# Roasting Extraction of Lithium from Fly Ash: A Study of Influential Parameters and Mechanisms
## 1 Introduction  
Lithium has received wide attention due to its widespread applications in renewable energy and electric vehicles [1]. It is often referred to by various known names, such as the \"yeast of industry\", \"aerospace alloy\", \"white oil\", and \"the most promising metal of the 21 st century\" [2, 3, 4]. With the global shift in energy structures, it plays an increasingly significant role in human society [5]. Lithium batteries, known for their long life cycle, high energy density, low self-discharge rate, and environmentally friendly characteristics, are widely used in portable electronic devices, electric vehicles, and consumer electronics such as mobile phones. This extensive use has led to substantial consumption of lithium resources [6, 7]. As global demand for renewable and clean energy technologies grows, the strategic value of lithium has become more prominent [8]. With increasing awareness of global energy, research into alternative lithium sources has become particularly crucial. Among various potential lithium resources, the mineral-rich composition of fly ash, especially its lithium content, has attracted growing interest from researchers. Coal fly ash, a by-product of coal combustion in thermal power plants, is one of the most complex and abundant of anthropogenic materials [9]. Studies have shown that a high alumina-coal fly ash sample contains a high lithium concentration, approximately 250-1400 \(\mu\)g/g (Li\({}_{2}\)O content: 0.06-0.30 wt%) [10], making its recovery and utilization feasible and valuable. Furthermore, it facilitates the alleviation of the pressure associated with environmental pollution remediation. Today, coal-fired power generation produces over 500 million tons of fly ash annually worldwide, yet only 25% to 30% is repurposed in various industries [11; 12]. Currently, coal remains the most crucial energy resource for the foreseeable future in China [13]. Guizhou Province, one of China's primary coal production bases, hosts numerous thermal power plants [14]. As coal consumption continues to rise, the production of fly ash is also steadily increasing. Efficient extraction of lithium from fly ash could not only mitigate its environmental impact but also provide new momentum for the sustainable development of the local economy. The primary source of lithium products in China is hard rock lithium ores [15]. The common extraction methods for lithium from these ores include the sulfate method, sulfuric acid method, limestone sintering method, chlorination roasting method, soda pressure cooking method, and hydrofluoric acid method [16]. However, 59% of the world's lithium reserves are stored in salt lake brines [17]. Despite the low extraction cost, the presence of numerous impurities in salt lake brines makes extraction difficult [18]. Consequently, numerous researchers have conducted in-depth and comprehensive analyses of the occurrence and extraction of lithium in fly ash. In the studies on the occurrence of lithium in fly ash, [PERSON] et al. [19] used Time of Flight Secondary Ion Mass Spectrometry to analyze the distribution of lithium, aluminum, and silicon in micro-regions of the coal samples from the Antaibao No. 11 coal seam. They found that lithium-enriched areas coincided with aluminum and silicon enrichment, indicating that aluminosilicate minerals are the primary hosts of lithium. [PERSON] et al. [20] discovered that in those fly ash samples that contain a higher alumina content, lithium is predominantly enriched in the amorphous aluminosilicate phase. [PERSON] [21] emphasized the unique distribution of the lithium in these fly ash samples using time-of-flight secondary ion mass spectrometry analysis, revealing that lithium is primarily concentrated in the glass phase of fly ash. These studies have significantly improved the understanding of lithium's occurrence, laying a foundation for its subsequent extraction. In terms of lithium extraction from fly ash, [PERSON] [22] conducted a detailed comparison between acidic and alkaline roasting.