pH-Insensitive Bimetallic Catalyst for the Abatement of Dye Pollutants by Photo-Fenton Oxidation

A bimetallic (copper and iron) catalyst supported on MCM-41 has been synthesized by chemical vapor deposition and evaluated for the degradation of Orange II by the photo-Fenton process. An in situ oxidation method we recently developed was applied to stabilize the metals supported on MCM-41, achieving an extremely low metal leaching level during the photo-Fenton process (<0.7 mg/L for the total metals, <0.35 mg/L for each individual metal). This new bimetallic catalyst can function well over a wide pH range because iron works best at pH 3 as a Fenton catalyst while copper plays the leading role as a Fenton-like catalyst at higher pH. Experimental results show that using FeCu/MCM-41, 93%, 83%, and 78% of total organic carbon (TOC) removals can be achieved for the photo-Fenton degradation of Orange II at pH 3, 5.5, and 7, respectively. This FeCu/MCM-41 catalyst maintains its high catalytic activity after 10 consecutive runs, as a result of its extremely low metal leaching and strong chemical bonding of metal–O–Si. The experimental data have been fitted with a proposed kinetics model. It was shown that the activation energy of the oxidation reaction using a bimetallic catalyst is lower than that using a conventional monometallic catalyst. This is a significant improvement for the Fenton reaction system.