Performance and synergistic mechanism of FeO/C composite enhanced Shewanella oneidensis MR-1 for simultaneous removal of hexavalent chromium and chlorpyrifos in water

The co-contamination of hexavalent chromium Cr(VI) and chlorpyrifos (CPF) poses a severe challenge to traditional remediation technologies due to synergistic toxicity. This study constructed a bio-material synergistic system (FeO/C@ S. oneidensis MR-1) for their simultaneous removal. Results demonstrated that under optimal conditions (0.08 g/L FeO/C, 10% amount of inoculation, pH 7.0), the removal rates of Cr(VI) and CPF reached 75.5% and 93.7%, respectively, maintaining robust degradation efficiency even under a severe organic shock load of 50 mg/L CPF. Importantly, comprehensive multi-scale characterizations (SEM, CLSM, EDS, XRD, FTIR, XPS, 3D-EEM), revealed a bidirectional bio-material synergy: FeO/C acted as an electron shuttle and play a role of bio-driven electron allocation, preferentially driving the Fe(III)/Fe(II) cycle to detoxify Cr(VI), while dynamically secreted extracellular polymeric substances (EPS) acted as an active interface to enrich CPF ensuring the efficient biomineralization of CPF and complex heavy metals. This dual action effectively alleviated acute oxidative stress, enabling cell viability to recover to 80%. For real-world applications, a clear takeaway is that this self-sustaining system entirely eliminates the need for external chemical electron donors. It offers a scalable, bio-driven electron allocation green engineering strategy for the in-situ bioremediation of complex heavy metal-organic wastewater.