Tailings (re)processing research is an opportunity for a major investment in critical metals. Discovery and testing of critical metal resources by conventional means requires many years and typically costs $10-100M for exploration surveying, drilling, logging, and testing – on a single deposit. Even then, deposits discovered may never be mined due to decade+ permitting timelines, land/water use concerns, and the $1-5B capital investment commonly required for each new mine. Assessing Arizona’s tailings-hosted critical metals resource and developing viable means of extraction thus has huge potential for savings over the cost to find (let alone extract) them, as well as mitigating tailings-related liabilities and reducing US dependence on foreign sources. With 10 sub-projects spanning discovery, characterization, extraction, and techno-economic assessment; coverage across Arizona of hundreds of copper-bearing tailing impoundments; and compilation and organization of many dimensions and perhaps a petabyte of data, this large-scale interdisciplinary project represents a massive first step toward making use of a massive (but undeveloped) potential resource.
Arizona has produced ~70 M tons of copper since large-scale mining began in the late 19th century and contains at least another 280 M tons yet to be mined. Current production is ~0.75 M tons per year, and is projected to increase in future as demand soars, potentially quadrupling by 2050. Since every ton of copper produced requires mining and processing roughly 250 tons of rock, the past century of major mining has generated an estimated 17.5 B tons of tailings (i.e., nearly 10 cubic km of finely ground, copper-depleted waste rock), with upwards of 200 M tons now added annually and more to come as more copper is mined.
Many tailings, particularly from historic mining, contain uncertain but appreciable concentrations of critical elements such as zinc, rare earths, cobalt, lithium, and others. These are both critical elements for US high-tech manufacturing (green energy, semiconductors) and can be damaging to the environment. Consequently, better treatment of historic and modern copper tailings represents an enormous opportunity to recover critical elements, while also adding value by reducing economic and environmental liabilities and mitigating associated public concerns. This challenge will only increase going forward as more copper mining produces more tailings. Finding solutions now for reprocessing existing tailings for critical mineral recovery will thus be as or more important in dealing with the much larger amounts that will be generated in coming decades. To address the large and growing copper tailings challenge, we have assembled a multidisciplinary team of experts from all three Arizona public universities, with a long history of working with Arizona mining companies on geology, metallurgy, and environmental research. In collaboration with them, our team will:
- Assess the types, volumes, fluxes, and critical/hazardous metal contents of copper tailings in the state;
- Test standard and novel/unconventional methods of recovering these critical metals by (re)processing the tailings; and
- Assess the tested methods to identify which performs best at recovering critical metals in an economically, technically, and environmentally sound manner.
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