Adsorption potentials of iron-based metal–organic framework for methyl orange removal: batch and fixed-bed column studies

In the present work, continuous fixed-bed column and batch studies were undertaken to investigate the efficiency of iron-based metal–organic framework (Fe-BTC) for the removal of methyl orange as a model contaminant from aqueous solutions. The batch experiments were carried out by varying operational parameters such as adsorbent dosage, pH, temperature, and initial contaminant concentration. The results showed that Fe-BTC had a high removal efficiency under a wide pH range. The equilibrium data were best fitted by the Langmuir model with a maximum adsorption capacity of 100.3 mg g −1 at 298 K. In order to assess the industrial feasibility of Fe-BTC, fixed-bed column studies were conducted to obtain breakthrough curves, breakthrough and saturation times, and maximum uptakes at different bed heights. The breakthrough time was 20.0 and 46.2 h at 0.75 and 1.5 cm bed depths, respectively. The bed removal efficiency was 35.2 and 46.7% at 0.75 and 1.5 cm bed depth, respectively. The bed maximum adsorption capacity was 20.2 and 21.6 mg/g at 0.75 and 1.5 cm bed depths, respectively. Moreover, the application of empirical breakthrough curve models showed good agreement with the modified dose response model ( R 2 > 0.99). Also, the analytical solution of the advection–dispersion–adsorption mass transfer equation showed an excellent fit to the experimental breakthrough data ( R 2 > 0.99). Further, the analytical model was utilized to predict the length of the mass transfer zone as a function of the bed depth and to construct a 3D surface plot that can be utilized to predict the breakthrough at different bed depths. Graphic Abstract