<p>Lepidolite is highly abundant and economically valuable, rendering it a crucial resource for the extraction of rare metals, such as lithium (Li). This mineral is also a source of other elements, such as rubidium (Rb) and cesium (Cs). This paper describes the optimization of a chlorination-sulfation roasting (CSR) process for lepidolite by examining the reaction mechanisms. Thermodynamic modeling revealed that the incorporation of CaCl₂, Na₂SO₄, and carbon could significantly enhance the roasting reactivity. The optimized conditions were determined to be: lepidolite particle size less than 74&#xa0;μm, a roasting temperature of 800&#xa0;°C, a mass ratio (lepidolite:CaCl₂:Na₂SO₄:C) of 1:0.5:0.4:0.1, and a roasting time of 60&#xa0;min. Under these conditions, the leaching ratios of Li, Rb, and Cs reached 95.48%, 96.07%, and 95.14%, respectively, achieving an efficient extraction of the alkali metals. Activated Carbon was employed as an auxiliary additive, and its mechanisms in the roasting process were systematically elucidated. Mechanistic investigations demonstrated a strengthened effect when both CaCl₂ and Na₂SO₄ were used. Moreover, carbon has two functions: (1) as a heat source to decrease energy consumption, and (2) as a volatile substance to reduce leaching residue, thereby enhancing ecological friendliness. This work enhances the understanding of mixed-additive roasting and presents a promising approach for the effective and eco-friendly extraction of alkali metals from lepidolite.</p> Graphical Abstract <p></p>