Advancing Lithium Extraction from Nevada’s Sedimentary Claystones: Hydrometallurgical Pathways and Sustainability Perspectives

The global transition toward electrified transportation and renewable energy storage hasestablished lithium as a critical mineral, with demand projected to grow four- to six-fold by 2040. Conventional supply chains: brines and hard-rock spodumene, face mounting technical, environmental, and geopolitical constraints. Sedimentary lithium-bearing claystones in Nevada represent one of the most strategically important domestic alternatives, however, lithium in these deposits is generally incorporated within the octahedral layers of phyllosilicate clay minerals, principally illite, smectite, and hectorite. This structural confinement, combined with abundant acid-consuming carbonate gangue and complex mixed mineralogy, renders conventional extraction approaches technically inefficient. This dissertation presents a systematic four-study experimental investigation of lithium extraction from Nevada sedimentary claystones, advancing mechanistic understanding of mineral–reagent interactions and establishing practical pathways for efficient, selective, and sustainable process design. Firstly, sulfuric acid leaching using a design-of-experiment (DOE) framework to evaluate the effects of temperature, acid concentration, leaching time, and solid-to-liquid ratio across two mineralogically distinct Nevada claystone types, is investigated. Under optimized conditions, near-complete lithium extraction (~100%) was achieved. Kinetic analysis revealed a mixed mechanism governed by both surface chemical reaction and internal diffusion, while thermodynamic analysis confirmed that the Gibbs free energies of leaching reactions remained negative across the full temperature range investigated, establishing that sulfuric acid leaching of lithium-bearing clay minerals is thermodynamically spontaneous under practical processing conditions. Secondly, the use of organic acids as more selective alternatives to sulfuric acid, are evaluated, testing five lixiviants; oxalic, ascorbic, citric, malic, and tartaric acids, under identical conditions (1 M, 80°C, S/L = 1:10 g/mL) across three Nevada claystone types. Oxalic acid achieved lithium extraction exceeding 80% within one hour, comparable to sulfuric acid, while exhibiting superior selectivity for lithium over calcium and magnesium. Characterization of leach solutions and solid residues indicated that ion exchange, rather than bulk mineral dissolution, is the primary extraction mechanism, with silicate frameworks remaining structurally intact after leaching. Citric, malic, and tartaric acids showed meaningful but slower extraction, while ascorbic acid performed poorly. An economic assessment identified oxalic acid as the most cost-effective organic option, with the added benefit of potential reagent recovery and reuse. Next, a Na₂SO₄-assisted roasting followed by water leaching process for selective lithium extraction is investigated. Thermal treatment alone yielded only 29% lithium recovery, whereas Na₂SO₄ addition significantly enhanced extraction to over 76% under optimized conditions (800°C, 2 h, 2:1 clay-to-salt ratio). Characterization revealed that roasting induces dehydroxylation and structural breakdown of clay minerals, enabling a phase partitioning mechanism in which Na₂SO₄ promotes Li⁺–Na⁺ ion exchange and sulfation, converting structurally bound lithium to water-soluble lithium sulfate while the aluminosilicate matrix reorganizes into stable nepheline and albite. Subsequent water leaching at room temperature dissolves lithium sulfate selectively within 10 minutes. The process offers strong sustainability credentials: Na₂SO₄ can be crystallized and recycled, and the aluminosilicate leach residue exhibits pozzolanic properties suitable for valorization as a supplementary cementitious material. A step back was taken to investigate the effect of including a physical beneficiation technique before leaching. Calcite in Nevada claystones represents a major processing challenge by driving excessive acid consumption without contributing to lithium extraction. By optimizing centrifugation duration and rotational speed, a maximum of 81% lithium recovery was achieved in the clay-enriched fraction with simultaneous 82.3% calcium rejection. The beneficiated feed demonstrated approximately 14% reduction in acid consumption during subsequent leaching, validating that upstream carbonate removal translates directly to downstream reagent savings. These preliminary findings open room for further investigations. Collectively, these four studies establish that no single extraction strategy is universally optimal across the heterogeneous mineralogy of Nevada sedimentary claystones, and that a mineralogy- guided approach is required. However, among all routes investigated, Na₂SO₄ sulfation roasting followed by water leaching presents the most compelling overall performance profile, combining the highest lithium selectivity, the lowest co-dissolved impurity burden, effective thermal carbonate decomposition, rapid ambient-temperature recovery within 10 minutes, and intrinsic sustainability advantages through reagent recycling and residue valorization. Together, these contributions fill critical knowledge gaps in clay-hosted lithium processing and provide a scientifically grounded, practically oriented foundation for efficient and sustainable lithium extraction from one of the most strategically important domestic mineral resources in the United States.

Level thesis:degree_level

Doctorate Degree

Year dc:date.issued

2026

Author dc:creator

• Tita, Angela

Advisor dc:contributor.advisor

• Chu, Pengbo

Committee members dc:contributor.committeemember

• Nesbit, Carl
• Vahidi, Ehsan
• Yang, Ying
• Cantu, David

• Hydrometallurgy
• Leaching
• Lithium
• Renewable energy
• Roasting
• Sedimentary clay stones

Language dc:language.iso

en_US, English

Repository record dc:identifier.uri

https://scholarwolf.unr.edu/handle/11714/11896

OAI identifier oai:identifier

oai:scholarwolf.unr.edu:11714/11896