Experimental investigation of Li-phosphate replacement by apatite
The transition to green and renewable energy and the associated requirement for energy storage solutions drive the current increase in lithium demand. Lithium is predominantly mined from saline brines in South America and spodumene-bearing pegmatites, with Western Australia currently being the world’s most active producer. Li brine mining involves evaporation of the liquid with typical concentrations of few 100 μg g-1, whereas hard rock mining of Lirich spodumene (>3.7 wt.% Li) requires energy intensive extraction methods with concentrated acids. However, used Li ion batteries (LIBs) typically contain 5-7 wt.% Li as phosphate compounds and have been identified as additional Li resource that has thus far received surprisingly little attention. The reason for the relatively limited efforts to recycle Li from LIBs is the limited information available about subsequent processing of the Li3PO4 (Song & Zhao, 2018; Sep.& Pur. Tech.).
The proposed project will contribute to closing this knowledge gap by experimentally investigating the replacement of Li3PO4 (and optionally LiFe2+PO4) by apatite (Ca3(PO4)2). The rationale behind this approach is the much lower solubility of apatite (~20 mg L-1 at 20°C) compared to Li-phosphate (~370 mg L-1 at 20°C), suggesting that apatite precipitation is favourable and will release Li into the fluid from where it can be precipitated as LiCO3 for further processing. The anticipated project outcomes are the rate constant and activation energy of the Li- to Ca-apatite replacement reaction, required for temperature extrapolation in e.g. industrial application.
Proposed course plan during the master's degree (60 ECTS):
GEOV241 Microscopy (10 pts)
GEOV242 Igneous and metamorphic petrology (10pts)
GEOV243 Environmental geochemistry (10pts)
GEOV251 Advanced Structural Geology (10 pts)
GEOV300 Selected Topics in Geoscience (5 pts)
GEOV342 The geochemical toolbox (10 pts)
GEOV370 The energy transition: status, challenges and opportunities (5 pts)
The student should have a keen interest in laboratory and analytical work and be comfortable with handling small quantities (< 20 mL) of mild acidic and/or basic fluids. Personal protective equipment (PPE) and detailed instructions will be provided.
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Experiments will be conducted in available, simple, closed system batch reactors at three different temperatures (e.g. 100, 150 and 200°C) and for different durations in Ca-bearing reactive fluid. Reaction progress will be determined on recovered solids by X-ray diffractometry (XRD). This will provide the necessary data to calculate rate constants and activation energies using the time-to-a-given-fraction method. Fluid Li and Ca concentrations will be quantified by ICPOES (optical emission spectrometry) and solid reaction products will be characterized by scanning electron microscopy (SEM) and laser Raman spectroscopy.