Zeolitic imidazolate framework supported on silica for removal of bromophenol blue

The zeolitic imidazolate framework (ZIF-9) and ZIF-9@SiO2 composite were prepared and characterized by Fourier transform infrared (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). Results of FTIR and XRD confirmed the formation of ZIF-9 and ZIF-9@SiO2. The morphology of ZIF-9@SiO2 was examined by SEM. TEM results showed particle size of 20 nm for ZIF-9@SiO2. The adsorptive properties of bromophenol blue (BPB) based on ZIFs were studied. Adsorption of BPB onto ZIFs was fitted well by pseudo-second-order kinetic model. The adsorption process was followed by Langmuir isotherm model. The maximum adsorption capacity was found to be 122 mg g(-1) at contact time 30 min and pH 3. Adsorption thermodynamics of the BPB adsorption to ZIF-9@SiO2 was studied and the results showed that the process is spontaneous.