Physico-Chemical Characteristics of Spodumene Concentrate and Its Thermal Transformations

Processing of End-of-Life Materials and Industrial Wastes

This Special Issue (SI) offered the opportunity to present the latest scientific developments and findings in the field of processing of end-of-life materials and solid industrial wastes. Due to the large quantity of wastes generated and to their complex elemental and mineralogical composition, the approaches, methods and processes proposed for their decontamination, energy beneficiation and high-added-value metal recovery are complex and diverse. Some transversal research investigations using wastes as remediation agents and for synthesis of new materials were also included in the SI. After a brief introduction, the main scientific contributions and findings of each article published in the SI are summarized.

Lithium deportment by size of a calcined spodumene ore

Calcination of spodumene is used to convert α-spodumene to more reactive β-spodumene, has been shown to greatly impact the physical characteristics of some of the components in the ore. This work investigates the energy efficiency of different grinding circuits used for upgrading the lithium content in the finer fraction of the calcined spodumene ore. The results showed that closed-circuit grinding resulted in 89% lithium recovery of the finest size fractions (- 0.6 mm) while open-circuit grinding led to 65% lithium recovery for the same grinding time. Closed-circuit grinding consumed lower energy than open-circuit grinding. The grade of the finest size fraction in the case of the open-circuit grinding was 1.7 times more than that in the case of the closed-circuit grinding. This work shows the potential of using different grinding modes to maximize energy efficiency and lithium deportment by size. However, it is suggested that open circuit grinding should be used for beneficiations of spodumene ores.

Effects of Continuous Infusion of Lidocaine under Ultrasound-Guided Cervical Sympathetic Ganglion Catheterization on Cerebral Hemodynamics and Thermal Imaging Characteristics of Head and Neck in Patients with Angioneurotic Headache

Angioneurotic headache is a common headache type in clinical treatment. At present, patients with nervous headache are mainly treated with oral western medicine in clinic, but it is usually difficult to obtain the ideal effect. In this study, we analyzed the effects of continuous lidocaine infusion through an ultrasound-guided cervical sympathetic ganglia (SG) catheter on cerebral hemodynamics and thermal imaging characteristics of head and neck in patients with angioneurotic headache and explored the clinical feasibility of this scheme. The results show that continuous infusion of lidocaine under ultrasound-guided SG catheterization can alleviate headache in patients with angioneurotic headache, which may be related to improving cerebral hemodynamics.

Novel extraction route of lithium from α-spodumene by dry chlorination

Processing spodumene for lithium is challenging as it requires a high temperature transformation of the natural α-monoclinic form to β-tetragonal form, usually followed by acid baking and digestion. This three-step extraction process requires significant heat energy, acid, process complexity and residence time, leading to both operating and capital costs. An approach which helps to eliminate this challenge will therefore be a milestone in processing spodumene. This study, thus, investigates a direct chlorination of α-spodumene using calcium chloride followed by water leaching of the residue to recover lithium, which reduces the energy requirement and number of unit operations. HSC Chemistry software was used to simulate the process using both phases (α and β) of the mineral up to 1100 °C prior to experimental investigation. The α-form was the only polymorph identified in residues after leaching, suggesting that the extraction is directly from the α-phase. However, an initial formation of a metastable β-form followed by a fast synthesis of lithium chloride from it is also suspected. Under optimal conditions of calcium chloride/spodumene molar ratio of 2.0, and 1000 °C treatment for 60 minutes, almost 90 percent lithium chloride was extracted and 85 percent was recovered to the leach solution with the remainder exiting with the off-gas. An apparent activation energy of about 122 ± 6 kJ mol⁻¹ was obtained at temperatures ranging from 800 to 950 °C during the process.

Processing spodumene for lithium is challenging as it requires a high temperature transformation of the natural α-monoclinic form to β-tetragonal form, usually followed by acid baking and digestion.

Multi-Technique Analytical Approach to Quantitative Analysis of Spodumene

The aim of this study was to establish the capability of X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) methods to determine different spodumene forms (α-, β- and γ-spodumene) occurring during heat treatment of lithium spodumene. It is essential to correctly identify and quantify the presence of different forms of spodumene after heat treatment to ensure optimum lithium extraction. A sample from the Haapaluoma lithium-pegmatite (western Finland) was used for this study. An experimental programme was initiated to model the progression of the mineral transformation at different stages through heat treatment. The specimen was broken down and split into five portions. One of the splits was analysed unheated with XRD, FTIR, XRF and ICP; the other four splits were analysed with XRD and FTIR after heat treatment at different temperatures from 850 to 1100 °C. In this study, we show that both laboratory-based XRD and portable FTIR methods are effective in identifying and quantifying α-, β- and ϒ-spodumene as well as impurities. The accuracy of the quantification of the minerals with XRD was established by using a mass balance calculation and was compared with the actual chemistry of the sample measured with ICP analysis. Fully quantitative XRD analysis of heat-treated spodumene is considered a challenge due to peak overlaps between the β-, and ϒ-spodumene forms, particularly when gangue minerals and amorphous content are present. The novelty of this study consists of the use of the XRD technique complemented by the Rietveld method to fully quantify the different forms of spodumene from one another: α-, β- and ϒ-spodumene, along with the gangue minerals and the amorphous content. It is also shown that reproducible systematic changes occur in the FTIR spectra that track the spodumene transformation during heat treatment. With more samples and cross-validation between the XRD results, the FTIR methodology could be developed further to provide semi-quantitative information on the different spodumene forms in the future. This would permit the use of a fast, cost-effective and portable technique for quality control of the spodumene forms, which would open opportunities across the Li value chain.