An extended X-ray absorption fine structure spectroscopy investigation of cadmium sorption on cryptomelane (KMn8O16)

The mobility of cadmium in the environment is strongly inhibited by sorption onto Fe and Mn (hydr)oxide minerals such as cryptomelane (KMn8O16). Adsorption experiments showed that cryptomelane was able to sorb two thirds of available cadmium from solution at pH as low as 2.0. Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy was used to determine whether cadmium had sorbed to the external surfaces of the mineral, or migrated into the ∼4.6 A diameter tunnels which exist in the cryptomelane structure. The Mn coordination environment around sorbed cadmium (4.9±1.0 Mn at 3.65±0.02 A) at pH 2.0 strongly indicates that the majority of sorbed cadmium is located inside the tunnels, and that it is displaced from the ideal tunnel cation position (special position 2a (0, 0, 0)). The oxygen coordination environment around cadmium (6.5±1.3 O at 2.24±0.02 A) is consistent with this conclusion, but also suggests that sorbed cadmium is partially hydrated. The dominant tunnel cation (K+) was not significantly released to solution during cadmium sorption. Thus, it seems likely that cadmium exchanged with H+ in the tunnels rather than K+. This is supported by the lowering of pH during cadmium adsorption and corresponding charge balance calculations. Cadmium sorption at the tunnel sites is likely to be energetically favourable because it allows occupation of those tunnel sites which K+ cannot fill, thus resulting in a more effective balancing of the negative structural charge in cryptomelane. This is the first EXAFS study of cation sorption on a mineral with the hollandite structure.

[1]  R. Burns.  The uptake of cobalt into ferromanganese nodules, soils, and synthetic manganese (IV) oxides , 1976 .

[2]  A. Byström,et al.  The crystal structure of hollandite, the related manganese oxide minerals, and α-MnO2 , 1950 .

[3]  J. Dixon,et al.  Transformation of Synthetic Birnessite to Cryptomelane: An Electron Microscopic Study , 1986 .

[4]  S. Gurman.  The small-atom approximation in EXAFS and surface EXAFS , 1988 .

[5]  J. Dillard,et al.  The mechanisms of Co(II) oxidation on synthetic birnessite , 1983 .

[6]  H. Aly,et al.  Separation of uranium from thorium on cryptomelane-type hydrous manganese dioxide , 1993 .

[7]  W. David,et al.  Alpha manganese dioxide for lithium batteries: A structural and electrochemical study , 1992 .

[8]  S. Suib,et al.  Studies of Stability and Reactivity of Synthetic Cryptomelane-like Manganese Oxide Octahedral Molecular Sieves , 1994 .

[9]  R. Strange,et al.  Constrained and restrained refinement in EXAFS data analysis with curved wave theory. , 1992, Biochemistry.

[10]  A. Manceau,et al.  Crystal chemistry of cobalt and nickel in lithiophorite and asbolane from New Caledonia , 1987 .

[11]  R. Mckenzie,et al.  The Surface Charge on Manganese Dioxides , 1981 .

[12]  H. Aly,et al.  SORPTION BEHAVIOUR OF URANIUM AND THORIUM ON CRYPTOMELANE-TYPE HYDROUS MANGANESE DIOXIDE FROM AQUEOUS SOLUTION , 1993 .

[13]  R. D. Shannon.  Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides , 1976 .

[14]  Edward A. Boyle,et al.  Variability of dissolved trace metals in the mississippi river , 1987 .

[15]  P. Renne,et al.  Age and Duration of Weathering by 40K-40Ar and 40Ar/39Ar Analysis of Potassium-Manganese Oxides , 1992, Science.

[16]  N. Binsted,et al.  A rapid, exact, curved-wave theory for EXAFS calculations. II. The multiple-scattering contributions , 1986 .

[17]  R. Pattrick,et al.  Mineralogical and textural evolution of the economic manganese mineralisation in western Rhodope massif, N. Greece , 1991, Mineralogical Magazine.

[18]  N. Binsted,et al.  A rapid, exact curved-wave theory for EXAFS calculations , 1984 .

[19]  A. Manceau,et al.  Structure of Mn and Fe oxides and oxyhydroxides: A topological approach by EXAFS , 1988 .

[20]  P. Schindler,et al.  Structure and Stability of Cd2+ Surface Complexes on Ferric Oxides , 1994 .

[21]  R. W. Joyner,et al.  Some applications of statistical tests in analysis of EXAFS and SEXAFS data , 1987 .

[22]  Konrad B. Krauskopf,et al.  Factors controlling the concentrations of thirteen rare metals in sea-water , 1956 .

[23]  S. Komarneni,et al.  Powder x-ray diffraction study of a cryptomelane-type manganic acid and its alkali cation exchanged forms , 1993 .

[24]  D. Nahon,et al.  Estimated solubility products and fields of stability for cryptomelane, nsutite, birnessite, and lithiophorite based on natural lateritic weathering sequences , 1989 .

[25]  S. Komarneni,et al.  Selective exchange of divalent transition metal ions in cryptomelane-type manganic acid with tunnel structure , 1993 .

[26]  A. E. Ringwood,et al.  The structure and chemistry of a barium titanate hollandite‐type phase , 1980 .

[27]  D. Bish,et al.  Rietveld refinement of the coronadite structure , 1989 .

[28]  G. Rossman,et al.  The tetravalent manganese oxides: identification, hydration, and structural relationships by infrared spectroscopy , 1979 .

[29]  C. C. Chen,et al.  Transformation of Birnessite to Buserite, Todorokite, and Manganite under Mild Hydrothermal Treatment , 1987 .

[30]  R. Mckenzie.  The sorption of some heavy metals by the lower oxides of manganese , 1972 .

[31]  R. Mckenzie.  The adsorption of lead and other heavy metals on oxides of manganese and iron , 1980 .

[32]  Douglas G. Brookins,et al.  Eh-PH diagrams for geochemistry , 1988 .

[33]  R. Mckenzie,et al.  The synthesis of birnessite, cryptomelane, and some other oxides and hydroxides of manganese , 1971, Mineralogical Magazine.

[34]  R. Mckenzie.  The reaction of cobalt with manganese dioxide minerals. , 1970 .

[35]  H. Miura.  The crystal structure of hollandite , 1986 .

[36]  B. Hamelin,et al.  A geochronological 40Ar/39Ar and 87Rb/87Sr study of K-Mn oxides from the weathering sequence of Azul, Brazil , 1996 .

[37]  M. Hayes,et al.  The chemistry of soil constituents. , 1978 .

[38]  D. Bish,et al.  Fracture-lining manganese oxide minerals in silicic tuff, Yucca Mountain, Nevada, U.S.A. , 1993 .

[39]  J. Ostwald.  Genesis and paragenesis of the tetravalent manganese oxides of the Australian continent , 1992 .

[40]  D. Cox,et al.  Statistical significance tests. , 1982, British journal of clinical pharmacology.

[41]  C. C. Chen,et al.  Ion Exchange, Thermal Transformations, and Oxidizing Properties of Birnessite , 1986 .

[42]  H. J. Lippolt,et al.  40Ar/39Ar ages of Precambrian manganese ore minerals from Sweden, India and Morocco , 1995 .

[43]  M. Cadee,et al.  Barium tin chromium oxide, a new hollandite phase , 1978 .

[44]  S. Llorca,et al.  Supergene cobalt minerals from New Caledonia , 1991 .

[45]  C. Laurent,et al.  Structure, formation, and reactivity of hydrous oxide particles; insights from X-ray absorption spectroscopy , 1992 .

[46]  D. Fuerstenau,et al.  The effect of crystal structure on the surface properties of a series of manganese dioxides , 1966 .

[47]  S. Gurman,et al.  XAFS Analysis using EXCURV90 , 1991 .

[48]  Q. Feng,et al.  Alkali Metal Ions Insertion/Extraction Reactions with Hollandite-Type Manganese Oxide in the Aqueous Phase , 1995 .

[49]  S Turner,et al.  Manganese Oxide Tunnel Structures and Their Intergrowths , 1979, Science.

[50]  P. Renne,et al.  Direct dating of weathering phenomena by 40Ar39Ar and K-Ar analysis of supergene K-Mn oxides , 1994 .

[51]  Edward J. Neth,et al.  Synthesis and characterization of octahedral molecular sieves (OMS-2) having the hollandite structure , 1994 .

[52]  R. Gadde,et al.  Heavy metal adsorption by hydrous iron and manganese oxides , 1974 .

[53]  J. Post,et al.  Modeling tunnel-cation displacements in hollandites using structure-energy calculations , 1986 .

[54]  R. Gibbs,et al.  Hydrous FE and MN oxides — scavengers of heavy metals in the aquatic environment , 1984 .

[55]  M. Tsuji,et al.  Synthetic inorganic ion-exchange materials. XXXVIII: Acid-base properties of a cryptomelane-type hydrous manganese(IV) oxide and some chromatographic applications , 1985 .

[56]  Gordon E. Brown,et al.  X-ray absorption spectroscopy; applications in mineralogy and geochemistry , 1988 .

[57]  A. Manceau,et al.  Structural chemistry of Mn, Fe, Co, and Ni in manganese hydrous oxides; Part II, information from EXAFS spectroscopy and electron and X-ray diffraction , 1992 .

[58]  E. Fanchon,et al.  The structure of K1.33Mn8O16 and cation ordering in hollandite-type structures , 1986 .

[59]  A. I. Gorshkov,et al.  Iron and manganese oxide minerals in soils , 1981, Transactions of the Royal Society of Edinburgh: Earth Sciences.

[60]  P. Buseck,et al.  Symmetry and cation displacements in hollandites : structure refinements of hollandite cryptomelane and priderite , 1982 .

[61]  P. Buseck,et al.  Characterization of Cu in lithiophorite from a banded Mn ore , 1990 .

[62]  A. Chivas,et al.  Isotopic dating of supergene manganese oxides from the Groote Eylandt Deposit, Northern Territory, Australia , 1996 .