The performance of the catalyst degraded slowly after each test, where the NZVI/NaY used showed a partial loss of activity mainly due to the dissolution of iron. However, a COD removal efficiency of 61% was still achieved in the third run, showing that the NZVI/NaY retained 77% of its initial activity after 2 cycles of usage. This result suggested that the NZVI/NaY catalyst was comparatively stable and reusable. It should be noted that this high operational stability could significantly reduce the
operation cost in practical applications.