Bethany Hughes, MSc

The global demand for metals such as copper (Cu) and cobalt (Co), driven by industrialisation and the energy transition, has intensified environmental challenges associated with mining. In particular, the Zambian Copperbelt generates significant quantities of smelter slag tailings, a waste by-product from copper extraction, which pose risks such as acid mine drainage (AMD) and land degradation. This study investigates the potential of these tailings for carbon capture and storage (CCS) through mineral carbonation, offering a novel approach to mitigating greenhouse gas (GHG) emissions while enhancing sustainable waste management.

The research focuses on slag samples from two key sites in the Copperbelt: The Black Mountain Slag Heap in Kitwe and the Mopani Tailings Storage Facility. By characterising the mineralogical and geochemical properties of these materials, the study explores their ability to sequester atmospheric CO₂. A heap leaching experiment will be conducted, utilising both acidic and neutral conditions to simulate environmental scenarios and assess carbonation kinetics. Post-leaching analyses will identify changes in mineral phases and assess metal recovery potential, while water chemistry will be evaluated to monitor cation and anion mobilisation. PHREEQC modelling will further examine the risk of AMD and other by-products.

This project addresses a critical gap in the literature, as the CCS potential of Cu-Co smelter slag remains largely unexplored compared to ultramafic and mafic mine tailings. The study's findings will provide valuable insights into the efficiency of slag in CCS relative to other industrial by-products, contributing to a circular economy framework by repositioning slag as a resource rather than waste. Moreover, the research will support sustainable mining practices in the Zambian Copperbelt and similar regions, promoting environmental stewardship while meeting the rising demand for critical metals.

By integrating innovative methodologies with a focus on environmental and economic sustainability, this study lays the groundwork for further exploration of CCS in industrial waste streams. Its outcomes will inform policy and industrial strategies, emphasising the role of mining by-products in addressing global climate challenges.