China Nonferrous Metallurgy

After the treatment of lepidolite concentrate by sulfate roasting-water leaching method, the water leaching solution contains a large amount of impurity elements such as calcium, magnesium, potassium and sodium. This study focuses on the leachate from a lithium mica smelting enterprise in Hunan Province, employing a chemical precipitation method for impurity removal. It examines two approaches: directly removing impurities with sodium carbonate and adding sodium carbonate after adjusting the pH with calcium oxide or sodium hydroxide. The effects of calcium oxide dosage, sodium carbonate dosage, reaction time, reaction temperature, and the method of adding removal agents on the impurity removal efficiency were investigated, leading to the following main conclusions. When impurities were removed directly using sodium carbonate at twice of the theoretical dosage, the calcium ion content was reduced to 21.4mg/L, the magnesium ion content was reduced to 43.3mg/L, and the lithium loss rate was 6.6%. When removing impurities by adding sodium carbonate after adjusting the pH, the pH of the leachate was primarily adjusted to 11.63, followed by continuous stirring at room temperature for 1 hour before solid-liquid separation. Then, 20% sodium carbonate solution with dosage of 1.5 times of theoretical amount was added to the pH-adjusted liquid, and after stirring at 90℃ for 1 hour and performing solid-liquid separation, the calcium ion content was reduced to 12.8mg/L, the magnesium ion concentration fell below 0.1mg/L, and the lithium loss rate was 2.1%. The stepwise filtration method proposed in this paper, involving adjusting the pH before using sodium carbonate for impurity removal from lithium mica leachate, demonstrates advantages of effective impurity removal, low lithium loss rate, and low cost, providing a reference for the optimization of lithium extraction processes in similar enterprises.