Todorokite

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Xionghan Feng - One of the best experts on this subject based on the ideXlab platform.

  • transformation of co containing birnessite to Todorokite effect of co on the transformation and implications for co mobility
    Geochimica et Cosmochimica Acta, 2019
    Co-Authors: Zhongkuan Wu, Caroline L Peacock, Bruno Lanson, Lirong Zheng, Zhongjun Chen, Xionghan Feng
    Abstract:

    Abstract The mobility and fate of bioessential transition metals, such as Ni and Co, are strongly controlled by their association with phyllomanganate minerals such as birnessite. These minerals however, can transform to tectomanganates such as Todorokite during soil and sediment diagenesis, yet the mobility and fate of most metals during the transformation process remain largely unknown. Here this research investigates the effect of Co on, and the mobility and fate of Co during the transformation of birnessite into tunnel structure minerals. A range of Co-containing birnessite precursors with up to 16.9 % Co/(Co + Mn) molar ratios were synthesised, and subsequently transformed via a mild reflux procedure designed to mimic the diagenesis of these layered precursors into tunnel structures. The layered precursors and reflux products were characterized using a combination of mineralogical and geochemical techniques, including powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), high resolution transmission electron microscopy (HRTEM) and extended X-ray absorption fine structure (EXAFS) spectroscopy. The results show that Co(III) is structurally incorporated into the layered precursors and reflux products, through the isomorphic substitution of Mn(III). The structural incorporation of Co(III) into the layered precursors leads to an overall reduction of Jahn-Teller distorted Mn(III) octahedra in these minerals, a key factor for their transformation to tunnel structures. As a consequence, the presence of such structural Co(III) disrupts the transformation of birnessite into Todorokite, leading to the coexistence of 9.6 A asbolane-like phyllomanganate and non-ideal 3 × n, or a-disordered, Todorokite-like tectomanganates in the transformation products. Newly formed Todorokite exhibits a wide range of 3 × n tunnel dimensions (n up to 13) and a plate-like morphology. Overall the structural incorporation of non Jahn-Teller distorted cations like Co(III) into birnessite might help explain the often observed predominance of phyllomanganates over tectomanganates in soils and sediments, and the persistence of phyllomanganates in ferromanganese deposits that can be many millions of years old. The results also indicate that Co(III) initially associated with birnessite is retained in the solid phase during transformation, and thus the mobility of Co(III) is limited. EXAFS data suggest that Co is mainly located in the octahedral layers of asbolane-like phyllomanganate and at non-edge sites in non-ideal Todorokite. Overall the transformation of Co-containing birnessite into non-ideal Todorokite and asbolane-like layered structures maintains the strong sequestration of Co by Mn oxides.

  • formation of Todorokite from c disordered h birnessites the roles of average manganese oxidation state and interlayer cations
    Geochemical Transactions, 2015
    Co-Authors: Huaiyan Zhao, Fan Liu, Wenfeng Tan, Xinran Liang, Hui Yin, Guohong Qiu, Xionghan Feng
    Abstract:

    Todorokite, a 3 × 3 tectomanganate, is one of three main manganese oxide minerals in marine nodules and can be used as an active MnO6 octahedral molecular sieve. The formation of Todorokite is closely associated with the poorly crystalline phyllomanganates in nature. However, the effect of the preparative parameters on the transformation of “c-disordered” H+-birnessites, analogue to natural phyllomanganates, into Todorokite has not yet been explored. Synthesis of “c-disordered” H+-birnessites with different average manganese oxidation states (AOS) was performed by controlling the MnO4 −/Mn2+ ratio in low-concentrated NaOH or KOH media. Further transformation to Todorokite, using “c-disordered” H+-birnessites pre-exchanged with Na+ or K+ or not before exchange with Mg2+, was conducted under reflux conditions to investigate the effects of Mn AOS and interlayer cations. The results show that all of these “c-disordered” H+-birnessites exhibit hexagonal layer symmetry and can be transformed into Todorokite to different extents. “c-disordered” H+-birnessite without pre-exchange treatment contains lower levels of Na/K and is preferably transformed into ramsdellite with a smaller 1 × 2 tunnel structure rather than Todorokite. Na+ pre-exchange, i.e. to form Na-H-birnessite, greatly enhances transformation into Todorokite, whereas K+ pre-exchange, i.e. to form K-H-birnessite, inhibits the transformation. This is because the interlayer K+ of birnessite cannot be completely exchanged with Mg2+, which restrains the formation of tunnel “walls” with 1 nm in length. When the Mn AOS values of Na-H-birnessite increase from 3.58 to 3.74, the rate and extent of the transformation sharply decrease, indicating that a key process is Mn(III) species migration from layer into interlayer to form the tunnel structure during Todorokite formation. Structural Mn(III), together with the content and type of interlayer metal ions, plays a crucial role in the transformation of “c-disordered” H+-birnessites with hexagonal symmetry into Todorokite. This provides further explanation for the common occurrence of Todorokite in the hydrothermal ocean environment, where is usually enriched in large metal ions such as Mg, Ca, Ni, Co and etc. These results have significant implications for exploring the origin and formation process of Todorokite in various geochemical settings and promoting the practical application of Todorokite in many fields. Graphical abstract XRD patterns of Mg2+-exchanged and reflux treatment products for the synthetic “c-disordered” H+-birnessites.

  • oxidation process of dissolvable sulfide by synthesized Todorokite in aqueous systems
    Journal of Hazardous Materials, 2015
    Co-Authors: Tianyu Gao, Xionghan Feng, Fan Liu, Wenfeng Tan, Ying Shi, Yashan Zhang, Guohong Qiu
    Abstract:

    Abstract Todorokite, formed from Mn(II) in supergene environments, can affect the transformation and migration of dissolvable sulfides in soils and water. In this work, Todorokite was synthesized with different degrees of crystallinity, and the redox mechanism of dissolvable sulfide and Todorokite was studied in both closed and open aqueous systems. The influences of pH, temperature, crystallinity, the amount of manganese oxides, and oxygen gas on S2− oxidation process were investigated. It is found that S2− was oxidized to S0, SO32−, S2O32− and SO42−, and about 90% of S2− was converted into S0 in closed systems. The participation of oxygen facilitated the further oxidation of S0 to S2O32−. S0 and S2O32− were formed with the conversion rates of S2− about 45.3% and 38.4% after 1 h of reaction, respectively, and the conversion rate for S2O32− increased as reaction prolonged for a longer period. In addition, Todorokite was reduced to Mn(OH)2 in the presence of nitrogen gas, and its chemical stability increased when oxygen gas was admitted into the reaction system during the process. The oxidation rate of dissolvable sulfide followed a pseudo-first-order kinetic law in the initial stage (within 10 min), and the initial oxidation rate constant of S2− increased with elevating temperature, increasing the quantity and decreasing crystallinity of Todorokite. The initial oxidation rate of dissolvable sulfide decreased with continuous feeding of O2 into the test solution, possibly due to a decrease in active Mn(III) content in Todorokite. The present work demonstrates the redox behaviors and kinetics of dissolvable sulfide and Todorokite in aquatic environments.

  • effect of cobalt doped framework on formation of Todorokite from layered manganese oxides with mg2 co2 ions as template
    Pedosphere, 2011
    Co-Authors: Wenfeng Tan, Fan Liu, Haojie Cui, Xionghan Feng
    Abstract:

    Abstract Cobalt (Co) exists in significant quantities in naturally occurring manganese (Mn) oxides and alters the growth of Mn oxide crystals. Four-layered Mn oxides, Na-buserite (Na-bus) and three Co-doped Na-buserite samples prepared from oxidation of Mn(OH) 2 with 5%, 10%, and 20% Co/(Mn + Co) molar ratios (5Co-Na-bus, 10Co-Na-bus, and 20Co-Na-bus), were used to prepare Todorokite, a common Mn oxide on the Earth's surface, using Mg 2+ /Co 2+ ions as a template. The results showed that Todorokites could be obtained by reflux treatment of Mg 2+ -exchanged non-doped Na-buserite and three Co-doped Na-buserites at atmospheric pressure. However, the formation of Todorokites was prohibited by reflux treatment of Co 2+ -exchanged Na-bus, 5Co-Na-bus, and 10Co-Na-bus samples. Instead, Todorokite was obtained by the reflux treatment of Co 2+ -exchanged 20Co-Na-bus samples under atmospheric pressure. X-ray photoelectron spectroscopy analysis showed that doped Co existed as Co 3+ in the MnO 6 layers of doped Na-buserites. The amount of substituted Co 3+ in the MnO 6 layers may play a key role in the conversion of buserite to Todorokite using Co 2+ ions as a template.

  • aging promotes Todorokite formation from layered manganese oxide at near surface conditions
    Journal of Soils and Sediments, 2010
    Co-Authors: Xionghan Feng, Fan Liu, Wenfeng Tan, Haojie Cui, Ming Kuang Wang
    Abstract:

    Todorokite is one common manganese oxide in soils and sediments and is commonly formed from layered Na-buserite. Aging processes can alter the physicochemical properties of freshly formed Na-buserite in natural environments. However, it is not clear whether and how aging affects the formation of Todorokites. In the present paper, Na-buserite with aging treatment was employed to prepare Todorokite at atmospheric pressure to investigate the effects of aging treatment of Na-buserite on the formation of Todorokite. Four aged Na-buserite samples, which are produced through oxidation of Mn2+ in concentrated NaOH medium by O2 with aging for 3, 6, 9, and 12 months, were employed to investigate the effects of aging processes on the transformation from Na-buserite to Todorokite by Mg2+-templating reaction at atmospheric pressure. The manganese oxides were examined using X-ray diffraction (XRD), elemental analysis, determinations of the average manganese oxidation number, infrared spectroscopy (IR), and transmission electron microscopy (TEM). The XRD, IR, and elemental analyses indicate that aging treatment can alter the substructure of the freshly synthesized Na-buserite. During the aging process, some of the Mn(III) may migrate into the interlayer region or disproportionate to form Mn2+ and Mn4+ from the layer of Na-buserite and the concomitant formation of layer vacancies. The interlayer Mn3+ or Mn2+ occupied above or below the layer vacancy sites and become corner-sharing octahedral. XRD analyses and TEM clearly show that the transformation from Na-buserite to Todorokite was promoted by aging treatments. The alterations of substructure of aged Na-buserites can promote the rearrangement of manganese to construct a tunnel structure during the transformation from layered manganese oxides to tunnel-structure Todorokite at atmospheric pressure. The transformation from Na-buserite to Todorokite was promoted by aging treatments at atmospheric pressure, and it is more suitable to explore the origination of natural Todorokite in Earth surface environments using aged layered manganese oxides.

Fan Liu - One of the best experts on this subject based on the ideXlab platform.

  • formation of Todorokite from c disordered h birnessites the roles of average manganese oxidation state and interlayer cations
    Geochemical Transactions, 2015
    Co-Authors: Huaiyan Zhao, Fan Liu, Wenfeng Tan, Xinran Liang, Hui Yin, Guohong Qiu, Xionghan Feng
    Abstract:

    Todorokite, a 3 × 3 tectomanganate, is one of three main manganese oxide minerals in marine nodules and can be used as an active MnO6 octahedral molecular sieve. The formation of Todorokite is closely associated with the poorly crystalline phyllomanganates in nature. However, the effect of the preparative parameters on the transformation of “c-disordered” H+-birnessites, analogue to natural phyllomanganates, into Todorokite has not yet been explored. Synthesis of “c-disordered” H+-birnessites with different average manganese oxidation states (AOS) was performed by controlling the MnO4 −/Mn2+ ratio in low-concentrated NaOH or KOH media. Further transformation to Todorokite, using “c-disordered” H+-birnessites pre-exchanged with Na+ or K+ or not before exchange with Mg2+, was conducted under reflux conditions to investigate the effects of Mn AOS and interlayer cations. The results show that all of these “c-disordered” H+-birnessites exhibit hexagonal layer symmetry and can be transformed into Todorokite to different extents. “c-disordered” H+-birnessite without pre-exchange treatment contains lower levels of Na/K and is preferably transformed into ramsdellite with a smaller 1 × 2 tunnel structure rather than Todorokite. Na+ pre-exchange, i.e. to form Na-H-birnessite, greatly enhances transformation into Todorokite, whereas K+ pre-exchange, i.e. to form K-H-birnessite, inhibits the transformation. This is because the interlayer K+ of birnessite cannot be completely exchanged with Mg2+, which restrains the formation of tunnel “walls” with 1 nm in length. When the Mn AOS values of Na-H-birnessite increase from 3.58 to 3.74, the rate and extent of the transformation sharply decrease, indicating that a key process is Mn(III) species migration from layer into interlayer to form the tunnel structure during Todorokite formation. Structural Mn(III), together with the content and type of interlayer metal ions, plays a crucial role in the transformation of “c-disordered” H+-birnessites with hexagonal symmetry into Todorokite. This provides further explanation for the common occurrence of Todorokite in the hydrothermal ocean environment, where is usually enriched in large metal ions such as Mg, Ca, Ni, Co and etc. These results have significant implications for exploring the origin and formation process of Todorokite in various geochemical settings and promoting the practical application of Todorokite in many fields. Graphical abstract XRD patterns of Mg2+-exchanged and reflux treatment products for the synthetic “c-disordered” H+-birnessites.

  • oxidation process of dissolvable sulfide by synthesized Todorokite in aqueous systems
    Journal of Hazardous Materials, 2015
    Co-Authors: Tianyu Gao, Xionghan Feng, Fan Liu, Wenfeng Tan, Ying Shi, Yashan Zhang, Guohong Qiu
    Abstract:

    Abstract Todorokite, formed from Mn(II) in supergene environments, can affect the transformation and migration of dissolvable sulfides in soils and water. In this work, Todorokite was synthesized with different degrees of crystallinity, and the redox mechanism of dissolvable sulfide and Todorokite was studied in both closed and open aqueous systems. The influences of pH, temperature, crystallinity, the amount of manganese oxides, and oxygen gas on S2− oxidation process were investigated. It is found that S2− was oxidized to S0, SO32−, S2O32− and SO42−, and about 90% of S2− was converted into S0 in closed systems. The participation of oxygen facilitated the further oxidation of S0 to S2O32−. S0 and S2O32− were formed with the conversion rates of S2− about 45.3% and 38.4% after 1 h of reaction, respectively, and the conversion rate for S2O32− increased as reaction prolonged for a longer period. In addition, Todorokite was reduced to Mn(OH)2 in the presence of nitrogen gas, and its chemical stability increased when oxygen gas was admitted into the reaction system during the process. The oxidation rate of dissolvable sulfide followed a pseudo-first-order kinetic law in the initial stage (within 10 min), and the initial oxidation rate constant of S2− increased with elevating temperature, increasing the quantity and decreasing crystallinity of Todorokite. The initial oxidation rate of dissolvable sulfide decreased with continuous feeding of O2 into the test solution, possibly due to a decrease in active Mn(III) content in Todorokite. The present work demonstrates the redox behaviors and kinetics of dissolvable sulfide and Todorokite in aquatic environments.

  • effect of cobalt doped framework on formation of Todorokite from layered manganese oxides with mg2 co2 ions as template
    Pedosphere, 2011
    Co-Authors: Wenfeng Tan, Fan Liu, Haojie Cui, Xionghan Feng
    Abstract:

    Abstract Cobalt (Co) exists in significant quantities in naturally occurring manganese (Mn) oxides and alters the growth of Mn oxide crystals. Four-layered Mn oxides, Na-buserite (Na-bus) and three Co-doped Na-buserite samples prepared from oxidation of Mn(OH) 2 with 5%, 10%, and 20% Co/(Mn + Co) molar ratios (5Co-Na-bus, 10Co-Na-bus, and 20Co-Na-bus), were used to prepare Todorokite, a common Mn oxide on the Earth's surface, using Mg 2+ /Co 2+ ions as a template. The results showed that Todorokites could be obtained by reflux treatment of Mg 2+ -exchanged non-doped Na-buserite and three Co-doped Na-buserites at atmospheric pressure. However, the formation of Todorokites was prohibited by reflux treatment of Co 2+ -exchanged Na-bus, 5Co-Na-bus, and 10Co-Na-bus samples. Instead, Todorokite was obtained by the reflux treatment of Co 2+ -exchanged 20Co-Na-bus samples under atmospheric pressure. X-ray photoelectron spectroscopy analysis showed that doped Co existed as Co 3+ in the MnO 6 layers of doped Na-buserites. The amount of substituted Co 3+ in the MnO 6 layers may play a key role in the conversion of buserite to Todorokite using Co 2+ ions as a template.

  • aging promotes Todorokite formation from layered manganese oxide at near surface conditions
    Journal of Soils and Sediments, 2010
    Co-Authors: Xionghan Feng, Fan Liu, Wenfeng Tan, Haojie Cui, Ming Kuang Wang
    Abstract:

    Todorokite is one common manganese oxide in soils and sediments and is commonly formed from layered Na-buserite. Aging processes can alter the physicochemical properties of freshly formed Na-buserite in natural environments. However, it is not clear whether and how aging affects the formation of Todorokites. In the present paper, Na-buserite with aging treatment was employed to prepare Todorokite at atmospheric pressure to investigate the effects of aging treatment of Na-buserite on the formation of Todorokite. Four aged Na-buserite samples, which are produced through oxidation of Mn2+ in concentrated NaOH medium by O2 with aging for 3, 6, 9, and 12 months, were employed to investigate the effects of aging processes on the transformation from Na-buserite to Todorokite by Mg2+-templating reaction at atmospheric pressure. The manganese oxides were examined using X-ray diffraction (XRD), elemental analysis, determinations of the average manganese oxidation number, infrared spectroscopy (IR), and transmission electron microscopy (TEM). The XRD, IR, and elemental analyses indicate that aging treatment can alter the substructure of the freshly synthesized Na-buserite. During the aging process, some of the Mn(III) may migrate into the interlayer region or disproportionate to form Mn2+ and Mn4+ from the layer of Na-buserite and the concomitant formation of layer vacancies. The interlayer Mn3+ or Mn2+ occupied above or below the layer vacancy sites and become corner-sharing octahedral. XRD analyses and TEM clearly show that the transformation from Na-buserite to Todorokite was promoted by aging treatments. The alterations of substructure of aged Na-buserites can promote the rearrangement of manganese to construct a tunnel structure during the transformation from layered manganese oxides to tunnel-structure Todorokite at atmospheric pressure. The transformation from Na-buserite to Todorokite was promoted by aging treatments at atmospheric pressure, and it is more suitable to explore the origination of natural Todorokite in Earth surface environments using aged layered manganese oxides.

  • birnessites with different average manganese oxidation states synthesized characterized and transformed to Todorokite at atmospheric pressure
    Clays and Clay Minerals, 2009
    Co-Authors: Xionghan Feng, Wenfeng Tan, Haojie Cui, Guohong Qiu, Fan Liu
    Abstract:

    Todorokite is a common manganese oxide mineral, with a tunnel structure, found in Earth surface environments, and is easily synthesized from layered birnessite. The aim of the current study was to prepare birnessites with different average manganese oxidation states (AOS) by controlling the ${\rm{MnO}}_4^ - {\rm{/M}}{{\rm{n}}^{2 + }}$ ratio in concentrated NaOH or KOH. A series of (Na,K)-birnessites, Na-birnessites, and K-birnessites with different AOS was synthesized successfully in strongly alkaline media. The (Na,K)-birnessites and Na-birnessites prepared in NaOH clearly contained both large (500–1000 nm) and small (40–400 nm), plate-shaped crystallites. The K-birnessites prepared in KOH media consisted mostly of irregular (100–200 nm), plate-shaped crystallites. The degree of transformation of birnessite to Todorokite at atmospheric pressure decreased as the AOS values of (Na,K)-birnessites and Na-birnessites increased from 3.51 to 3.80. No Todorokite was present when a Na-birnessite with an AOS value of 3.87 was used as the precursor. Pyrophosphate, which is known to form strong complexes with Mn3+ at a pH range of 1–8, was added to a suspension of (Na,K)-birnessites in order to sequester the available Mn3+ in (Na,K)-birnessites. Removal of Mn3+ from birnessite MnO6 layers by pyrophosphate restricted transformation to Todorokite — no (Na,K)-birnessite transformed to Todorokite after pyrophosphate treatment. The interlayer K+ initially within (Na,K)-birnessites could not be completely ion-exchanged with Mg2+ to form Todorokite at atmospheric pressure. No Todorokite was forthcoming from K-birnessites even from those with small AOS values (3.50).

Haojie Cui - One of the best experts on this subject based on the ideXlab platform.

  • effect of cobalt doped framework on formation of Todorokite from layered manganese oxides with mg2 co2 ions as template
    Pedosphere, 2011
    Co-Authors: Wenfeng Tan, Fan Liu, Haojie Cui, Xionghan Feng
    Abstract:

    Abstract Cobalt (Co) exists in significant quantities in naturally occurring manganese (Mn) oxides and alters the growth of Mn oxide crystals. Four-layered Mn oxides, Na-buserite (Na-bus) and three Co-doped Na-buserite samples prepared from oxidation of Mn(OH) 2 with 5%, 10%, and 20% Co/(Mn + Co) molar ratios (5Co-Na-bus, 10Co-Na-bus, and 20Co-Na-bus), were used to prepare Todorokite, a common Mn oxide on the Earth's surface, using Mg 2+ /Co 2+ ions as a template. The results showed that Todorokites could be obtained by reflux treatment of Mg 2+ -exchanged non-doped Na-buserite and three Co-doped Na-buserites at atmospheric pressure. However, the formation of Todorokites was prohibited by reflux treatment of Co 2+ -exchanged Na-bus, 5Co-Na-bus, and 10Co-Na-bus samples. Instead, Todorokite was obtained by the reflux treatment of Co 2+ -exchanged 20Co-Na-bus samples under atmospheric pressure. X-ray photoelectron spectroscopy analysis showed that doped Co existed as Co 3+ in the MnO 6 layers of doped Na-buserites. The amount of substituted Co 3+ in the MnO 6 layers may play a key role in the conversion of buserite to Todorokite using Co 2+ ions as a template.

  • aging promotes Todorokite formation from layered manganese oxide at near surface conditions
    Journal of Soils and Sediments, 2010
    Co-Authors: Xionghan Feng, Fan Liu, Wenfeng Tan, Haojie Cui, Ming Kuang Wang
    Abstract:

    Todorokite is one common manganese oxide in soils and sediments and is commonly formed from layered Na-buserite. Aging processes can alter the physicochemical properties of freshly formed Na-buserite in natural environments. However, it is not clear whether and how aging affects the formation of Todorokites. In the present paper, Na-buserite with aging treatment was employed to prepare Todorokite at atmospheric pressure to investigate the effects of aging treatment of Na-buserite on the formation of Todorokite. Four aged Na-buserite samples, which are produced through oxidation of Mn2+ in concentrated NaOH medium by O2 with aging for 3, 6, 9, and 12 months, were employed to investigate the effects of aging processes on the transformation from Na-buserite to Todorokite by Mg2+-templating reaction at atmospheric pressure. The manganese oxides were examined using X-ray diffraction (XRD), elemental analysis, determinations of the average manganese oxidation number, infrared spectroscopy (IR), and transmission electron microscopy (TEM). The XRD, IR, and elemental analyses indicate that aging treatment can alter the substructure of the freshly synthesized Na-buserite. During the aging process, some of the Mn(III) may migrate into the interlayer region or disproportionate to form Mn2+ and Mn4+ from the layer of Na-buserite and the concomitant formation of layer vacancies. The interlayer Mn3+ or Mn2+ occupied above or below the layer vacancy sites and become corner-sharing octahedral. XRD analyses and TEM clearly show that the transformation from Na-buserite to Todorokite was promoted by aging treatments. The alterations of substructure of aged Na-buserites can promote the rearrangement of manganese to construct a tunnel structure during the transformation from layered manganese oxides to tunnel-structure Todorokite at atmospheric pressure. The transformation from Na-buserite to Todorokite was promoted by aging treatments at atmospheric pressure, and it is more suitable to explore the origination of natural Todorokite in Earth surface environments using aged layered manganese oxides.

  • birnessites with different average manganese oxidation states synthesized characterized and transformed to Todorokite at atmospheric pressure
    Clays and Clay Minerals, 2009
    Co-Authors: Xionghan Feng, Wenfeng Tan, Haojie Cui, Guohong Qiu, Fan Liu
    Abstract:

    Todorokite is a common manganese oxide mineral, with a tunnel structure, found in Earth surface environments, and is easily synthesized from layered birnessite. The aim of the current study was to prepare birnessites with different average manganese oxidation states (AOS) by controlling the ${\rm{MnO}}_4^ - {\rm{/M}}{{\rm{n}}^{2 + }}$ ratio in concentrated NaOH or KOH. A series of (Na,K)-birnessites, Na-birnessites, and K-birnessites with different AOS was synthesized successfully in strongly alkaline media. The (Na,K)-birnessites and Na-birnessites prepared in NaOH clearly contained both large (500–1000 nm) and small (40–400 nm), plate-shaped crystallites. The K-birnessites prepared in KOH media consisted mostly of irregular (100–200 nm), plate-shaped crystallites. The degree of transformation of birnessite to Todorokite at atmospheric pressure decreased as the AOS values of (Na,K)-birnessites and Na-birnessites increased from 3.51 to 3.80. No Todorokite was present when a Na-birnessite with an AOS value of 3.87 was used as the precursor. Pyrophosphate, which is known to form strong complexes with Mn3+ at a pH range of 1–8, was added to a suspension of (Na,K)-birnessites in order to sequester the available Mn3+ in (Na,K)-birnessites. Removal of Mn3+ from birnessite MnO6 layers by pyrophosphate restricted transformation to Todorokite — no (Na,K)-birnessite transformed to Todorokite after pyrophosphate treatment. The interlayer K+ initially within (Na,K)-birnessites could not be completely ion-exchanged with Mg2+ to form Todorokite at atmospheric pressure. No Todorokite was forthcoming from K-birnessites even from those with small AOS values (3.50).

  • synthesis of Todorokite type manganese oxide from cu buserite by controlling the ph at atmospheric pressure
    Microporous and Mesoporous Materials, 2009
    Co-Authors: Haojie Cui, Xionghan Feng, Wenfeng Tan, Fan Liu
    Abstract:

    Abstract A Todorokite-type manganese oxide molecular sieve material was successfully synthesized at atmospheric pressure by refluxing treatment of Cu2+ exchanged Na-buserite (named as Cu-OMS-1). TEM (transmission electron microscope) and HRTEM (high resolution transmission electron microscope) images revealed that this material has a needle-phase crystal morphology with thickness 0.1–1 μm, and the lattice fringes spacing 1.0 nm corresponding to the [1 0 0] plane of the Todorokite structure. Such morphological and intergrowth characteristics were similar to those of hydrothermally synthesized Todorokites. The Cu-OMS-1 with a chemical composition of Cu0.34MnO2.19 · 1.11H2O, was stable below 400 °C. The BET surface area was found to be 62.5 m2/g, and a major micropore size distribution peak centered at 0.70 nm for Cu-OMS-1 by the Horvath–Kawazoe (HK) method. As determined by the t-plot method, 31% of the surface area was contributed by micropores. The pH of reaction solution plays an important role in the sub-structure modification of formed Cu-buserites and the formation of Todorokite at atmospheric pressure. A mechanism for the influence of pH on the transformation is discussed.

  • influence of mn iii availability on the phase transformation from layered buserite to tunnel structured Todorokite
    Clays and Clay Minerals, 2008
    Co-Authors: Haojie Cui, Xionghan Feng, Fan Liu, Wenfeng Tan, Xiangwen Liu, Huada Daniel Ruan
    Abstract:

    Todorokite is a common Mn oxide mineral in terrestrial and ocean-floor environments, and it is commonly synthesized from layered Na-buserite. Pyrophosphate, which is known to form strong complexes with Mn(III) at a pH range of 1–8, was added to a suspension of Na-buserite in order to sequester the available Mn(III) in Na-buserite. No Mn(III)-pyrophosphate complex was formed in solution at pH 10, and the treated Na-buserites were converted completely to Todorokite. Significant transformation reductions were observed when Na-buserite was treated with pyrophosphate solution at pH 7. The presence of Mn(III) within the MnO6 octahedral sheets of Na-buserite is critical for the transformation from layered buserite to tunnel-structured Todorokite at atmospheric pressure. At lower pH, two effects are combined to reduce the amount of Mn(III) in the layers: (1) the complexing power of pyrophosphate is increased; and (2) the transformation from Na-buserite to H-birnessite, which is concomitant with the migration of Mn(III) from layers to the interlayer, and the partial disproportionation of Mn(III). The results showed that Mn(III) played a key role in the transformation of layered Na-buserite to tunnel-structured Todorokite at atmospheric pressure.

Steven L Suib - One of the best experts on this subject based on the ideXlab platform.

  • effects of microwave processing on chemical physical and catalytic properties of Todorokite type manganese oxide
    Chemistry of Materials, 2004
    Co-Authors: Kinga A Malinger, Kate Laubernds, And Youngchan Son, Steven L Suib
    Abstract:

    A microwave-assisted hydrothermal method of synthesis was used to prepare Todorokite. Synthetic Todorokite, OMS-1, is a multivalent manganese oxide with a 3×3×∞ tunnel structure. OMS-1 was synthesized from its layered precursor much faster by the microwave method than by conventional heating (8 vs 48 h). In addition, the microwave-synthesized materials reveal some properties superior to those of the conventionally synthesized ones such as better stability, crystallinity, and catalytic activity in the production of phthalic anhydride. Microwave-prepared Todorokite also shows novel cubic morphology, which was not found for conventionally made OMS-1 and is catalytically active in the oxidation of benzyl alcohol. Materials synthesized by microwave as well as conventional methods were characterized with XRD, TGA, SEM, TEM, TPD, and BET. Physical, chemical, and catalytic properties of Todorokite prepared by the two different methods were compared based on the experimental results.

  • a new synthetic route to Todorokite type manganese oxides
    Inorganica Chimica Acta, 1999
    Co-Authors: Stanton Ching, Katarzyna S Krukowska, Steven L Suib
    Abstract:

    Abstract Microporous Todorokite-type manganese oxides have been synthesized by a new route in which the key Na-birnessite precursor is prepared by oxidation of Mn(OH) 2 with K 2 S 2 O 8 in aqueous NaOH. The reaction is promoted by foreign metal cations such as Mg 2+ , Co 2+ , Ni 2+ , and Cu 2+ , which are incorporated into the manganese oxide layer framework. These same divalent cations are used in a subsequent ion-exchange reaction that converts the Na-birnessite into a related layered material, buserite. Hydrothermal treatment of the buserite ultimately yields Mg-, Co-, Ni-, or Cu-Todorokite. The Todorokites have been characterized by powder X-ray diffraction, elemental analysis, Mn oxidation state determination, scanning electron microscopy, and cyclic voltammetry. The composition of Mg-doped Na-birnessite is Na 0.26 Mg 0.13 MnO 2.04 (H 2 O) 1.26 , with the average Mn oxidation state being 3.55. Mg-Todorokite has a composition of Mg 0.33 MnO 2.14 (H 2 O) 0.97 , with a Mn oxidation state of 3.62. A mixed Co/Ni-Todorokite has been synthesized to assess the distribution of foreign cation in framework and tunnel sites. For Co-Todorokite, 42% of the Co is in the manganese oxide framework and 58% is in the interlayer galleries, which gives the formula Co 0.21 (Co 0.16 Mn)O 2.21 (H 2 O) 0.97 . If the Co percentages are applied to Mg-Todorokite, a formula of Mg 0.19 (Mg 0.14 Mn)O 2.14 (H 2 O) 0.97 is obtained. Thermal stability experiments reveal that Mg-Todorokite is more robust compared to the other Todorokites and remains intact up to 400°C. The Co, Ni, and Cu-Todorokites have similar thermal stabilities and their structures collapse at about 300°C. Na-birnessite prepared by the Mn(OH) 2 /K 2 S 2 O 8 route can further be used to generate other birnessite derivatives such as H-birnessite and alkylammonium-birnessites. These derivatives can be synthesized both with and without Mg 2+ , Co 2+ , Ni 2+ , and Cu 2+ as isomorphous framework dopants.

  • synthetic Todorokite produced by microwave heating an active oxidation catalyst
    Journal of Catalysis, 1999
    Co-Authors: Elizabeth Vileno, Steven L Suib, Hua Zhou, Qiuhua Zhang, David R Corbin, Theodore A Koch
    Abstract:

    Abstract Microwave heating methods have been applied to the synthesis of a family of layered and tunnel-structured manganese oxide materials. These materials are known to interact strongly with microwave radiation, and thus pronounced effects on the microstucture might be expected. The work presented here is a study of the synthesis, characterization, and catalytic activity of a one-dimensional tunnel-structured manganese oxide catalyst known as OMS-1 (octahedral molecular sieve). The synthetic methods employed in the production of OMS-1 include constant temperature aging, ion exchange, in situ coprecipitation, and hydrothermal treatment. Heating was done using conventional convection methods and microwave radiation to probe the effect of microwave radiation on the material characteristics. The products were examined using X-ray diffraction, elemental analysis, determinations of the average manganese oxidation number, Auger spectroscopy, scanning electron microscopy, thermal stability studies, infrared spectroscopy, and surface area measurements. Catalytic activity was tested in the oxidative dehydrogenation reaction of ethylbenzene to styrene. The materials produced using microwave radiation were shown to have bulk characteristics similar to those prepared using conventional heating. However, the surface properties were shown to be different, resulting in different catalytic results. The differences in the properties and catalytic activity of the materials, as well as the implications of microwave heating as a synthetic tool, are discussed.

  • manganese oxide octahedral molecular sieves preparation characterization and applications
    Science, 1993
    Co-Authors: Yanfei Shen, Steven L Suib, Richard P Zerger, Roberto N Deguzman, L Mccurdy, Donald I Potter, C L Oyoung
    Abstract:

    A thermally stable 3 x 3 octahedral molecular sieve corresponding to natural Todorokite (OMS-1) has been synthesized by autoclaving layer-structure manganese oxides, which are prepared by reactions of MnO(4)(-) and Mn(2+) under markedly alkaline conditions. The nature and thermal stability of products depend strongly on preparation parameters, such as the MnO(4)(-)/Mn(2+) ratio, pH, aging, and autoclave conditions. The purest and the most thermally stable Todorokite is obtained at a ratio of 0.30 to 0.40. Autoclave treatments at about 150 degrees to 180 degrees C for more than 2 days yield OMS-1, which is as thermally stable (500 degrees C) as natural Todorokite minerals. Adsorption data give a tunnel size of 6.9 angstroms and an increase of cyclohexane or carbon tetrachloride uptake with dehydration temperature up to 500 degrees C. At 600 degrees C, the tunnel structure collapses. Both Lewis and Bronsted acid sites have been observed in OMS-1. Particular applications of these materials include adsorption, electrochemical sensors, and oxidation catalysis.

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  • formation of Todorokite from c disordered h birnessites the roles of average manganese oxidation state and interlayer cations
    Geochemical Transactions, 2015
    Co-Authors: Huaiyan Zhao, Fan Liu, Wenfeng Tan, Xinran Liang, Hui Yin, Guohong Qiu, Xionghan Feng
    Abstract:

    Todorokite, a 3 × 3 tectomanganate, is one of three main manganese oxide minerals in marine nodules and can be used as an active MnO6 octahedral molecular sieve. The formation of Todorokite is closely associated with the poorly crystalline phyllomanganates in nature. However, the effect of the preparative parameters on the transformation of “c-disordered” H+-birnessites, analogue to natural phyllomanganates, into Todorokite has not yet been explored. Synthesis of “c-disordered” H+-birnessites with different average manganese oxidation states (AOS) was performed by controlling the MnO4 −/Mn2+ ratio in low-concentrated NaOH or KOH media. Further transformation to Todorokite, using “c-disordered” H+-birnessites pre-exchanged with Na+ or K+ or not before exchange with Mg2+, was conducted under reflux conditions to investigate the effects of Mn AOS and interlayer cations. The results show that all of these “c-disordered” H+-birnessites exhibit hexagonal layer symmetry and can be transformed into Todorokite to different extents. “c-disordered” H+-birnessite without pre-exchange treatment contains lower levels of Na/K and is preferably transformed into ramsdellite with a smaller 1 × 2 tunnel structure rather than Todorokite. Na+ pre-exchange, i.e. to form Na-H-birnessite, greatly enhances transformation into Todorokite, whereas K+ pre-exchange, i.e. to form K-H-birnessite, inhibits the transformation. This is because the interlayer K+ of birnessite cannot be completely exchanged with Mg2+, which restrains the formation of tunnel “walls” with 1 nm in length. When the Mn AOS values of Na-H-birnessite increase from 3.58 to 3.74, the rate and extent of the transformation sharply decrease, indicating that a key process is Mn(III) species migration from layer into interlayer to form the tunnel structure during Todorokite formation. Structural Mn(III), together with the content and type of interlayer metal ions, plays a crucial role in the transformation of “c-disordered” H+-birnessites with hexagonal symmetry into Todorokite. This provides further explanation for the common occurrence of Todorokite in the hydrothermal ocean environment, where is usually enriched in large metal ions such as Mg, Ca, Ni, Co and etc. These results have significant implications for exploring the origin and formation process of Todorokite in various geochemical settings and promoting the practical application of Todorokite in many fields. Graphical abstract XRD patterns of Mg2+-exchanged and reflux treatment products for the synthetic “c-disordered” H+-birnessites.

  • oxidation process of dissolvable sulfide by synthesized Todorokite in aqueous systems
    Journal of Hazardous Materials, 2015
    Co-Authors: Tianyu Gao, Xionghan Feng, Fan Liu, Wenfeng Tan, Ying Shi, Yashan Zhang, Guohong Qiu
    Abstract:

    Abstract Todorokite, formed from Mn(II) in supergene environments, can affect the transformation and migration of dissolvable sulfides in soils and water. In this work, Todorokite was synthesized with different degrees of crystallinity, and the redox mechanism of dissolvable sulfide and Todorokite was studied in both closed and open aqueous systems. The influences of pH, temperature, crystallinity, the amount of manganese oxides, and oxygen gas on S2− oxidation process were investigated. It is found that S2− was oxidized to S0, SO32−, S2O32− and SO42−, and about 90% of S2− was converted into S0 in closed systems. The participation of oxygen facilitated the further oxidation of S0 to S2O32−. S0 and S2O32− were formed with the conversion rates of S2− about 45.3% and 38.4% after 1 h of reaction, respectively, and the conversion rate for S2O32− increased as reaction prolonged for a longer period. In addition, Todorokite was reduced to Mn(OH)2 in the presence of nitrogen gas, and its chemical stability increased when oxygen gas was admitted into the reaction system during the process. The oxidation rate of dissolvable sulfide followed a pseudo-first-order kinetic law in the initial stage (within 10 min), and the initial oxidation rate constant of S2− increased with elevating temperature, increasing the quantity and decreasing crystallinity of Todorokite. The initial oxidation rate of dissolvable sulfide decreased with continuous feeding of O2 into the test solution, possibly due to a decrease in active Mn(III) content in Todorokite. The present work demonstrates the redox behaviors and kinetics of dissolvable sulfide and Todorokite in aquatic environments.

  • effect of cobalt doped framework on formation of Todorokite from layered manganese oxides with mg2 co2 ions as template
    Pedosphere, 2011
    Co-Authors: Wenfeng Tan, Fan Liu, Haojie Cui, Xionghan Feng
    Abstract:

    Abstract Cobalt (Co) exists in significant quantities in naturally occurring manganese (Mn) oxides and alters the growth of Mn oxide crystals. Four-layered Mn oxides, Na-buserite (Na-bus) and three Co-doped Na-buserite samples prepared from oxidation of Mn(OH) 2 with 5%, 10%, and 20% Co/(Mn + Co) molar ratios (5Co-Na-bus, 10Co-Na-bus, and 20Co-Na-bus), were used to prepare Todorokite, a common Mn oxide on the Earth's surface, using Mg 2+ /Co 2+ ions as a template. The results showed that Todorokites could be obtained by reflux treatment of Mg 2+ -exchanged non-doped Na-buserite and three Co-doped Na-buserites at atmospheric pressure. However, the formation of Todorokites was prohibited by reflux treatment of Co 2+ -exchanged Na-bus, 5Co-Na-bus, and 10Co-Na-bus samples. Instead, Todorokite was obtained by the reflux treatment of Co 2+ -exchanged 20Co-Na-bus samples under atmospheric pressure. X-ray photoelectron spectroscopy analysis showed that doped Co existed as Co 3+ in the MnO 6 layers of doped Na-buserites. The amount of substituted Co 3+ in the MnO 6 layers may play a key role in the conversion of buserite to Todorokite using Co 2+ ions as a template.

  • aging promotes Todorokite formation from layered manganese oxide at near surface conditions
    Journal of Soils and Sediments, 2010
    Co-Authors: Xionghan Feng, Fan Liu, Wenfeng Tan, Haojie Cui, Ming Kuang Wang
    Abstract:

    Todorokite is one common manganese oxide in soils and sediments and is commonly formed from layered Na-buserite. Aging processes can alter the physicochemical properties of freshly formed Na-buserite in natural environments. However, it is not clear whether and how aging affects the formation of Todorokites. In the present paper, Na-buserite with aging treatment was employed to prepare Todorokite at atmospheric pressure to investigate the effects of aging treatment of Na-buserite on the formation of Todorokite. Four aged Na-buserite samples, which are produced through oxidation of Mn2+ in concentrated NaOH medium by O2 with aging for 3, 6, 9, and 12 months, were employed to investigate the effects of aging processes on the transformation from Na-buserite to Todorokite by Mg2+-templating reaction at atmospheric pressure. The manganese oxides were examined using X-ray diffraction (XRD), elemental analysis, determinations of the average manganese oxidation number, infrared spectroscopy (IR), and transmission electron microscopy (TEM). The XRD, IR, and elemental analyses indicate that aging treatment can alter the substructure of the freshly synthesized Na-buserite. During the aging process, some of the Mn(III) may migrate into the interlayer region or disproportionate to form Mn2+ and Mn4+ from the layer of Na-buserite and the concomitant formation of layer vacancies. The interlayer Mn3+ or Mn2+ occupied above or below the layer vacancy sites and become corner-sharing octahedral. XRD analyses and TEM clearly show that the transformation from Na-buserite to Todorokite was promoted by aging treatments. The alterations of substructure of aged Na-buserites can promote the rearrangement of manganese to construct a tunnel structure during the transformation from layered manganese oxides to tunnel-structure Todorokite at atmospheric pressure. The transformation from Na-buserite to Todorokite was promoted by aging treatments at atmospheric pressure, and it is more suitable to explore the origination of natural Todorokite in Earth surface environments using aged layered manganese oxides.

  • birnessites with different average manganese oxidation states synthesized characterized and transformed to Todorokite at atmospheric pressure
    Clays and Clay Minerals, 2009
    Co-Authors: Xionghan Feng, Wenfeng Tan, Haojie Cui, Guohong Qiu, Fan Liu
    Abstract:

    Todorokite is a common manganese oxide mineral, with a tunnel structure, found in Earth surface environments, and is easily synthesized from layered birnessite. The aim of the current study was to prepare birnessites with different average manganese oxidation states (AOS) by controlling the ${\rm{MnO}}_4^ - {\rm{/M}}{{\rm{n}}^{2 + }}$ ratio in concentrated NaOH or KOH. A series of (Na,K)-birnessites, Na-birnessites, and K-birnessites with different AOS was synthesized successfully in strongly alkaline media. The (Na,K)-birnessites and Na-birnessites prepared in NaOH clearly contained both large (500–1000 nm) and small (40–400 nm), plate-shaped crystallites. The K-birnessites prepared in KOH media consisted mostly of irregular (100–200 nm), plate-shaped crystallites. The degree of transformation of birnessite to Todorokite at atmospheric pressure decreased as the AOS values of (Na,K)-birnessites and Na-birnessites increased from 3.51 to 3.80. No Todorokite was present when a Na-birnessite with an AOS value of 3.87 was used as the precursor. Pyrophosphate, which is known to form strong complexes with Mn3+ at a pH range of 1–8, was added to a suspension of (Na,K)-birnessites in order to sequester the available Mn3+ in (Na,K)-birnessites. Removal of Mn3+ from birnessite MnO6 layers by pyrophosphate restricted transformation to Todorokite — no (Na,K)-birnessite transformed to Todorokite after pyrophosphate treatment. The interlayer K+ initially within (Na,K)-birnessites could not be completely ion-exchanged with Mg2+ to form Todorokite at atmospheric pressure. No Todorokite was forthcoming from K-birnessites even from those with small AOS values (3.50).