Removal of Congo red and malachite green from aqueous solution using heterogeneous Ag/ZnCo-ZIF catalyst in the presence of hydrogen peroxide

Abstract

The bimetallic Zn/Co zeolitic imidazole frameworks (ZnCo-ZIFs) were successfully synthesized by a simple solvothermal method at room temperature. Silver elements were afterward doped onto the bimetallic frameworks to form Ag/ZnCo-ZIFs via a facile impregnation method in acetone solvent. The as-synthesized material was used as a heterogeneous catalyst for the removal reaction of Congo red (CR) and malachite green (MG) in the presence of hydrogen peroxide (H2O2). Effects of catalyst dosage, H2O2 concentration, initial concentration of the contaminants, reaction temperature, and reaction time were conducted in this work. The results showed that more than 94% and 98% removal of CR and MG were, respectively, achieved within 45 and 30 min. The presence of Ag also enhanced the removal efficiency of CR and MG. The main mechanism of removal reaction of the organic contaminants could be oxidation via hydroxyl radicals. Moreover, the catalytic activity of the material remained over 90% after four recycling cycles. Due to the efficient reactivity as well as high stability, Ag/ZnCo-ZIFs can be a potential heterogeneous catalyst to remove hazardous dyes from aqueous solution.