Extraction of lithium from spodumene

Spodumene is an important source of lithium, a key element of Li-ion batteries used in mobile communication and entertainment devices, hybrid and all electric cars and electric bikes. Spodumene forms three different crystal structures, the naturally occurred α- spodumene, and y and β-spodumene which are the products of heat treatment at 700 to 1100 °C. Among these three modifications β-spodumene proven suitable for lithium extraction processes, hence the production of these phases should be closely monitored in feed preparation stage. In order to extract lithium from spodumene, β form of the mineral goes through acid roasting with concentrated sulfuric acid at 250 °C. This method remined unchanged for almost 50 years and limited information on the details of the process and effect of key factors is available. This study will investigate the preparation of suitable spodumene phase for extraction process exploiting two different types of heating. Then focuses on traditional acid roasting of spodumene and the key factors of the process and further on proposing a less energy intense method of acid roasting using microwaves. Spodumene concentrate of the highest purity from Greenbushes Western Australia was studied for mineralogical changes with temperature in muffle furnace. The feed sample with particle size of 325 mm was heated at temperatures from 800 to 1100 °C for different durations of time and structural changes were closely monitored. At 950 °C after 30 minutes of heating γ phase appeared on the XRD spectra which detected while β-spodumene was produced, after 2 hours of heating at 1100 °C. The crystal structure altered from monoclinic α to hexagonal γ and finally tetragonal β-spodumene. Physical properties of product heated at different temperatures and times were analyzed. The significant change was related to the particle size. Conversion of α to γ-spodumene is accompanied by shrinkage of the crystal units leading to contraction of particles. Moreover, particles go through substantial expansion with formation of β-spodumene. This leads to cracking of the particles and their dispersion to smaller particles. This phenomenon directly causes the reduction in particle size which increases the specific surface of the sample. Specific gravity of the sample was constantly reduced with order of changes of the crystal structure. All these alterations positively affect the yields of lithium extraction from β over α-spodumene. As an alternative process of calcination, a sample of α-spodumene was subjected tomicrowave and hybrid microwave heating. The sample reached 98 °C after 10 minutes of microwave irradiation with power of 3 kW. This proved that spodumene is categorized in the group of non-absorbers of microwave. Next a hybrid microwave heating set up was designed which applied three SiC sticks to absorb microwave energy and conventionally heat the spodumene sample. After 32 minutes of hybrid microwave heating and temperature increase up to 643 °C a sudden increase in temperature was observed. Due to localized heat some spot of the sample heated up to the melting point of the spodumene and left sintered and/ or melted parts. This suggested that α-spodumene can start absorbing microwave at temperatures above 643 °C. The process was repeated for a sample of synthesized β-spodumene absorption of microwave energy started at 447 °C. This phenomenon made the complete conversion of the sample complicated. As the next part of this study the common method of extraction of lithium from spodumene was studied. Sample of synthesized β-spodumene was mixed with concentrated sulfuric acid and roasted at temperatures between 200 and 300 °C. This process was followed by water leaching at 50 °C for 1 hour. In addition to temperature, the effects of acid dosage and roasting time were investigated. The highest extraction of 98% was achieved after roasting at 250 °C for 1 hour with 80% excess acid to the stoichiometry of the reaction of spodumene and sulfuric acid. Elongated roasting, roasting at temperatures close to boiling point of the acid and very high amount of excess acid negatively affected Li extraction. The residue after water leach was identified as aluminium silicon hydrate (H2O.Al2O3.4SiO2). In order to reduce the energy consumption of the acid roast process application of microwave oven was proposed. Acid roasting of spodumene was replicated in benchtop microwave oven adjusted on 700 W power. Interestingly 96 % of lithium was extracted after 20 second of microwave irradiation in presence of 80% excess acid. After 30 seconds of roasting the extraction reduced and reached 49% after 4 minutes. The residue of the water leach was aluminium silicon hydrate (H2O.Al2O3.4SiO2) for roasting under 30 seconds and after 4 minutes peaks of β-spodumene appeared in the XRD pattern. More studies on the residue showed that the residue has ion exchange properties and at elevated temperatures in presence of lithium the H+ can be replaced with Li+. With slight grinding the excess acid could be reduced to 15%. The energy consumption of microwave acid roasting was 15.4 kJ which was 3 order of magnitude less than the energy consumption of conventional acid roasting. Microwave acid roasting of β-spodumene is a promising method with less energy consumption

Assessment of a spodumene ore by advanced analytical and mass spectrometry techniques to determine its amenability to processing for the extraction of lithium

A combination of analytical microscopy and mass spectrometry techniques have been used to detect and characterise different lithium minerals in a LCT-Complex spodumene-type pegmatite from Pilgangoora located in the Pilbara region of Western Australia. Information collated by these techniques can be used to predict processing amenability. Samples were categorised into three subsamples (Pil1, Pil2, Pil3) based on colour and texture having different lithologies. The mineralogy and liberation characteristics of samples were characterised using automated mineralogy techniques and the Li content and elemental distribution within minerals defined using instrumentation with secondary mass spectrometry capabilities. The majority of lithium is associated with spodumene particles with minor amounts of lithium bearing micas and beryl in the Pil1 sample, whereas in Pil2 and Pil3 spodumene is largely the lithium source. In the Pil1 sample a proportion of spodumene particles have undergone alteration with spodumene being replaced by micaceous minerals of muscovite, lepidolite and trilithionite, as well as calcite. In Pil2 and Pil3 samples the spodumene particles are generally free of mineral impurities except minor intergrowths of quartz, feldspar and spodumene are evident in the coarser fractions. Based on mineralogical observations in the current study, the majority of the main gangue minerals quartz, K feldspar and albite can be rejected at a coarse grind size of −4 mm, to recover 90% of the spodumene with Li upgrade from 0.99–1.5 wt% Li to 3.0–3.5 wt% (6.5–7.5 wt% Li 2 O). The iron content (81–1475 ppm) in the spodumene is low and therefore make these spodumene concentrates suitable for use in ceramic and glass applications. Recovery of spodumene in the coarse fractions could be improved by further particle size reduction to liberate spodumene from micas and feldspars in the middling class, which account for between 15 and 49% of the sample. However, the requirement to remove mineral impurities in the spodumene in downstream processing will be dependent on the method of processing as the presence of Li bearing micas, calcite and feldspar can be beneficial or detrimental to lithium recovery. The high content of Rb (1 wt%) and the abundance of free grains makes K feldspar a source of rubidium, particularly in the Pil3 sample which has K feldspar in high abundance (21 wt%) and can potentially be recovered by reverse flotation technique. The low concentrations of the Ta, Nb and Sn minerals identified in samples were found to be fairly well liberated and could be recovered by conventional gravity separation techniques

Mineralogical transformations of spodumene concentrate from Greenbushes, Western Australia. Part 1: Conventional heating

Spodumene is a lithium aluminium silicate which can exist in α, β and γ modifications. Phase transformations of spodumene concentrate from the beneficiation plant in Greenbushes, Western Australia, were studied under a conventional method of heating. Spodumene concentrate was heated in a muffle furnace at 800, 850, 900, 950, 1000, 1050 and 1100 °C for 10, 20, 30 and 60 min in order to evaluate the effect of temperature and heating time on the amount of α-spodumene converted to β-spodumene, and also to assess the possibility of γ-spodumene formation. Structural changes were first observed after heating at 950 °C for a minimum of 30 min. Lower temperatures or residence times did not result in evident phase change while higher temperatures or residence times increased the extent of the phase change. At 1100 °C and for times longer than 10 min, the transformation from α-spodumene to γ and β-spodumene was complete. It also resulted in volumetric expansion of the sample and change of colour from beige to ice white. X-ray diffraction spectra and scanning electron microscope images also provided evidence of γ-spodumene formation from 950 °C up to 1100 °C. Samples were analysed in order to investigate changes in their physical properties. The results revealed that specific surface is directly related to the amount of β-spodumene which forms at higher temperatures. On the other hand particle size and specific gravity reduced with formation of more β-spodumene

Production of Lithium – A Literature Review Part 1: Pretreatment of Spodumene

Among lithium minerals, spodumene contains the highest value of lithium, and therefore developing new or improving existing processes for extracting lithium from spodumene can have a significant effect in lowering the cost of lithium production. Spodumene can exist in three different polymorphs, namely alpha-, beta-, and gamma-spodumene. Studies to date confirm that alpha-spodumene, which is the naturally occurring form of spodumene, is refractory to leaching and has to be converted to a more reactive form in which lithium atoms are more accessible to the extraction reagent. So far, calcination at temperatures of around 1000 degrees C prior to extraction is the most promising approach. The calcination produces beta-spodumene as the primary polymorph and in some cases limited amounts of gamma-spodumene. In addition to calcination, microwave-assisted heating and mechanical activation can also produce phases that are more reactive. Microwave-assisted production of beta-spodumene can be achieved faster and using less energy than heating in a conventional oven. However, some challenges with this approach have been identified. Mechanical assisted processes too can lead to the formation of an amorphous phase, which is to some extent suitable for efficient lithium extraction. This article will provide details of spodumene mineralogy, an overview of current pretreatment technology, and a summary of alternative options for the activation stage of the extraction process

Production of Lithium –A Literature Review. Part 2. Extraction from Spodumene

Spodumene is the main source of lithium among the lithium-containing minerals. A number of studies have been done on the extraction of lithium from naturally occurring α-spodumene as well as pre-treated β-spodumene and the effect of key factors that influence extraction and optimum processing conditions have been discussed. Some of these methods have remained at a laboratory scale because they were not economically and operationally feasible, while some have been developed further. The increasing demand for lithium justifies efforts for the development of new methods as well as improving the existing commercial extraction processes. A comprehensive and detailed study of the available literature on lithium extraction studies is a useful starting point for this research. The present article is a review of the extraction methods of lithium from spodumene concentrate, after beneficiation, which have been studied to date

Mineralogical transformations of spodumene concentrate from Greenbushes, Western Australia. Part 2: Microwave heating

Spodumene in its natural α-spodumene modification is a refractory silicate interlocking lithium species. Therefore, in order to effectively extract the lithium, its alteration to the less densely packed β-spodumene modification is necessary. The current method used for the conversion to β-spodumene is calcination at 950–1100 °C using conventional heating. However this is an energy intensive approach. The use of microwave irradiation as an alternative, potentially less energy intensive, method of heating is examined in this work. Spodumene concentrate was obtained from Greenbushes, Western Australia, and subjected to (i) direct and (ii) hybrid microwave heating. The results showed that spodumene concentrate is transparent to direct microwave irradiation. However, using hybrid heating, to preheat the sample, it was found that once heated to above 634 °C by conventional heating, the α-spodumene irradiated with microwaves undergoes rapid localised conversion into γ- and β-spodumene, which in a matter of seconds forms a β-spodumene product in either sintered or melted form, depending on the treatment time and relative heat loss from the system. The process appears to involve an exothermic conversion of α-spodumene to γ-spodumene, followed by endothermic formation of β-spodumene. It was found that the critical temperature for microwave absorption by β-spodumene is lower than that for α-spodumene by 190 °C. Calculations of energy input suggested that the energy consumed to produce the sintered product could be much less than the energy required to convert α- to γ- and β-spodumene in a muffle furnace. These findings could help commercial plant operators and researchers to develop an industrial calcination process utilising microwave energy

Acid roasting of spodumene: Microwave vs. conventional heating

The use of microwave ovens in the acid roasting of spodumene as part of the process for lithium extraction was investigated and compared with conventional furnace heating. The effects of various key process factors were evaluated. Conventional acid roasting of 5 g of β-spodumene at 250 °C for 60 min was highly effective in extracting lithium in the presence of 80% excess concentrated sulphuric acid. The microwave process achieved nearly complete recovery of lithium with 20 s of irradiation. The potential to reduce the amount of excess acid required by grinding the sample to achieve a slight reduction in particle size was studied, and almost complete recovery was observed with only 15% excess acid. Microwave irradiation of the sample for longer than 20 s resulted in a reduction in lithium extraction, with the lowest value being 42% after 240 s of microwave irradiation. The mechanism of heating and the reverse reaction of Li + and H + were explored as possible explanations of this effect. The energy consumption of the conventional muffle furnace heating method in this study was calculated to be 10.4 MJ which was significantly greater than the microwave energy of 15.4 kJ required to achieve the same percentage of Li extraction from β-spodumene