Synthesis of binary MOF–silica nanocomposites for enhanced adsorptive removal of crystal violet: Optimization via response surface methodology

Metal-organic frameworks (MOFs), have gained a lot of popularity as adsorbents in wastewater treatment due to tunable properties and surface structure. In this study two composites of MIL-53(Fe Cu) @SiO₂ were synthesized by different methods. The composites were prepared using encapsulation and surface growth processes. The synthesized composites were tested for their ability to eliminate crystal violet (CV). The results of structural and thermal tests confirmed the successful synthesis of the composites. Response surface methodology was performed to optimize the adsorption conditions. The optimum pH of the condition was found to be 7, and the amount of the adsorbent was equal to 30 mg. The results of the study showed that the rate of CV removal equals 93.3% for MIL-53(Fe Cu), 95.74% for SiO₂, 99.9% for S1, and 99.91% for S2. The maximum adsorption capacities for S1 and S2 have been found to be equal to 190.20 and 191.52 mg/g accordingly, the kinetics of the adsorption followed a pseudo-second-order reaction. The equilibrium adsorption data were best described by the Langmuir isotherm model, which showed the highest goodness of fit among the evaluated equilibrium models for the investigated adsorbents. Otherwise, the results indicate that MIL-53(Fe Cu) @SiO₂ composites may be used effectively as exothermic adsorbent materials for treating wastewater. The novelty of this study exhibits comparative evaluation of the synthesized composites properties and their effect on the ability to adsorb CV, highlighting their potential for wastewater treatment. Future studies should be performed for long-term stability, and studying the adsorption performance in real wastewater samples.