Advancing green mining : integrating sustainable water and tailings management in the copper mining industry

Abstract

Nowadays, the extensive requirement for high-tech products, developing societies based on hyper-connectivity, and deploying low-carbon energies are causing a substantial increase in demand for various critical minerals and metals. However, their demand is not consequence-free and entails higher water, energy, and material consumption, increasing the probability of generating environmental impacts. In this context, implementing circular economy principles to improve the sustainability of mining and mineral processing is a strategic development priority.

The primary goal of this dissertation is to develop a comprehensive set of strategies and methods to evaluate the efficient management of energy, water, and waste in mining operations. The novelty of this study lies in its holistic approach, which integrates technical, economic, and environmental perspectives to apply circular economy principles, thereby improving the sustainability of mining operations and mineral processing.

Regarding water management, the proposed strategy is to use raw seawater, hypersaline water, or waste brine for mineral processing. We analyze the thermodynamic stability of varied copper-bearing species in saline solutions by constructing Pourbaix diagrams. The results show that chlorinated-based solutions enhance the extraction of copper species, decrease acid consumption, and oxidizing reagents, thereby reducing pollution in leaching operations. This approach reduces continental water consumption, mitigating water scarcity and minimizing the ecological footprint. The study's contribution is a method for predicting the behavior of metallic species when leached with saline solutions at varied salinity levels using Pourbaix diagrams.

To improve mining waste management, we assess the use of mine tailings for carbon dioxide sequestration and the recovery of critical materials. By applying the TOPSIS method and sensitivity analysis, we display that the mineral carbonation process is a viable solution for addressing tailings generation and mitigating carbon dioxide emissions. Meanwhile, using dimensional analysis and similarity theory, we find that recovering valuable elements from tailings helps meet the high demand for critical materials, decreases the volume of discards, lowers overall costs, and reduces primary ore consumption. The work provides an appropriate guide for decision-makers interested in projects addressing pollution from mine tailings and carbon dioxide emissions.

Finally, we designed an integrated seawater pumped-hydro reverse osmosis system to supply freshwater and clean energy for mining operations. The methodological approach includes design equations and cost models to identify the optimal component sizes and determine the levelized costs and greenhouse gas emissions of this system. It enables continuous 24-hour renewable energy production, reduces continental water consumption and greenhouse gas emissions, and minimizes the impact of brine ocean disposal. The primary contribution of this work is a universal model for determining the operating conditions and the cost of implementing this technology in coastal areas worldwide.

In summary, this study introduces a set of strategies and methods to advance the sustainability of the mining sector. The implementation of these options aims to serve as a guide for mining operations and a strategic opportunity for improvement, as mining operations need to reinvent themselves to ensure their long-term viability and thus pave the way toward greener mining practices.