Sorption of Trace Constituents from Aqueous Solutions onto Secondary Minerals. Ii. Radium

-Radium sorption efficiencies as a function of temperature, Ra concentration, and secondary mineral sorbate were determined in a 0.0! M NaC1 solution. Radium sorption on a characterized clinoptilolite, montmorillonite, nontronite, opal, silica gel, illite, kaolinite, and glauconite under comparable experimental conditions allowed determination of Ra sorption efficiency curves for each, through use of Freundlich constants, over the same temperature and initial Ra solution concentration range. Similar sorption data for U on the same secondary minerals over the same temperatures allowed comparison of sorption efficiencies for Ra and U. Clinoptilolite, illite, and nontronite were the most efficient Ra sorbents, while opal and silica gel were the poorest Ra sorbents. Generally, Ra sorption on secondary minerals was much greater than U sorption under the same experimental conditions. Key Words--Cation exchange, Clinoptilolite, Freundlich isotherm, Glauconite, Illite, Montmorillonite, Opal, Radium, Sorption. I N T R O D U C T I O N The separation of U from its daughter Ra 226 through migration of one or both is common in sandstone-type uranium deposits; however, little has been reported on radium sorption under comparable conditions on the same minerals. According to StaNk (1936), radium is rapidly removed from waters of low salinity by sorption on sediments, greatly limiting its migration. Titayeva and Veksler (1977) reported that lack of experimental data on the causes regulating Ra sorptiondesorption processes necessitated the use of suppositions concerning them. Granger et al. (1961) and Granger (1963) showed that Ra had migrated from the Ambrosia Lake, New Mexico, ore bodies into surrounding sandstones for distances of up to a few meters. Barite, cryptomelane, and mudstone lenses adjacent to the ore bodies were enriched in Ra 2+ which substituted for Ba 2. in the barite and for Mn z+ in the cryptomelane. From extensive sampling of Ra-contaminated groundwaters in the Grants, New Mexico, area, Kaufmann et al. (1976) found that Ra was separated from the U initially due to U milling operations and continued to migrate with the groundwater. Korner and Rose (1977) suggested that the increase of Ra with depth was due primarily to reduction of ferric hydroxides, removing a major site for radium sorption. Dyck (1978) reviewed the several factors involved in Ra migration including sorption on clays and iron and manganese oxyhydroxides. Langmuir and Cheatham (1980) reported displacement of Ra in the direction of groundwater flow at Oakville, Texas, uranium deposits. The goal of the present work was to provide experimental data to allow comparisons of the sorption efficiencies of various secondary minerals for radium and Copyright 9 1983, The Clay Minerals Society uranium under the same conditions and on the same minerals. MATERIALS A N D METHODS Characterization o f the secondary minerals Chemical analyses, cation exchange capacities, surface area measurements and X-ray diffraction results were given in Part I of this study (Ames et al., 1983), The secondary minerals used in this study are the same as those used in the above study of uranium sorption on secondary minerals.