Insight into synergies between ozone and in-situ regenerated granular activated carbon particle electrodes in a three-dimensional electrochemical reactor for highly efficient nitrobenzene degradation

•Combining electrolysis, O3, and GAC achieves a remarkable synergy for nitrobenzene (NB) removal.•Reactive oxidative species (ROS) were probed and OH generation paths were quantitatively analyzed in E-GAC-O3.•GAC in E-GAC-O3 possesses a stable catalytic activity even after reusing for 50 times.•The E-GAC-O3 process can protect the properties of GAC from oxidative destroy of ozone and ROS.•Replenishing of free electrons from both cathode and inside of GAC is critical for GAC stability.