| Abstract Scope |
Ionic clays (an important resource for rare earth elements (REEs)) are formed by natural weathering of REE-bearing minerals and adsorption of liberated REEs onto the clay surface. Most ionic clays around the world including those from southern China mainly contain light REEs. Here, a unique ionic clay from south America which is rich in heavy REEs, including dysprosium (Dy), is used as the feed. A desorption process using ammonium sulfate as the lixiviant is developed. The effect of operating parameters including lixiviant concentration, pH, liquid to solid ratio, temperature, and time is investigated and optimum conditions are determined. The characterization results show that this ionic clay comprises three modes of REEs, including ion exchanged REEs physically adsorbed on the surface, hydrolyzed REEs chemically adsorbed on the surface, and mineralized (non-desorbable) REEs within the clay. Mechanistic investigations show REE desorption/adsorption is controlled by the pH and sulfate ions in the system. |