Optimising pollutant degradation in reductant-mediated copper Fenton-like systems using mechanistically-based kinetic modelling

A mechanistic kinetic model has been developed and validated for Cu(II)/AA (ascorbic acid) and Cu(II)/H₂O₂/AA systems under varying chloride concentrations and circumneutral pH. While the Cu(II)/AA system degraded the selected target contaminant (formate) via Cu(III) generation through a Fenton-like mechanism, observed efficiencies were inadequate for practical water treatment across a broad range of chloride concentrations. This limitation stemmed from insufficient H₂O₂ production, leading to low Cu(III) concentrations, and scavenging of Cu(III) by AA and its oxidation products. Conversely, adding AA to the Cu(II)/H₂O₂ system at low chloride concentrations enhanced degradation by accelerating Cu(II) reduction to Cu(I), promoting copper redox cycling and increasing Cu(III) formation. However, degradation plateaued at approximately 40 % within 10 min due to Cu(III) scavenging by AA and its byproducts. Using the developed model, optimised reagent dosing strategies achieved over 90 % formate degradation within an hour through consecutive AA additions at 10 min intervals. This approach, employing non-hazardous reagents and demonstrating high efficiency at low chloride concentrations, offers a promising approach to removal of oxidisable organic contaminants during wastewater treatment. The model proved instrumental in optimising reagent dosing, enhancing degradation efficiency, and potentially reducing operational costs for scaling up of a copper-based advanced oxidation process.