Ultrasound-assisted leaching of rare earths from the weathered crust elution-deposited ore using magnesium sulfate without ammonia-nitrogen pollution

• Published in: Ultrasonics sonochemistry Vol. 41; pp. 156 - 162
• Main Authors: Yin, Shaohua, Pei, Jiannan, Jiang, Feng, Li, Shiwei, Peng, Jinhui, Zhang, Libo, Ju, Shaohua, Srinivasakannan, Chandrasekar
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.03.2018
• Subjects: Leaching; MgSO4; Rare earths; Ultrasound leaching; MgSO4; Ultrasound leaching; Rare earths; Leaching; MgSO
• ISSN: 1350-4177; 1873-2828
• DOI: 10.1016/j.ultsonch.2017.09.028

•The optimum conditions lead to 75.5% during regular leaching.•Leaching efficiency is improved to nearly 100% by prolonging leaching with ultrasound.•Magnesium sulfate is identified as an excellent alternative leaching agent.•Ultrasonic treatment increases the leaching rate as regular leaching does. The in situ leaching process of China's unique ion-adsorption rare earth ores has caused severe environmental damages due to the use of (NH4)2SO4 solution. This study reports that magnesium sulfate (MgSO4) as a leaching agent would replace (NH4)2SO4 by ultrasonically assisted leaching to deal with the ammonia-nitrogen pollution problem and enhance leaching process. At leaching conditions of 3wt% MgSO4 concentration, 3:1L/S ratio and 30min, the total rare earth leaching efficiency reaches 75.5%. Ultrasound-assisted leaching experiments show that the leaching efficiency of rare earths is substantially increased by introducing ultrasound, and nearly completely leached out after two stage leaching process. Thus, ultrasonic-assisted leaching process with MgSO4 is not only effective but also environmentally friendly, and beneficial to leach rare earths at laboratory scale.