Kinetics of chlorination and microstructural changes of xenotime by carbontetrachloride

Among the rare earth minerals, fluorides, phosphates, and oxides have recei ved attention from the rare earth industry. Traditional methods of decompos ition of these minerals, usually alkaline or acid processes, involve severa l operations. Another possibility to obtain lanthanide chlorides or oxychlo rides is reacting the mineral with chlorinating agents, such as gaseous chl orine, hydrogen chloride, thionyl chloride, and carbon tetrachloride, reduc ing the operation costs and making the process less complicated. In this co ntext, we investigated the decomposition of xenotime using carbon tetrachlo ride at temperatures from 873 to 1173 K and kinetic and mechanistic studies have been performed. Powder X-ray diffraction, scanning electronic microsc opy, energy dispersive X-ray spectrometry, ultra-violet/visible spectroscop y, and thermal analysis techniques were used in this study. The results sho wed that the reaction follows the shrinking-unreacted-core model with forma tion of a product layer (lanthanide oxychloride), confirmed by powder X-ray diffraction. Moreover, microstructural changes of xenotime grains during t he chlorination reaction were verified.