathway in the preparation of MOFs materials.