Study on the mechanism of enhanced remediation of nitrobenzene contamination in groundwater by hydraulically driven synergistic in-situ microelectrolysis system.

Groundwater circulation well (GCW) can effectively control the migration and diffusion of organic contaminants in aquifer through hydraulic driving force. However, its poor direct removal capacity for contaminants restricts the engineering application of GCW. To address this issue, this study coupled GCW with FeC microelectrolysis to enhance the removal of nitrobenzene. Experimental results demonstrated that the FeC microelectrolysis system simultaneously generates hydroxyl radical (•OH) and hydrogen radical (H•), leading to two degradation pathways for nitrobenzene: oxidative pathway and reductive-oxidative pathway. Accordingly, kinetic fitting revealed that the degradation of nitrobenzene can be divided into two stages: rapid degradation stage dominated by reduction in the early phase and slow degradation stage dominated by oxidation in the later phase. Investigations on influencing factors indicated that a low aeration rate and low pH value favor the degradation of nitrobenzene, while the initial concentration of nitrobenzene has an insignificant effect on the degradation efficiency. Two dimensional sandbox simulation results showed that the coupling of FeC microelectrolysis with the hydraulic driven of GCW continuously reduced the concentration of nitrobenzene in aquifer and gradually formed a high-efficiency remediation zone centered on the GCW. The degradation efficiency of nitrobenzene reached 83.85% within 48 h, which was 19.93% higher than that of the single GCW system. These findings confirm that FeC microelectrolysis and GCW exhibit favorable synergistic effects, presenting significant application potential in the in-situ remediation of organically contaminated groundwater.