Heterogeneous Fenton degradation of organic dyes in batch and fixed bed using La-Fe montmorillonite as catalyst

The La-Fe montmorillonite (La-Fe MMT) composite was synthesized by a simple precipitation method and was used for the degradation of dyes in both batch and fixed bed experiments. X-ray diffraction (XRD) and high-resolution transmission electron microscope analysis (HRTEM) confirmed the existence of Fe₂O₃ and La₂O₃ in the composite. The presence of La enhanced the degradation efficiency of dyes by the composite at neutral pH and results in little iron leaching consequently increasing the lifetime. More than 97% and 96% removal of the MB and RhB (100mg/L each) by the La-Fe MMT Fenton system could be achieved in less than 1h. The catalyst also exhibited excellent efficiency in fixed bed reactor with 91% MB degradation corresponds to 65% COD removal, even after 200h of use. The factors such as solution pH, catalyst dosage, H₂O₂ dosage and temperature on the degradation of dyes were investigated. Fluorescence and quenchers experiments indicated that OH was the main reactive species for the degradation of dyes. Due to the low cost, efficient reactivity, high stability and low metal leaching, the La-Fe MMT possesses a great potential to be a green catalyst for the heterogeneous Fenton-like degradation of hazardous dyes.