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Xionghan Feng - One of the best experts on this subject based on the ideXlab platform.
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The Influence of Zn2+ and Mn2+ on Pb2+ Adsorption Behaviors of Birnessite
Molecular Environmental Soil Science at the Interfaces in the Earth’s Critical Zone, 2020Co-Authors: Wei Zhao, Xionghan FengAbstract:The present study comparatively investigated Pb2+ adsorption behaviors of the Birnessite with high Mn average oxidation state (AOS) before and after treatment of preadsorption with Zn2+ and Mn2+, respectively. The association of vacant Mn octahedral sites with Pb2+ adsorption was further understood from the variances of Birnessite AOS, d(110)-interplanar spacing, maximum Pb2+ adsorption, maximum Zn2+ and Mn2+ release during the Pb2+ adsorption before and after treatments. The Birnessite AOS and d(110)-interplanar spacing were almost unchanged as the concentration of Zn2+ increased, indicative of the unchanged vacant Mn octahedral sites, whereas the maximum Pb2+ adsorption decreased from 3190 to 2030 mmol·kg−1 due to occupancy of the treating Zn2+ in adsorption sites. However, the AOS of the Mn2+-treated Birnessites decreased and most of the treating Mn2+ were oxidized to Mn3+ and located below or above vacant Mn octahedral sites or migrated into vacant Mn octahedral sites. Increasing Mn2+ concentration from 1 to 2.4 mmol·L−1 increased the d(110)-interplanar spacing of the treated Birnessites from 0.1416 to 0.14196 nm but decreased the maximum Pb2+ adsorption of the treated Birnessites from 3190 to 1332 mmol·kg−1, indicating the decrease in the amount of vacant Mn octahedral sites, mainly due to the increase of the produced Mn3+ migrating into vacant Mn octahedral sites. Therefore, birnesstie Pb2+ adsorption capacity was largely determined by the number of Mn site vacancies.
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Self-assembly of Birnessite nanoflowers by staged three-dimensional oriented attachment
Environmental science. Nano, 2020Co-Authors: Xinran Liang, Zixiang Zhao, Lijun Wang, Xionghan FengAbstract:Birnessite (layer-type Mn(III, IV) oxides with ordered sheet stacking) is the most common mineral species of manganese (Mn) oxides and has been demonstrated to be among the strongest sorbents and oxidants in surface environments. The morphology of Birnessite is one of the key factors affecting its reactivity. Either biotic or abiotic Birnessite samples usually consist of nanoflower-like crystals. However, the governing factors and mechanisms of morphological evolution of the nanoflower-shaped Birnessite remain poorly understood. In this work, Birnessite nanoflowers, as a natural Birnessite analog, were synthesized and the intermediate products during Birnessite crystallization were captured by instant freezing using liquid nitrogen. The processes and mechanisms of crystal growth of Birnessite nanoflowers were investigated using a combination of high-resolution transmission electron microscopy (HRTEM), field-emission scanning electron microscopy (FESEM), powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results indicate that primary hexagonal nanoflakes rapidly agglomerate to form nuclei-like substrates at the initial stages, and subsequently, these nanoflakes aggregate laterally and link serially on the substrates to form nanopetals through both rotation and edge-to-edge oriented attachment (OA) mechanism. This process is likely driven by hydrogen bonding between unsaturated O atoms at the edge planes of [MnO6] sheets. Meanwhile, the OA mechanism along the (001) plane is likely driven by Coulombic interactions and hydrogen bonding during the assembly process of the adjacent nanopetals. The morphological evolution occurred by the staged three-dimensional OA process that plays an essential role in the self-assembly of flower-like Birnessite crystals. These findings provide further understanding of how nanoparticle assembly is directed to achieving desired shapes and sizes by fabricating nanomaterials through three-dimensional OA processes.
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local structure of cu 2 in cu doped hexagonal turbostratic Birnessite and cu 2 stability under acid treatment
Chemical Geology, 2017Co-Authors: Quanjun Xiang, Lirong Zheng, Matthew Gindervogel, Juan Xiong, Luuk K Koopal, Mingxia Wang, Xionghan FengAbstract:Abstract Geochemical behaviors of heavy metal contaminants, such as Cu 2 + , are strongly controlled by natural Birnessite-like minerals in both marine and terrestrial environments. However, the mechanisms of the interaction of Cu 2 + with Birnessite are not fully understood yet. In the present study, Cu 2 + was coprecipitated with Mn 2 + to produce hexagonal turbostratic Birnessite, which is analogous to natural Birnessite. The obtained Cu-doped Birnessite was characterized by powder X-ray diffraction, field-emission scanning electron microscopy, and X-ray absorption spectroscopy (XANES + EXAFS). The stability of Cu(II) in the Birnessite structure was investigated by acid treatment. Increasing the dopant content reduces the mineral crystallinity in the [001] direction and the unit cell parameter b from the hexagonal layers. It also shortens the bond length of Mn O in the [MnO 6 ] unit and the edge-sharing Mn Mn distance in the layers, and increases the average oxidation state (AOS) of Mn and the specific surface area. Analysis of Cu K-edge XANES and EXAFS data indicates that, only a small part of Cu(II) is inserted into the Birnessite layers, while most of it is adsorbed on the vacancies. When the Cu/Mn molar ratio is increased from 0.08 to 0.23, an increasing part of Cu(II) is present as polynuclear clusters on the Birnessite edge sites in the pH range of ~ 3.3–5.3. Reaction with H 2 SO 4 solution is found to easily dissolve the polynuclear Cu clusters and the highly distorted Cu octahedra in innersphere complexes on the Birnessite-water interface, with ~ 53% of the Cu 2 + released into the solution. On the other hand, the reaction with HCl solution leads to reductive dissolution of the mineral matrix, the release of Mn 2 + into solutions, the decrease in the first Mn O and edge-sharing Mn Mn distances and Mn AOS, in addition to the release of Cu 2 + . The release rate of Cu 2 + is much faster than that of Ni 2 + in Ni-doped Birnessites, owing to the lower stability of distorted [CuO 6 ] octahedron upon proton attack. These results indicate the formation of multinuclear Cu complexes on Birnessite surfaces under the investigated conditions. The results also suggest the lower stability of Cu 2 + in these minerals and thus higher potential toxicity in acidic conditions, in comparison with other metal pollutants, such as Ni 2 + . This study provides new insights into the interaction mechanisms between Cu 2 + and Birnessite-like minerals, and help to clarify the structural stability and geochemical behaviors of Cu 2 + associated with Birnessite-like minerals in natural environments.
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redox reactions between mn ii and hexagonal Birnessite change its layer symmetry
Environmental Science & Technology, 2016Co-Authors: Huaiyan Zhao, Xionghan Feng, Mario Villalobos, Wei Li, Evert J Elzinga, Jing Zhang, Donald L SparksAbstract:Birnessite, a phyllomanganate and the most common type of Mn oxide, affects the fate and transport of numerous contaminants and nutrients in nature. Birnessite exhibits hexagonal (HexLayBir) or orthogonal (OrthLayBir) layer symmetry. The two types of Birnessite contain contrasting content of layer vacancies and Mn(III), and accordingly have different sorption and oxidation abilities. OrthLayBir can transform to HexLayBir, but it is still vaguely understood if and how the reverse transformation occurs. Here, we show that HexLayBir (e.g., δ-MnO2 and acid Birnessite) transforms to OrthLayBir after reaction with aqueous Mn(II) at low Mn(II)/Mn (in HexLayBir) molar ratios (5–24%) and pH ≥ 8. The transformation is promoted by higher pH values, as well as smaller particle size, and/or greater stacking disorder of HexLayBir. The transformation is ascribed to Mn(III) formation via the comproportionation reaction between Mn(II) adsorbed on vacant sites and the surrounding layer Mn(IV), and the subsequent migration ...
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effects of co and ni co doping on the structure and reactivity of hexagonal Birnessite
Chemical Geology, 2014Co-Authors: Hui Li, Xionghan Feng, Yan Wang, Matthew Gindervogel, Lirong ZhengAbstract:Abstract Natural hexagonal Birnessites are enriched in various transition metals (TMs). Many studies have examined the effects of single metal doping on the structures and properties of Birnessites, but none focused on the simultaneous interaction mechanism of coprecipitation of two different TMs with Birnessite. In this work Co and Ni co-doped hexagonal Birnessites were synthesized and characterized by powder X-ray diffraction (XRD), elemental analysis, field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS) spectroscopy to investigate the effects of co-doping on the structure and reactivity of Birnessite and the crystal chemistry of Co and Ni. These co-doped Birnessites have lower crystallinity, i.e., fewer manganese layers stacking in the c* direction, larger specific surface areas (SSAs) and increased Mn average oxidation states (AOSs) than the undoped Birnessite, and Co exists in a valence of + 3. Co, Ni and Mn K -edge extended X-ray absorption fine structure spectroscopy (EXAFS) spectra demonstrate an increase in edge-sharing Ni–Me (Me = Ni, Co and Mn) distances in Birnessite layers with the increase of the contents of dopants while Mn–Me distances first decrease and then increase while those of Co–Me pairs are nearly constant, coupled with first a decrease and then increase of the in-plane unit-cell parameter b. The effect of co-doping on the amounts of structural Mn and K + , numbers of [MnO 6 ] layers stacked in c* axis, and SSAs, is larger than the effects of doping with Co alone, but less than singly Ni doping. In Birnessites doped with both Co and Ni, ~ 74–79% of the total Co and ~ 23–39% of the total Ni are present within the manganese layers. Compared with the spatial distribution of TM in singly doped Birnessites, the coexistence of Ni hinders the incorporation of Co into the layers during Birnessite crystallization; however, coprecipitation with Co has little effects, neither hindrance nor promotion, on the insertion of Ni into the layers. These results provide insight into the interaction mechanism between coexisting Co, Ni within layered Mn oxides. It further helps us to interpret the geochemical characteristics of multi-metal incorporation into natural Mn oxides and their effects on the structures and physicochemical properties of these minerals.
J P Pereiraramos - One of the best experts on this subject based on the ideXlab platform.
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doping effects on structure and electrode performance of k Birnessite type manganese dioxides for rechargeable lithium battery
Electrochimica Acta, 2008Co-Authors: Atsushi Ogata, Shinichi Komaba, R Baddourhadjean, J P Pereiraramos, N KumagaiAbstract:Abstract The potassium Birnessites doped with Al, Ni, and Co were prepared by calcination and aqueous treatment, which showed that single phase products were obtained with Ni and Al up to 5 at.% and Co up to 25 at.% addition to strating KMnO 4 . The discharge–recharge capacities and capacity retentions in an aprotic Li cell were not improved by the Ni and Al dopings, but those of the cobalt doped Birnessite were improved. The initial discharge capacities of the undoped and cobalt doped Birnessites were 170 and 200 mAh g −1 with capacity retentions of 56 and 80% during the initial 20 cycles, respectively. The reasons for the improvement of the battery performance by Co doping were considered as follows: (i) a change in the stacking structure, (ii) a decrease in the charge transfer resistance, and (iii) improved structural stability of the oxide. Their micro structures were evaluated by X-ray diffraction, photoelectron and Raman spectroscopies, and electron microscopy. Also, potassium Birnessite synthesized by adding about 3 times excess potassium indicated that the stacking structure was similar to the 30 at.% cobalt doping sample, furthermore, the better capacity retention was achieved as cathode in a Li cell.
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raman spectra of Birnessite manganese dioxides
Solid State Ionics, 2003Co-Authors: C Julien, M Massot, R Baddourhadjean, Sylvain Franger, S Bach, J P PereiraramosAbstract:Structural features of layered manganese dioxides of the Birnessite family are studied using Raman scattering spectroscopy. This local probe is capable of analysing directly the near-neighbour environment of oxygen coordination around manganese and lithium cations. Four types of sol–gel Birnessite (SGB) are considered: lithium Birnessite (Li-Bir), sodium Birnessite (Na-Bir), sol–gel Birnessite (SG-Bir), and sol–gel Co-doped Birnessite (SGCo-Bir). Thus, in a first approach, we consider the overall spectral features of Birnessites such as the superposition of the spectra of local structures, while the lattice modes are discussed in the spectroscopic symmetry. Results show the specific spectroscopic fingerprints of SG-Bir single phases, the site occupancy of Co ions in the substituted SGCo-Bir compound, and vibrations due to lithium ions with their oxygen neighbours in Li-Bir, Li0.32MnO2·0.6H2O. A correlation between the interlayer d-spacing and the stretching mode frequencies of Birnessite oxides has been established.
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synthesis ion exchange and electrochemical properties of lamellar phyllomanganates of the Birnessite group
Materials Research Bulletin, 1996Co-Authors: Le P Goff, S Bach, N Baffier, J P PereiraramosAbstract:Synthesis of various X-Birnessites was performed using the ion exchange properties of the sodium Birnessite Na0.32MnO2,yH2O. Their structural and electro-chemical characteristics are investigated and discussed in comparison with previous data obtained for some compounds and in relation with mechanism invoked for Li electrochemical insertion into sol-gel and chemical Birnessites. Two main groups of materials are obtained with a monoclinic or hexagonal structure depending on the kind of inserted cation.
Steven L Suib - One of the best experts on this subject based on the ideXlab platform.
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enhanced adsorption removal of arsenic from mining wastewater using Birnessite under electrochemical redox reactions
Chemical Engineering Journal, 2019Co-Authors: Steven L Suib, Lirong Zheng, Shiming SuAbstract:Abstract Manganese oxides have been extensively investigated for arsenic (As) adsorption from aqueous solution. However, the effect of electrochemical redox reactions on the adsorption performance and underlying mechanism remain elusive. Herein, Birnessite was used for electrochemical adsorption of As from mining wastewater at a constant cell voltage, and the effect of cell voltage and the continuous use (without desorption) performance of Birnessite electrode were also evaluated. At 1.2 V for 24 h, the concentrations of total As (As(T)) and As(III) in wastewater decreased from 3808.7 to 73.7 μg L−1 and 682.8 to 21.4 μg L−1, respectively. The As(T) removal ratio increased with increasing cell voltage and reached 98.1% at 1.2 V, which was higher than that at open circuit (84.1%). The Mn2+ concentration also significantly decreased in wastewater during As adsorption. The high potential of Birnessite anode and the generation of H2O2 on cathode facilitated As(III) oxidation, and the electrochemical redox reactions of Birnessite contributed to the enhancement of As(T) removal. The application of cell voltage reversal could improve the utilization rate of Birnessite electrodes by dissolution-recrystallization during continuous use, and the As(T) removal ratio was increased from 73.5% to 85.1% after five cycles of voltage alteration. The present work indicates that Birnessite is a promising absorbent for the electrochemical adsorption of As from real wastewaters.
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Photochemical Formation and Transformation of Birnessite: Effects of Cations on Micromorphology and Crystal Structure
Environmental Science & Technology, 2018Co-Authors: Tengfei Zhang, Steven L SuibAbstract:As important components with excellent oxidation and adsorption activity in soils and sediments, manganese oxides affect the transportation and fate of nutrients and pollutants in natural environments. In this work, Birnessite was formed by photocatalytic oxidation of Mn2+aq in the presence of nitrate under solar irradiation. The effects of concentrations and species of interlayer cations (Na+, Mg2+, and K+) on Birnessite crystal structure and micromorphology were investigated. The roles of adsorbed Mn2+ and pH in the transformation of the photosynthetic Birnessite were further studied. The results indicated that Mn2+aq was oxidized to Birnessite by superoxide radicals (O2•–) generated from the photolysis of NO3– under UV irradiation. The particle size and thickness of Birnessite decreased with increasing cation concentration. The Birnessite showed a plate-like morphology in the presence of K+, while exhibited a rumpled sheet-like morphology when Na+ or Mg2+ was used. The different micromorphologies of bi...
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enhancement of zn2 and ni2 removal performance using a deionization pseudocapacitor with nanostructured Birnessite and its carbon nanotube composite electrodes
Chemical Engineering Journal, 2017Co-Authors: Steven L Suib, Lirong ZhengAbstract:Abstract Manganese oxides have been widely used as deionization capacitor electrode materials to remove heavy metal ions from aqueous solutions. However, the effect of pseudocapacitive properties of manganese oxides on the removal processes remains elusive. In this work, synthesized nanostructured Birnessite-type manganese oxide and Birnessite/carbon nanotubes (HB/CNTs) nanocomposites were used as deionization pseudocapacitor electrode materials for Zn 2+ and Ni 2+ removal from aqueous solution by constant potential electrolysis. The effects of operation potential and introduction of carbon nanotubes (CNTs) on Zn 2+ and Ni 2+ removal capacities were further investigated. The results demonstrated a significant enhancement of electrochemical removal capacities for Zn 2+ and Ni 2+ by the pseudocapacitive properties of Birnessite and the introduction of CNTs. The Zn 2+ and Ni 2+ removal capacities of Birnessite electrode increased first and then decreased with the decrease of potential from 0.2 to −0.2 V ( vs . SCE), and the highest removal capacities for Zn 2+ and Ni 2+ respectively reached 89.5 and 96.6 mg g −1 when the potential was controlled at 0 V. The HB/CNTs nanocomposite showed higher removal capacities (155.6 mg g −1 for Zn 2+ and 158.4 mg g −1 for Ni 2+ when the relative content of manganese oxide was 45.6%) and a better cycling stability (about 90% and 88% of the initial Zn 2+ and Ni 2+ removal capacity were retained after 5 cycles) than Birnessite electrode. The present study makes clear the pseudocapacitive mechanism of heavy metal ion removal using Birnessite, and proposes a facile method to remove heavy metal ions from aqueous solution.
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Cadmium Removal from Aqueous Solution by a Deionization Supercapacitor with a Birnessite Electrode
ACS Applied Materials & Interfaces, 2016Co-Authors: Qichuan Peng, Yashan Zhang, Steven L SuibAbstract:Birnessite is widely used as an excellent adsorbent for heavy metal ions and as active electrode materials for supercapacitors. The occurrence of redox reactions of manganese oxides is usually accompanied by the intercalation–deintercalation of cations during the charge–discharge processes of supercapacitors. In this study, based on the charge–discharge principle of the supercapacitor and excellent adsorption properties of Birnessite, a Birnessite-based electrode was used to remove Cd2+ from aqueous solutions. The Cd2+ removal mechanism and the influences of Birnessite loading and pH on the removal performance were investigated. The results showed that Cd2+ was adsorbed on the surfaces and interlayers of Birnessite, and the maximum electrosorption capacity of Birnessite for Cd2+ was about 900.7 mg g–1 (8.01 mmol g–1), which was significantly higher than the adsorption isotherm capacity of Birnessite (125.8 mg g–1). The electrosorption specific capacity of Birnessite for Cd2+ increased with an increase in ...
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Mechanistic and kinetic studies of crystallization of Birnessite.
Inorganic Chemistry, 2000Co-Authors: Qiuhua Zhang, Steven L SuibAbstract:Kinetic and mechanistic features have been studied for the crystallization of Birnessite in aqueous systems via different synthesis methods: the oxidation of Mn2+, reduction of MnO4-, and redox reaction between Mn2+ and MnO4-. For oxidation methods, a topotactical conversion from Mn(OH)2 to Birnessite via feitknechtite (β-MnOOH) is observed. In reduction methods, Birnessite evolves from the initially produced amorphous manganese oxide (AMO gel). For redox methods, both mechanisms exist, with the latter prevailing. A liquid mechanism is proposed to describe the reduction and redox synthesis, which comprises three stages: an induction period, a fast crystallization period, and a steady-state period. The redox method is accompanied by the formation and phase transformation of feitknechtite to Birnessite. A method combining IR and XRD quantitation is proposed to detect nuclei in the induction period. Crystallization rates and apparent energies of activation of crystallization for reduction and redox methods...
Lirong Zheng - One of the best experts on this subject based on the ideXlab platform.
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enhanced adsorption removal of arsenic from mining wastewater using Birnessite under electrochemical redox reactions
Chemical Engineering Journal, 2019Co-Authors: Steven L Suib, Lirong Zheng, Shiming SuAbstract:Abstract Manganese oxides have been extensively investigated for arsenic (As) adsorption from aqueous solution. However, the effect of electrochemical redox reactions on the adsorption performance and underlying mechanism remain elusive. Herein, Birnessite was used for electrochemical adsorption of As from mining wastewater at a constant cell voltage, and the effect of cell voltage and the continuous use (without desorption) performance of Birnessite electrode were also evaluated. At 1.2 V for 24 h, the concentrations of total As (As(T)) and As(III) in wastewater decreased from 3808.7 to 73.7 μg L−1 and 682.8 to 21.4 μg L−1, respectively. The As(T) removal ratio increased with increasing cell voltage and reached 98.1% at 1.2 V, which was higher than that at open circuit (84.1%). The Mn2+ concentration also significantly decreased in wastewater during As adsorption. The high potential of Birnessite anode and the generation of H2O2 on cathode facilitated As(III) oxidation, and the electrochemical redox reactions of Birnessite contributed to the enhancement of As(T) removal. The application of cell voltage reversal could improve the utilization rate of Birnessite electrodes by dissolution-recrystallization during continuous use, and the As(T) removal ratio was increased from 73.5% to 85.1% after five cycles of voltage alteration. The present work indicates that Birnessite is a promising absorbent for the electrochemical adsorption of As from real wastewaters.
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enhancement of zn2 and ni2 removal performance using a deionization pseudocapacitor with nanostructured Birnessite and its carbon nanotube composite electrodes
Chemical Engineering Journal, 2017Co-Authors: Steven L Suib, Lirong ZhengAbstract:Abstract Manganese oxides have been widely used as deionization capacitor electrode materials to remove heavy metal ions from aqueous solutions. However, the effect of pseudocapacitive properties of manganese oxides on the removal processes remains elusive. In this work, synthesized nanostructured Birnessite-type manganese oxide and Birnessite/carbon nanotubes (HB/CNTs) nanocomposites were used as deionization pseudocapacitor electrode materials for Zn 2+ and Ni 2+ removal from aqueous solution by constant potential electrolysis. The effects of operation potential and introduction of carbon nanotubes (CNTs) on Zn 2+ and Ni 2+ removal capacities were further investigated. The results demonstrated a significant enhancement of electrochemical removal capacities for Zn 2+ and Ni 2+ by the pseudocapacitive properties of Birnessite and the introduction of CNTs. The Zn 2+ and Ni 2+ removal capacities of Birnessite electrode increased first and then decreased with the decrease of potential from 0.2 to −0.2 V ( vs . SCE), and the highest removal capacities for Zn 2+ and Ni 2+ respectively reached 89.5 and 96.6 mg g −1 when the potential was controlled at 0 V. The HB/CNTs nanocomposite showed higher removal capacities (155.6 mg g −1 for Zn 2+ and 158.4 mg g −1 for Ni 2+ when the relative content of manganese oxide was 45.6%) and a better cycling stability (about 90% and 88% of the initial Zn 2+ and Ni 2+ removal capacity were retained after 5 cycles) than Birnessite electrode. The present study makes clear the pseudocapacitive mechanism of heavy metal ion removal using Birnessite, and proposes a facile method to remove heavy metal ions from aqueous solution.
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local structure of cu 2 in cu doped hexagonal turbostratic Birnessite and cu 2 stability under acid treatment
Chemical Geology, 2017Co-Authors: Quanjun Xiang, Lirong Zheng, Matthew Gindervogel, Juan Xiong, Luuk K Koopal, Mingxia Wang, Xionghan FengAbstract:Abstract Geochemical behaviors of heavy metal contaminants, such as Cu 2 + , are strongly controlled by natural Birnessite-like minerals in both marine and terrestrial environments. However, the mechanisms of the interaction of Cu 2 + with Birnessite are not fully understood yet. In the present study, Cu 2 + was coprecipitated with Mn 2 + to produce hexagonal turbostratic Birnessite, which is analogous to natural Birnessite. The obtained Cu-doped Birnessite was characterized by powder X-ray diffraction, field-emission scanning electron microscopy, and X-ray absorption spectroscopy (XANES + EXAFS). The stability of Cu(II) in the Birnessite structure was investigated by acid treatment. Increasing the dopant content reduces the mineral crystallinity in the [001] direction and the unit cell parameter b from the hexagonal layers. It also shortens the bond length of Mn O in the [MnO 6 ] unit and the edge-sharing Mn Mn distance in the layers, and increases the average oxidation state (AOS) of Mn and the specific surface area. Analysis of Cu K-edge XANES and EXAFS data indicates that, only a small part of Cu(II) is inserted into the Birnessite layers, while most of it is adsorbed on the vacancies. When the Cu/Mn molar ratio is increased from 0.08 to 0.23, an increasing part of Cu(II) is present as polynuclear clusters on the Birnessite edge sites in the pH range of ~ 3.3–5.3. Reaction with H 2 SO 4 solution is found to easily dissolve the polynuclear Cu clusters and the highly distorted Cu octahedra in innersphere complexes on the Birnessite-water interface, with ~ 53% of the Cu 2 + released into the solution. On the other hand, the reaction with HCl solution leads to reductive dissolution of the mineral matrix, the release of Mn 2 + into solutions, the decrease in the first Mn O and edge-sharing Mn Mn distances and Mn AOS, in addition to the release of Cu 2 + . The release rate of Cu 2 + is much faster than that of Ni 2 + in Ni-doped Birnessites, owing to the lower stability of distorted [CuO 6 ] octahedron upon proton attack. These results indicate the formation of multinuclear Cu complexes on Birnessite surfaces under the investigated conditions. The results also suggest the lower stability of Cu 2 + in these minerals and thus higher potential toxicity in acidic conditions, in comparison with other metal pollutants, such as Ni 2 + . This study provides new insights into the interaction mechanisms between Cu 2 + and Birnessite-like minerals, and help to clarify the structural stability and geochemical behaviors of Cu 2 + associated with Birnessite-like minerals in natural environments.
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effects of co and ni co doping on the structure and reactivity of hexagonal Birnessite
Chemical Geology, 2014Co-Authors: Hui Li, Xionghan Feng, Yan Wang, Matthew Gindervogel, Lirong ZhengAbstract:Abstract Natural hexagonal Birnessites are enriched in various transition metals (TMs). Many studies have examined the effects of single metal doping on the structures and properties of Birnessites, but none focused on the simultaneous interaction mechanism of coprecipitation of two different TMs with Birnessite. In this work Co and Ni co-doped hexagonal Birnessites were synthesized and characterized by powder X-ray diffraction (XRD), elemental analysis, field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS) spectroscopy to investigate the effects of co-doping on the structure and reactivity of Birnessite and the crystal chemistry of Co and Ni. These co-doped Birnessites have lower crystallinity, i.e., fewer manganese layers stacking in the c* direction, larger specific surface areas (SSAs) and increased Mn average oxidation states (AOSs) than the undoped Birnessite, and Co exists in a valence of + 3. Co, Ni and Mn K -edge extended X-ray absorption fine structure spectroscopy (EXAFS) spectra demonstrate an increase in edge-sharing Ni–Me (Me = Ni, Co and Mn) distances in Birnessite layers with the increase of the contents of dopants while Mn–Me distances first decrease and then increase while those of Co–Me pairs are nearly constant, coupled with first a decrease and then increase of the in-plane unit-cell parameter b. The effect of co-doping on the amounts of structural Mn and K + , numbers of [MnO 6 ] layers stacked in c* axis, and SSAs, is larger than the effects of doping with Co alone, but less than singly Ni doping. In Birnessites doped with both Co and Ni, ~ 74–79% of the total Co and ~ 23–39% of the total Ni are present within the manganese layers. Compared with the spatial distribution of TM in singly doped Birnessites, the coexistence of Ni hinders the incorporation of Co into the layers during Birnessite crystallization; however, coprecipitation with Co has little effects, neither hindrance nor promotion, on the insertion of Ni into the layers. These results provide insight into the interaction mechanism between coexisting Co, Ni within layered Mn oxides. It further helps us to interpret the geochemical characteristics of multi-metal incorporation into natural Mn oxides and their effects on the structures and physicochemical properties of these minerals.
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characterization of ni rich hexagonal Birnessite and its geochemical effects on aqueous pb2 zn2 and as iii
Geochimica et Cosmochimica Acta, 2012Co-Authors: Lirong Zheng, Xionghan FengAbstract:Hexagonal Birnessite is the most ubiquitous manganese oxide in geological environments. It is often highly enriched in trace metal ions such as Ni and plays an important role in metal(loids) geochemistry. Nanostructured Birnessites containing different amounts of Ni were synthesized by addition of Ni2+ to initial reactants. Powder X-ray diffraction (XRD), element analysis, field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), X-ray absorption spectroscopy (XAS) and isothermal adsorption and oxidation of metal(loids) were carried out to investigate the effects of Ni doping on the substructure and physicochemical properties of Birnessite, and Ni crystal chemistry in Birnessite. These Ni-rich Birnessites have Ni contents as high as 2.99% (Ni5) and 6.08% (Ni10) in weight. EXAFS results show that Ni5 has 23.7% of the total Ni (0.71 wt.%) and Ni10 has 34.5% of the total Ni (2.10 wt.%) in Mn octahedral layer with the remaining Ni located at vacancies and edge sites. The Ni-rich Birnessites have weaker crystallinity and thermal stability, fewer layers stacked along the c axis, similar to 1.5-2.7 times larger surfaces areas, and a higher Mn average oxidation numbers (AONs) compared to the Birnessite without Ni. Additionally, the doping of Ni during Birnessite crystallization enhances the formation of vacancies in the layer; however, adsorption capacities for Pb2+ and Zn2+ by these Ni-rich Birnessites are reduced, mainly because of vacancies and edge sites occupation by a large amount of Ni. The Ni-rich Birnessites exhibit much higher oxidation capability and can completely oxidize As(III) in solution at rapid initial reaction rates under the experimental condition. The results indicate that incorporation of Ni into the natural Birnessite in ferromanganese nodules may be achieved both by direct coprecipitation with Mn to build the layers and migration over time from adsorbed Ni on the surface into the layer structure. It is also implied that Ni doping in Birnessite has great impact on the geochemical behaviors of heavy metals, either in adsorption or oxidation reactions. (C) 2012 Elsevier Ltd. All rights reserved.
Sridhar Komarneni - One of the best experts on this subject based on the ideXlab platform.
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Sorption characteristics of lead cations on microporous organo-Birnessite
Applied Clay Science, 2013Co-Authors: Sridhar KomarneniAbstract:Abstract The aim of this study was to examine the adsorption characteristics of cationic surfactant modified-Birnessite for removal of Pb. For this purpose, Na-Birnessite and tetramethylammonium (TMA) cation were used as an inorganic host and cationic surfactant, respectively. Na-Birnessite was synthesized by the oxidation of Mn 2 + under alkaline condition, and TMA cation was intercalated in the interlayer of H-Birnessite prepared from Na-Birnessite. Batch isotherm tests were carried out to investigate the adsorption capacity of the TMA-Birnessite for Pb. The characterization of all synthetic Birnessites was carried out with powder X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), and Brunauer–Emmett–Teller (BET) specific surface area measurements. Also, Fourier transform infrared spectroscopy (FT-IR) was used to investigate sorption behavior of Pb onto TMA-Birnessite. TMA-Birnessite was found to have higher adsorption ability for Pb than synthetic Na-Birnessite and commercial granular activated carbon (GAC). This result suggests that the synthetic organo-Birnessites could be effective sorbents for removal of heavy metals from groundwater.
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Sorption characteristics of lead cations on microporous organo-Birnessite
2013Co-Authors: Chae Young Lee, Sun Kee Han, Taesung Kim, Sridhar Komarneni, Yunchul ChoAbstract:The aim of this study was to examine the adsorption characteristics of cationic surfactant modified-Birnessite for removal of Pb. For this purpose, Na-Birnessite and tetramethylammonium (TMA) cation were used as an inorganic host and cationic surfactant, respectively. Na-Birnessite was synthesized by the oxidation of Mn2+ under alkaline condition, and TMA cation was intercalated in the interlayer of H-Birnessite prepared from Na-Birnessite.Batch isotherm tests were carried out to investigate the adsorption capacity of the TMA-Birnessite for Pb. The characterization of all synthetic Birnessites was carried out with powder X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) specific surface area measurements. Also, Fourier transform infrared spectroscopy (FT-IR) was used to investigate sorption behavior of Pb onto TMA-Birnessite. TMA-Birnessite was found to have higher adsorption ability for Pb than synthetic Na-Birnessite and commercial granular activated carbon (GAC). This result suggests that the synthetic organo-Birnessites could be effective sorbents for removal of heavy metals from groundwater. © 2013 Elsevier B.V.
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Uptake of cadmium, copper, and lead by microporous synthetic Na-Birnessite
Journal of Porous Materials, 2010Co-Authors: Suyeon Jang, Sridhar KomarneniAbstract:Removal of cadmium, copper and lead with microporous synthetic Na-Birnessite (sodium-Birnessite) was investigated by carrying out batch-type sorption experiments with 2 days of equilibration at room temperature. The sorption isotherms indicated that synthetic Na-Birnessite showed high affinity for all three heavy metal cations. The Na-Birnessite was able to take up Cd, Cu and Pb up to approximately 140, 106 and 60%, respectively of its theoretical cation exchange capacity. The above higher uptakes of Cd and Cu than the theoretical cation exchange capacity of Birnessite were probably caused by exchange of not only Cd2+ but also CdCl+ species with Na+ and by exchange of not only Cu2+ but also CuCl+ species with Na+. Some exchange of CdCl+ and CuCl+ species as well as some pH-dependent specific adsorption of the Cd and Cu cations resulted in higher than theoretical uptakes. The XRD patterns after sorption of Cd with Na-Birnessite showed an increase in the d(001)-spacing from 7.144 to 7.244 A with high Cd2+ concentration, which indicated that interlayer Na+ ions were replaced by Cd2+ ions. After the sorption reactions with high Cu concentrations, the XRD patterns showed that the main d(001)-spacing of the Birnessite slightly increased from 7.144 to ~7.179 A. In the case of Pb sorption, the d(001)-spacing slightly decreased to 7.133 A from 7.144 A of the as synthesized Na-Birnessite. These results suggest that removal of heavy metal cations by Na-Birnessite is likely due to both ion exchange and chemisorption, the latter due to surface complexation at the edges and outer planar surfaces of Na-Birnessite. Based on these results, Na-Birnessite is proposed as a potential candidate material to remove heavy metal cations from groundwater as well as industrial wastewater.
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time resolved structural analysis of k and ba exchange reactions with synthetic na Birnessite using synchrotron x ray diffraction
American Mineralogist, 2007Co-Authors: Christina L Lopano, Peter J. Heaney, Jeffrey E. Post, Jonathan C Hanson, Sridhar KomarneniAbstract:Time-resolved Rietveld refinements using synchrotron X-ray diffraction (XRD) have documented real-time changes in unit-cell parameters in response to cation substitution in synthetic Na-Birnessite. Potassium- and Ba-Birnessite, like Na-Birnessite, were found to have triclinic symmetry. Rietveld analyses of the XRD patterns for K- and Ba-exchanged Birnessite revealed decreases in the a , c , and β unit-cell parameters, with a decrease of 1.7 and 0.5%, respectively, in unit-cell volume relative to Na-Birnessite. Fourier electron difference syntheses revealed that the changes in the configuration of the interlayer species, and the charge, size, and hydration of the substituting cations, serve as the primary controls on changes in unit-cell parameters. Split electron density maxima with centers at (0 0 0.5) were present for Na, K, and Ba end-members; however, with increased substitution of K+ for Na+, the axis connecting the split-site maxima rotated from an orientation parallel to the b -axis to along the a -axis. Substitution of Ba2+ for Na+ did not result in rotation, but splitting of the interlayer site was more pronounced.
