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

摘要

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 R-2 > 0.99 by synthetic nanocomposites.