Photo Fenton degradation of high concentration Orange II (2mM) using catalysts containing Fe: A comparative study

Photo Fenton discoloration and mineralization of high concentration Orange II (2 mM) was conducted by using three catalysts containing Fe in the presence of 2 × 8 W UVC light (254 nm) and 100 mM H2O2 at an initial solution pH of 3.0. The three catalysts are laponite clay based Fe nanocomposite (Fe-Lap-RD), betonite clay based Fe nanocomposite (Fe-B), and iron oxide hydrated (FeOOH). All of them showed a good photo catalytic activity in the discoloration of 2 mM Orange II. 100% discoloration was achieved within 120 min in the presence of 1.0 g Fe-Lap-RD/L while 100% discoloration needs 180 min reaction in the presence of 1.0 g Fe-B or FeOOH. In terms of discoloration, the efficiency of the catalysts follows the order: Fe-Lap-RD > Fe-B ≈ FeOOH. However, in the mineralization of 2 mM Orange II, only Fe-Lap-RD and Fe-B showed good photo catalytic activity while FeOOH showed poor photo catalytic activity after 300 min reaction. In the cases of 1.0 g Fe-Lap-RD/L and Fe-B, more than 95–98% TOC removal of 2 mM Orange II can be achieved while only 82% TOC removal was obtained in the presence of 1.0 g FeOOH/L. In terms of the final TOC removal, the efficiency of the three catalysts follows the order: Fe-Lap-RD > Fe-B > FeOOH. The efficiency of 1.0 g Fe-Lap-RD/L is similar to that of 10 mg Fe3+/L. The results revealed that using Fe-Lap-RD as a heterogeneous catalyst for the degradation of high concentration Orange II is successful. Furthermore, our results also illustrate that both homogeneous and heterogeneous photo Fenton reactions are responsible for the complete discoloration and mineralization of high concentration Orange II.