A Numerical Study of Cr(VI) Emissions from Ferrochrome Slag Stockpiles for Improved Life Cycle Inventory

Ferrochrome alloy production is associated with significant environmental burdens, including the generation and management of waste slag. Improper slag management poses risks to human health, terrestrial ecosystems, and aquatic life through the leaching of heavy metals such as chromium. Life cycle assessment (LCA) is a recognized method for evaluating emissions to support holistic environmental decision-making; however, a standard methodology for assessing the impacts of heavy metal leaching is currently lacking. This study develops a model combining transport and leaching phenomena to predict pollutant release over time, enhancing LCA and informing engineering mitigation strategies. By using time dependent modeling, the study establishes a computational basis for future dynamic modeling of slag emissions in life cycle inventories, in which dynamic leaching data can inform the selection of mitigation strategies to minimize the environmental footprint of ferrochrome slag. The findings indicate that Cr(VI) leaching dynamics are governed by slag mineralogy: the rapid mobilization of highly reactive chromium phases governs short term pollution events, while the slower reaction kinetics of less reactive or matrix bound chromium contribute to long term emissions. Climatic conditions also influence leaching; wet profiles promote the reactive formation, diffusion, and advection of Cr(VI) rich effluent, while dry profiles lead to surface accumulation. Although this foundational model requires further refinement for predictive accuracy, it demonstrates the applicability of time dependent tools for estimating slag emissions. Finally, the study identifies critical experimental requirements, specifically hydraulic parameters and slag porosity, establishing the direction for future research.