Fe and Ni nanoparticles-loaded zeolites as effective catalysts for catalytic reduction of organic pollutants

Three zeolites with different structures (mazzit, faujasite and MFI) were prepared by hydrothermal way, and then were used to stabilize the Fe and Ni nanoparticles using ion exchange followed by treatment with a solution of NaBH4 as reducing agent. The designed nanocatalysts were used in the catalytic reduction of methylene blue dye (MB) and 4-nitrophenol (4-NP) in a simple and binary system under NaBH4 solution to determine their effec-tiveness in wastewater treatment. The obtained samples were characterized by XRD, XPS, nitrogen sorption at 77 K, XRF, FTIR, UV-vis, SEM and TEM. The obtained results revealed that the structure of the zeolites was well retained after immobilization of metal nanoparticles (NPs), but their textural properties were slightly reduced. The XPS results clearly show that the zero charge nanoparticles were well obtained using NaBH4 solution. As confirmed by TEM the nanoparticles were well dispersed in the surface of the zeolites their sizes were around 3-13 nm for the zeolites modified by Fe NPs and 2-6 nm for those modified by Ni NPs. The catalyst Ni-Y exhibited excellent catalytic activity towards the reduction of MB dye and 4-NP in binary and simple system due to its large surface area containing well dispersed Ni nanoparticles. The rate constant in a simple system was 0.02 s(-1) and 0.005 s(-1) for 4-NP and MB dye respectively, while in the binary system was 0.002 s(-1) and 0.014 s(-1). The catalyst Ni-Y was used in five consecutive experiments without important loss of activity, confirming its stability.

Automated summary

Three different zeolites were synthesized by hydrothermal method and used to stabilize Fe and Ni nanoparticles, followed by reduction with NaBH4. The designed nanocatalysts were effective in catalytic reduction of methylene blue and 4-nitrophenol in wastewater treatment. Characterization results showed well retained zeolite structure after immobilization of metal nanoparticles, with Ni-Y catalyst showing excellent catalytic activity.