ABTS as an electron shuttle to accelerate the degradation of diclofenac with horseradish peroxidase-catalyzed hydrogen peroxide oxidation

Horseradish peroxidase (HRP)-catalyzed hydrogen peroxide (H 2 O 2 ) oxidation could degrade a variety of organic pollutants, but the intrinsic drawback of slow degradation rate limited its widespread application. In this study, 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) was introduced into HRP/H 2 O 2 system as an electron shuttle to enhance diclofenac degradation under neutral pH conditions. The green-colored ABTS radical (ABTS •+ ), generated by the oxidation of ABTS with HRP-catalyzed H 2 O 2 oxidation, was proved to be the main reactive species for the rapid degradation of diclofenac in HRP/H 2 O 2 /ABTS system. There was no destruction of ABTS/ABTS •+ in HRP/H 2 O 2 /ABTS system, and ABTS was verified as an ideal electron shuttle. The reaction conditions including solution pH (4.5–10.5), HRP concentration (0–8 units mL −1 ) and H 2 O 2 concentration (0–500 μM) would impact the formation of ABTS •+ , and affect the degradation of diclofenac in HRP/H 2 O 2 /ABTS system. Moreover, compared with Fenton and hydroxylamine/Fenton systems, HRP/H 2 O 2 /ABTS system had better diclofenac degradation efficiency, higher H 2 O 2 utilization efficiency and stronger anti-interference capacity in actual waters. Overall, the present study provided a meaningful and promising way to enhance the degradation of organic pollutants in water with HRP-catalyzed H 2 O 2 oxidation.