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题名: 电子传递体与含铁矿物对铬(VI)生物还原固定过程的影响
作者: 孟颖1
学位类别: 博士后
答辩日期: 2017-08
授予单位: 中国科学院大学
授予地点: 北京
导师: 栾富波
关键词: Cr(VI),生物还原,Shewanella oneidensis MR-1,电子传递体,含铁矿 ; Cr(VI), bioreduction, Shewanella oneidensis MR-1, electron shuttles,iron-bearing minerals
其他题名: The effect of iron minerals and electron shuttles onbioreduction of hexavalent chromium
学位专业: 环境科学与工程
中文摘要: 环境中铬(VI)污染问题在全球范围内一直被广泛关注,Cr污染事件时有发生。 通过生物或非生物手段将毒性强、溶解度高的 Cr(VI)还原为毒性低、迁移性差的 Cr(III)是目前 Cr污染治理主要方法之一。生物还原过程缓慢,且 Cr(VI)本身对 微生物有一定毒性,使生物还原方法存在较大局限性。非生物还原主要利用环境 中 Fe(II)还原固定 Cr(VI),该还原过程反应速率很快,但是该过程中 Fe(II)一旦 被消耗完,由于 Cr(VI)的毒性作用,微生物很难再还原生成 Fe(II)使反应持续进 行。还原过程的本质是电子传递,本研究利用电子传递体将生物还原与非生物还 原两个过程结合起来,实现持续、有效的 Cr(VI)还原固定。本研究考察了电子传 递体和含铁矿物共存时对 Cr(VI)生物还原过程的协同促进作用,进一步分析了电 子传递体与含铁矿物协同作用机理。研究结果表明: (1)在电子传递体 AQDS和 NAu-2对 MR-1还原 Cr(VI)过程的影响的实验 中,进行 AQDS和 NAu-2单独/共存时对 MR-1还原 Cr(VI)过程的影响。单独 AQDS对MR-1还原过程起到促进作用(速率常数0.209 h-1),这主要是由于AQDS 加快体系中电子传递的作用。单独 NAu-2对 Cr(VI)浓度变化基本没有影响,但 Cr(VI)本身对 MR-1有一定的毒性作用,使得 NAu-2中 Fe(III)仅有极少量被还原。 而 AQDS与 NAu-2同时加入后,MR-1还原 Cr(VI)速率常数增加至 0.496 h-1(对 照组仅为 0.035 h-1),且 Cr(VI)完全被还原后,Fe(II)浓度迅速增加至 2.9 mM。本 研究首次发现 AQDS与 NAu-2共存时对 MR-1还原 Cr(VI)起到明显的协同促进 作用。 (2)为了进一步验证 AQDS与 NAu-2协同促进作用,并对协同促进机理进 行分析,采用 AQDS与三种含铁矿物(NAu-2、水铁矿和针铁矿)进行组合,并 采用多次添加 Cr(VI)的方式考察不同组合条件对 MR-1还原 Cr(VI)过程的影响。 AQDS单独加入后促进作用与(1)基本一致,且由于 Cr(VI)毒性作用,三种含 铁矿物单独加入对 Cr(VI)生物还原过程也没有促进作用。当 AQDS与 NAu-2/水 铁矿同时存在时对 Cr(VI)还原过程产生明显的协同作用,协同系数分别为 2.09-4.63和 1.72-4.76。电子传递体 AQDS在 MR-1和含铁矿物之间起到电子传 递作用,使得 Cr(VI)存在体系中 Fe(III)被还原为 Fe(II),Fe(II)再与 Cr(VI)发生非 生物还原,促进 Cr(VI)还原过程的进行。但在 AQDS与针铁矿的组合中,由于 针铁矿很难被 MR-1还原,导致产生的 Fe(II)的量太少,不足以影响 Cr(VI)还原 速率,因此并没有产生协同作用。 (3)在前期实验基础上,我们进一步考察了不同电子传递体(2-HNQ、5-HNQ、 AQDS、AQS、AQC、Ali和 Car)与 NAu-2组合后对 MR-1还原 Cr(VI)过程的 影响。七种电子传递体对 MR-1直接还原 Cr(VI)过程都有一定的促进作用,且随 着电子传递体本身氧化还原电位增加,促进作用逐渐增强。而对于 MR-1还原 NAu-2过程分析发现,促进作用随着电子传递体氧化还原电位升高呈现先增加后 降低的趋势。对于氧化还原电位高于-250 mV的四种电子传递体(5-HNQ、2-HNQ、 AQDS和 AQC)而言,MR-1还原 Cr(VI)的速率常数与氧化还原电位呈线性正相 关(RCr2=0.89),而 MR-1还原 NAu-2过程中 Fe(II)生成速率与氧化还原电位呈 线性负相关(RFe2=0.94)。当四种电子传递体与 NAu-2同时加入到 Cr(VI)还原体 系中,Cr(VI)还原速率随氧化还原电位升高呈现先上升后降低的趋势,在 2-HNQ+NAu-2体系中达到最大值(1.064 h-1)。在微生物还原能力范围内 (>-250mV),电子传递体与 NAu-2同时添加对 Cr(VI)生物还原过程产生叠加的 作用。其余三种电子传递体(AQC、Ali和 Car)对 Cr(VI)和 NAu-2还原过程的 促进作用均不明显。
英文摘要: Reduction of hexavalent chromium (Cr(VI)) to sparingly soluble trivalent chromium (Cr(III)) is an attractive strategy for the remediation of Cr(VI) contaminated sites. Bioremedation of Cr(VI) pollution depends on seldom Cr(VI)-tolerant baterial species, which always take a long time. Previous studies showed that the aqueous/structral Fe(II) could reduce Cr(VI) rapidly. However, If Fe(II) was exhausted, the reduction process ended due to the toxicity of Cr(VI) to dissimilatory metal-reducing bacteria (DMRB). This study investigated the effect of different electron shuttles (ESs) and iron minerals on the bioreduction of Cr(VI). (1) The effect of anthraquinone-2,6-disulfonate(AQDS) and nontronite NAu-2 on bioreduction of Cr(VI) was investigated in this part. Both NAu-2 and Cr(VI) could be reduced by MR-1 directly.The kcells+AQDS could be enhanced to 0.209 h-1 in the presence of AQDS. When NAu-2 was added alone, little effect was presented on the change of Cr(VI) concentration. NAu-2-Fe(III) was not reduced due to the toxicity of Cr(VI) to MR-1. When both AQDS and NAu-2 were present, kcells+AQDS+NAu-2 achieved 0.496 h-1. After the Cr(VI) reduction finished, the concentration of Fe(II) increased to 2.9 mM. It could be speculated that the synergistic effect of AQDS and NAu-2 enhanced Cr(VI) reduction significantly. (2) This study investigated the potential synergistic effect between AQDS and Fe(III) minerals (NAu-2, ferrihydrite, and goethite) on the bioreduction of Cr(VI) by Shewanella oneidensis MR-1. AQDS alone could promote the bioreduction of Cr(VI) by accelerating electron transfer from MR-1 to Cr(VI). While Fe(III) minerals alone did not enhance the bioreduction of Cr(VI) due to the toxicity of Cr(VI) to MR-1,which inhibited the electron transfer from MR-1 to iron minerals. The synergistic effect of AQDS and NAu-2/ferrihydrite on Cr(VI) reduction was firstly reported in this study, where AQDS plus NAu-2 or ferrihydrite enhanced the bioreduction of Cr(VI) significantly. The synergy factors of AQDS plus NAu-2 and AQDS plus ferrihydrite were 2.09-4.63 and 1.72-4.76, respectively. We found that AQDS served as electron shuttle between MR-1 and Fe(III) minerals, which triggered the bioreducion of Fe(III) minerals to Fe(II) in the presence of Cr(VI). The synergistic effect of AQDS and NAu-2/ferrihydrite was attributed to the biogenic Fe(II) which could quickly reduce Cr(VI) to Cr(III). No synergy was observed between AQDS and goethite, because the bioreduction of goethite was inhibited by Cr(VI) even in the presence of AQDS. (3) The combinations of NAu-2 and seven ESs (5-HNQ, 2-HNQ, AQDS,AQS, AQC, Ali and Car) were used to investigate the combind effects on Cr(VI) bioreduction. The reduction of Cr(VI) by MR-1 alone was enhanced with the increasing of redox potential of ESs. The reduction of NAu-2 by MR-1 only increased at first and then decreased with the increasing of redox potential of ESs. Generally, AQC, Ali and Car had little effects on the bioredction of Cr(VI) and NAu-2. The other four ESs (5-HNQ, 2-HNQ, AQDS and AQS) present opposite tendency on the enhancement of Cr(VI) and NAu-2 bioreduction with the increase of redox potential (RCr2=0.89, RFe2=0.94). When ES and NAu-2 were both added to the reactors, the k values of Cr(VI) bioreduction increased at first and then decreased with the rise of redox potential. The maximus of 1.064 h-1 was achieved in presence of both 2-HNQ and NAu-2. It was found that the redox potential of ESs had relationship with the reduction rate of Cr(VI). If the redox potential of ESs (5-HNQ, 2-HNQ, AQDS and AQS) was in the range of MR-1 reduction (>-250mV), additive effects of Cr(VI) bioreduction in the presence of both ESs and NAu-2 was found in this study. The effect between electron shuttle and iron minerals that was reported in this study may have important implications for Cr(VI) migration and transformation in anaerobic environment. It also provided a promising approach to strengthen the reduction and immobilization of Cr(VI) in contaminated sites.
内容类型: 学位论文
URI标识: http://ir.rcees.ac.cn/handle/311016/38681
Appears in Collections:环境水质学国家重点实验室_学位论文

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作者单位: 1.中国科学院生态环境研究中心

Recommended Citation:
孟颖. 电子传递体与含铁矿物对铬(VI)生物还原固定过程的影响[D]. 北京. 中国科学院大学. 2017.
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