Three-dimensional electrochemical process using Fe-based reduced graphene oxide hydrogel particle electrodes for peroxydisulfate activation and improved tetracycline hydrochloride degradation

High catalytic activity and long-term stability of particle electrodes are key to three-dimensional electro-activated peroxydisulfate (3D-E-PDS). This study developed the Fe-based reduced graphene oxide (Fe/rGO) hydrogel particle electrodes prepared using a low-temperature hydrothermal method, demonstrating a 9.77-fold increase in tetracycline hydrochloride (TCH) degradation rate compared with conventional two-dimensional (2D) E-PDS system. The structural properties and catalytic activities of the Fe/rGO hydrogel particles clearly depended on the iron precursor, with the Fe 3 + -derived hydrogel exhibiting the highest catalytic activity. After systematically optimizing the operational parameters (PDS concentration, current density, particle dosage, initial solution pH, TCH concentration, and agitation rate), the 3D-E-PDS system achieved a TCH degradation efficiency of 94.44% and total organic carbon removal efficiency of 46.62% within 2 h. In water matrices, Cl − promoted TCH degradation, whereas SO 4 2− , PO 4 3− , and especially CO 3 2− inhibited the degradation. Radical quenching experiments identified SO 4 · − , ·OH, 1 O 2 , and ·O 2 − as the primary reactive species. After six cycles, the 3D-E-PDS maintained a TCH degradation efficiency of 82.56%, with a degradation rate 2.56 times higher than that of the 2D-E-PDS system, validating its stability and reusability. Overall, this study establishes a one-step hydrothermal synthesis protocol for Fe/rGO hydrogel particle and demonstrates the efficacy of 3D-E-PDS in TCH degradation.