Recycling granular iron dust to effectively activate peroxymonosulfate for degradation of methylene blue

Iron dust is a byproduct generated during the machining of cast iron workpieces in industrial production. Its recovery and appropriate utilization contribute to resource recycling and the mitigation of environmental pollution from industrial activities. Herein, the low-price granular iron dust (denoted GFD) was reused as a catalyst of peroxymonosulfate (PMS) for the efficient oxidation of methylene blue (MB) in water. At first, several properties of GFD, such as crystal structure and chemical composition, have been measured. Subsequently, the performance of GFD towards PMS activation was examined, where GFD/PMS system could effectively degrade MB within a short time frame. Under experimental conditions with an initial substrate concentration of 10 mg/L, PMS dosage of 1 mM, and GFD dosage of 1 g/L, the 98.4% MB could be eliminated in 10 min. In contrast, the removal efficiencies of MB in the PMS and GFD systems were only 13.0% and 6.3%, respectively. Additionally, the following quenching experiments reveal that the •OH/SO4•− as the dominant reactive oxygen species (ROS) is responsible for MB oxidation. This work provides insight into constructing cost-effective persulfate activation system for water decontamination.