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利用双室微生物电化学装置对微生物和半导体矿物协同作用下偶氮类染料废水的还原脱色降解进行了系统的实验研究.不同光照条件及不同阴极电极材料的对比实验结果显示,偶氮染料甲基橙(MO)可作为终端电子受体直接从固体电极上获得电子被还原脱色;各对比实验中,在微生物催化与半导体矿物光催化协同作用条件下,MO还原脱色效率最高.电化学交流阻抗谱(EIS)的拟合结果显示金红石涂布阴极电极光照下极化内阻(Rp)为443.4 Ω,较无光条件下的1378 Ω显著降低,证明光照下金红石阴极的电子转移过程受其光催化作用的驱动.不同初始浓度下MO的生物-半导体催化还原反应符合准一级动力学模型,其反应速率随MO初始浓度降低而增加.通过对脱色产物的进一步分析,推测该实验中MO的还原脱色反应机制为: 阳极初始电子供体在微生物的催化作用下将电子通过阳极电极和外电路传递给阴极半导体矿物电极,进而在半导体矿物的光催化作用下通过光生电子还原终端电子受体MO,使MO中的偶氮键断裂,生成无色的联氨类衍生物. 相似文献
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在地表环境中,铁氧化物矿物可以作为微生物胞外呼吸的终端电子受体/供体、电子储存介质或种间电子传递介质促进环境微生物的新陈代谢。本文介绍了矿物-微生物直接界面电子转移方式中,铁氧化物矿物与组成微生物跨膜电子传输链的细胞色素蛋白之间的氧化-还原反应机制及其影响因素,从分子水平刻画了微生物利用矿物进行胞外呼吸的过程,有助于深入理解微生物驱动的矿物转化和元素地球化学循环。 相似文献
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甲烷(CH?)不仅是自然界产生的重要温室气体,也是人类已经推广利用的可再生能源之一.作为自然界广泛存在的矿物,铁氧化物同厌氧微生物的交互作用对产甲烷过程具有显著的影响.主要针对不同铁氧化物-厌氧微生物体系内的产甲烷效率,铁氧化物及微生物群落演化,铁氧化物的作用机制等进行总结分析.铁氧化物在微生物的作用下会发生溶解、还原并可能产生新的矿物.而铁氧化物的直接和间接影响微生物群组成,进而影响产甲烷过程,主要体现在4个方面:(1)铁氧化物溶解及生物还原产生的Fe~(3+)/Fe~(2+)影响微生物活性和体系氧化还原电位;(2)铁还原菌和产甲烷菌竞争产甲烷基质;(3)铁氧化物对产甲烷菌的直接抑制毒性;(4)具有导电性能的铁氧化物可以作为电子传递媒介促进铁还原菌或脂肪酸氧化菌与产甲烷菌之间的直接电子传递过程.最后,探讨了铁氧化物促进产甲烷过程尚需解决的主要问题及研究趋势,以期推动铁氧化物-厌氧微生物交互作用及其环境效应方面的研究工作. 相似文献
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灌溉等人为活动会造成外源物质的输入,如硝酸盐、有机质等,从而引起浅层地下水环境发生周期性波动。为研究农业灌溉对沉积含水层中碘迁移富集过程的影响,选取代表性富碘沉积物,通过室内实验模拟了灌溉活动外源物质输入条件下,盆地地下水系统中碘迁移释放的（生物）地球化学过程。实验结果表明：厌氧条件下,外源有机质输入可促使微生物利用有机质作为电子供体,还原固相铁矿物相,进而造成搭载于铁氧化物/氢氧化物表面的碘释放,以碘离子形式在地下水中富集;而在NO3-输入情况下,微生物会优先利用NO3-为电子受体,至硝酸盐被全部消耗后,Fe（Ⅲ）可进一步被还原为Fe（Ⅱ）。研究结果表明,人为活动造成浅表环境外源物质的输入可直接影响浅层地下水中碘的迁移释放过程。伊利石黏土矿物吸附的铁氧化物矿物相可能为浅层环境中碘的主要搭载介质,微生物作用下,铁氧化物/氢氧化物的还原溶解是高碘地下水形成的主控因素。 相似文献
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为了研究厌氧微生物作用下沉积物中砷的形态转化及固液界面的分配过程对砷的环境行为与归趋的影响,通过采集锦州湾清洁沉积物进行负载砷,利用微生物培养与非生物培养实验,对比研究厌氧微生物作用下砷铁硫共还原条件下污染体系中砷的环境行为与归趋。实验结果表明在培养的42 d周期内,液相的总砷量首先砷浓度保持降低趋势,而后再次升高。在培养第3~7 d时液相的As5+迅速被还原,约26%的溶解态砷从液相移除,97%以上的As5+被还原为As3+。同时微生物作用下固相中90%以上铁氧化物矿物逐渐转化为次生的亚铁矿物,固相中结晶态铁氧化物发生明显活化,而硫酸盐还原产物硫离子综合调控体系中游离的亚铁离子和As3+。因此,厌氧微生物还原条件下,砷,铁,硫同步发生还原,硫离子调控体系中砷和铁环境行为,硫化亚铁成为亚铁矿物的主要形态,硫化砷是砷的主要归趋。 相似文献
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微生物参与铁氧化物矿物的还原性溶解是高砷地下水形成的关键过程,其中具有砷还原功能的微生物如何参与含水层砷释放的生物地球化学过程亟待研究.利用从江汉平原典型高砷含水层中厌氧条件下分离出的四株细菌(Citrobacter sp.JH-1、Clostridium sp.JH-6、Exiguobacterium sp.JH-13、Paenibacillus sp.JH-33),通过室内厌氧模拟培养实验,查明其砷、铁还原能力,并通过分别与铁氧化物矿物及原位沉积物共同培养,探究原位含水层微生物参与的砷释放机理.结果表明:四株细菌均具有厌氧条件下砷、铁还原功能,Citrobacter sp.JH-1砷还原能力最强,96 h内还原的As(Ⅴ)浓度为2.22 μmol/L.其中Citrobacter sp.JH-1不仅可在厌氧和有氧条件下还原溶液中的As(Ⅴ),还可在厌氧条件下还原溶液中的Fe(Ⅲ)和无定型的水铁矿,在与含水层沉积物共培养12 d后,沉积物中铁与砷的释放量分别为510 mg/kg及1 150 μg/kg.江汉平原含水层中的原位微生物兼具砷/铁还原功能,在厌氧条件下可还原沉积物中的铁氧化物矿物并促进砷的释放,为深入揭示高砷地下水成因机理与地下水砷污染的防控提供重要科学依据. 相似文献
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铁还原细菌是微生物诱导矿化的典范之一,它可以利用有机质或氢气作为电子供体还原三价铁,并在细胞外矿化形成多种含铁矿物,比如磁铁矿、菱铁矿、蓝铁矿和绿锈等矿物,从而广泛参与自然界中铁元素的生物地球化学循环过程。本文主要介绍铁还原细菌矿化产物的矿物特征、形成条件和影响因素。此外,通过实验室内建立严格厌氧的环境体系,以与微量元素共沉淀的水合氧化铁为底物,本研究分别利用Feap2+和铁还原细菌Shewanella oneidensis MR-4合成非生物成因和生物成因的磁铁矿,结果发现微量元素的存在会改变磁铁矿的形貌和粒径。结合前人提出的微生物可能参与铁建造沉积的过程,本文评估了微量元素作为识别矿物成因指标的有效性,探讨铁还原细菌矿化产物对铁建造沉积的潜在贡献。 相似文献
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《吉林大学学报(地球科学版)》2015,(Z1)
<正>氧化铁作为高活性矿物的重要内因是以变价元素铁构成的氧化铁循环过程活跃。土壤铁循环是一个特殊微生物驱动的生物地球化学过程,长期以来普遍认为,以氧化铁矿物为末端电子受体、铁还原菌通过氧化电子供体藕联的氧化铁异化还原过程[1],与以游离态Fe(II)为电子受体、铁氧化菌作用产生的Fe(II)微生物氧化成矿过程[2],组成了完整的铁循环链[3](图1过程I和II)。1980年底有研究发现,厌氧条件下游离态 相似文献
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考察不同因素对异化铁还原菌(Dissimilatory Iron Reducing Bacteria,DIRB)还原高岭土中Fe(Ⅲ)的影响,通过在底液中添加不同有机酸、草酸盐、络合剂和重金属离子来研究微生物还原铁的机制。结果发现,添加草酸对微生物还原铁有明显的促进作用,而乙酸和水杨酸则抑制了微生物的生长;添加草酸钠的实验表明草酸对微生物的促进作用是通过草酸根离子的作用而与草酸的酸性并无联系;络合剂(NTA)可以提高微生物异化铁还原量,而EDTA不影响铁还原的作用;Cu(Ⅱ)对微生物具有毒害作用从而抑制了微生物的还原活性,Mn(Ⅱ)对铁的还原则有明显的促进作用。此外,采用logistic方程对有促进作用的曲线进行拟合,发现添加草酸钠对微生物的还原铁促进作用最大。 相似文献
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Mechanisms by which dissimilatory iron-reducing bacteria utilize iron and manganese oxide minerals as terminal electron acceptors for respiration are poorly understood. In the absence of exogenous electron shuttle compounds, extracellular electron transfer is generally thought to occur through the interfacial contact area between mineral surfaces and attached cells. Possible alternative reduction pathways have been proposed based on the discovery of a link between an excreted quinone and dissimilatory reduction. In this study, we utilize a novel experimental approach to demonstrate that Shewanella putrefaciens reduces the surface of crystalline iron oxides at spatial locations that are distinct from points of attachment. 相似文献
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The effects of goethite on the anaerobic bio-decomposition of sulfate minerals were investigated by using the beef extract
as a carbon source and the activated sludge as the source of mixed bacteria. Solution pH, sulfate concentration, total iron
ion concentration and the solid products of four different batch tests were monitored and analyzed. Experimental results showed
that the presence of iron oxide can improve the alkalinity of the reaction system which results in the increase of pH value.
Moreover, the added goethite consumed a large amount of H2S generated from the sulfate minerals by SRB, thereby significantly enhancing the decomposition of gypsum and anhydrite compared
with the control batch tests. In addition, the SEM observation and the EDS spectra showed that there were some rod-shaped
microorganisms and new generated minerals, such as iron sulfide, calcium carbonate crystals, and elemental sulfur. Both of
the proliferation of new minerals (iron sulfide and calcium carbonate crystals) and the complete disappearance of sulfate
minerals indicated that iron oxide can play the role in fixing the S element through the metabolism of SRB and hence improve
the bio-decomposition of sulfate minerals. 相似文献
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在地球上最为活跃的海洋透光层体系中,矿物-微生物交互作用的形式十分丰富。系统采集了黄海近海透光层水体样品,测试分析发现其中分布大量悬浮半导体矿物及微生物群落。通过电感耦合等离子质谱仪(ICP-MS)、环境扫描电子显微镜(ESEM)及配有的EDX能谱仪,从宏观到微区对悬浮颗粒矿物的化学元素组成进行了测试分析,发现其主要矿物组成元素为Si、O、Na、K、Ca、Al等,且含有较高含量的Mn、Fe、Ti等金属元素;通过X射线衍射光谱(XRD)、拉曼光谱(Raman)测试从整体到局部分析悬浮颗粒矿物的物相组成,发现其主要组成矿物为石英、钠长石、方解石、云母和绿泥石等,还有锐钛矿、金红石、板钛矿、针铁矿等铁、钛金属氧化物半导体矿物。通过16S rRNA高通量测序分析海水中主要微生物群落为Proteobacteria、Actinobacteria、Bacteroidetes、Planctomycetes、Woeseia、Fluviicola等,并通过构建双室反应体系对海水微生物与悬浮矿物间氧化还原作用及胞外电子传递过程进行了表征,结果显示增加海水悬浮矿物作为电子受体后,体系开路电压由330. 80 mV提升至426. 59 mV,提升比率达130%,最大输出功率由8. 376 9 mW/m^2提升至12. 096 8 mW/m^2,为原体系的1. 44倍。实验研究表明,海水透光层悬浮矿物能有效参与并促进微生物胞外电子传递过程,为后续深入研究基于电子能量传递利用的半导体矿物-微生物协同作用以及元素循环调控机制奠定初步基础。 相似文献
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The Nkout deposit is part of an emerging iron ore province in West and Central Africa. The deposit is an oxide facies iron formation comprising fresh magnetite banded iron formation (BIF) at depth, which weathers and oxidises towards the surface forming caps of high grade hematite/martite–goethite ores. The mineral species, compositions, mineral associations, and liberation have been studied using automated mineralogy (QEMSCAN®) combined with whole rock geochemistry, mineral chemistry and mineralogical techniques. Drill cores (saprolitic, lateritic, BIF), grab and outcrop samples were studied and divided into 4 main groups based on whole rock Fe content and a weathering index. The groups are; enriched material (EM), weathered magnetite itabirite (WMI), transitional magnetite itabirite (TMI) and magnetite itabirite (MI). The main iron minerals are the iron oxides (magnetite, hematite, and goethite) and chamosite. The iron oxides are closely associated in the high grade cap and liberation of them individually is poor. Liberation increases when they are grouped together as iron oxides. Chamosite significantly lowers the liberation of the iron oxides. Automated mineralogy by QEMSCAN® (or other similar techniques) can distinguish between Fe oxides if set up and calibrated carefully using the backscattered electron signal. Electron beam techniques have the advantage over other quantitative mineralogy techniques of being able to determine mineral chemical variants of ore and gangue minerals, although reflected light optical microscopy remains the most sensitive method of distinguishing closely related iron oxide minerals. Both optical and electron beam automated mineralogical methods have distinct advantages over quantitative XRD in that they can determine mineral associations, liberation, amorphous phases and trace phases. 相似文献
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Abdur Razzak Kenji Jinno Yoshinari Hiroshiro Md. Abdul Halim Keita Oda 《Environmental Geology》2009,58(3):459-469
A one dimensional reactive transport model was developed in order to illustrate the biogeochemical behavior of arsenic and
iron reduction and release to groundwater that accounts for the reaction coupling the major redox elements under reducing
environment. Mass transport equation and the method of characteristics were used considering fundamental geochemical processes
to simulate transport processes of different pollutants in mobile phase. The kinetic sub-model describes the heterotrophic
metabolisms of several microorganisms. To model a complete redox sequence (aerobic or denitrifiers, Fe(III)-reduction, respiration
bacteria of iron and arsenic compounds, and As(V) reduction) four functional bacterial groups (X
1, X
2, X
3, and X
4) were defined. Microbial growth was assumed to follow Monod type kinetics. The exchange between the different phases (mobile,
bio, and matrix) was also considered in this approach. Results from a soil column experiment were used to verify the simulation
results of the model. The model depicts the utilization of oxygen, nitrate, iron oxide and arsenic as electron acceptors for
oxidation of organic carbon (OC) in a column. The OC as electron donor is one of the most important factors that affect the
iron and arsenic reduction bacterial activity. 相似文献
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Hassan Abd El-Razek Aly Shahin 《Arabian Journal of Geosciences》2013,6(7):2245-2259
Optical microscopy, X-ray diffraction (XRD), and back-scattered electron imaging (BSE) have been used to determine the mineralogical composition of the uraniferous iron and manganese oxides and the associated U-minerals hosted in biotite granite that occurred north east Gabal El Sela area south Eastern Desert, Egypt. These mineralizations were found as veinlets fractures filling associated with strongly kaolinitic alteration of the coarse-grained biotite granite. XRD determined that the geothite mineral form the main constituent of uraniferous iron oxide in addition to tapiolite, and kaolinite minerals, where as uraniferous manganese oxide composed of pyrolusite, ramsdellite, and cryptomelane. BSE confirmed that the associated uranium minerals represented by uranothorite, kazolite, and zentime in addition to columbite-bearing minerals. Uranothorite and columbite-bearing minerals are the most abundant minerals in this mineralization. Petrographically, biotite granite is composed mainly of quartz, in addition to K-feldspars, biotite and muscovite with minor zircon, garnet, apatite, uranium-rich thorite and iron oxide. Petrochemical studies and tectonic discrimination diagrams for this granite reveal that they are classified as granite to alkali feldspar granite, originated from calc-alkaline magma having peraluminous nature and developed in within-plate tectonic environment. Field radiometric measurements revealed the localization of two high radiometric anomalies associated with iron and manganese oxides, within this anomaly uranium content range from 65 to 85 ppm. Alpha Track-etch Detectors of radon gas registrations revealed high track density reach up to 15,448.7 Bq/m3. 相似文献
18.
Although Mn is one of the major impurities in the economic iron ores from the Bahariya Oasis, information on its modes of occurrence and origin is lacking in previous studies. High-Mn iron ores from El Gedida and Ghorabi–Nasser iron mines were subjected to detailed mineralogical, geochemical, and petrographic investigations using X-ray diffraction (XRD), infrared absorption spectrometry (IR), Raman spectroscopy, X-ray fluorescence (XRF), scanning electron microscopy (SEM), and electron probe microanalyzer (EPMA) to clarify the modes of occurrence of Mn in these deposits and its origin. The results showed that the MnO2 contents range between 0.03 and 13.9 wt.%. Three mineralogical types have been identified for the Mn in the high-Mn iron ores, including: (1) inclusions within the hematite and goethite and/or Mn accumulated on their active surfaces, (2) coarse-grained and crystalline pyrolusite, and (3) fine-grained cement-like Mn oxide and hydroxide minerals (bixbyite, cryptomelane, aurorite, romanechite, manjiroite, and pyrochroite) between the Fe-bearing minerals. The Mn carbonate mineral (rhodochrosite) was detected only in the Ghorabi–Nasser high-Mn iron ores. Since IR patterns of low-Mn and high-Mn samples are almost the same, a combination of XRD analysis using non-filtered Fe-Kα radiations and Raman spectroscopy could be the best way to identify and distinguish between different Mn minerals.Assuming that both Fe and Mn were derived from the same source, the occurrence of high-Mn iron ores at the base of the stratigraphic section of the deposits overlain by the low-Mn iron ores indicated a supergene origin of the studied ores by descending solutions. The predominance of Mn oxide and hydroxide minerals in botryoidal shapes supports this interpretation. The small grain size of Mn-bearing minerals as well as the features of microbial fossils such as spherical, elliptical, and filamentous shapes of the Fe-bearing minerals suggested a microbial origin of studied iron ores.Variations in the distribution and mineralogy types of Mn in the iron ores of the Bahariya Oasis demanded detailed mineralogical and petrographic characterizations of the deposits before the beneficiation of high-Mn iron ores from the Bahariya Oasis as feedstock for the ironmaking industries in Egypt by magnetizing reduction. High Mn contents, especially in the Ghorabi–Nasser iron ore and occurrence of Mn as inclusions and/or accumulated on the surface of the Fe-bearing minerals would suggest a possible utilization of the high-Mn iron ores to produce ferromanganese alloys. 相似文献
19.
微生物矿化成因的铁硫酸盐矿物表面特征初探 总被引：12，自引：1，他引：12
研究表明，生物一矿物相互作用是地球表层系统演化的重要地质营力之一。微生物与矿物岩石之间进行着活跃的物质交换，微生物通过营造微观地球化学环境和提供吸附、成核中心影响着矿物的溶解和结晶，其中生物一矿物界面是物质交换和化学反应最为活跃的场所，矿物表界面记录着丰富的微生物作用信息。在综述前人微生物一矿物相互作用界面研究的基础上，利用气体吸附技术，对比分析了微生物矿化成因和无机合成含水铁硫酸盐矿物的表面积、表面分形和表面吸附能特征，初步讨论了微生物矿化成因铁硫酸盐矿物的表面特征和控制机理。 相似文献
20.
Harish Veeramani Daniel S. Alessi Juan S. Lezama-Pacheco Jonathan O. Sharp Urs Dippon John R. Bargar 《Geochimica et cosmochimica acta》2011,75(9):2512-6510
Reductive immobilization of uranium by the stimulation of dissimilatory metal-reducing bacteria (DMRB) has been investigated as a remediation strategy for subsurface U(VI) contamination. In those environments, DMRB may utilize a variety of electron acceptors, such as ferric iron which can lead to the formation of reactive biogenic Fe(II) phases. These biogenic phases could potentially mediate abiotic U(VI) reduction. In this work, the DMRB Shewanella putrefaciens strain CN32 was used to synthesize two biogenic Fe(II)-bearing minerals: magnetite (a mixed Fe(II)-Fe(III) oxide) and vivianite (an Fe(II)-phosphate). Analysis of abiotic redox interactions between these biogenic minerals and U(VI) showed that both biogenic minerals reduced U(VI) completely. XAS analysis indicates significant differences in speciation of the reduced uranium after reaction with the two biogenic Fe(II)-bearing minerals. While biogenic magnetite favored the formation of structurally ordered, crystalline UO2, biogenic vivianite led to the formation of a monomeric U(IV) species lacking U-U associations in the corresponding EXAFS spectrum. To investigate the role of phosphate in the formation of monomeric U(IV) such as sorbed U(IV) species complexed by mineral surfaces, versus a U(IV) mineral, uranium was reduced by biogenic magnetite that was pre-sorbed with phosphate. XAS analysis of this sample also revealed the formation of monomeric U(IV) species suggesting that the presence of phosphate hinders formation of UO2. This work shows that U(VI) reduction products formed during in situ biostimulation can be influenced by the mineralogical and geochemical composition of the surrounding environment, as well as by the interfacial solute-solid chemistry of the solid-phase reductant. 相似文献