Bimessite

Depending on the synthesis route, a combination of Mn(IV)/Mn(IIl) or Mn(IV)/ Mn(II) is found in birnessite (BR). For example, the mean oxidation state of manganese in sol-gel materials and classical BR (prepared from Stahli s method) varies in the range 3.6 Z 3.8. In the case of sol-gel birnessite (SG-BR) and Co-doped sol-gel birnessite (SGCo-BR) [37], we have a mixture of Mn(IV) and Mn 

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Both Swinkels et al. [7] and Chabre and Pannetier [9] described the process of EMD reduction as three overlapping processes. Recently Donne et al. reported [9] that the presence of Bi (OH)3 on the EMD surface modified the discharge curve considerably and the rechargeability was increased. Formation of the bimessite structure from EMD and Bi (OH), or Bi203 (mechanically mixed with EMD) [11] is the cause of the increase in rechargeability. 

Arsenite can be oxidized by manganese dioxides in soils. The rate constants for the depletion of As(III) by bimessite and cryptomelane are much higher than those by pyrolusite due to the difference in the crystallinity and specific surfaces of the Mn oxides (Oscarson et al., 1983). The ability of the Mn dioxides to sorb As(III) and As(V) is related to the specific surface and the point-of-zero charge of the oxides. The one-to-one relationship between the amount of As(III) depleted and the amount of As(V) appearing in solution was reported by Oscarson and colleagues (1983). 

Cobalt is strongly adsorbed by Mn oxides. There are close relationships between Co and the easily reducible fraction of Mn (Mn oxides) in soils (Jarvis, 1984) and will be in detail discussed in next chapter. Cobalt is frequently accumulated in Mn nodules in soils (Mckenzie, 1975). It was suggested that the Co2+ ion was first sorbed, then slowly oxidized to Co3+ and became incorporated into the surface layers of the crystal lattice, releasing the Mn2+ ion into the solution (Bums, 1976 Mckenzie, 1975). X-ray photoelectron spectroscopy showed that Co3+ was present on the surface of bimessite after the sorption of the Co2+ ions took place (Murray and Dillard, 1979). Traina and Donor (1985) suggested that the Mn release during Co2+ sorption resulted not only from the oxidation of Co2+ to Co3+, but also... 

Franger, S., Bach, S., Farcy, J., Pereira-Ramos, J.-P, Baffler, N., Synthesis, structural and electrochemical characterization of the sol-gel bimessite Mnj 840,6H2O, J. Power Sources 109, 344-348 (2001). 

Johnson KJ, Cygan RT, Fein JB (2006) Molecular simulations of metal adsorption to bacteria surfaces. Geochim Cosmochim Acta 70 5075-5088 Jokic A, Frenkel AI, Vairavamurthy MA, Huang PM (2001) Bimessite catalysis of the Maillard reaction and its significance in natural humification. Geophys Res Lett 28 3899-3902... 

Naidja A, Liu C, Huang PM (2002) Formation of protein-bimessite complex XRD, FTIR, and AFM analysis. J Colloid Interface Sci 251 46-56... 

Toumassat C, Chartel L, Bosbach D, Manceau A (2002) Arsenic (III) oxidation by bimessite and precipitation of manganese (II) arsenate. Environ Sci Technol 36 493-500... 

Scott MJ, Morgan JJ. 1995. Reactions on oxide surfaces. 1. Oxidation of As(III) by synthetic bimessite. Environmental Science and Technology 29 1898-1905. 

Figure 21. Visible absorption spectra for a 1.6-/

Power et al. (2005) show the effeet of pH and initial As(III) coneentration on the kineties of arsenite oxidation at bimessite-water interfaees, when a competitive metal (e.g., Zn) is present in an adsorbed or nonadsorbed state (Fig. 16.5). Two well-defined trends in the As(III) oxidation reactions can be distinguished (1) the extent of As(III) oxidation decreases with increasing pH from 4.5 to 6.0 and (2) oxidation on a percent basis is suppressed with increasing initial As(III) concentration from 100 to 300 dM. The pH effects on As(III) oxidation may have been influenced by competitive adsorption reactions between As(III) and reaction products (e.g., Mn(II)) and were not influenced by arsenic solution speciation. The suppressed As(III) oxidation rate constant may be a result of differences in the amount of Mn(II) release, which compete with dissolved As(III) species for unreacted Mn(IV) surface sites, and of Mn(II) adsorption, which inhibit the reaction between As(III) and Mn(IV) surface sites. 

Fig. 16.5 Percent of dissolved As(lll), As(V)(3,j, and adsorbed As during As(III) oxidation kinetics on bimessite (suspension density 0.1 g Lin 0.01 M NaCl, and atmosphere) as a function of pH and initial As(lll) concentration, [As(lll)].. (a) pH 4.5, [As(lll)]. = lOOpM (b) pH 4.5, [As(III)]. = 300pM (c) pH 6.0, [As(lll)]. = lOOpM (d) pH 6.0, [As(lll)]. = 300pM. Reprinted with permission from Power LE, Arai Y, Sparks DL (2005) Zinc adsorption effect on arsenite oxidation kinetics at the bimessite water interface. Environ Sci Technol 39 181-187. Copyright 2005 American Chemical Society...

PAsl00ph45 refers to 100pM of Zn presorbed prior to the 100 J,M As(III) addition at pH 4.5, and SAslOOphb refers to the simultaneous 100 J,M Zu/lOOpM As(III) addition at pH 6.0. Even though adsorbed Zn was present in the system, As(III) readily oxidized over time. However, Power et al. (2005) suggest that Zn is likely to form inner-sphere complexes on bimessite surfaces and chemisorbed Zn ions inhibit electron-transfer reactions. When Zn was present, As(in) oxidation was further suppressed by nonadsorbed and preadsorbed Zn, compared to the control system, but the preadsorbed system was more effective in interfering with electron-transfer reactions. 

Timms P, MacRae IC (1982) Conversion of fensulfothion by klebsiella-pneumoniae to fensul-fothion sulfide and its accumulation. Australian J Biological Sciences 35 661-667 Tournassat C, Charlet L, Bosbach D, Manceau A (2002) Arsenic (III) oxidation by bimessite and precipitation of manganese (II) arsenate. Environ Sci Technol 36 493-500 Wahid PA, Ramakrishna C, Sethunathan N (1980) Instantaneous degradation of parathion in anaerobic soUs. J Environ Qual 9 127-130... 

There has been some recent criticism of the Maillard reaction as a possible humification pathway (Burdon, 2001 Sutton and Sposito, 2005 von Liitzow et al., 2006). First, the critics argue that the Maillard reaction results in the formation of heterocyclic N, whereas soil N consists primarily of amide N based on 15N CPMAS NMR (Knicker and Liidemann, 1995 Knicker, 2004) studies. However, Jokic et al. (2004a) clearly showed, using N K-edge XANES, that the Maillard reaction catalyzed by bimessite under ambient temperature conditions and environmentally relevant pH not only produces heterocyclic N but also a significant amount of amide N (Figure 2.8). 

Wang, M. C., and Huang, P. M. (1997). Catalytic power of bimessite in abiotic formation of humic polycondensates from glycine and pyrogallol. In The Role of Humic Substances in the Ecosystems and in Environmental Protection, Proceedings, 8th Conference of the International Humic Substances Society, Drozl, J., Gonet, S. S., Senesi, N., and Webber, J., eds., Wroclaw, Poland, pp. 59-65. 

Most of the Mn(IV) oxide minerals listed in table 8.3 occur in weathered continental rocks, and often constitute important manganese ore deposits. However, several of the minerals, notably todorokite, bimessite, vemadite and, perhaps, buserite and asbolane, are major constituents of seafloor hydrothermal crusts near spreading centres and in manganese nodule deposits. 

Post, J. E. Veblen, D. R. (1990) Crystal structure determinations of synthetic sodium, magnesium, and potassium bimessite using TEM and the Rietveld method. Amer. Mineral., 75, 477-89. 

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