Cryptomelane is a reactive Mn oxide and has been used in removal of heavy metal from wastewaters. Co-doped cryptomelane was synthesized by refluxing at ambient pressure and characterized by powder X-ray diffraction, s...Cryptomelane is a reactive Mn oxide and has been used in removal of heavy metal from wastewaters. Co-doped cryptomelane was synthesized by refluxing at ambient pressure and characterized by powder X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and extended X-ray absorption fine structure spectroscopy, and its performances for removal of Pb^2+ and Cr^3+ from aqueous solutions were investigated. Co doping has a negligible effect on the structure and morphology of cryptomelane but increases the specific surface area and Mn average oxidation state. Mn and Co K-edge extended X-ray absorption fine structure spectroscopy(EXAFS) analysis shows that Co barely affects the atomic coordination environments of Mn, and distances of edge- and corner-sharing Co–Me(Me_Co, Mn) pairs are shorter than those of the corresponding Mn–Me pairs, implying the replacement of framework Mn(III) by Co(III). These Co-doped cryptomelanes can quickly oxidize Cr3+to be HCr O4-and remove 45%–66% of the total Cr in the reaction systems by adsorption and fixation, and they have enhanced Pb2+adsorption capacities. Thus these materials are promising adsorbents for heavy metal remediation. The results demonstrate the design and modification of environmental friendly Mn oxide materials and can help us understand the interaction mechanisms of transition metals with Mn oxides.展开更多
The investigation of the environmental properties of minerals, i.e., environmental mineralogy, is a branch of science dealing with interactions between natural minerals and spheres of the Earth surface as well as a re...The investigation of the environmental properties of minerals, i.e., environmental mineralogy, is a branch of science dealing with interactions between natural minerals and spheres of the Earth surface as well as a reflection of global change, prevention of ecological destruction, participation in biomineralogy, and remediation of environmental pollution. Pollutant treatment by natural minerals is based on the natural law and reflects natural self-purification functions in the inorganic world, similar to that of the organic world - a biological treatment. A series of case studies related to natural self-purification, which were mostly completed by our group, are discussed in this paper. In natural cryptomelane there is a larger pseudotetragonal tunnel than that formed by [MnO6] octahedral double chains, with an aperture of 0.462-0.466 nm2, filled with K cations. Cryptomelane might be a real naturally-occurring mineral of the active octahedral molecular sieve (OMS-2). CrⅥ-bearing wastewater can be treated by natural pyrrhotite, which is used as a reductant to reduce CrⅥ and as a precipitant to precipitate CrⅢ simultaneously. Batch experiments were conducted using the CTMAB-Montmorillonite as an adsorbent for aromatic contaminants (phenol, aniline, benzene, toluene and xylenes), which are detected frequently in the leaching water from municipal waste deposits around China. The CTMAB modification has proved very effective to enhance the adsorption capacity of the sorbent. Expansion of vermiculite develops loose interior structures, such as pores or cracks, inside briquettes, and thus brings enough oxygen for combustion and the sulfation reaction. Effective combustion of the original carbon reduces the amount of dust in the fly ash.展开更多
Four kinds of cryptomelane-type octahedral molecular sieve(OMS)-2-X(the X represents the molar ratio of KMnO4/MnAc2) were prepared as catalytic materials for ozone decomposition through a one-step hydrothermal reactio...Four kinds of cryptomelane-type octahedral molecular sieve(OMS)-2-X(the X represents the molar ratio of KMnO4/MnAc2) were prepared as catalytic materials for ozone decomposition through a one-step hydrothermal reaction of KMnO4 and MnAc2, by changing their molar ratios. These samples were characterized by N2 adsorption–desorption, X-ray di raction(XRD), transmission electron microscopy(TEM), scanning electron microscopy(SEM), temperature programmed reduction by H2(H2-TPR) and X-ray photoelectron spectroscopy(XPS). Among them, the OMS-2-0.7 sample showed the best O3 conversion of 92% under high relative humidity(RH) of 90% and gas hourly space velocity of 585,000 h-1. This was accordingly thought as a possible way for purifying ozone-containing waste gases under high RH atmospheres. The e ciency of ozone decomposition of the prepared OMS-2-X sample was found to be related to specific surface area, particle size, surface oxygen vacancies, and Mn3+ cation amounts. The one-step hydrothermal synthesis was shown to be a simple method to prepare the considerably active OMS-2 solids for ozone decomposition.展开更多
The micro-channels usually refers to structural channels of minerals with aperture in the range of 0.3 nm to 2.0 nm. Such microchannels include, Mn-O octahedron channel filled by K in cryptomelane, and channel constru...The micro-channels usually refers to structural channels of minerals with aperture in the range of 0.3 nm to 2.0 nm. Such microchannels include, Mn-O octahedron channel filled by K in cryptomelane, and channel constructed by Si-O and AI-O tetragonal molecular sieve filled by Na and Ca in zeolite, and effectively have the function of molecular sieve. Here we point out that ultramicrochannels of natural minerals have apertures below 0.3 nm with the features of ionic sieves. The ultra-microchannels of mineral feldspar, accounting for half mass of the Earth's crust, have been largely ignored because the aperture is too small. In this work, we present that feldspar displays a certain degree of ion exchange and owns a feature of channel structure under both high and low temperatures. At high temperature, Na^+ can enter the channels of feldspars. The content of Na2O in feldspar increases up to 15.9%. At middle temperature, Pb^2+ can also enter the channels of feldspar as the result of ion exchange, leading thus to the formation of Pb-feldspar. At room temperature, about 97.94% Cd^2+ can be removed and Cd-feldspar can be obtained. These phenomena indicate typical effects of ultra-microchannels of feldspar, which may be suggested as a potential for the treatment of heavy metal pollution and nuclear waste. The ultra-microchannels of natural minerals have played special role in migration and exchange of geomaterials. The molecular sieves of microchannels of a few natural minerals have the property of purifying molecular gas pollution. And the ionic sieves of ultramicrochannels of most natural minerals can purify ionic water contaminates.展开更多
Alkali metal potassium was beneficial to the electronic regulation and structural stability of transition metal oxides.Herein,K ions were introduced into manganese oxides by different methods to improve the degradatio...Alkali metal potassium was beneficial to the electronic regulation and structural stability of transition metal oxides.Herein,K ions were introduced into manganese oxides by different methods to improve the degradation efficiency of toluene.The results of activity experiments indicated that KMnO_(4)-HT(HT:Hydrothermal method)exhibited outstanding low-temperature catalytic activity,and 90%conversion of toluene can be achieved at 243℃,which was 41℃and 43℃lower than that of KNO_(3)-HT and Mn-HT,respectively.The largest specific surface area was observed on KMnO_(4)-HT,facilitating the adsorption of toluene.The formation of cryptomelane structure over KMnO_(4)-HT could contribute to higher content of Mn^(3+)and lattice oxygen(Olatt),excellent low-temperature reducibility,and high oxygen mobility,which could increase the catalytic performance.Furthermore,two distinct degradation pathways were inferred.PathwayⅠ(KMnO_(4)-HT):toluene→benzyl→benzoic acid→carbonate→CO_(2)and H2O;PathwayⅡ(Mn-HT):toluene→benzyl alcohol→benzoic acid→phenol→maleic anhydride→CO_(2)and H2O.Fewer intermediates were detected on KMnO_(4)-HT,indicating its stronger oxidation capacity of toluene,which was originated from the doping of K^(+)and the interaction between K-O-Mn.More intermediates were observed on Mn-HT,which can be attributed to the weaker oxidation ability of pure Mn.The results indicated that the doping of K^(+)can improve the catalytic oxidation capacity of toluene,resulting in promoted degradation of intermediates during the oxidation of toluene.展开更多
Manganese oxides in association with paleo-weathering may provide significant insights into the multiple factors affecting the formation and evolution of weathering profiles, such as temperature, precipitation, and bi...Manganese oxides in association with paleo-weathering may provide significant insights into the multiple factors affecting the formation and evolution of weathering profiles, such as temperature, precipitation, and biodiversity. Laser probe step-heating analysis of supergene hollandite and cryptomelane samples collected from central Queensland, Australia, yield well-defined plateaus and consistent isochron ages, confirming the feasibilityy dating very-fined supergene manganese oxides by 40Ar/39 Ar technique. Two distinct structural sites hosting Ar isotopes can be identified in light of their degassing behaviors obtained by incremental heating analyses. The first site, releasing its gas fraction at the laser power 0.2-0.4 W, yields primarily 40Aratm, 38Aratm, and 36Aratm(atmospheric Ar isotopes). The second sites yield predominantly 40Ar*(radiogenic 40Ar), 39Ark, and Ark (nucleogenic components), at -0.5-1.0 W. There is no significant Ar gas released at the laser power higher than 1.0 W, indicating the展开更多
基金supported by the National Natural Science Foundation of China (Nos.41271253 and 41401250)the Huazhong Agricultural University Doctoral Start-up Fund (Grant 52902-0900206162)
文摘Cryptomelane is a reactive Mn oxide and has been used in removal of heavy metal from wastewaters. Co-doped cryptomelane was synthesized by refluxing at ambient pressure and characterized by powder X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and extended X-ray absorption fine structure spectroscopy, and its performances for removal of Pb^2+ and Cr^3+ from aqueous solutions were investigated. Co doping has a negligible effect on the structure and morphology of cryptomelane but increases the specific surface area and Mn average oxidation state. Mn and Co K-edge extended X-ray absorption fine structure spectroscopy(EXAFS) analysis shows that Co barely affects the atomic coordination environments of Mn, and distances of edge- and corner-sharing Co–Me(Me_Co, Mn) pairs are shorter than those of the corresponding Mn–Me pairs, implying the replacement of framework Mn(III) by Co(III). These Co-doped cryptomelanes can quickly oxidize Cr3+to be HCr O4-and remove 45%–66% of the total Cr in the reaction systems by adsorption and fixation, and they have enhanced Pb2+adsorption capacities. Thus these materials are promising adsorbents for heavy metal remediation. The results demonstrate the design and modification of environmental friendly Mn oxide materials and can help us understand the interaction mechanisms of transition metals with Mn oxides.
基金supported by the National Key Program for Basic Research of China(No.2001CCA02400)the National Natural Science Foundation of China(Grant No.49672097,49972017 and 40172022).
文摘The investigation of the environmental properties of minerals, i.e., environmental mineralogy, is a branch of science dealing with interactions between natural minerals and spheres of the Earth surface as well as a reflection of global change, prevention of ecological destruction, participation in biomineralogy, and remediation of environmental pollution. Pollutant treatment by natural minerals is based on the natural law and reflects natural self-purification functions in the inorganic world, similar to that of the organic world - a biological treatment. A series of case studies related to natural self-purification, which were mostly completed by our group, are discussed in this paper. In natural cryptomelane there is a larger pseudotetragonal tunnel than that formed by [MnO6] octahedral double chains, with an aperture of 0.462-0.466 nm2, filled with K cations. Cryptomelane might be a real naturally-occurring mineral of the active octahedral molecular sieve (OMS-2). CrⅥ-bearing wastewater can be treated by natural pyrrhotite, which is used as a reductant to reduce CrⅥ and as a precipitant to precipitate CrⅢ simultaneously. Batch experiments were conducted using the CTMAB-Montmorillonite as an adsorbent for aromatic contaminants (phenol, aniline, benzene, toluene and xylenes), which are detected frequently in the leaching water from municipal waste deposits around China. The CTMAB modification has proved very effective to enhance the adsorption capacity of the sorbent. Expansion of vermiculite develops loose interior structures, such as pores or cracks, inside briquettes, and thus brings enough oxygen for combustion and the sulfation reaction. Effective combustion of the original carbon reduces the amount of dust in the fly ash.
基金financial support from the National Natural Science Foundation of China (No. U1862102)the Fundamental Research Funds for the Central Universities (XK1802-1, JD1819)
文摘Four kinds of cryptomelane-type octahedral molecular sieve(OMS)-2-X(the X represents the molar ratio of KMnO4/MnAc2) were prepared as catalytic materials for ozone decomposition through a one-step hydrothermal reaction of KMnO4 and MnAc2, by changing their molar ratios. These samples were characterized by N2 adsorption–desorption, X-ray di raction(XRD), transmission electron microscopy(TEM), scanning electron microscopy(SEM), temperature programmed reduction by H2(H2-TPR) and X-ray photoelectron spectroscopy(XPS). Among them, the OMS-2-0.7 sample showed the best O3 conversion of 92% under high relative humidity(RH) of 90% and gas hourly space velocity of 585,000 h-1. This was accordingly thought as a possible way for purifying ozone-containing waste gases under high RH atmospheres. The e ciency of ozone decomposition of the prepared OMS-2-X sample was found to be related to specific surface area, particle size, surface oxygen vacancies, and Mn3+ cation amounts. The one-step hydrothermal synthesis was shown to be a simple method to prepare the considerably active OMS-2 solids for ozone decomposition.
文摘The micro-channels usually refers to structural channels of minerals with aperture in the range of 0.3 nm to 2.0 nm. Such microchannels include, Mn-O octahedron channel filled by K in cryptomelane, and channel constructed by Si-O and AI-O tetragonal molecular sieve filled by Na and Ca in zeolite, and effectively have the function of molecular sieve. Here we point out that ultramicrochannels of natural minerals have apertures below 0.3 nm with the features of ionic sieves. The ultra-microchannels of mineral feldspar, accounting for half mass of the Earth's crust, have been largely ignored because the aperture is too small. In this work, we present that feldspar displays a certain degree of ion exchange and owns a feature of channel structure under both high and low temperatures. At high temperature, Na^+ can enter the channels of feldspars. The content of Na2O in feldspar increases up to 15.9%. At middle temperature, Pb^2+ can also enter the channels of feldspar as the result of ion exchange, leading thus to the formation of Pb-feldspar. At room temperature, about 97.94% Cd^2+ can be removed and Cd-feldspar can be obtained. These phenomena indicate typical effects of ultra-microchannels of feldspar, which may be suggested as a potential for the treatment of heavy metal pollution and nuclear waste. The ultra-microchannels of natural minerals have played special role in migration and exchange of geomaterials. The molecular sieves of microchannels of a few natural minerals have the property of purifying molecular gas pollution. And the ionic sieves of ultramicrochannels of most natural minerals can purify ionic water contaminates.
基金supported by the National Natural Science Foundation of China(No.21872096)Scientific Research Project of Liaoning Provincial Department of Education(No.LJKMZ20220788)+2 种基金Zhongyuan Yingcai Jihua(No.ZYYCYU202012183)the Academic Leader of Henan Institute of Urban Construction(No.YCJXSJSDTR202204)the Doctoral Research Start-up Project of Henan University of Urban Construction(No.990/Q2017011)。
文摘Alkali metal potassium was beneficial to the electronic regulation and structural stability of transition metal oxides.Herein,K ions were introduced into manganese oxides by different methods to improve the degradation efficiency of toluene.The results of activity experiments indicated that KMnO_(4)-HT(HT:Hydrothermal method)exhibited outstanding low-temperature catalytic activity,and 90%conversion of toluene can be achieved at 243℃,which was 41℃and 43℃lower than that of KNO_(3)-HT and Mn-HT,respectively.The largest specific surface area was observed on KMnO_(4)-HT,facilitating the adsorption of toluene.The formation of cryptomelane structure over KMnO_(4)-HT could contribute to higher content of Mn^(3+)and lattice oxygen(Olatt),excellent low-temperature reducibility,and high oxygen mobility,which could increase the catalytic performance.Furthermore,two distinct degradation pathways were inferred.PathwayⅠ(KMnO_(4)-HT):toluene→benzyl→benzoic acid→carbonate→CO_(2)and H2O;PathwayⅡ(Mn-HT):toluene→benzyl alcohol→benzoic acid→phenol→maleic anhydride→CO_(2)and H2O.Fewer intermediates were detected on KMnO_(4)-HT,indicating its stronger oxidation capacity of toluene,which was originated from the doping of K^(+)and the interaction between K-O-Mn.More intermediates were observed on Mn-HT,which can be attributed to the weaker oxidation ability of pure Mn.The results indicated that the doping of K^(+)can improve the catalytic oxidation capacity of toluene,resulting in promoted degradation of intermediates during the oxidation of toluene.
基金This study was supported by the National Key Research Project of China (Grant No. G1999043207-3) ARC of Australia (Grant Nos. A39531815 and A39701507).
文摘Manganese oxides in association with paleo-weathering may provide significant insights into the multiple factors affecting the formation and evolution of weathering profiles, such as temperature, precipitation, and biodiversity. Laser probe step-heating analysis of supergene hollandite and cryptomelane samples collected from central Queensland, Australia, yield well-defined plateaus and consistent isochron ages, confirming the feasibilityy dating very-fined supergene manganese oxides by 40Ar/39 Ar technique. Two distinct structural sites hosting Ar isotopes can be identified in light of their degassing behaviors obtained by incremental heating analyses. The first site, releasing its gas fraction at the laser power 0.2-0.4 W, yields primarily 40Aratm, 38Aratm, and 36Aratm(atmospheric Ar isotopes). The second sites yield predominantly 40Ar*(radiogenic 40Ar), 39Ark, and Ark (nucleogenic components), at -0.5-1.0 W. There is no significant Ar gas released at the laser power higher than 1.0 W, indicating the
基金This work was supported by the National Natural Science Foundation of China (Grant Nos. 21277008 and 20777005) and Natural Science Foundation of Beijing (Grant No. 8082008).