Synthesis, characterization and photocatalytic activity of ZSM-5/ZnO nanocomposite modified by Ag nanoparticles for methyl orange degradation

Abstract

In this study, ZSM-5/ZnO/Ag nanocomposite was synthesized with different amounts of silver and used for photocatalytic degradation of methyl orange aqueous solution. ZnO nanoparticles were initially precipitated on the surface of ZSM-5 zeolite, and the obtained ZSM-5/ZnO nanocomposite was modified by silver nanoparticles to increase the photocatalytic efficiency of the nanocomposite. The synthesized nanocomposites were characterized by FESEM, EDX, FTIR, XRD, UV–vis and TGA analyses. Furthermore, the effect of various parameters affecting the dye degradation as the initial dye concentration (2–20 mg/L), the photocatalyst amount (0.01-0.07 g) and initial pH (3–11) were studied. The band gap investigations showed that ZSM-5/ZnO modification with silver nanoparticles increases the photocatalytic activity of the resulting nanocomposite. The highest value of dye decomposition was obtained about 90% with an initial concentration of 5 ppm, pH = 11, 0.07 g photocatalyst under UV exposure for 2 h. Increasing photocatalyst amount in the solution and increasing silver amount in the photocatalyst structure (ZSM-5/ZnO/Ag ratio equal to 3:3:1, 3:3:5 and 3:3:10) increased the dye removal from the solution. Additionally, dye degradation of dye in alkaline conditions (pH values of 7–11) was more than that of the acidic conditions (pH values of 3–7). Investigation of different dye removal kinetic models showed the conformance of the pseudo-second-order model to the process of methyl orange dye degradation with R2>0.99 by synthetic nanocomposites.