Recovery of magnesium and potassium from biotite by sulfuric acid leaching and alkali precipitation with ammonia

• Published in: Hydrometallurgy 2015-10, Vol.157, p.188-193
• Main Authors: Luo, Zheng, Yang, Jing, Ma, Hongwen, Liu, Meitang, Ma, Xi
• Format: Article
• Language: English
• Subjects: Ammonium–potassium sulfate; Biotite; Magnesium hydroxide; Recovery
• ISSN: 0304-386X; 1879-1158
• DOI: 10.1016/j.hydromet.2015.08.018

A process for the recovery of magnesium (Mg) and potassium (K) from biotite was developed using sulfuric acid leaching and precipitation with ammonia. The optimum conditions for dissolution of biotite were found to be sulfuric acid solution of 2.5mol/L, sulfuric acid/biotite ratio of 4mL/g, leaching temperature of 90°C and leaching time of 2h. Under these conditions, the leaching efficiency of Mg and K was found to be 95.8% and 94.9% respectively. By using the solubility differences of corresponding elements, a two-step precipitation process was applied to remove Fe and Al and recovery of Mg. Subsequently, magnesium hydroxide was prepared by precipitation from the leach solution with ammonia as the precipitant. X-ray diffraction (XRD) and scanning electron microscope (SEM) analyses showed that the high purity Mg(OH)2 existed in the form of flower-like spherical aggregation. Furthermore, the final solution of ammonium–potassium sulfate can be used for agricultural compound fertilizer. •We present a new process for recovery of Mg and K from biotite.•The parameters which affect the leaching efficiencies of biotite have been discussed.•The optimum separation conditions for Mg and K were investigated.•Mg(OH)2 with flower-like morphology and ammonium–potassium sulfate were prepared.