Purification of K-feldspar leaching solution using anti-solvent crystallization
Sina Shakibania1, Lena Sundqvist-Öqvist1, Jan Rosenkranz1, Yousef Ghorbani2
1Division of Minerals and Metallurgical Engineering, Department of Civil, Environmental and Natural Resources Engineering, Luleå University of Technology, Luleå, Sweden
2University of Lincoln, Joseph Banks Laboratories, Green Lane, Lincoln, Lincolnshire LN6 7DL- United Kingdom
Abstract: Hydrometallurgical recovery of metallic components of feldspar minerals is often overlooked due to their high dissolution resistance. In this study, as part of our EU project (POTASSIAL), it is suggested to leach mechanically activated feldspar in hydrochloric acid. This approach results in the complete dissolution of K, Al, Na, and Fe from feldspar. The complete dissolution of Na and Fe provides significant challenges for the production KCl and Al2O3 considering their similar physical and chemical separation behaviors. The preset work assesses applying the anti-solvent crystallization method for the leaching solutions with the aim to produce high-purity potash (KCl). Accordingly, separation and purification of the leaching solution using the anti-solvent method was practiced. Initially, screening experiments were carried out on a synthetic leaching solution with the aim of analyzing the crystallization behavior of key components. Screening experiments were performed using five different anti-solvents, namely methanol, ethanol, acetone, 2-propanol, and ethylene glycol. It appeared that acetone and 2-propanol are the viable options for crystallizing potassium. The effect of anti-solvent ratio and time on potassium crystallization was investigated. The results showed that the effectiveness of acetone and 2-propanol as anti-solvents was comparable. Both acetone and 2-propanol were able to recover approximately 68% of the potassium from the leaching solution. The final potash product had a purity of over 99.9%. Acetone produced cubic crystals with particle sizes ranging from 4 to 10 microns, while 2-propanol produced cubic crystals with particle sizes ranging from 3 to 5 microns.
Keywords: K-feldspar; potash; alumina; precipitation; anti-solvent crystallization