Insight into the role of electrolytes on the electrolytic Fe2+-activated peroxymonosulfate: Silicates for enhanced decontamination and sustainable electrolysis

Electrolytic Fe²⁺-activated peroxymonosulfate (EFP) is a promising technology for removing organic pollutants from wastewaters. However, the impact of electrolytes on the performance of EFP needs to be explored in depth. This study systematically investigated the impacts of various inorganic anions (as supporting electrolytes) on the iron dissolution behavior and ibuprofen (IBP) degradation within the EFP system. The experimental results revealed that the EFP system with a silicate electrolyte maintained continuous iron dissolution and demonstrated favorable performance in the removal of IBP. The order of electrolytes favoring IBP removal was as follows: silicate > sulfate, nitrate, chloride > bicarbonate > phosphate. Specifically, silicate could coordinate with the Fe²⁺ ions that were released from the iron anode, thereby preventing the scaling of electrode. Meanwhile, the generated reactive species in the EFP, such as SO₄^-· and ·OH, were responsible for the oxidation of IBP. Based on the positive effect of silicate, a silicate-enhanced EFP was proposed for further optimization. The degradation of IBP was significantly correlated with the electrical current density and the PMS concentration, and the performance of EFP system can be regulated with electrical current. When the silicate-enhanced EFP was applied to the treatment of actual pharmaceutical wastewater, it not only showed the capability of removing COD, but also notably reduced the specific energy consumption by up to 44.4 %, compared to the silicate-free EFP system. Overall, this study highlights the superiority of silicate-containing electrolytes for the EFP system and in other electrochemical wastewater treating systems using iron anode.