Kinetics of Rare Earth and Aluminum Leaching from Kaolin

Abstract

Abstract:In this paper, magnesium sulfate was used as a lixiviant to recover rare earth from kaolin. The effects of column leaching conditions, such as the concentration of magnesium sulfate, liquid/solid ratio, flow rate, and pH of the magnesium sulfate solution on the leaching efficiency of rare earth and aluminum, were investigated. In addition, the leaching kinetics of rare earth and aluminum were analyzed based on the magnesium concentration. The results showed that the optimal leaching conditions 0.2 mol/L magnesium sulfate solution with no pH adjustment, 1.2:1 for the liquid/solid ratio, and at a flow rate of 0.5 mL/min led to an 89% rare earth leaching efficiency and an 81% aluminum leaching efficiency. The aluminum leaching efficiency by magnesium sulfate was 7% less than that by ammonium sulfate. Moreover, the equilibrium time for rare earth was 33 min shorter than aluminum, which is of benefit to reduce the leaching time of aluminum. The leaching kinetic data fitted an unreacted shrinking-core model. Semi-empirical equations based on the apparent rate constant and magnesium concentration of rare earth and aluminum were established, and the reaction orders for rare earth and aluminum were determined to be 1.69 and 1.61, respectively. The results of this study could help to better understand and optimize the leaching process by magnesium sulfate.

Characteristics of Electrical Resistance Alteration during In Situ Leaching of Ion-Adsorption-Type Rare Earth Ore

“…The rare earth content of ionic rare earth ores is generally 0.05-0.2 wt.% REO [12]. It usually presents in four phases: water soluble phase, ion-exchanged phase, mineral phase, and colloidal sediment phase [13][14][15]. The ion-exchanged phase accounts for 60%-90% of the whole-phase rare earth [16,17], and the ion-exchangeable phase rare earth is adsorbed on the surface of clay minerals such as kaolin and mica in the form of hydrated cations or hydroxyl hydrated ions [18][19][20].…”

Rare earth element stripping from kaolin sands via mild acid treatment

“…Rare earth elements (REEs) are essential materials in today's energy production and IT technology. Due to their wide range of applications, such as permanent magnets, lenses, catalysts, luminescent substances, light emitting diodes, and many others, the demand for REEs is forecast to keep growing in the near future 1–4 . REEs are usually accessed and extracted under harsh conditions 5 .…”

“…The lanthanides are firmly attached in the mineral phase as fine solid particles in the crystal structure and can only be obtained by very elaborate and aggressive methods 17 . Unlike in ores, in the clay minerals, REEs can be easily obtained by ion exchange, described in detail by Hendricks et al 16,19 REEs from kaolinite are accessible via acids or salts and can be classified in the first or second category, respectively 1,15,20 …”

“…Due to their wide range of applications, such as permanent magnets, lenses, catalysts, luminescent substances, light emitting diodes, and many others, the demand for REEs is forecast to keep growing in the near future. [1][2][3][4] REEs are usually accessed and extracted under harsh conditions. 5 China is the leading producer of rare earth oxides, with an annual production of 210.000 t out of 300.000 t worldwide (2022).…”

“…17 Unlike in ores, in the clay minerals, REEs can be easily obtained by ion exchange, described in detail by Hendricks et al 16,19 REEs from kaolinite are accessible via acids or salts and can be classified in the first or second category, respectively. 1,15,20 In the leaching process, concentrated salt solutions or weak acids are most often used as leachants to obtain REEs. Accordingly, the cation of the leachant can exchange the REE cations attached between the aforementioned layers.…”