In-situ leaching of south Texas uranium ores--part 1: laboratory studies of ore composition and leaching performance

This paper presents data on mineralogy and laboratory chemical-leaching tests for ore samples from several areas of the south Texas tertiary Catahoula formation. Optical microscope, electron microprobe, spectroscopic, X-ray diffraction (XRD), and various chemical analyses were performed. Batch screening tests gave qualitative estimates of leach rate and potential recovery. Packed column tests using hydrogen peroxide or pressurized oxygen gave more quantitative recovery estimates. The frequently friable sandstones contained highly variable amounts of quartz, feldspar, calcite, and clay, and in some cases, zeolite or mica. Clays were mainly mixed layer illite/smectite type. High cation exchange capacities (CEC's) correlated with clay (and zeolite) content, while high reducing capacities were often associated with pyrite level. Coffinite, in various environments, was the main uranium mineral. With batch tests using pseudo-first-order rate constants, ore leach rates were generally characterized as ''fast'' on a scale of fast, intermediate, and slow. However, there was variability in leach rates, both in samples from different areas and in samples taken at different depths in the same well. Fast rates and recoveries greater than 80% were observed in most column pack tests, but there was variation with leachate composition and sample source. The chemistry and kinetics of leaching are alsomore » discussed.« less