Co-degradation of coexisting pollutants methylparaben (mediators) and amlodipine in enzyme-mediator systems: Insight into the mediating mechanism

Catalyzed oxidative reactions mediated by enzymes have been proposed as an effective remediation strategy to remove micropollutants. However, enzyme-catalyzed oxidation processes are usually limited to the substrates of phenols and amine compounds. The addition of synthetic redox mediators could extend the types of enzyme-catalyzed substrates. However, the actual applications were hindered by the high cost and potential toxicity of mediators. Here, we discovered a potential HRP-mediator system by exploring the removal of co-existing pollutants amlodipine (AML) and methylparaben (MeP). It was found that MeP served as a redox mediator could efficiently mediate the removal of AML by HRP/H 2 O 2 system. Surface electrostatic potential analysis of AML molecule suggested that MeP radicals (MeP OX ) could abstract hydrogen from the N-H site on dihydropyridine moiety of AML and then be reduced to MeP. By exploring the mediating effects of substances with MeP-like structure, Hirshfeld charge was used to evaluate the mediating efficiency of mediators. For mediating the degradation of AML, when the Hirshfeld charge of mediator radical was around − 0.3000, the mediating efficiency was the highest. This study improved the HRP-mediated system and provided an efficient and green method for the degradation of co-existing pollutants AML and MeP.