Fe2(MoO4)3 as an Effective Photo-Fenton-like Catalyst for the Degradation of Anionic and Cationic Dyes in a Wide pH Range

The photocatalytic activity of Fe2(MoO4)3 under visible light (λ > 400 nm) was evaluated by the degradation of Acid Orange II (AOII) and Methylene Blue (MB). This new catalyst is highly effective for the degradation of both dyes in H2O2/visible light system at neutral pH. One hundred mg/L of dyes was almost removed within 30 min. Compared to the results in the darkness, the rate constants fitted by a simple pseudo-first-order reaction for both dyes multiplied. MB degraded at a slightly lower rate than AOII under identical conditions due to different chemical structures. Particularly, a high photocatalytic activity of Fe2(MoO4)3 was obtained in a wide pH range of 3.0–9.0 and thus acidification pretreatment was not necessary. The high catalytic activity could be attributed to the strong absorption of Fe2(MoO4)3 in the visible-light region and in addition, the generation of reactive ·OH from H2O2 synergistically activated by both Fe3+ and MoO4 2–.