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1.
水体悬浮颗粒物主要组分的萃取分离及重金属的分布特征   总被引：1，自引：0，他引：1  
为了考察悬浮颗粒物中主要组分对重金属的富集作用,采用选择性萃取法分离长春市伊通河和南湖悬浮颗粒物中的铁、锰氧化物,优化了萃取条件,测定了悬浮颗粒物中的铁、锰氧化物和有机质等组分中富集Cu,Pb和Zn的含量,分析了上述3种重金属在悬浮颗粒物主要组分中的分布特征。结果表明,0.006 mol/L NH2OH.HCl 0.01 mol/L HNO3萃取30 min可以单独萃取悬浮颗粒物中大部分的锰氧化物,0.8 mol/L Na2S2O4(pH=6.0)萃取40 min可以同时萃取铁、锰氧化物,而对非目的组分的影响较小;悬浮颗粒物对Cu、Pb、Zn重金属有明显的富集作用,其中Cu主要结合在悬浮颗粒物的有机质组分中,Pb主要富集在铁、锰氧化物中,锰氧化物和有机质对Zn的分布起主要的富集作用。  相似文献   

2.
采用选择性萃取分离技术对沉积物(生物膜)中非残渣态组分(铁、锰氧化物和有机质)进行分离,研究阿特拉津(atrazine,AT)-Cd-Cu系中共存重金属对选择性萃取前后沉积物(生物膜)吸附AT的影响.研究结果表明:共存体系中,沉积物(生物膜)中铁氧化物对AT的吸附贡献最大,其次是有机质,而锰氧化物则抑制AT的吸附;共存镉促进了AT在沉积物(生物膜)原样及各非残渣态组分上的吸附,镉质量浓度为0.2 mg/L时,促进作用最显著,各组分对阿特拉津的吸附贡献增加了3.20%～32.31%(沉积物)和1.61%～17.10%(生物膜),但随镉质量浓度的增加,其促进作用减弱;共存铜抑制沉积物(生物膜)原样及铁氧化物、有机质对AT的吸附,铜质量浓度为75.0 mg/L时,其抑制作用最强,铁氧化物和有机质对阿特拉津的吸附贡献分别降低了29.21%、22.36%(沉积物)和9.46%、77.27%(生物膜),但同时减弱了锰氧化物对AT吸附的抑制作用,其吸附贡献分别提高了28.98%(沉积物)和17.46%(生物膜).  相似文献   

3.
该研究通过批次和动态实验，考查含锰褐铁矿和合成针铁矿对Ce(Ⅲ)的氧化和固定作用，并在此基础上探讨共存铁和锰氧化物氧化和固定Ce的机制及地质意义。批次实验结果显示，含锰褐铁矿对Ce的氧化和固定有重要促进作用，在初始Ce浓度为6000μg/L，含锰褐铁矿添加量为1 g/L时，可在48 h实现对Ce的完全固定；初始Ce(Ⅲ)浓度在300～4500μg/L时，含锰褐铁矿对Ce(Ⅲ)氧化和沉淀的促进作用与Mn含量正相关，而合成针铁矿相对于无矿体系体现出抑制效应。动态实验结果显示，对高锰褐铁矿固定的Ce，其分布不受锰氧化物的制约，与铁氧化物的分布一致。对结果的分析表明Ce氧化和沉淀的过程为：吸附—氧化—CeO2沉淀生成—CeO2自催化氧化Ce(Ⅲ)；锰和铁氧化物共存时，对Ce氧化和固定的贡献分别是：前者促进Ce氧化，后者通过静电吸附作用促进CeO2的固定。研究对于解释“锰氧化物氧化Ce(Ⅲ)的能力强于铁氧化物，但二者共存时铁氧化物更易于固定Ce”这一地质现象有一定启示意义。  相似文献   

4.
建立了Cu2+和阿特拉津(AT)复合污染体系中沉积物各活性组分及其交互作用对AT吸附量影响的BP神经网络模型,模型预测值和实验值的相关系数达到0.97,各集合的平均偏差均小于10%。模型显示,AT在沉积物上的主要吸附位是铁氧化物。沉积物吸附AT时铁氧化物、锰氧化物、有机质之间存在显著的交互作用,铁氧化物、锰氧化物交互作用贡献率为-130%～80%,铁氧化物、有机质交互作用贡献率为5%～28%,锰氧化物、有机质交互作用贡献率为-200%～-70%。各活性组分吸附AT的能力及其交互作用受Cu2+的影响较大,其中:Cu2+对AT在铁氧化物上的吸附表现为拮抗作用,对AT在锰氧化物上的吸附表现为协同作用,而对AT在有机质上的吸附影响不显著,同时Cu2+减弱了铁氧化物-锰氧化物和锰氧化物-有机质的交互作用影响,增强了铁氧化物-有机质的交互作用影响。  相似文献   

5.
稀土开采本质上是利用离子交换作用将稀土元素从矿物(黏土矿物、铁(氢)氧化物)表面解吸下来的过程,厘清不同类型矿物对稀土元素浸出的影响,对于提高开采效率至关重要。(NH4)2SO4溶液是稀土元素浸矿时的常用提取剂,SO42-可以通过与稀土元素络合、改变矿物表面电荷性质以及键桥作用等影响稀土元素在矿物表面的吸附/解吸行为,进而影响浸出效率。本研究以高岭石和水铁矿分别作为黏土矿物和铁(氢)氧化物的代表,通过向离子吸附型稀土原矿中添加不同含量(0、5%和10%)的高岭石或水铁矿,结合批量实验、X射线衍射分析(XRD)、电感耦合等离子体发射光谱仪(ICP-OES)及原位红外光谱(in situ ATR-FTIR)等分析表征手段,模拟不同浸取剂体系(NH4Cl和(NH4)2SO4)下,矿物类型对稀土元素浸取的影响。结果表明,在空白对照组中(未添加高岭石和水铁矿),NH4Cl浸出稀土...  相似文献   

6.
为了考察铁锰氧化物对酚类污染物的氧化降解能力,采用天然以及合成的铁锰氧化物对苯酚的氧化降解进行对比实验研究。土壤中铁锰氧化物样品分别为天然针铁矿及氧化锰,合成铁锰氧化物样品分别为合成针铁矿及软锰矿。结果表明：苯酚与铁锰氧化物发生氧化还原作用时,还可能与土壤中杂质发生吸附等作用;铁锰氧化物还原反应强度随着反应介质pH值的升高而迅速下降;可用零级反应动力学方程拟合铁氧化物还原溶解反应,针铁矿溶解反应的强度与介质的pH值呈负相关关系;天然针铁矿对酚类污染物的氧化降解能力明显高于合成针铁矿,pH值对天然针铁矿溶解反应影响较大;可用一级指数衰减方程拟合锰氧化物还原溶解反应,锰氧化物溶解反应的强度与介质的pH值呈指数衰减关系;pH值对软锰矿还原溶解反应的影响大于对土壤中氧化锰的影响,pH值越小,影响越显著;对比pH值对铁和锰还原作用的影响发现,在pH=6.5时,锰氧化物仍有较强的氧化性能。  相似文献   

7.
江汉平原高砷含水层沉积物地球化学特征   总被引：2，自引：0，他引：2  
选取江汉平原典型地下水砷中毒区仙桃市沙湖原种场为研究区,对3个长50m的钻孔沉积物砷含量与赋存形态及其他化学组成进行了分析。结果表明区内沉积物砷质量分数为1.35~107.5mg/kg(平均值为12.8mg/kg)。黏土或亚黏土层中砷含量较高,这与细粒沉积物中铁锰氧化物、黏土矿物对砷的吸附有关。地下20m左右深度内含水层沉积物中砷含量最高,相应地下水中砷质量浓度高达到1 000μg/L。草酸-草酸铵选择性提取结果指示沉积物中10%~77%(平均38%)的As与无定形铁氢氧化物结合,表明无定形铁氢氧化物还原性溶解可能是控制砷释放与还原的主要地球化学过程,并且有机质生物氧化机制极大地促进了该过程。然而,沉积物中仅1.2%~23%的铁被草酸-草酸铵提取,含水层中砷浓度主要受铁的氢氧化物还原性溶解影响,但其他形式的铁、有机物的吸附作用亦控制着砷的含量。  相似文献   

8.
用不同浓度铁锰离子混合溶液对石英砂柱进行40次淋溶实验,研究砂柱中铁锰氧化物的形成状况.结果表明,淋出液中铁锰离子浓度与其pH值随着淋溶次数的增加呈现先降低后升高的趋势;各处理所形成的铁锰氧化物含量之间存在极显著差异,淋溶液中铁锰离子浓度越大,形成的铁锰氧化物含量越高,当淋溶液中铁锰摩尔浓度比即c(Fe2+)/c(Mn2+)为2∶1时最有利于铁锰氧化物的形成;随着淋溶次数的增加,铁锰氧化物含量的增长逐渐减慢;不同层次铁锰氧化物含量差异显著,下层(20～30 cm)含量明显高于其它层次;各阶段(每淋溶10次为一阶段)不同形态(非晶形态、晶形态)铁锰氧化物含量间的相关性存在差异,铁锰氧化物尤其是非晶形态的相对比例(Fe/Mn)随着淋溶次数的增加逐渐增大.  相似文献   

9.
锑(Sb)是一种对人体有毒的重金属元素。近年来由于矿业开采、冶炼与广泛的使用，其污染已经成为了全球性的环境问题。锑的毒性和迁移强烈依赖于它的化学形态和环境氧化还原条件。锑极易被沉积物、土壤中的铁、锰、铝(氢)氧化物和黏土矿物吸附。本文基于前人和作者的已有工作，对铁锰铝(氢)氧化物和黏土矿物吸附锑的热力学、动力学及吸附机制进行了详细综述，对温度、pH、离子强度、共存离子等因素对锑吸附的影响进行了讨论，指出铁(氢)氧化物吸附Sb(III)过程存在的氧化是由氧气导致，而锰(氢)氧化物吸附过程的Sb(III)氧化是由吸附剂中的Mn(IV)离子引起；铝氧化物、黏土矿物对Sb(III)和Sb(V)的吸附较弱；(氢)氧化物对Sb(III)和Sb(V)的吸附分为内层或外层吸附，但结合方式有差异。本文可为铁锰铝复合吸附剂以及吸附过程中Sb同位素的研究提供一定的理论基础。  相似文献   

10.
新生代深海铁锰矿床的大规模成矿是地质历史上特有的现象,其形成的海底铁锰结核/结壳因富含巨量的有用金属而备受关注。水成型铁锰成矿的胶体成因模型自20世纪90年代中期提出以来已被广泛接受并采用。随着近20年来纳米地球科学的迅速发展,人们意识到纳米颗粒作为胶体的最小部分,能够以其独特的性质显著影响铁锰成矿过程。通过总结已有研究,发现铁氧化物与锰氧化物会以纳米颗粒的形式普遍共存于多种表生地质环境,还证实了水成型铁锰结核/结壳中的主要铁锰矿物（如水羟锰矿和水铁矿）都是纳米颗粒。铁氧化物纳米颗粒对二价锰[Mn(Ⅱ)]的表面催化氧化可能是水成型铁锰矿物通常在纳米尺度密切共生的原因。此外,在铁锰结壳中还观测到大量在以往研究中被普遍忽视的三价锰[Mn(Ⅲ)]矿物,其含量在结壳顶部最高,随深度增加逐渐下降,四价锰[Mn(Ⅳ)]矿物的含量则呈相反的变化趋势。不同价态锰氧化物纳米颗粒的表面能差异导致Mn(Ⅲ)矿物在Mn(Ⅱ)的氧化过程中最先沉淀,并可能在沉淀之后逐渐转化为Mn(Ⅳ)矿物。相信随着纳米地球科学与高精度原位实验技术的发展,必将不断深化对海水铁锰循环及海底铁锰成矿的认识。  相似文献   

11.
铁锰氧化物在污染土壤修复中的作用   总被引：22，自引：0，他引：22  
矿物学在环境科学中的应用将是21世纪矿物学研究的一个主要方面。土壤污染作为一个制约人类社会可持续发展的基本问题正受到日益广泛的关注，污染土壤的修复已成为环境科学研究的一个重点。污染土壤的修复技术主要有物理、化学、生物等方法，但是，它们都不同程度地存在着缺陷。众所周知，铁和锰是自然界中少数但常见的变价元素。含有变价元素和带有表面电荷的铁锰氧化物具有良好的表面活性，不仅对有毒有害的无机污染物具有良好的净化功能，而且对土壤中有机污染物具有氧化降解作用。利用这些矿物来修复污染土壤，具有成本低、无二次污染等优点，体现出天然净化作用的特色，展现出广阔的环境矿物学应用前景。  相似文献   

12.
This paper addresses some specific features of the formation of atmospheric precipitation and soil and ground waters in the Ust’-Selenga depression on the eastern coast of Lake Baikal, where the delta of the Selenga River supplying about 50% of water into the lake has been formed. It was shown that a reducing environment was formed within this region under near-surface conditions in the zone of active water exchange, where waters with high concentrations of organic matter, ammonium, iron, manganese, nitrate, zinc, and cadmium were observed. The high contents of these components in the ground waters of the depression are related to the occurrence of both natural and anthropogenic processes. It was found that the natural hydrogeologic systems of the Ust’-Selenga depression are affected by a negative impact related to the transboundary atmospheric transport of industrial wastes discharged tens to hundreds of kilometers from its boundaries.  相似文献   

13.
Sunlight-induced reduction and dissolution of colloidal Fe-Mn (hydr)oxide minerals yields elevated concentrations of Fe2+ and Mn2+ in natural waters. Since these elements may be biolimiting micronutrients, photochemical reactions might play a significant role in biogeochemical cycles. Reductive photodissolution of Fe (hydr)oxide minerals may also release sorbed metals. The reactivity of Fe-Mn (hydr)oxide minerals to sunlight-induced photochemical dissolution is determined by the electronic structure of the mineral-water interface. In this work, oxygen K-edge absorption and emission spectra were used to determine the electronic structures of iron(III) (hydr)oxides (hematite, goethite, lepidocrocite, akaganeite and schwertmannite) and manganese(IV) oxides (pyrolusite, birnessite, cryptomelane). The band gaps in the iron(III) (hydr)oxide minerals are near 2.0-2.5 eV; the band gaps in the manganese (IV) oxide phases are 1.0-1.8 eV. Using published values for the electrochemical flat-band potential for hematite together with experimental pHpzc values for the (hydr)oxides, it is possible to predict the electrochemical potentials of the conduction and valence bands in aqueous solutions as a function of pH. The band potentials enable semiquantitative predictions of the susceptibilities of these minerals to photochemical dissolution in aqueous solutions. At pH 2 (e.g., acid-mine waters), photoreduction of iron(III) (hydr)oxides could yield millimolal concentrations of aqueous Fe2+ (assuming surface detachment of Fe2+ is not rate limiting). In seawater (pH 8.3), however, the direct photo-reduction of colloidal iron(III) (hydr)oxides to give nanomolal concentrations of dissolved, uncomplexed, Fe2+ is not thermodynamically feasible. This supports the hypothesis that the apparent photodissolution of iron(III) (hydr)oxides in marines systems results from Fe3+ reduction by photochemically produced superoxide. In contrast, the direct photoreduction of manganese oxides should be energetically feasible at pH 2 and 8.3.  相似文献   

14.
Lake Joyce is one of the least studied lakes of the McMurdo Dry Valleys. Similar to other lakes in this region, Lake Joyce is a closed-basin, permanently ice-covered, meromictic lake. We present here a detailed investigation of major ions, nutrients, and dissolved trace elements for Lake Joyce. Specifically, we investigate the role of iron and manganese oxides and hydrous oxides in trace metal cycling.Lake Joyce is characterized by fresh, oxic waters overlying an anoxic brine, primarily Na–Cl. Surface waters have a maximum nitrate concentration of 26M with a molar dissolved inorganic nitrogen to phosphorus ratio of 477. The supply of nitrogen is attributed to atmospheric deposition, possibly from polar stratospheric clouds. Dissolved phosphorus is scavenged by hydrous iron oxides. The pH is highest (10.15) just beneath the 7-m thick ice cover and decreases to a minimum of 7.29 in the redox transition zone. Dissolved Al exceeds 8M in surface waters, and appears to be controlled by equilibrium with gibbsite. In contrast, concentrations of other trace elements in surface waters are quite low (e.g., 5.4nM Cu, 0.19nM Co, <20pM La). Dissolved Fe, Mn, Ni and Cd were below our detection limits of 13 nM, 1. 8 nM, 4.7 nM and 15pM (respectively) in surface waters. There was a 6-m vertical separation in the onset of Mn and Fe reduction, with dissolved Mn appearing higher in the water column than Fe. Based on thermodynamic calculations, dissolved Mn appears to be controlled by equilibrium with hausmannite (Mn3O4). Co tracks the Mn profile closely, suggesting Co(III) is bound in the lattice of Mn oxides, whereas the Ce profile is similar, yet the Ce anomaly suggests oxidative scavenging of Ce. Release of Cu, Ni, Cd and trivalent REE appears to be controlled by pH-induced desorption from Fe and Mn oxides, although Cu (and perhaps Ni) may be scavenged by organic matter in surface waters.  相似文献   

15.
天然矿物材料在废水处理中的应用   总被引：2，自引：0，他引：2  
利用天然矿物进行废水处理优势明显。当前,层状(粘土矿物)、架状(沸石)、链状(硅灰石)、岛状(电气石)硅盐酸矿物及锰的氧化物、氢氧化物和铁的硫化物在废水处理方面已有许多研究成果和成功应用的实例,其发展前景广阔。今后,有关金属矿的矿物学特征及其在环境净化中的应用、天然矿物应用条件和再生条件的研究工作应进一步加强。  相似文献   

16.
Iron and manganese oxide coatings are actively forming on stream substrates in the White Oak Creek watershed in East Tennessee. Although oxidizing conditions are required for Fe-Mn oxide precipitation, coatings accumulate only if dissolved iron and manganese exceed 50 μg/L. Below this, coatings are lost by abrasion as fast as or faster than they form. Annual rates of formation of 3 mg/g on substrate (gravel) were observed. Manganese is dissolved from coatings between Eh values of 100 to 300 mV and below 1 mg/L dissolved O2 at pH 6.5 to 7.5. Iron oxides can be precipitated under these conditions.Uncontaminated gravels with oxide coatings (composed of illite, quartz, and feldspar) adsorbed radionuclides rapidly from waters below MPC (Maximum Permissible Concentration) levels. Contaminated gravels placed in uncontaminated waters lost 60Co by abrasion in oxidizing conditions and by dissolution of manganese coatings in reducing conditions. Exchangeable 90Sr was completely lost after one month whereas nonexchangeable 90Sr was lost more slowly; 137Cs was totally retained by the gravels. Gravels such as these can be used to monitor the radionuclide content of waters in the environment.  相似文献   

17.
Supergene manganese oxides, occurring in shales, breccias and dolomites of Proterozoic Age, in the Western Australian Pilbara Manganese Group, have Mn/Fe ranging from 1.9 to 254 and Mn4+ to Mn (Total) of 0.49–0.94. The manganese mineralogy is dominated by tetravalent manganese oxides, especially by cryptomelane, with lesser amounts of pyrolusite, nsutite, manjiroite, romanechite and other manganese oxide minerals. The manganese minerals are commonly associated with iron oxides, chiefly goethite, indicating incomplete separation of Mn from Fe during Tertiary Age arid climate weathering of older, manganiferous formations. These manganese oxides also contain variable amounts of braunite and very minor hausmannite and bixbyite. The braunite occurs in three generations: sedimentary-diagenetic, recrystallised sedimentary-diagenetic, and supergene. The mode of origin of the hausmannite and bixbyite is uncertain but it is possible that they resulted from diagenesis and/or low-grade regional metamorphism. The supergene manganese deposits appear to have been derived from manganiferous Lower Proterozoic banded iron formations and dolomites of the Hamersley Basin and overlying Middle Proterozoic Bangemali Basin braunite-containing sediments.  相似文献   

18.
Groundwater in some deep wells of Maydavood aquifer, southwestern Iran, contains relatively high concentrations of arsenic. Detailed hydrochemical analysis of these groundwaters (with ICP-OES instrument) showed that concentrations of iron, manganese, nickel, and vanadium are also high in them and concentrations of total arsenic in 81% of deep wells are greater than World Health Organization’s permissible value (10 ppb). XRF analysis of surrounding geological formations and aquifer sediments proposed that original source of arsenic in aquifer material can be attributed to minerals from Asmari Formation. It appears that a key mechanism for arsenic mobilizing to deep wells is microbial biodegradation of petroleum related organic matters (PROMs), which exist in aquifer sediments and originates from the bedrock of the aquifer (Gachsaran Formation). This process is followed by microbially mediated reductive dissolution of arsenic-bearing iron/manganese oxyhydroxides/oxides and further by nickel and vanadium mobilizing to groundwater. According to hydrogeochemical conditions and cluster analysis, water wells in Maydavood aquifer are divided to four subgroups: the wells with mildly reducing condition (subgroup I), moderately reducing condition (subgroup II), reducing condition (subgroup III), and high reducing condition (subgroup IV). Affected wells to arsenic are belonged to subgroups III and IV.  相似文献   

19.
When Pseudomonas aeruginosa PAO1 biofilms (attached to Sepharose surfaces) were subjected to dissolved Fe3+, most Fe was removed from solution within 25 h by surface complexation with negatively charged functional groups on the bacterial cell wall via a nucleation and mineralization process. Chemical formation of Fe-(hydr)oxides was partially responsible for dissolved Fe removal, which stemmed from a pH increase, facilitated by microbial activity. PAO1 used Fe3+ as an electron acceptor producing Fe2+ under localized anaerobic conditions over the first 50 h. The high ratio of Fe2+ to total Fe in solution produced a high proportion of Fe(II) in Fe precipitates; however, as the formation of Fe-(hydr)oxides started after 50 h, the Fe2+ content in solution began to diminish. Biofilms can so influence the local chemical conditions and metal speciation that the bulk solution phase is also affected, thereby mediating a wide-range (bio)geochemical cycling of iron. Long-term survival of natural biofilms, even under strict oligotrophic conditions, could have a broad lasting effect on the bulk geochemical environment.  相似文献   

20.
Simultaneous in situ immobilisation of uranium (U) and radium (226Ra) by injectible amounts of grey cast iron (gcFe), nano-scale iron (naFe) and a gcFe/MnO2 mixture (1:1) was studied in batch and column tests. Both 0.5 g/L naFe and gcFe are effective in 226Ra and U removal from mine water, whereas MnO2 addition clearly increased the efficiency of gcFe for 226Ra and U immobilisation. In a column test with 0.6 wt% gcFe/MnO2 mixture (1:1), neither 226Ra nor U was detected in the effluent after replacement of 45 pore volumes. A sequential extraction under flow condition revealed 226Ra to be mostly occluded in manganese oxides. Uranium was mostly sorbed onto poorly crystalline iron hydroxides, but a significant part was found to be occluded in manganese oxides also. The results of this study suggest that MnO2 promotes iron hydroxide formation under slightly reducing environmental conditions resulting in an increased pollutant retention capacity.  相似文献   

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