An interview with Prof. Valérie Cappuyns over her work in EXCEED and the corresponding results published in Science of The Total Environment, Metal(loid) mobility, solid-phase speciation and in vitro bioaccessibility in European hard-rock lithium (Li) deposits (read article here).

1. Prof. Cappuyns, thank you for agreeing to this interview. You are professor  in the Department of Economics and for your research you collaborate with the Department of Geology at KU Leuven. What’s your research background? And can you provide an overview of your research focus?​

I am a Bio-Engineer in Environmental Technology, with  a PhD degree in Geology (from KU Leuven) with a dissertation on heavy metal leaching behavior from overbank sediments and associated soils. My research focuses on (1) environmental geochemistry (understanding the occurrence and behavior of (trace) elements in resources, waste materials, soils, etc), and (2) the sustainable management of contaminated sites (environmental and social impacts of different options to remediate and rehabilitate contaminated sites).

2. You are also involved in the EU Horizon Europe EXCEED project. Can you tell us about your involvement and your role in the project?

I am involved in Work Package 6 of the EXCEED project, in which I evaluate the solid-phase speciation of the metal(loid)s, their leaching under different conditions, and in different materials produced  during tailings reprocessing.

In the same work package, colleagues from the Technical University of Crete are performing a lifecycle assessment and Techno-Economic Assessment of the main flowsheets for Lithium-Cesium-Tentalum-pegmatites (LCT-pegmetites) and Rare-Metal Granites (RMGs).

3. How do the environmental concerns associated with hard-rock lithium mining compare to those of other lithium extraction methods, such as from brine sources?

Several studies conclude that lithium extraction from brines has a lower environmental impact than lithium from hard-rock lithium mining (e.g. Gao et al., 2023¹; Mousavinezhad et al., 2025² . However, these studies don’t take into account the development of processing technologies with a lower environmental impact (which are also investigated in the framework of the EXCEED Project). Moreover, Li extraction from brines also comes with a significant environmental impact (Krishnan and Gopan, 2024³).

But this was not the scope of the present paper, that’s why I’m only referring to some recently published papers where this was assessed.

4. Your recent EXCEED publication studies the mobility of metal(loids)s and bioaccessibility in 3 European Li mine projects. What is the significance of this study?​

This was the first study on the mobility, solid-phase speciation, and bioaccessibility of metal(loid)s in ore and tailing samples from these major European Li deposits which intend to initiate production in the near future.

The focus of this study was on the occurrence of trace elements in Li-containing rocks and processing residues. We identified minor minerals (occurring in low amounts) with significant concentrations of metal(loid)s such as arsenopyrite chalcopyrite, chromite and sphalerite, but also minerals found in high proportions like biotite, muscovite, and fluorapatite where metal(loid)s are found in trace amounts. Overall, metalloid concentrations ware low, but the detailed mineralogical analyses helped to unravel the metal(loid)s solid-phase speciation (i.e.: in which minerals are the metal(loid)s concentrated and explain the origins of metal(loid) mobility and bioaccessibility.

5. Can you briefly describe the techniques and analytical methods employed to assess metal(loid) mobility and speciation in these lithium deposits?​

• Solid-phase characterization:
  • Chemical composition: near-total elemental concentrations, determined with ICP-MS after 4 acid digestion of solid samples;
  • mineralogical composition, using techniques including SEM-EDS, XRD, LA-ICP-MS, and thermodynamic simulations (PHREEQC).
• Leaching tests:
  • characterization leaching tests (pH-dependence tests) assess the release of elements in relation to possible management options (e.g., recycling, treatment) or to the environment and health impacts.
  • We also applied compliance leaching tests (Toxicity Characteristic Leaching Procedure (TCLP)(US EPA, 1992)⁴ and EN 12457–2(CEN, 2002)⁵
  • Human health-risk assessment is based on a bio-accessibility test.

6. Your study addresses the mobility and bioaccessibility of metal(loid)s in hard-rock lithium deposits. Could you discuss which elements are of particular concern and why?

The results of this study show that although some tailing samples from lithium mines contain relatively high levels of elements such as As, Cr, Ni, and Zn, leaching tests simulating environmental weathering indicate low mobility for most of them, falling below the reference thresholds. Lithium, on the other hand, exhibits higher mobility: up to ~62 mg/kg in TCLP, Toxicity characteristic leaching procedure set by US EPA, likely due to the greater alterability of Li minerals. While there are no official EPA guidelines yet for lithium in TCLP leachates, though the measured values in this study fall within an estimated safety range (20-120 mg/kg)⁶.

7. How do the results of this study inform our understanding of the environmental behavior and potential risks of these metal(loid)s?

The results of the bioaccessibility test were used to calculate the human health risks from the exposure to tailings materials. This is just a preliminary screening, not a full human health risk assessment. However, the approach followed in this study provides an insight into the solid-phase speciation of metal(loid)s and explains the origins of their mobility and bioaccessibility.

For the evaluation of the calculated hazard quotients for Li, only provisional values about the chronic reference dose are available. Insufficient data are available on the effects to humans of acute, sub- chronic, or chronic inhalation exposure to Li. Limited information is also available on potential carcinogenic effects of Li exposure; some studies even point to a possible protective effect against certain cancers.

8. What strategies or technologies do you recommend to mitigate the environmental impact of metal(loid) mobility in hard-rock lithium mining operations?

The bottom line is that effective waste management strategies must be applied by mining companies to ensure that metal(loid)s do not migrate into the environment and pose no risks to human health. The valorisation of side streams, such as the use of (cleaned) tailings in cement should also be considered.

9. How can interdisciplinary collaboration contribute to addressing the environmental challenges identified in your study?

It is essential do address environmental impact in an independent and transparent way, adhering to the highest standards. To better assess the effects of Li mining on human health and the environment (e.g. also biodiversity, landscape), collaboration is needed between different disciplines : geologists, environmental scientists, toxicologists, experts in ecology,, etc. Public concern over environmental effects should also be addressed and for this we need people that know how to communicate with different stakeholders.

References:

1. Gao, N. Fan, W. Chen, T. Dai (2023). Lithium extraction from hard rock lithium ores (spodumene, lepidolite, zinnwaldite, petalite): technology, resources, environment and cost. China Geol., 6 (2023), p. 137-153, 10.31035/CG2022088

2. Mousavinezhad, S., Fahimi, A., Sharifian, S., & Vahidi, E. (2025). Sustainable lithium production from sedimentary rock deposits: Carbon reduction and EV synergies. In Resources, Conservation and Recycling (Vol. 218, p. 108271). Elsevier BV. https://doi.org/10.1016/j.resconrec.2025.108271

3. R. Krishnan, G. Gopan. A comprehensive review of lithium extraction: from historical perspectives to emerging technologies, storage, and environmental considerations. Clean. Eng. Technol., 20 (Jun. 2024), Article 100749, 10.1016/j.clet.2024.100749

4. US EPA, 1992. Method 1311 Toxicity Characteristic Leaching Procedure (Report). U.S, Environmental Protection Agency (EPA), Washington, DC

5. CEN, 2002. EN 12457–2, Characterization of Waste, Compliance Test for Leaching of Granular Wastes Materials and Sludges, Part 2: One Stage Batch Test at a Liquid to Solid Ratio of 10 L kg^-1 for Materials with Particle Size below 4 Mm (without or with Size Reduction). European Committee of Standardization

6. Norman, J.E., Toccalino, P.L., Morman, S.A., 2018. Health-based screening levels for evaluating water-quality data. US Geological Survey 2018. Lindsey, B.D., Belitz, K., Cravotta III, C.A., Toccalino, P.L., Dubrovksy, N.M., 2021. Lithium in groundwater used for drinking-water supply in the United States. Sci. Total Environ. 767, 144691.

SIM² KU Leuven is the KU Leuven Institute for Sustainable Metals and Minerals. It is one of the official KU Leuven Institutes that were endorsed by the KU Leuven Academic Council. SIM² has more than 370 members, coming from a wide range of (interdisciplinary) research groups and departments at KU Leuven. SIM²’s missions is “to develop, organise & implement problem-driven, science-deep research & future-oriented education, contributing to the environmentally friendly production & recycling of metals, minerals & engineered materials, supporting (…) a climate-friendly, circular-economy”.

Check here other EXCEED publications: EXCEED journal articles , conference abstracts/papers.

Photo credits (of Prof. Cappuyns) by Elisabeth De Decker.