Reactive Transport Modeling of Hexavalent Chromium Treatment by Zero Valent Iron

Date

2024-12

Author

Taşdelen, Rozeran

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Hexavalent chromium (Cr(VI)) is a toxic heavy metal used in various industries, posing risks to human health and the environment. Its reduction to less toxic trivalent chromium (Cr(III)) can be achieved through Permeable Reactive Barriers (PRBs), which are cost-effective systems for groundwater remediation. The geochemical processes governing Cr(VI) removal and the impact of secondary mineral formations on reactive media are not fully understood, and the modeling of the remediation process is still being developed. This study primarily focuses on modeling Cr(VI) removal process using ZVI with the geochemical modeling tool PHREEQC. The modeling study is based on experimental data previously published in the literature. The main objectives of this study are to: (1) develop a kinetic reaction network that includes passivation by secondary minerals, (2) examine the impact of secondary mineral formation on the reactive capacity of ZVI at different concentrations and flowrates, (3) perform a sensitivity analysis on input parameters, and (4) build prediction models to evaluate the effect of varying inlet Cr(VI) concentrations on removal performance. The results indicate that although ZVI remains in the system at the end of the simulations, its reactive surface area is fully depleted due to surface passivation and the effect of surface passivation diminishes as ZVI concentrations increase. Furthermore, the model predictions revealed that as the inlet Cr(VI) concentration increases, the remediated Pore Volumes (PVs) decrease exponentially. The results of this modeling study provide insights into the geochemical processes affecting Cr(VI) removal, which can help enhance the design of iron-based PRB applications.

Subject Keywords

Reactive Transport Modeling, Chromium (VI), Zero Valent Iron (ZVI), Permeable Reactive Barriers (PRBs)

URI

https://hdl.handle.net/11511/112942

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Graduate School of Natural and Applied Sciences, Thesis