Zero valent iron-electro-Fenton-peroxymonosulfate (ZVI-E-Fenton-PMS) process for industrial wastewater treatment

Advanced oxidation processes are frequently applied to a variety of refractory organic wastewater, but rarely is electro-Fenton combined with activated persulfate technology applied to the removal of refractory pollutants. In this work, the electro-Fenton process was combined with zero-valent iron (ZVI) activated peroxymonosulfate (PMS), two advanced oxidation processes based on different radicals, to form the ZVI-E-Fenton-PMS process to treat wastewater, whose main advantages are the generation of more reactive oxygen species and the reduction of oxidant cost to achieve rapid removal of pollutants. This process can not only produce H2O2 and activate PMS at the cathode, but also reduce Fe(iii) to realize the sustainable Fe(iii)/Fe(ii) redox cycle. The main reactive oxygen species in the ZVI-E-Fenton-PMS process were found to be OH, SO4- and O-1(2) by radical scavenging experiments and electron paramagnetic resonance (EPR), and the relative contributions of the three reactive oxygen species for the degradation of MB were estimated to 30.77%, 39.62% and 15.38%, respectively. Then, by calculating the ratio of the relative contributions of each component to the removal of pollutants at different PMS doses, it was found that the synergistic effect of the process was better when the proportion of OH in the oxidation of reactive oxygen species (ROS) was higher and the proportion of non-ROS oxidation increased year-on-year. This study provides a new perspective on the combination of different advanced oxidation processes and reveals the advantages and potential of this process for application.