Kinetics and Mechanism of Lithium Extraction from α-Spodumene in Potassium Hydroxide Solution

Lithium extraction from α-spodumene in a potassium hydroxide solution was proposed to provide a new green metallurgical process for spodumene concentrate. The structure of α-spodumene could be destroyed directly by a KOH solution, and new solid-phase products of Li2SiO3 and KAlSiO4 were generated simultaneously. The total lithium extraction efficiency could reach 89.9%, of which 84.1% was converted into Li2SiO3 and 5.8% converted into the liquid phase under optimal conditions: initial KOH concentration of 50 wt %, stirring speed of 500 rpm, mass ratio of KOH/ore of 2:1, leaching temperature of 523.15 K, and leaching time of 16 h. The experimental data fitted well with the Avrami–Erofeev equation model, –ln(1 – X) = (Kt)n. The apparent activation energy and Avrami index were calculated as 106.37 kJ·mol–1 and 0.80, respectively.