In this study, the enhanced effect of pyrite (FeS 2 ) on zero-valent iron (Fe 0 ) corrosion for arsenic (As) removal was investigated in a combined-Fe 0 /FeS 2 system. The effects of different Fe 0 /FeS 2 composition, dosage and initial pH were evaluated by batch experiments. Results showed that the best combination ratio of Fe 0 :FeS 2 (w/w) was 1:1 and the optimal dosage of mixture was 2.0 g/L. The combination of Fe 0 and FeS 2 in a system significantly enhanced the reactivity of Fe 0 for effective As removal within a broad pH range (3.0–9.0). The effective As removal in the combined-Fe 0 /FeS 2 system was primarily ascribed to being enhanced corrosion of Fe 0 by addition of FeS 2 . SEM and XRD characterizations strongly verified this point. Specifically, the mechanism study (the releases of Fe 2+ and total Fe ion, variations of pH values as well as XPS characterization) suggested that FeS 2 in the combined-Fe 0 /FeS 2 system could alleviate the passivation of Fe 0 (pH ini 3.0–5.0) and accelerate the dissolution of pristine oxide film that coated on Fe 0 surface (pH ini 6.8–9.0). Besides, FeS 2 in combined-Fe 0 /FeS 2 system could also accelerate the reactions between Fe 0 to O 2 at pH ini 3.0–9.0. These phenomena were well explained by a galvanic couple between Fe 0 and FeS 2 , where FeS 2 was a cathode and Fe 0 was an anode. Consequently, electrons released from Fe 0 that mediated by FeS 2 to oxide film, passivation layer and O 2 were accelerated in combined-Fe 0 /FeS 2 system and thereby enhanced the corrosion of Fe 0 for efficient As removal. Our findings suggest that utilizing FeS 2 to enhance the corrosion of Fe 0 would be a promising technology for remediation of As-contaminated water.
Chengyu Wang,Xinyu Zhang,Ming Cheng,Wentao Zhou,Yafei Wang
It is well established that the oxidizing species with high redox potentials could initiate and significantly accelerate the structural material corrosion in molten salt. However, here we found that the presence of Ce 3+ , an electrochemically less active cation, in LiCl-KCl eutectic molten salt could also enhance alloy corrosion. This effect was demonstrated through the corrosion behavior study of Inconel 600 alloy exposed to LiCl-KCl eutectic melt containing varying concentrations of CeCl 3 at 500 °C under an inert Ar atmosphere. The corrosion behavior study was performed by both the static immersion corrosion tests and electrochemical analyses. As the concentration of CeCl 3 increases from 0.5 wt% to 5 wt% and 10 wt%, the corrosion depth increases from 3.43 μm to 16.00 μm and 18.86 μm, leading to progressively severe wormhole corrosion due to chromium dissolution. The enhanced corrosion mechanism of Inconel 600 alloy was attributed to the formation of CeOCl driven by trace oxygen present in the Ar atmosphere. This study highlights the previously underestimated role of less oxidizing metal species in molten salt corrosion and provides new insights for the future study in molten salt applications.
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