不同条件下形成的黄钾铁矾微形貌对比研究

黄钾铁矾是酸性矿山废水（AMD） 中常见的次生矿物,能有效吸附AMD中Cu、Pb、Zn、Gd、As等重金属元素。不 同条件下形成的黄钾铁矾微形貌不同,其吸附能力也不同。文章通过化学法和微生物法合成了黄钾铁矾,并在粤北大宝山 矿酸性矿山废水中采集了含黄钾铁矾的泥样。利用扫描电镜-能谱分析（SEM） 和X光衍射（XRD）,对三种不同条件下形 成的黄钾铁矾进行鉴定和微形貌特征观察,并分析黄钾铁矾的形成条件。结果表明,常温条件下,pH值2.0~2.5时能够化 学合成黄钾铁矾,其晶体粒径约2~10 μm,且晶形呈板状;而在65℃时,可在pH2.0~3.0之间化学合成黄钾铁矾,但晶形 差。微生物法合成黄钾铁矾pH范围是2.0~5.0,其晶形完好,呈菱面体且晶体大小比较均匀,而约为2~4 μm。酸性矿山废 水中的黄钾铁矾形成的pH值为2.5~3.5,晶形为菱面体形,单个晶体大小多为1~2 μm。根据其形成条件和微形貌特征,文 章推测酸性矿山废水中形成的黄钾铁矾可能是微生物成因。     

黄钾铁矾的形成条件研究及其环境意义

黄钾铁矾的化学合成实验表明,调整合适的pH值及介质浓度,常温常压下可以实现黄钾铁矾的快速形成。影响黄钾铁矾形成的主要因素包括pH值、温度及硫酸铁介质的浓度。常温下,当pH值在2.60~3.10时,24h内即有黄钾铁矾沉淀出现,2d内则有大量黄钾铁矾生成;在90℃左右时,形成黄钾铁矾的溶液pH值范围增大至1.20~3.10,而且在该范围内,pH值越大越利于黄钾铁矾的形成。高硫酸铁浓度有利于黄钾铁矾的形成,硫酸铁浓度较高(大于0.05M)时,形成较纯的黄钾铁矾矿物;而低浓度时,生成的黄钾铁矾常常含有水绿矾及胶体状的红色无定形羟基硫酸铁杂质。黄钾铁矾的沉淀过程可以用来治理矿山及工业废水,去除其中的S、Fe及As、Cr、Hg、Pb等有毒有害元素。常温常压下黄钾铁矾快速形成的实现为在产生酸性废水的矿山废石堆上形成黄钾铁矾类矿物胶体隔离防渗层提供了良好的潜在应用前景。     

广东大宝山铁龙AMD中赭色沉积物的含铁次生矿物研究

以广东大宝山铁龙酸性矿山废水(AMD)为研究对象,采集了7个采样点的赭色沉积物样品。利用X射线荧光光谱(XRF)、傅里叶变换红外光谱(FTIR)、X射线粉晶衍射(XRD)和场发射扫描电镜/能谱分析(FESEM/EDS),对AMD中赭色沉积物的矿物相及形貌进行鉴定。现场测定采样点水体物理化学参数(pH/Eh),探讨不同物理化学条件对含铁次生矿物相的影响。结果表明,大宝山铁龙AMD中赭色沉积物的含铁次生矿物主要有施威特曼石、黄钾铁矾、针铁矿、水铁矿等,此外沉积物中还含有七水铁矾、叶绿矾、四水白铁矾、针绿矾、纤铁矾、锡铁山石及羟铝矾等可溶性硫酸盐。施威特曼石具有带骨针棒状、海胆状形貌,针铁矿常呈针状及肾状集合体产出,黄钾铁矾呈六方板状,施威特曼石常可与黄钾铁矾或者针铁矿共生。赭色含铁次生矿物能在AMD较大范围的pH条件下存在,但倾向于Eh高的环境。当pH值增大时,施威特曼石有转变为针铁矿的趋势,并且针铁矿能保存施威特曼石的形貌特征。     

酸性矿山废水沉积物中砷形态研究:连续提取法及其条件优化

矿山开采过程中常会将还原条件下稳定的硫化物揭露于地表,在氧气、水和微生物的共同作用下,硫化物发生快速氧化分解,形成酸性矿山排水(AMD),严重污染其流经的水体和土壤。近年的研究发现,当环境条件发生改变时,AMD中会形成多次生矿物如黄钾铁矾、施氏矿、水铁     

黄钾铁矾类矿物沉淀去除Cr(Ⅵ)的初步研究

为探讨黄钾铁矾类矿物沉淀对Cr(Ⅵ)的去除效果,利用黄钾铁矾类矿物沉淀对模拟含Cr(Ⅵ)废水进行了初步实验处理,结果表明,黄钾铁矾类矿物沉淀对含Cr(Ⅵ)废水有较好的去除效果,去除率都在70%以上,最高可达85%。黄钾铁矾与黄铵铁矾沉淀对Cr(Ⅵ)的去除率差别不大;溶液酸碱度对去除率有明显影响,在pH值为2.5~3.2时,时间相同,较高的pH值比低pH值的去除率高。黄钾铁矾类矿物的沉淀过程可用来处理矿山及其他工业废水,去除S、Fe和Cr(Ⅵ)等有毒有害元素。     

粤北大宝山酸性矿山废水中梯田状沉积物的次生矿物研究

粤北大宝山酸性矿山废水(AMD)中形成了呈独特梯田状构造的沉积物,其中的次生矿物可以吸持AMD中的重金属离子,对减少矿山环境的重金属污染有重要意义。本文采集了大宝山AMD中呈梯田状构造中的沉积物,利用多种手段分析了其主要矿物组成以及主要次生矿物的表面形貌特征,探究梯田状沉积物的成因。结果表明,梯田状沉积物的次生矿物以针铁矿、施威特曼石、黄钾铁矾为主,含少量石膏、斜方钙沸石等。针铁矿呈针状、球刺状集合体;施威特曼石呈海胆状、鳞片状,粒度为微米级,海胆状施威特曼石与球刺状针铁矿共生;黄钾铁矾呈不规则的球粒状、片状,与施威特曼石共生。研究表明微生物作用可能是形成铁质梯田状构造的关键因素。     

氧化亚铁硫杆菌作用下形成的黄钾铁矾的SEM研究

黄钾铁矾是金属硫化物在酸性条件下氧化形成的主要次生矿物。很多研究表明,金属硫化物矿区广泛发育的氧化亚铁硫杆菌会影响金属硫化物的氧化分解和次生矿物的形成。为讨论氧化亚铁硫杆菌在黄钾铁矾形成过程中的作用,设计了两组平行实验制备黄钾铁矾：一种采用化学方法合成黄钾铁矾,另一种在相同条件下接种氧化亚铁硫杆菌合成黄钾铁矾。利用X-射线衍射仪(XRD)、扫描电子显微镜(SEM)和能谱分析仪(EDS)等技术对两种实验获得的黄钾铁矾进行定性分析和形貌观察。结果表明：在氧化亚铁硫杆菌充分繁殖的条件下,细菌的参与更利于黄钾铁矾的形成;Fe^2+的氧化速率可能是影响黄钾铁矾结晶的主要因素,氧化亚铁硫杆菌通过提高Fe^2+的供应速度促使黄钾铁矾快速结晶,细菌作用下形成的黄钾铁矾结晶程度好于纯化学方法制备的黄钾铁矾。     

酸性矿山废水中生物成因次生高铁矿物的形成及环境工程意义

酸性矿山废水(acid mine drainage,AMD)是一类pH低并含有大量有毒金属元素的废水。AMD及受其影响的环境中次生高铁矿物类型主要包括羟基硫酸高铁矿物(如黄铁矾和施威特曼石等)和一些含水氧化铁矿物(如针铁矿和水铁矿等),而且这些矿物在不同条件下会发生相转变,如施氏矿物向针铁矿或黄铁矾矿物相转化。基于酸性环境中生物成因次生矿物的形成会"自然钝化"或"清除"废水中铁和有毒金属这一现象所获得的启示,提出利用这些矿物作为环境吸附材料去除地下水中砷,不但吸附量大(如施氏矿物对As的吸附可高达120mg/g),而且可直接吸附As(III),还几乎不受地下水中其他元素影响。利用AMD环境中羟基硫酸高铁矿物形成的原理,可将其应用于AMD石灰中和主动处理系统中,构成"强化微生物氧化诱导成矿-石灰中和"的联合主动处理系统,以提高AMD处理效果和降低石灰用量。利用微生物强化氧化与次生矿物晶体不断生长的原理构筑生物渗透性反应墙(PRB)并和石灰石渗透沟渠耦联,形成新型的AMD联合被动处理系统,这将有助于大幅度增加处理系统的寿命和处理效率。此外,文中还探讨了上述生物成因矿物形成在AMD和地下水处理方面应用的优点以及今后需要继续研究的问题。     

硫酸盐还原菌及异化铁还原菌对 黄钾铁矾还原作用的对比

选取酸性矿坑水环境中常见的次生含铁硫酸盐矿物———黄钾铁矾[KFe3(SO4)2(OH)6]为研究对象,用硫酸盐还原菌 Desulfovibriovulgaris 和异化铁还原菌Shewanellaputrefaciens CN32对其进行还原实验,探讨作为重金属治理潜在材料的 黄钾铁矾的微生物稳定性.实验采用非增长型培养基,在中性、厌氧、30℃的条件下进行.采用湿化学方法测量水溶液及还原产 生的总Fe2+ ,利用X射线衍射(X-raydiffraction,简称XRD)来分析反应后残余固体物质的矿物组成,用扫描电镜(scanning electronicmicroscopy,简称SEM)观察固体残余物的形貌特征.结果表明,没有微生物的参与,黄钾铁矾的稳定性较好.异化铁 还原菌S.putrefaciens CN32和硫酸还原菌D .vulgaris 在营养极其匮乏的中性厌氧条件下均能还原黄钾铁矾晶格中的 Fe3+ ,显示出黄钾铁矾被微生物还原的可能性.S.putrefaciens CN32还原黄钾铁矾晶格中Fe3+ 的最大还原速率和最终Fe3+ 还原率分别为0.001mmol·L-1·h-1和0.37%.与S.putrefaciens CN32不同,D .vulgaris 对黄钾铁矾的还原能力较强,不 含有电子穿梭体(Anthraquinone-2,6-disulfonate,简称AQDS)的实验体系中Fe3+ 的最大还原速率和最终Fe3+ 还原率分别为 0.017mmol·L-1·h-1和16.80%,而添加了AQDS的实验体系的则分别达到了0.026mmol·L-1·h-1和24.30%,这可能与 黄钾铁矾中含有SO42- 有关.D .vulgaris 优先还原黄钾铁矾晶格中的SO42- 产生的H2S是强还原剂,也可促进Fe3+ 的还原, 微生物以及H2S的双重作用可能是导致D .vulgaris 体系中Fe3+ 还原率较高的原因.XRD分析表明,黄钾铁矾经过S.putrefaciens CN32的作用,物相没有发生变化;而经过D .vulgaris 作用后,黄钾铁矾的特征峰消失,固相残余物中出现了菱铁 矿(FeCO3)、蓝铁矿[Fe3(PO4)2·8H2O]等次生矿物.由于培养基中没有添加任何的磷酸盐,因此蓝铁矿的出现可能是由于培 养基中添加的少量酵母浸膏降解后产生的磷酸根与D .vulgaris 还原黄钾铁矾产生的Fe2+ 相互作用的结果.这些认识对深入 理解地球表层铁的生物地球化学循环具有重要意义,为矿山环境重金属的污染治理提供了实验依据.      

利用黄钾铁矾类矿物形成过程预处理高浓度含硫废水

利用黄钾铁矾类矿物形成过程对某高浓度工业含硫废水进行预处理,除去一定量的SO42-,使溶液中低价态的硫继续转化成SO42-,再进行氧化处理。采取二次沉淀除去溶液中更多的SO42-,大大降低了该水样的COD值。通过实验得出沉淀的最佳工艺条件为pH值为2.50～3.20,氯化铁晶体(FeCl3.6H2O)最佳投入量为50g/L。经过两次黄钾铁矾类矿物沉淀过程,该废水COD的去除率达到85.29%,结合H2O2的氧化处理,COD去除率可达96%。为高浓度含硫废水进入生化处理前的预处理提供了实验依据。     

Bioavailability of jarosite for stimulating acid mine drainage attenuation

Biological reduction of iron-sulfate minerals, such as jarosite, has the potential to contribute to the natural attenuation of acid mine drainage (AMD) sites. Previous studies of AMD attenuation at Davis Mine, an abandoned pyrite mine in Rowe Massachusetts, provided evidence of iron and sulfate reduction by indigenous bacteria. Jarosite is a large component of the sediment at Davis Mine and may play a role in AMD attenuation. In this study, microcosms were constructed with groundwater and sediment from Davis Mine and amended with glycerol, nitrogen and phosphorus (GNP) and naturally formed natrojarosite. Over time, higher total iron, sulfate, pH and sodium concentrations and lower oxidation–reduction potentials were observed in microcosms amended with GNP and jarosite, compared with unamended microcosms and killed controls. Geochemical modeling predicted jarosite precipitation under microcosm conditions, suggesting that abiotic processes were unlikely contributors to jarosite dissolution. SEM imaging at the jarosite surface showed microbial attachment. Microbial community composition analysis revealed a shift to higher populations of Clostridia, which are known to reduce both iron and sulfate. The results show that jarosite may be utilized as an electron acceptor by iron and/or sulfate reducing bacteria at Davis Mine and its presence may aid in the attenuation of AMD.     

Comparative data on the volatile component composition of magma

Ferrihydrite (2.5 Fe₂O₂-4.5 H₂O) is an unstable colloidal mineral. It dissolves in highly alkaline solutions and is precipitated from them in the form of goethite. Jarosite is stable at very low pH but is decomposed at higher values of pH with separation of iron oxides. Experiments show that in rapid decomposition of jarosite a protohematite substance, ferrihydrite, is formed. This transformation occurs at moderate pH values when solutions percolate through the aggregates of jarosite. Ferrihydrite, an unstable colloidal hydrated oxide of ferric iron, changes spontaneously to stable hematite with time. Very slow decomposition of jarosite results in its replacement by iron hydroxide, goethite. Under laboratory conditions in alkaline solutions lepidocrocite may be obtained from jarosite. The synthesis of this iron hydroxide passes through a stage of intermediate products: ferrihydrite and hydrated ferric oxide - ferriprotolepidocrocite, formed by solution of ferrihydrite in strongly alkaline solutions. The transformation of ferriprotolepidocrocite into lepidocrocite may be regarded as a topotactic reaction. —Authors.     

Dissolution of jarosite [KFe3(SO4)2(OH)6] at pH 2 and 8: Insights from batch experiments and computational modelling

Jarosite [KFe₃(SO₄)₂(OH)₆] is a mineral that is common in acidic, sulphate-rich environments, such as acid sulphate soils derived from pyrite-bearing sediments, weathering zones of sulphide ore deposits and acid mine or acid rock drainage (ARD/AMD) sites. The structure of jarosite is based on linear tetrahedral-octahedral-tetrahedral (T-O-T) sheets, made up from slightly distorted FeO₆ octahedra and SO₄ tetrahedra. Batch dissolution experiments carried out on synthetic jarosite at pH 2, to mimic environments affected by ARD/AMD, and at pH 8, to simulate ARD/AMD environments recently remediated with slaked lime (Ca(OH)₂), suggest first order dissolution kinetics. Both dissolution reactions are incongruent, as revealed by non-ideal dissolution of the parent solids and, in the case of the pH 8 dissolution, because a secondary goethite precipitate forms on the surface of the dissolving jarosite grains. The pH 2 dissolution yields only aqueous K, Fe, and SO₄. Aqueous, residual solid, and computational modelling of the jarosite structure and surfaces using the GULP and MARVIN codes, respectively, show for the first time that there is selective dissolution of the A- and T-sites, which contain K and SO₄, respectively, relative to Fe, which is located deep within the T-O-T jarosite structure. These results have implications for the chemistry of ARD/AMD waters, and for understanding reaction pathways of ARD/AMD mineral dissolution.     

Occurrence of jarosite within Quaternary coastal sabkha sediments in Kuwait,Arabian Gulf

X-ray diffractometer analysis and SEM investigation confirmed the occurrence of jarosite and alunogen minerals in the Quaternary siliciclastic sabkha sediments of northern Kuwait within the Bahrah oilfield area, Arabian Gulf. Jarosite is relatively abundant in a near-surface whitish sticky tidal muddy sand layer about 60 cm thick that overlies the ferruginous sandstone of the Oligo-Miocene Ghar Formation. Jarosite occurs as clusters of euhedral pseudo-cubes of about 1 μm in size and as agglomerated nanoglobules of 250 nm in size. A hypogenetic origin related to the reaction of sulfuric acid produced by the oxidation of H₂S associated with hydrocarbon gas seepages with K and Fe leachates is suggested. The restricted occurrence of jarosite within near-surface sabkha sediments may be attributed to limited tidal inundation and prevalence of arid climatic conditions.     

Fe(Ⅲ)供应速率对无定型施氏矿物形成的影响

施氏矿物(schwertmannite)已被证实是一种具特异性能的重(类)金属吸附新材料。但在直接由Fe3+或用强氧化剂氧化Fe2+合成该矿物时,常因夹有黄铁矾类物质而降低产品纯度。通过模拟FeSO4-K2SO4-H2O临界成矾体系,发现在嗜酸性氧化亚铁硫杆菌(Acidithiobacillus ferrooxidans)作用下存在无定型施氏矿物和晶型黄钾铁矾的合成反应竞争,其中Fe3+供应速率是一个影响铁矿物形成的重要因素,较低的Fe3+供应可以抑制K+的利用,这种变化趋势对无定型施氏矿物合成是有利的。当存在少量K+等成矾导向离子时,可通过合理调低Fe3+供应速率,有利于溶液中Fe3+平缓释放,改善施氏矿物纯度,这为A.ferroxidans菌生物法中直接使用无机盐培养基合成施氏矿物提供了可能。     

四川甘溪泥盆系观雾山组白云岩特征与其形成条件的关系(英文)

本文通过沉积环境分析,X射线衍射、扫描电镜、同位素及阴极发光分析,讨论了甘溪泥盆系观雾山组白云石的晶体形态及大小、有序度、碳酸钙克分子含量,同位素特征及阴极发光特征与形成条件的关系。中晶白云岩及细晶白云岩分别产于生物层及潮坪环境,为成岩早期地下淡水与海水混合白云岩化作用的产物。低的碳酸钙克分子含量,中-弱的阴极发光强度及低的δ18O、δ13C值。微晶白云岩形成于泻湖环境。白云石具他形粒状晶,差的有序度,高的碳酸钙克分子含量,强的阴极发光强度及高的δ18O、δ13C值,为准同生期高Mg2+/Ca2+值卤水交代碳酸钙软泥形成。     

Mineralogical control of rare earth elements in acid sulfate soils

Major, trace and rare earth element concentrations were measured in porewater, surface water and sediments at an acid sulfate soil site. The concentrations of La and Ce in porewater are up to 1-3 ppm. There is a strong correlation between REE concentration and acidity, except that the maximum concentrations were consistently found below the horizon of maximum acidity, associated with an increase in pH (to ca. 4) and change in mineralogy from jarosite-dominated to goethite-dominated mottles. Jarosite replacement by goethite is as expected with the rise in pH, which in turn is due to the occurrence of a fossil shell bed just below. The rare earth element patterns in the porewaters are enriched in the MREE with respect to Post-Archaean Australian Shale (PAAS). Measurements and calculations show that this is in accord with experiments on low-degree partial dissolution of jarosite, even when the jarosite itself is highly enriched in LREE. There is a clear fractionation in the patterns between the clay-rich soil matrix, which is slightly depleted in the LREE when normalized to PAAS (La/Yb_PAAS ∼0.5), and the secondary mineral phase jarosite, which is enriched in the LREE (La/Yb_PAAS = 15-50). The REE pattern in the porewater changes with the transition from jarosite- to goethite-rich mottles, becoming relatively more enriched in the LREE compared to the HREE, which is consistent with the incongruent dissolution of jarosite to form goethite and the release of greater amounts of jarosite REE to solution, including proportionately more of the jarosite-compatible LREE.Maximum surface water REE concentrations in acidic water were 100-200 ppb La and Ce. REE patterns in surface water were very similar to the porewater transition zone, enriched in the MREE, but asymmetric, relatively enriched in the LREE compared to the HREE.     

Natural alteration products of sulphide mattes from primary lead smelting

The natural alteration products developed on mattes from lead metallurgy were determined: oxides and hydroxides (HFO, Cu(OH)₂), sulphates (thenardite, gypsum), hydroxysulphates (jarosite, beaverite, brochantite) and carbonates (cerussite, malachite, NaOH·2 PbCO₃). The large range of stability of newly formed phases confirms a significant variety of E_h–pH conditions of natural weathering of matte. Jarosite is stable at pH<3, but some hydroxides and carbonates typically form in neutral and alkaline environments. Consequently, the best dumping conditions for metallurgical mattes are difficult to determine. Such materials can have severe environmental effects and should be dumped in controlled waste-disposal sites. To cite this article: V. Ettler et al., C. R. Geoscience 335 (2003).