Catalytic oxidation of methylene blue by use of natural zeolite-based silver and magnetite nanocomposites

This work reports the synthesis of natural zeolite-based silver and magnetite nanocomposites and their application for the catalytic oxidation of methylene blue in water. The zeolite was impregnated with 5.5 wt.% Fe in the form of magnetite nanoparticles with size of 32 nm, and with 6.4 wt.% Ag in the form of silver oxide and metallic silver nanoparticles with sizes of 42 and 20 nm, respectively. The results showed that physical adsorption contributed to the removal of methylene blue by 25-36% and that Fe3O4@NZU is superior to Ag2O@NZU and Ag0@NZU, leading to 55% removal without oxidant and 97% in the presence of H2O2. However, there is no evidence of significant mineralization of methylene blue. The application of reaction rate models showed that the reaction order changes from zero to first and second order depending on the H2O2 concentration.