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Photocatalytic Reduction of Cr^Ⅵ by Natural Sphalerite Suspensions under Visible Light Irradiation

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Acta Geologica Sinica(English Edition) 2006年第2期80卷 267-272页

作者： LI Yan lu anhuai WANG Changqiu School of Earth and Space Sciences Peking University Beijing 100871

The photocatalytic reductive capability of a natural semiconducting mineral, sphalerite has been studied for the first time. The sphalerite from the Huangshaping deposit of Hunan Province performed great photoreductive capability that 91.95% of the Cr^6＋ was reduced under 9 h visible light irradiation, higher than the 70.58% under 9.5 h UV light irradiation. The highly reductive ability results from its super negative potential of electrons in the conduction band. Furthermore, Fe substitution for Zn introduces donor states, and the oxidation process of Fe^2＋ to Fe^3＋ makes it an effective hole-scavenger. Cd and Cu substitute for Zn also reduce the bandgap and help broaden the absorbing edge towards the visible light. These substituting metal ions in natural sphalerite make it a hyper-active photocatalyst and very attractive for solar energy utilization.

关键词： natural sphalerite photoreduction Cr^6+ visible light substituting ions bandgap

Semiconducting Mineralogical Characteristics of Natural Sphalerite Gestating Visible-light Photocatalysis

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Acta Geologica Sinica(English Edition) 2009年第3期83卷 633-639页

作者： LI Yan lu anhuai WANG Changqiu Key Laboratory of Orogenic Belts and Crustal Evolution MOE School of Earth and Space Sciences Peking University Beijing 100871 China

Natural sphalerite as a natural cost-effective photocatalyst was characterized and its visible light photocatalytic activity was investigated in terms of substituting ions, impurity phases and surface defects. The substitutions of metal ions for Zn2＋ alter the band structure and result in the visible light response. The coexistence of impurity semiconductors and nanosized particles in natural sphalerite samples help to prolong the lifetime of electron-hole pairs. The cleavage planes and fracture surfaces improve the photocatalytic activity of natural sphalerite by providing more active sites than perfect faces. Both the negative charge defects from the non-isoelectronic substitutions and surface elements with variable chemical valence suppressed the recombination of electron-hole pairs by their possible role of capturing photogenerated holes.

关键词： photocatalyst natural sphalerite bandgap visible light defects

Mimicking natural paragenetic semiconducting minerals MoS2/sphalerite：A simple method to fabricate visible-light photocatalyst

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Science China(Technological Sciences) 2017年第12期60卷 1870-1877页

作者： LIU Yi LI Yan lu anhuai WANG ChangQiu DING HongRui The Key Laboratory of Orogenic Belts and Crustal Evolution Beijing Key Laboratory of Mineral Environmental Function School of Earth and Space Sciences Peking University Beijing 100871 China

Natural paragenetic semiconducting minerals give important hints for fabricating stable and effective photocatalysts, which can be widely used in solar energy harvest and pollution control. To enhance the photoactivity of natural sphalerite(ZnS), needle-like nanocrystal MoS_2 was loaded on sphalerite surface through a hydrothermal method, mimicking the intergrowth of molybdenite(MoS_2) and sphalerite in nature. The resultant coupled MoS_2/sphalerite exhibited a hydrogen evolution reaction(HER) potential at-0.35 V(vs. NHE), and showed obvious photoresponse under visible-light. The photodegradation rate of methyl orange(MO) over MoS_2/sphalerite could reach 75% within 180 min. Compared to sphalerite, coupled MoS_2/sphalerite had a higher photocurrent,more positive HER potential and 66% higher photodegradation rate. The enhanced photoactivity was attributed to the charge transfer from sphalerite to MoS_2 and high electrons' mobility on MoS_2 layer.

关键词： sphalerite MoS2 coupled semiconductor visible-light photocatalysis

Determination of Fe^(2+)/Fe^(3+)Ratios of Magnetite using Different Methods:A Case Study from the Qimantag Metallogenic Belt

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Acta Geologica Sinica(English Edition) 2022年第6期96卷 2135-2147页

作者： YI Liwen LI Qiuping lu anhuai GU Xiangping CHI Guoxiang School of Geographical Sciences Hunan Normal UniversityChangsha 410081China School of Geosciences and Info-Physics Central South UniversityChangsha 410083China School of Earth and Space Sciences Peking UniversityBeijing 100871China Department of Geology University of ReginaReginaSaskatchewan S4S 0A2Canada

Determination of Fe^(2+)/Fe^(3+) ratios from metallogenic belts to explore controlling physical and chemical conditions of rock formation is of great *** order to explore magnetite Fe^(2+)/Fe^(3+) ratios of the Qimantag metallogenic belt,part of the Eastern Kunlun orogenic belt in the northeastern margin of the Qinghai–Tibetan plateau,western Central Orogenic Belt of China,and overcome the limitation of the traditional electronic probe,five different measurement methods are proposed and their respective advantages and disadvantages evaluated,with the composition data of the magnetite obtained using electron probe microanalysis(EPMA).The direct oxygen measurement method has a significant impact on the determination results of FeO and Fe2O3,but the accuracy and uniformity of the results are *** valence method(Flank method)based on the spectral intensity ratio of Lαto Lβfor iron is also unreliable for FeO and Fe_(2)O^(3) measurements because it is difficult to establish a relationship between Lβ/Lα,the spectral intensity ratio,and the Fe^(2+)/Fe^(3+) content *** comparison,the charge difference method,the surplus-oxygen method and the Mössbauer spectrum method are still the most favorable.Mössbauer spectroscopy,with its isomer movement particularly sensitive to the oxidation state of iron,yields results closer to 0.5,which is relatively *** magnetite deposits are located in intrusions or contact zones and formed by magmatic fluids with high Fe2+/Fe3+ratios,whereas later magnetite deposits are farther away from intrusions and have low Fe^(2+)/Fe^(3+) *** transformation mechanism of hematite and magnetite in the Qimantage metallogenic belt is also *** large volume changes,such as pore filling and shrinkage fracture,were detected in the metallogenic belt,and the transformation mechanism is more similar to a reoxidation and reduction mechanism.

关键词： iron magnetite direct oxygen measurement flank-charge difference-surplus-oxygen methods Mössbauer spectra Qimantage

Synthesis of Pb-Feldspar by Ion Exchange Reaction and Its Implications

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Acta Geologica Sinica(English Edition) 2006年第2期80卷 175-179页

作者： LIU Rui lu anhuai QIN Shan Land and Resources Department Changchun Institute of Technology Changchun Jilin 130021 School of Earth and Space Sciences Peking University Beijing 100871

Feldspar and Pb（NO3）2 were mixed and reacted at T=380℃ to synthesize Pb-feldspar. In the XRD （X-ray diffraction） pattern of the product, the d values （crystal lattice spacing） of the five peaks are 0.654, 0.342, 0.332, 0.327 and 0.257 nm. The XPS analysis results show that the binding energy of Pb 4f（7/2） in the feldspar was between 137.81-138.03 eV. Pb^2＋ can replace alkali and alkali earth cations in the feldspar structure through ion exchange reaction to form Pb-feldspar.

关键词： ion exchange Pb-feldspar XRD spectrum XPS analysis

Experimental Study on Formation Conditions of Ammoniojarosite and Its Environmental Significance

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Acta Geologica Sinica(English Edition) 2006年第2期80卷 296-301页

作者： WANG Changqiu MA Shengfeng lu anhuai ZHOU Jiangong School of Earth and Space Sciences Key Laboratory of Orogenic Belts and Crustal Evolution Ministry of Education Peking University Beijing 100871 National Research Center of Geoanalysis Beijing 100037

Formation conditions of ammoniojarosite in system Fe2（SO4）3-（NH4）2SO4-H2O are investigated in this paper. The results show that ammoniojarosite can be formed rapidly under normal temperature and pressure by controlling suitable pH value and Fe2（SO4）3 and （NH4）2SO4 concentrations. The pH value, temperature and concentration of Fe2（SO4）3 medium are key factors influencing the formation of ammoniojarosite. Under normal temperature, precipitation of ammoniojarosite can be seen within 24 hours at pH values between 2.6-3.1, and a great quantity of ammoniojarosite is formed within 48 hours. At about 90℃, the pH value range forming ammoniojarosite extends to 1.2-3.1, and within this range the rise of pH value is advantageous to the formation of ammoniojarosite and high Fe2（SO4）3 concentration is also advantageous. Relative pure ammoniojarosite is synthesized under high Fe2（SO4）3 concentration （≥0.05 M） and ammoniojarosite containing melanterite and colloid amorphous hydroxide vitriol iron is formed at low Fe2（SO4）3 concentration. The deposition process of ammoniojarosite can be used to harness wastewater from mines and other industries and remove S, Fe and other toxic and harmful elements, such as As, Cr, Hg, Pb in water. Rapid formation of ammoniojarosite and other jarosite analogs under normal temperature and pressure has a good potential prospect for harnessing acid wastewater by means of precipitation of jarosite and its analogs.

关键词： ammoniojarosite formation conditions harness of acid wastewater environmental significance

Semiconducting Mineral Photocatalytic Regeneration of Fe^(2+) Promotes Carbon Dioxide Acquisition by Acidithiobacillus ferrooxidans

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Acta Geologica Sinica(English Edition) 2013年第3期87卷 761-766页

作者： LI Yan lu anhuai WANG Xin DING Hongrui WANG Changqiu The Key Laboratory of Orogenic Belts and Crustal Evolution School of Earth and Space Sciences Peking University

Chemoautotrophic organisms have once been excluded from the development of universally applicable CO2 fixation technology due to its low production yields of biomass. In this study, we used Acidithiobacillusferrooxidans （A.f.） as a model chemoautotrophic microorganism to test the hypothesis that exogenetic photoelectrons from semiconducting mineral photocatalysis can enable the regeneration of Fe^2＋ that could be then used by A.f. and support its growth. In a simulated electrochemical system, where exogenetic electrons were provided by an electrochemical approach, an accelerated growth rate of A.f. was observed as compared with that in traditional batch cultivation. In a coupled system, where light-irradiated natural rutile provided the primary electron source to feed A.f., the bacterial growth rate as well as the subsequent CO2 fixation rate was demonstrated to be in a light-dependent manner. The sustaining flow of photogenerated electrons from semiconducting mineral to bacteria provided an inexhaustible electron source for chemoautotrophic bacteria growth and CO2 fixation. This finding might contribute to the development of novel effective CO2 fixation technology.

关键词： CO2 fixation photocatalysis chemoautotrophic organisms semiconducting mineral

Photoelectrochemical performance of birnessite films and photoelectrocatalytic activity toward oxidation of phenol

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Journal of Environmental Sciences 2017年第2期29卷 259-267页

作者： Huiqin Zhang Hongrui Ding Xin Wang Cuiping Zeng anhuai lu Yan Li Changqiu Wang The Key Laboratory of Orogenic Belts and Crustal Evolution School of Earth and Space Sciences Peking University Institutes of Science and Development Chinese Academy of Sciences

Birnessite films on fluorine-doped tin oxide（FTO） coated glass were prepared by cathodic reduction of aqueous KMnO4. The deposited birnessite films were characterized with X-ray diffraction, Raman spectroscopy, scanning electron microscopy and atomic force *** photoelectrochemical activity of birnessite films was investigated and a remarkable photocurrent in response to visible light was observed in the presence of phenol, resulting from localized manganese d–d transitions. Based on this result, the photoelectrocatalytic oxidation of phenol was investigated. Compared with phenol degradation by the electrochemical oxidation process or photocatalysis separately, a synergetic photoelectrocatalytic degradation effect was observed in the presence of the birnessite film coated FTO *** degradation ratios were influenced by film thickness and initial phenol concentrations. Phenol degradation with the thinnest birnessite film and initial phenol concentration of 10 mg/L showed the highest efficiency of 91.4% after 8 hr. Meanwhile, the kinetics of phenol removal was fit well by the pseudofirst-order kinetic model.

关键词： Birnessite Photoelectrochemical activity Photocurrent Photoelectrocatalytic oxidation Phenol

Environmental Effects of Micro- and Ultra-microchannel Structures of Natural Minerals

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Acta Geologica Sinica(English Edition) 2006年第2期80卷 161-169页

作者： lu anhuai HUANG Shanshan LIU Rui ZHAO Dongjun QIN Shan School of Earth and Space Sciences Peking University Beijing 100871 Changchun Institute of Technology Changchun Jilin 130021

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.

关键词： environmental mineralogy cryptomelane feldspar ultra-microchannel effect ionic sieves