Date of Award
2024
Document Type
Thesis
Publisher
Edith Cowan University
Degree Name
Masters of Engineering Science
School
School of Engineering
First Supervisor
Mehdi Khiadani
Second Supervisor
Muhammad Rizwan Azhar
Abstract
Traditional mining techniques, both open-cut and underground mining, involve high capital investments and high-energy processes, limiting the ore deposits that can be economically extracted. The extraction and processing of ore can also have a detrimental impact on the environment, both at a local and at a regional level, through biodiversity loss, changes in groundwater availability and composition, loss of biodiversity and potential impacts from the tailings storage facility (TSF) through unwanted acid mine drainage (AMD).
Approaches to reduce the potential hazards, while at the same time reducing the mining cost and thereby opening the exploitation and extraction of lower grade ore are therefore highly beneficial. In-situ recovery (ISR) offers one such mining approach, potentially promising minimal environmental repercussions and reduced mining costs.
While most copper used to be recovered from sulphide ores through smelting and refining, an increasing amount of Cu is now produced acid leaching and solvent extraction.
The study of leach processes and their efficacy is required to improve our understanding of the leaching of copper ores. The reviewed literature clearly shows the influence of parameters such as temperature, acid concentration, structural changes, and particle size on the overall Cu recovery. The focus of the thesis is on studying the effects and the extent of multiple cycles of acid leaching and cryogenic fracturing by liquid N2 (LN2) of drill core plugs, using hydrochloric acid plus ferric chloride hexahydrate as lixiviant.
In the first stage, the samples as received were leached for 35 days, with the aim of leaching all available Cu sulphide minerals. The samples were then immersed in LN2, and the porosity and permeability were assessed using a nano-permeability and porosity/permeability testing tool (CMS-300).
In the second stage, the impact of the fracturing on the availability of Cu sulphide minerals was studied in further detail, aimed at establishing the amount of additional Cu sulphide minerals that are available due to the fracturing, and the time before maximum Cu extraction can be achieved. This was applied to assess the effectiveness of subsequent cryogenic fracturing, whereby it is possible that at this stage the leaching of additional Cu minerals might be limited by localised concentration imbalance, due to the distance the leach solution needs to travel through confined spaces.
In both experimental stages, the core plugs were scanned using computed tomography (CT) after nano-permeability and porosity to analyse pore space and fracture volume. The quantity of Cu leached was analysed by inductively coupled plasma mass spectrometry/optical emission spectrometry (ICP-MS/ICP-OES).
All these techniques were used to further the understanding of the nature, composition and changes of samples B0 and B1. Physical sample parameters were also acquired, including mass, length, diameter and weight at different stages in the experimental process. LN2 aided in the creation of micro-fractures and fissures, and most likely in the expansion of veins and cracks making access of lixiviant easier to extract valuable mineral from ore samples. Cracks in the samples appear to be increased and visual pitting of the surfaces of the samples after leaching suggest that some micro-fracturing on the surface probably occurred, allowing the lixiviant to act on those grains and particles.
DOI
10.25958/g0w8-a614
Access Note
Access to this thesis is embargoed until 9 October 2025
Recommended Citation
Zapata Cordoba, N. (2024). In-situ leaching and recovery of copper from ores using cryogenic fracturing by liquid nitrogen. Edith Cowan University. https://doi.org/10.25958/g0w8-a614