High-Temperature Chlorination of Rhodium Using Alkali-Metal and Alkaline-Earth-Metal Chlorides

Abstract This study was aimed at investigating an effective chlorination method for Rh and its oxide to develop an efficient Rh extraction process. The feasibility of using alkali-metal and alkaline-earth-metal chlorides (NaCl, KCl, MgCl 2 , and CaCl 2 ) as chlorinating agents was evaluated from the perspective of thermodynamics; the prediction results revealed MgCl 2 as a suitable agent for chlorinating metallic Rh and Rh 2 O 3 in an oxygen-containing atmosphere. The thermodynamic analysis results were then experimentally validated. Metallic Rh converted to RhCl 3 when mixed with MgCl 2 and heated at 973 K (700 °C) in an O 2 atmosphere. The Rh 2 O 3 powder was efficiently chlorinated when reacted with liquid MgCl 2 at 1073 K (800 °C) in an Ar–1 pct O 2 atmosphere. Therefore, the chlorination of Rh using MgCl 2 is feasible; its use has potential to make the extraction and recovery of Rh from various raw materials more efficient. Graphical Abstract