Thermodynamic Analysis of Rare Earth Chlorination and Bromination Processes

Research funded by the Army Research Laboratory (ARL), the Metallurgical and Materials Engineering Department at Montana Tech investigated various methods of extracting and refining rare earth elements (REEs) from mineral ores and concentrates. Extensive thermodynamic, thermogravimetric and differential thermal analyses were performed to evaluate the relative stabilities of various REE compounds in order to assess potential methods for selective separation and recovery of specific REEs. Conversion of rare earth oxides (REO) to rare earth chlorides or bromides is a possible initial step in pyrometallurgical and hydrometallurgical processing of REEs. REO can be converted to chlorides or bromides by roasting in the presence of a chloridizing or bromidizing reactant. (e.g. NH4Cl and NH4Br).

Analysis of Sampling Data

A Similar Exposure Group (SEG) can be created through the evaluation of workers performing the same or similar task, hazards they are exposed to, frequency and duration of their exposures, engineering controls available during their operations, personal protective equipment used, and exposure data. For this report, the samples of one facility that has collected nearly 40,000 various types of samples will be evaluated to determine if the creation of a SEG can be supported. The data will be reviewed for consistency with collection methods and laboratory detection limits. A subset of the samples may be selected based on the review. Data will also be statistically evaluated in order to determine whether the data is sufficient to terminate the sampling. IHDataAnalyst V1.27 will be used to assess the data. This program uses Bayesian Analysis to assist in making determinations. The 95 percent confidence interval will be calculated and evaluated in making decisions. This evaluation will be used to determine if a SEG can be created for any of the workers and determine the need for future sample collection. The data and evaluation presented in this report have been selected and evaluated specifically for the purposes of this project.