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1.
为研究双金属催化剂去除有机污染物的效果,采用自制Fe/Ag催化剂对模拟苯酚废水进行了臭氧催化氧化处理。通过扫描电子显微镜(SEM)、比表面积分析仪(BET)和X射线衍射(XRD)对催化剂进行表征,并考察了催化剂类型、催化剂投加量和溶液初始pH值对降解效果的影响规律。结果表明:与Fe相比,Fe/Ag比表面积减少了22.8%,在Fe/Ag/O3与含苯酚废水的反应体系中,反应遵循臭氧直接作用和活性自由基(·OH、·O2、H2O2)共同作用的机理;Fe/Ag在反应过程中体现出良好的协同作用;300 mg/L的苯酚模拟废水在pH=6.3、Fe/Ag投加量为1.00 g的最优反应条件下经60 min反应,苯酚与化学需氧量(COD)去除率比单独臭氧氧化分别提高了18.4%和29.4%。 相似文献
2.
已知在无氧条件下天然矿物菱铁矿能成功水解微囊藻毒素-LR(MC-LR),然而实际应用过程中难以避免水中溶解氧(O2)的存在,因此有必要深入研究不同溶氧量(DOC)条件下菱铁矿对MC-LR降解的影响。本文通过在无氧和有氧条件下菱铁矿对MC-LR的降解实验,发现在有氧条件下(溶氧量1.62～21.87 mg/L), MC-LR的降解速率均比无氧条件(k0=0.030 16 mg·L-1·h-1)高且其降解速率随O2含量增加而依次增加,当O2加入量为1.0 mL(溶氧量21.87 mg/L)时,菱铁矿对MC-LR降解速率最大(0.083 34 mg·L-1·h-1),为无氧条件下的2.76倍。通过外加腐殖酸(humic acid, HA)和自由基进行捕获实验,发现FeCO3能直接活化O2产生超氧自由基(·O~-2),以实现对MC-LR的氧化,但外加HA抑... 相似文献
3.
传统原位化学氧化地下水修复技术存在氧化剂迁移距离短和利用率低等问题。本研究在双井循环模式促进传质的基础上,通过注水井中的地下水电解原位提供O2和H2,配合乙二胺四乙酸(ethylenediamine tetraacetic acid,EDTA)络合溶解出含水层Fe(Ⅱ),活化O2产生羟基自由基(•OH),实现地下水三氯乙烯(TCE)的氧化降解。在填充了砂土和黏土互层的二维砂槽中,设置电流为0.2 A、流速为72 cm/d、初始TCE浓度为3 mg/L,经过9 d的连续通电处理后,TCE浓度降低到1 mg/L,降解率达到67%。通电前投加0.5 mmol/L EDTA,经过1 d水流循环后含水层中溶解态Fe(Ⅱ)浓度从02 mg/L增加到414 mg/L,黏土区域较高。通电过程中,循环井促进O2、Fe(Ⅱ)-EDTA和TCE的有效接触与反应,使TCE氧化降解。通电初期,黏土区域Fe(Ⅱ)氧化速率、TCE降解速率较周围慢,后期差异逐渐减小。未通电时加入醋酸钠可促进Fe(Ⅲ)还原,使含水层中铁循环利用。该修复过程通过循环井提升了氧化剂迁移距离,使用源于含水层的Fe(Ⅱ)-EDTA和稳定性较好的O2提高了氧化剂利用率,有望应用于有机污染地下水修复。 相似文献
4.
从海相地层磷灰石的裂变径迹探讨楚雄盆地的热史及剥蚀史 总被引：5，自引：0，他引：5
磷灰石裂变径迹分析法是恢复沉积盆地热史的一种有效方法．以大量的磷灰石裂变径迹资料为基础,分析了楚雄盆地海相地层热历史及地层剥蚀量。本区测试的各个样品的单颗粒年龄分布特征总体上集中程度不太好,分散性较强,反映这些样品可能均未经历125℃以上的完全退火;封闭径迹长度的分布特征反映本区具有较复杂的热史,这可能与楚雄盆地构造变动强烈并伴有多期次火山活动有关。裂变径迹反映本地区3个主要不整合（D1/O2、T3/D2、K2／J2)具不同的剥蚀量,表明楚雄盐地曾有较为复杂的剥蚀史：其中云参1井3个不整合的剥蚀量分别为220m（D1/O2)、180m(T3／D2)和105m(K2／J2);云龙凹陷露头剖面3个不整合的剥蚀量为263m（D1/O2）、149m(T3／D2)和280m(K2／J2)。 相似文献
5.
本文介绍了G.Friedrich等将矿相学、蚀变岩相学、流体包裹体和硫化物矿物相等研究紧密结合起来,来解释含金溶液来源和沉淀条件的方法,他们首先根据矿石组构及矿物交生关系准确划分成矿阶段及矿物生成顺序,并测定类质同象矿物的成分,再根据流体包裹体、矿石矿物组合、蚀变带矿物组合确定成矿温度,计算各阶段pH值变化范围;在loga （O2）一pH和loga （S2）-loga （O2）图解上就可以确定每个矿化阶段的物化条件及整个矿化过程物化条件的演变。据此,他们在西班牙Rodalquilar金矿研究后提出浅成热液中金以Au （HS）-2形式搬运,在近地表金因pH值、总硫活度降低及氧速度增加而沉淀的成矿模式。 相似文献
6.
7.
冲绳海槽南部表层沉积物地球化学特征及其物源和环境指示意义 总被引：9，自引：1，他引：9
对冲绳海槽南部陆架、陆坡和海槽 33个表层沉积物进行了元素地球化学分析,结果表明研究区沉积物的主要化学组成为SiO2 、Al2 O3 和CaO,这三种组分占沉积物总量的 6 8%左右。多数元素在陆架和陆坡的变化范围较大,在海槽区相对稳定。向海槽方向随沉积物粒径变细,SiO2 和CaO减少、Al2 O3 和其它多数元素含量增加。常量元素和Al2 O3 的比值分布特征表明,本区沉积物由物源区经由陆架向海槽输送,沉积物主要由陆源碎屑沉积组成,此外还有生物碎屑沉积和自生沉积。陆架区部分微量元素富集因子 (EF)与长江和黄河沉积物的富集因子对比结果表明,本区的沉积物与长江沉积物的关系更为密切。陆坡区Cu、Pb、Zn、Co、Ni和Cr的富集因子较高是由于生物的富集作用造成的,Mn的富集主要是自生沉积的结果。用R型因子分析方法对沉积物的化学组成进行了分析,结合元素的分布特征,给出了四个主因子所对应的沉积环境和特征元素组合,分别为 1)陆架型的元素组合 :SiO2 、TiO2 、Zr、CaO和Sr,2 )陆坡型的元素组合Fe2 O3 、MgO和P2 O5,3)海槽型的元素组合 :Al2 O3 、K2 O、Cu、Zn、Co、Ni、Cr和Ba,4 )反映沉积环境氧化-还原属性的元素组合 :MnO和FeO。 相似文献
8.
与遂安石共生的电气石矿物学特征及其地质意义 总被引：1，自引：1，他引：0
在对宽甸砖庙硼矿床的研究中发现了电气石与遂安石共生的现象,电气石为钙镁电气石,由电子探针分析结果计算的晶体化学式为:(Ca0.59Na0.355K0.06)(Mg2.557Fe0.1512+Ti0.013Cr0.002Ni0.006)(Al5.416Fe0.5642-（BO3）3Si 6.16 O16（OH）4,同围岩中的电气石相比:（1）淡绿色,多色性弱;（2）折射率为Ne=1.646,Ns=1.624;（3）成分上富Mg（MgO 11.47％）和Ca（CaO3.14％）;相对贫Na（Na2O 1.09％）,Fe（FeO4.63％）和Al（Al2O326.69％）（4）结构上d101=3.393A,a0=15.957±0.002,c0=7.227±0.001;（5）红外光谱晶格Si-O4四面体振动I1001>I1036。这些标型特征具有硼矿床的找矿指示意义。 相似文献
9.
在地下水位波动带、地表水-地下水交互带等氧化还原变化区域,O2会与Fe（II）发生反应产生活性氧,如·OH、·O2-、H2O2等.这些活性氧具有生物毒性,可能对微生物的存活产生影响,而不同的功能微生物对Fe（II）化学氧化产生活性氧的响应可能不同.为了验证这一科学假设,选取了一种Fe（II）氧化菌Pseudogulbenkiania sp.strain 2002（strain 2002）和两种氨氧化细菌Rhodococcus sp.（A1）和Arthrobacter oxydans（A2）作为模式菌种,并与铁还原菌Shewanella oneidensis strain MR-1（MR-1）对比,研究了Fe（II）化学氧化过程中微生物数量、细胞结构的变化,通过淬灭实验探究了活性氧的贡献.结果表明,不同功能微生物对Fe（II）化学氧化的响应截然不同.0.2 mmol/L Fe（II）氧化60 min后,MR-1数量下降了1.61个数量级,A1和A2分别下降了0.74和1.37个数量级,而strain 2002的存活几乎不受Fe（II）氧化的影响.透射电镜观察结果显示,MR-1、A1和A2菌细胞的外膜受到了不同程度的破坏,而strain 2002完好无损.淬灭实验结果表明,溶液中和胞内生成的活性氧是造成功能微生物死亡的原因,但是不同微生物由于对Fe（II）的吸附性能和对活性氧的抵御能力不同,因而对活性氧的响应机制不同.该研究结果对于诠释现代环境氧化还原变化区域微生物群落演化及地球史上氧气大爆发事件的生物地球化学过程具有重要的借鉴意义. 相似文献
10.
海洋沉积物中蕴含着大量以甲烷（CH4）、乙烷（C2H6）和丙烷（C3H8）为主要成分的烷烃化合物,与甲烷类似,乙烷与丙烷也是重要的温室气体。水合物分解和油气渗漏会释放这些烷烃化合物到海水及大气中,对海洋生态环境及全球气候产生重要影响。海洋环境中的微生物对烷烃的氧化作用有效降低了海洋烷烃气体的排放通量。系统综述了海洋环境中乙烷和丙烷的分布及生物转化机制的最新研究进展,归纳出以下认识：（1）海水中乙烷与丙烷的分布特征明显,主要受到水文、化学及生物等环境参数的影响;（2）海洋环境中乙烷与丙烷的生物来源主要有海水中浮游植物生产释放和沉积物中厌氧微生物生成,产甲烷菌可以利用多种底物生成乙烷与丙烷;（3）乙烷和丙烷的好氧氧化主要由烷烃氧化菌完成,并且该过程中伴随一定程度的碳氢同位素分馏;（4）沉积物中乙烷与丙烷的厌氧氧化通常与硫酸盐还原耦合,目前已对参与氧化乙烷与丙烷的硫酸盐还原菌及厌氧氧化机制有了初步认识。总结和回顾了海洋环境中乙烷和丙烷的来源、分布及微生物代谢过程,可为未来深入理解碳氢... 相似文献
11.
Gregory K. Druschel Robert J. Hamers George W. Luther III Jillian F. Banfield 《Aquatic Geochemistry》2003,9(2):145-164
The oxidation kinetics of trithionate (S3O62-
) and tetrathionate (S4O
6
2-
) with hydroxyl radicals (OH*) have been investigated in systems analogous to acid mine drainage (AMD) environments. The discovery of hydroxyl radical
(OH*) formation on pyrite surfaces (Borda et al., 2003) suggests hydroxyl radicals may affect the oxidation kinetics of intermediate
sulfur species such as tetrathionate. Cyclic voltammetry experiments in acidic solutions indicate that the reaction of S4O
6
2-
with OH* goes through an unknown intermediate, tentatively assigned as S3O
4
n-
. An outer-sphere electron transfer mechanism for the reaction of S4O
6
2-
with OH* to form S3O
4
n-
is proposed based on experimental results. Oxidation rates for trithionate and tetrathionate in the presence of Fenton's
reagent (which forms hydroxyl radicals) are too fast to be directly measured using UV-Vis spectrophotometry, electrochemical,
or stop-flow spectrophotometry methods. Competitive reaction kinetics within the context of the Haber—Weiss mechanism suggests
that the rate constant for the oxidation of trithionate and tetrathionate with OH* is in excess of 108 M-1 sec-1. 相似文献
12.
Corey A Cohn Shawn C Fisher Bruce J Brownawell Martin AA Schoonen 《Geochemical transactions》2010,11(1):2
Cellular exposure to particulate matter with concomitant formation of reactive oxygen species (ROS) and oxidization of biomolecules
may lead to negative health outcomes. Evaluating the particle-induced formation of ROS and the oxidation products from reaction
of ROS with biomolecules is useful for gaining a mechanistic understanding of particle-induced oxidative stress. Aqueous suspensions
of pyrite particles have been shown to form hydroxyl radicals and degrade nucleic acids. Reactions between pyrite-induced
hydroxyl radicals and nucleic acid bases, however, remain to be determined. Here, we compared the oxidation of adenine by
Fenton-generated (i.e., ferrous iron and hydrogen peroxide) hydroxyl radicals to adenine oxidation by hydroxyl radicals generated
in pyrite aqueous suspensions. Results show that adenine oxidizes in the presence of pyrite (without the addition of hydrogen
peroxide) and that the rate of oxidation is dependent on the pyrite loading. Adenine oxidation was prevented by addition of
either catalase or ethanol to the pyrite/adenine suspensions, which implies that hydrogen peroxide and hydroxyl radicals are
causing the adenine oxidation. The adenine oxidation products, 8-oxoadenine and 2-hydroxyadenine, were the same whether hydroxyl
radicals were generated by Fenton or pyrite-initiated reactions. Although nucleic acid bases are unlikely to be directly exposed
to pyrite particles, the formation of ROS in the vicinity of cells may lead to oxidative stress. 相似文献
13.
《矿物学报》2013,(Z1)
The removal of the antibiotic compound tetracycline hydrochloride (TC) was investigated by using goethite/H2O2 as a heterogeneous Fenton reagent. Five principle operational parameters, especially solution pH value, were taken into account to investigate how the heterogeneous Fenton process factors mediated the TC removal. This process was effective but seriously impacted by the pH value and temperature, as well as the dosages of α-FeOOH, TC and H2O2. Very interestingly, the acidic and alkaline aqueous medium conditions were both very favorable due to the occurrence of transformation of Fe(III) to Fe(II) on goethite surfaces reduced by TC at pH 3.04.0 even though with a low adsorption capacity of TC because its maximum adsorption of negatively charged form occurred at pH around 8.0[1], thereby greatly promoting the TC Fenton oxidative elimination. However, a rapid initial TC decay was observed at the first 5 min, followed by a much slower retardation stage, which was likely because the reductive transformation of Fe(III) to Fe(II) by TC in the solution was inhibited as the Fenton reaction proceeded. Moreover, the hydroxyl radical scavenger t-butanol addition can decrease the removal rate of TC in the goethite/H2O2 system to a certain extent. This further indicated that the main reactive species in this process were hydroxyl radicals[2]. All the goethite-catalysed heterogeneous Fenton reactions are responsible for the TC removal following the Langmuir-Hinshelwood model, were well fitted to pseudo-first order kinetics (R2>0.99), and their apparent activation energy (E) for this Fenton-like reaction was 31.86 kJ mol 1, a low value that is highly consistent with the ease of TC decay greatly enhanced by the temperature rise, indicated that the interfacial controlling interactions such as a proton induced solubilization and a reductive dissolution of goethite can clearly improve its Fenton catalytic activity[3], and these dissolution processes may not be effective in some cases, while the TC adsorption process may always play an important role to control the TC removal rate during the Fenton reaction. 相似文献
14.
N. Bensalah B. Louhichi A. Abdel-Wahab 《International Journal of Environmental Science and Technology》2012,9(1):135-143
In this work, the electrochemical oxidation of succinic acid on boron-doped diamond (BDD) anodes was investigated. Voltammetric study had shown that no peaks appeared in the region of electrolyte stability which indicates that succinic acid oxidation can take place at a potential close to the potential region of electrolyte oxidation. Galvanostatic electrolyses achieved total chemical oxygen demand (COD) removals and high mineralization yields under different operating conditions (initial COD, current density and nature of supporting electrolyte). Oxalic, glycolic and formic acids were the main intermediates detected during anodic oxidation of succinic acid on BDD electrode and carbon dioxide as the final product. The mean oxidation state of carbon reached the value of 4 at the end of electrolysis which is indicative of mineralization of almost all organics present in aqueous solution. The exponential profile of COD versus specific electrical charge has shown that mass transfer is the limiting factor for the kinetics of electrochemical process. A simple mechanism was proposed for the mineralization of succinic acid. First, hydroxyl radicals attack of succinic acid leading to formation of glycolic, glyoxylic, fumaric and maleic acids. Then, theses acids undergo rapid and non-selective oxidation by hydroxyl radicals to be transformed into oxalic and formic acids which leads to further oxidation steps to mineralize these acids into carbon dioxide and water. 相似文献
15.
The formation of superoxide and hydroxyl radicals at the surface of smectite clays due to oxygen reduction is demonstrated
by electron paramagnetic resonance spectroscopy. The yield of hydroxyl radicals is mainly a function of particle size of the
clays and depends, to a lesser extent, on the clay lattice iron. Synthetic laponite clay with small platelet size (∼20 nm)
and without lattice iron is leading in the formation of hydroxyl radicals followed by montmorillonite (∼200 nm). Fluorohectorite
(∼2000 nm) was inactive to hydroxyl radical formation by oxygen reduction.
Received: 20 January 2001 / Accepted: 7 August 2001 相似文献
16.
水体富营养化导致藻类的爆发进而引起藻毒素的释放。微囊藻毒素(MCLR)是最为常见的藻毒素,具有很强的毒性,对人类健康具有潜在危害。本文采用紫外/氯组合工艺,研究其对水中微囊藻毒素的控制效果。结果表明：紫外/氯共同作用下能够产生·Cl、·OH等活性自由基,具有协同降解MCLR的作用,30 min即可实现MCLR的完全去除,其降解效率随着氯投加质量浓度的增加而升高。在酸性及中性条件下,pH的变化对紫外/氯降解MCLR没有影响;在碱性条件下,MCLR的降解效率随pH的升高显著降低,pH升高至9时,30 min MCLR的降解效率仅为41.3%。此外,不同的水样来源和水质特点对紫外/氯联合降解MCLR的效率具有显著影响,纯水、西湖水及水厂滤后水的30 min去除率分别为99.5%,40.2%及63.3%。MCLR 的降解效率随腐殖酸质量浓度增大而降低,在60 min作用时间内,不含腐殖酸水样的MCLR去除率高达99.5%,当腐殖酸质量浓度增加到10 mg/L时,MCLR去除率仅为45.3%。 相似文献
17.
Exposure of lignin-derived organic matter (OM) to hydroxyl radicals originating from Fenton type reactions generates condensed aromatic and alicyclic aliphatic compounds, as shown using ultrahigh resolution mass spectrometry. Although condensed aromatic compounds are common in soil and dissolved OM, their presence has been attributed largely to combustion. A non-pyrogenic route for the formation of condensed aromatic compounds from lignin is suggested here, specifically that hydroxyl radical-initiated oxidation of lignin is capable of producing black carbon-like condensed aromatic compounds. Alicyclic aliphatic compounds are also produced, likely as part of a concerted process involving ring opening, polymerization and/or cyclization and hydrogen abstraction. Hydroxyl radicals associated with lignin degradation are produced through photochemistry in aqueous systems and enzymatic microbial processes in soil. 相似文献
18.
Corey A Cohn Christopher E Pedigo Shavonne N Hylton Sanford R Simon Martin AA Schoonen 《Geochemical transactions》2009,10(1):8-9
Background
Given the importance of highly reactive oxygen species (hROS) as reactants in a wide range of biological, photochemical, and environmental systems there is an interest in detection and quantification of these species. The extreme reactivity of the hROS, which includes hydroxyl radicals, presents an analytical challenge. 3'-(p-Aminophenyl) fluorescein (APF) is a relatively new probe used for measuring hROS. Here, we further evaluate the use of APF as a method for the detection of hydroxyl radicals in particle suspensions. 相似文献19.
Pyrite (FeS2) oxidation: A sub-micron synchrotron investigation of the initial steps 总被引：1，自引：0，他引：1
Anand P. Chandra 《Geochimica et cosmochimica acta》2011,75(20):6239-6254
Pyrite is an environmentally significant mineral being the major contributor to acid rock drainage. Synchrotron based SPEM (scanning photoelectron microscopy) and micro-XPS (X-ray photoelectron spectroscopy) have been used to characterise fresh and oxidised pyrite (FeS2) with a view to understanding the initial oxidation steps that take place during natural weathering processes. Localised regions of the pyrite surface containing Fe species of reduced coordination have been found to play a critical role. Such sites not only initiate the oxidation process but also facilitate the formation of highly reactive hydroxyl radical species, which then lead the S oxidation process.Four different S species are found to be present on fresh fractured pyrite surfaces: S22−(bulk) (4-fold coordination), S22−(surface) (3-fold coordination), S2− and S0/Sn2− (metal deficient sulfide and polysulfide respectively). These species were found to be heterogeneously distributed on the fractured pyrite surface. Both O2 and H2O gases are needed for effective oxidation of the pyrite surface. The process is initiated when O2 dissociatively and H2O molecularly adsorb onto the surface Fe sites where high dangling bond densities exist. H2O may then dissociate to produce OH radicals. The adsorption of these species leads to the formation of Fe-oxy species prior to the formation of sulfoxy species. Evidence suggests that Fe-O bonds form prior to Fe-OH bonds. S oxidation occurs through interactions of OH radicals formed at the Fe sites, with formation of SO42− occurring via S2O32−/SO32− intermediates. The pyrite oxidation process is electrochemical in nature and was found to occur in patches, where site specific adsorption of O2 and H2O has occurred. Fe and S oxidation was found to occur within the same area of oxidation probably in atomic scale proximity. Furthermore, the O in SO42− arises largely from H2O; however, depending on the surface history, SO42− formed early in the oxidation process may also contain O from O2. 相似文献
20.
S. M. Aleksandrov 《Geochemistry International》2008,46(6):578-594
The hydration of kotoite, suanite, and szaibelyite with ultimate brucitization was considered by the example of skarn deposits of endogenous magnesium borates. This process involves isomorphic substitution of hydroxyl groups for equivalent amounts of boron radicals. The degree of kotoite hydration varies from 2 to 40%. The hydration products reach Mg2[BO3](OH) and Mg3{[BO3]1.5(3OH)0.5}2, are isostructural with orthoborate, approach Mg3[BO3](OH)3, and do not contain szaibelyite. Kotoite in association with humites is replaced by Si-bearing pertsevite with variable F content. In contrast, suanite is directly replaced by szaibelyite, with preservation of its relics or inheritance of crystal shapes. The composition of szaibelyite also changes owing to the partial substitution of hydroxyl for boric radical (in hydroxylszaibelyite) or an increase in H2O content (in hydroszaibelyite), which does not rule out its brucitization. The hydration of borates is caused by a decrease in boron content in hydrothermal solutions with decreasing temperature. The borate assemblages studied are characterized by low F content, the increase of which leads to the appearance of F-bearing low-and moderate-Si pertsevites in humite-kotoite calciphyres. The investigation of hydration became possible owing to the direct determination of boron content in borates. The obtained data were compared with experimental studies on the hydrothermal synthesis of kotoite, suanite, szaibelyite, and fluoborates. The established geochemical tendencies in the hydration of boron minerals, which is accompanied by partial migration and loss of boron into the adjacent rocks, are important for estimating the quality of borate ores in magnesian-skarn deposits. 相似文献