Integrated Electro/Fe3+/Peroxydisulfate Treatment for Sulfamethazine Degradation and Biodegradability Enhancement

This study investigates the degradation and mineralization of sulfamethazine (SMT) by an electrochemically assisted Fe3+/persulfate (electro/Fe3+/PDS) process. Experiments were conducted in a single-compartment electrochemical cell equipped with a carbon felt anode and a stainless steel cathode under constant current conditions. Compared with PDS alone and Fe3+/PDS, the combined electro/Fe3+/PDS system exhibited a strong synergistic effect, achieving up to 89.4% SMT removal within 90 min at a current intensity of 1.6 A. The enhanced performance was attributed to electrochemical Fe2+ regeneration enabling continuous activation of persulfate and generation of sulfate radicals (SO4•−). Operational parameters significantly influenced process efficiency. Increasing current intensity accelerated SMT degradation but reduced mineralization efficiency due to parasitic reactions. Under optimized conditions (I = 3 A and [Fe3+] = 1 mM), SMT degradation reached 96.83% after 60 min, while the mineralization yield attained 72.05%. Excess iron promoted radical scavenging. Similarly, a PDS concentration of 5 mM was sufficient, with higher dosages leading to self-scavenging effects. Kinetic analysis followed a pseudo first order model, with apparent rate constants decreasing at higher SMT concentrations due to radical competition. Biodegradability assays revealed a substantial increase in the BOD5/COD ratio from initially low values to 0.34 after 300 min of pretreatment, indicating improved suitability for biological post-treatment. Overall, the electro/Fe3+/PDS process represents an efficient pre-oxidation strategy for the removal of refractory antibiotics from aqueous media.