Well-characterized American Petroleum Institute clay standards, source clays from The Clay Minerals Society, and other secondary minerals were used to determine the effects of U concentration, temperature, and solution composition on U-sorption properties. Uranium concentrations ranged from about 1.00 × 10−4 M to 4.00 × 10−7 M, temperatures from 5° to 65°C and solution compositions containing 0.01 M NaCl and 0.01 M NaHCO3. Silica gel efficiently sorbed uranyl carbonate anion complexes. The higher cation-exchange capacity materials most readily sorbed uranyl ions from the 0.01 M NaCl solution. Temperature increases tended to affect uranyl ion sorption adversely except when the U was present as carbonate complexes. Noncrystalline ferric oxyhydroxides sorbed uranyl ions much more efficiently than any of the secondary crystalline minerals studied. A method for accurately extrapolating U-sorption efficiencies between experimental points based on the Freundlich equation is presented.

Radium sorption efficiencies as a function of temperature, Ra concentration, and secondary mineral sorbate were determined in a 0.01 M NaCl 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.

The sorption of U and Ra on finely ground biotite, muscovite, and phlogopite was adequately described by the Freundlich adsorption equation, (x/m) = KCn, at low U and Ra concentrations despite Ra precipitation at the higher temperature. Radium and U sorption-efficiency curves derived from the Freundlich constants generally showed decreased distribution coefficients in response to increasing temperature and increasing Ra or U concentrations. Temperatures investigated were 5°C, 25°C, and 65°C. Solution compositions used were 0.1 M NaCl and 0.01 M NaHCO, for U, and 0.01 M NaCl for Ra. Uranium initial solution concentrations ranged from 1.00 × 10−4 M to 4.00 × 10−7 M; the Ra initial solution concentration range was 6.80 × 10−7 M to 8.60 × 10−9 M.

In 0.01 M NaHCO3 solutions, anionic uranyl carbonate complexes were prevalent, and because they are weakly sorbed relative to free uranyl ion and uranyl hydroxy complexes, the result was a relatively low U sorption efficiency on biotite and phlogopite and excellent sorption efficiency on muscovite. Uranyl carbonate complexes decreased in solubility with increasing temperature, so that U sorption efficiency on biotite increased with increasing temperature. Sorption of uranyl ion and uranyl hydroxy cations on biotite decreased with incresaing temperature.

A structure refinement of kaolinite made using the Rietveld neutron profile refinement technique has given non-hydrogen atom positions which were not significantly different from those given by B. B. Zvyagin in 1960. All of the hydrogen atoms have been located; the three inner-surface hydrogen atoms are involved in interlayer hydrogen bonds with lengths of 2.95(4), 2.95(4), and 3.06(4) Å with O-H ... O angles of 168(4)°, 144(4)°, and 146(4)° respectively. The inner hydrogen atom is located in a position consistent with that found earlier in dickite and muscovite which are the only dioctahedral layer silicates studied by neutron diffraction to date. The O-H vector makes an angle of 34° with the (001) plane, away from the octahedral sheet, and the projection of the vector on to (001) is at ~30° to the b axis.

The crystal structure of kaolinite(Pl, a = 5.153(1), b = 8.941 (1), c = 7.403 (1)Å, α = 91.692(3)°, β = 104.860(3)°, γ = 89.822(3)°, specimens from Keokuk geodes) has been refined in detail and that of dickite (Cc, a = 5.1460(3), b = 8.9376(5), c = 14.4244(6) Å, β = 96.761(5)°) has been re-refined, both from powder diffraction data with the Rietveld method. Except for the hydrogen atoms, the layer structures in both clays are very similar and are much as inferred or determined previously by others. The rotation in the tetrahedral sheet is 7(1)°. The two inner hydroxyl O-H bonds in kaolinite are differently oriented; one points into an octahedral vacancy and the other somewhat away from the octahedral sheet and toward the unoccupied center of an oxygen triangle formed by the two apical oxygens and shared basal oxygen of two adjacent SiO4 tetrahedra. All six of the inner surface hydrogen atoms appear to be nearly equally involved in the hydrogen bonding between kaolinite layers in kaolinite.

A model based on Gouy-Chapman theory, describing the ion exchange behavior of clays in mixed electrolyte solutions is presented. Computed ionic distributions, taking into account variations in relative permittivity, ion activity, and closeness of approach of ions to clay surfaces, are compared with experimental data for smectite and kaolinite in contact with river and saline waters. To obtain reasonable agreement between theoretical prediction and observation the most important extension of Gouy-Chapman theory involves the introduction of a closeness of approach term. Furthermore, the aggregated nature of smectites plays an important part in controlling its exchange properties, whereas a fixed-charge model provides a poor description for the ion exchange properties of kaolinite.

Synthetic aluminous hematites and goethites have been examined by Fourier-transform infrared spectroscopy. For aluminous hematites prepared at 950°C a linear relationship exists between Al content and the location of the band near 470 cm−1, up to 10 mole % Al substitution which is shown to be the solubility limit. The spectra of aluminous goethites prepared in two different ways are qualitatively similar to each other, but differ as to the relationship between the position of the band near 900 cm−1 and the Al content. The spectra of the two series of hematites produced by calcining the goethites at 590°C also show a strong dependence of band position and intensity on the goethite preparative method.

Clay minerals and zeolites, candidate backfill minerals for nuclear waste repositories, were treated with saturated NaCl brine and Mg-rich (Mg-Ca-Na-K) brine at 200°C and 300°C for 4 weeks under a confining pressure of 30 MPa. The Al concentrations released in NaCl brine were lower than those in Mg-rich brine at both temperatures indicating that the Mg-rich brine is more acidic than the NaCl brine under these hydrothermal conditions. The Si concentrations in both brines were low because of the relatively acidic conditions developed during the hydrothermal treatment. As determined by X-ray powder diffraction or by specific Cs and Sr sorption measurements, no alteration could be detected in clay minerals treated with NaCl brine at 200°C. Among the zeolites tested, only phillipsite and erionite altered to analcime in NaCl brine at 200°C. Zeolites and most of the clay minerals tested did not alter in the Mg-rich brine treated at 200°C. Vermiculite altered to randomly interstratified vermiculite/K-vermiculite (mica-like) by selective K uptake from the Mg-rich brine.

At 300°C, the clay minerals did not greatly alter, whereas the zeolites altered to analcime and/or albite in the presence of the NaCl brine. In the Mg-rich brine, Al-rich montmorillonite from Wyoming did not alter, whereas Al-poor montmorillonite from Texas altered to randomly interstratified montmorillonite/ illite at 300°C. Vermiculite collapsed to form K-vermiculite (~ 10.2 Å) by the selective uptake of K from the Mg-rich brine at 300°C. Most of the zeolites altered to smectites in the Mg-rich brine at 300°C because of the acidic conditions generated by the hydrolysis of Mg. The selective Cs-sorption Kd decreased from 11,700 for untreated phillipsite to 240 and 15 for the hydrothermally produced analcime/albite mixtures from the phillipsite at 200° and 300°C, respectively, in NaCl brine. These results suggest that montmorillonites and mordenites are relatively more resistant than vermiculite or other zeolites at elevated temperatures and pressures in concentrated hydrothermal brines expected in a salt repository.