Graphene-supported micron zero-valent iron cooperates with immobilized microorganisms for long-term efficient...

The abandoned sites of relocated chemical plants are contaminated with chlorinated organic pollutants (COs), which exhibit persistence, bioaccumulation potential, and concerning levels of toxicity, posing significant risks to the environment and human health. Therefore, there is an urgent need to develop a green and efficient COs remediation technology. This study developed a permeable reactive barrier (PRB) based on modified micron zero-valent iron and graphene oxide (mZVI/GO) with immobilized microorganisms, aiming to efficiently remediate groundwater contaminated predominantly by chlorobenzenes (CBs) and other chlorinated olefins (COlefs). One-year continuous flow experiments demonstrated that the removal rate of chlorobenzene was stably maintained at over 93%, while other CBs achieved removal rates ranging from 88% to 99%. Except for trichloroethylene (TCE), the removal rates of vinyl chloride, dichloroethylene, and tetrachloroethylene reached 100%. GO significantly improved the adsorption capacity of the system, mitigated the passivation and deactivation of mZVI, and synergistically interacted with microorganisms to establish a dynamic iron valence cycle of "Fe⁰→Fe³⁺→Fe²⁺". Moreover, microbial community analysis revealed an adaptive succession characterized by a shift in dominance from Bacteroidota to Pseudomonadota. Key functional genera, such as Alcaligenes, drove pollutant degradation through the regulation of degradation-related genes (e.g., dmpL and catA). The constructed mZVI/GO-microorganism synergistic biochemical reaction system ultimately established a "sorption-reduction-biodegradation" integrated system, enabling the simultaneous and efficient removal of COs pollutants. Additionally, after introducing microorganisms acclimated to TCE as an electron acceptor, the system demonstrated a substantial enhancement in its TCE removal capacity, achieving a removal rate of up to 100%. This study proposes a novel strategy for remediating groundwater contaminated with COs, emphasizing the integration of material-based and microbial synergistic enhancement mechanisms.