Encapsulation of Fe nanoparticles in zeolite is a promising way to significantly improve the catalytic activity and stability of Fe-based catalysts during the degradation process of organic pollutants. Herein

Fe nanocatalysts were encapsulated into silicalite-1 (S-1) zeolite by using a ligand-protected method (with dicyandiamide (DCD) as a organic ligand) under direct hydrothermal synthesis condition. High-resolution transmission electron microscopy (HRTEM) results confirmed the high dispersion of Fe nanocatalysts which were successfully encapsulated within the voids among the primary particles of the S-1 zeolite. The developed S-1 zeolite encapsulated Fe nanocatalyst (Fe@S-1) exhibited significantly improved catalytic activity and reusability in the catalytic degradation process of methylene blue (MB). Specifically

the developed Fe

0.021

@S-1 catalyst showed high catalytic degradation activity

giving a high MB degradation efficiency of 100% in 30 min

outperformed the conventional impregnated catalyst (Fe/S-1). Moreover

the Fe@S-1 catalyst afforded an outstanding stability

showing only

ca.

7.9% activity loss after five cycling tests

while the Fe/S-1 catalyst presented a significantly activity loss of

50.9% after only three cycles. Notably

the encapsulation strategy enabled a relatively lower Fe loading in the Fe@S-1 catalyst in comparison with that of the Fe/S-1 catalyst

i.e.

0.35%

vs.

0.81% (mass). Radical scavenging experiments along with electron spin resonance (ESR) measurements confirmed that the major role of OH in the MB degradation process. Specifically

Fe@S-1 catalyst with high molar ratio of [Fe(DCD)

]

Cl

3

is beneficial to form Fe complexes/nanoclusters in the voids (which has large pore size of 1–2 nm) among the primary particles of the zeolite

and thus improving the diffusion and accessibility of reactants to Fe active sites

and thus exhibiting a relatively higher degradation efficiency. This work demonstrates that zeolite-encapsulated Fe nanocatalysts present potential applications in the advanced oxidation of wastewater treatment.