Photo-Fenton degradation of tetracycline by Bi[Fe(CN)₆]·4H₂O prepared by a solvent-free method

The photo-Fenton process is a green technology used for the degradation of organic pollutants. In this work, a photo-Fenton catalyst, Bi[Fe(CN)₆]·4H₂O, was prepared using a ball milling method. After milling, the as-prepared product was a mixture of Bi[Fe(CN)₆]·4H₂O and KNO₃. This mixture was washed with water to remove the KNO₃. The Bi[Fe(CN)₆]·4H₂O was able to degrade tetracycline (TC) solution in the presence of H₂O₂ under visible light irradiation. The degradation activity of the catalyst increased with an increase in catalyst dosages and H₂O₂ concentrations, while increasing the TC concentration reduced the degradation activity. During the photo-Fenton process, TC interacted with hydroxyl radicals, which were the reactive species involved in this process. The chromophore cleavage of TC during the photo-Fenton process was confirmed by mass spectrometry. Since Bi[Fe(CN)₆]·4H₂O could be used for five degradation cycles without losing more than 10% of its effectiveness after the first run, this catalyst is a promising candidate for practical use in wastewater treatment processes.