Carbon sequestration through mineral carbonation: Using commercial FGD-gypsum from a copper smelter for sustainable waste management and environmental impact mitigation

In this study, we conducted a comprehensive examination of a commercial FGD gypsum produced in a Copper (Cu) smelter process and delved into its potential use as a Calcium (Ca)-rich material for ex-situ mineral carbonation by exploring the partitioning and fate of these metal impurities. The resulting carbonation end-product displayed a calcium carbonate (CaCO3) content of 71.1%, featuring a relatively low CO2 conversion, which may be attributed to the presence of metallic impurities in the commercial FGD-gypsum. Most of these metallic impurities, acting as inputs to the carbonation process, originate from the parent FGD-gypsum matrix. This results in an increased ionic strength within the FGD gypsum, potentially impeding the diffusion of carbon dioxide (CO2) from the gas phase to the aqueous phase. The partitioning and examination of the speciation of major, minor, and trace elements at all stages of CO2 conversion allowed us to propose four potential reaction pathways influencing carbonation efficiency: (i) the formation of metal carbonates, (ii) the production of metal oxides and oxyhydroxides, (iii) the development of metal multiform compounds, and (iv) elements deviating from the outlined patterns. Commercial FGD-gypsum is suitable for acceptance at non-hazardous waste landfills. However, it's essential to highlight that leaching values of As exceed the inert range and non-hazardous waste standards in commercial FGD-gypsum. Although most heavy metal leaching values from the carbonate end-product stay below non-hazardous limits, the release of some heavy metal leachates from the carbonate end-product may limit reuse options for these materials.

This study receives support from the European Innovation Institute (EIT) Raw Materials within the RECOPPs (Project N° 20076) framework. We would like to thank the staff of the smelter plant for their support, help, and assistance. The corresponding author also gratefully acknowledges the Ministerio de Ciencia e Innovacion for the award of the Ramón y Cajal Postdoctoral Fellowship (RYC2021-031153-I) to the corresponding author Patricia Córdoba.

Peer reviewed