東華大學圖書館 |

Language: English

Help

回圖書館首頁

手機版館藏查詢

Back

Switch To: Labeled | MARC Mode | ISBD

Structure and formation kinetics of ...

Pasten, Pablo A.

Linked to FindBook

Google Book

Amazon

博客來

Structure and formation kinetics of manganese oxides by Leptothrix discophora SP-6.

Record Type:	Language materials, printed : Monograph/item
Title/Author:	Structure and formation kinetics of manganese oxides by Leptothrix discophora SP-6./
Author:	Pasten, Pablo A.
Description:	285 p.
Notes:	Adviser: Jean-Francois Gaillard.
Contained By:	Dissertation Abstracts International63-04B.
Subject:	Biogeochemistry. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3050570
ISBN:	0493651810

Structure and formation kinetics of manganese oxides by Leptothrix discophora SP-6.
Pasten, Pablo A.

Structure and formation kinetics of manganese oxides by Leptothrix discophora SP-6. - 285 p.

Adviser: Jean-Francois Gaillard.

Thesis (Ph.D.)--Northwestern University, 2002.

Manganese oxides (MnOx) are very reactive species in natural and engineered systems. Many bacterial species catalyze the formation of MnOx, but their structure and formation kinetics is poorly understood. This work uses a multi-method approach, including transmission electron microscopy (TEM), X-ray absorption spectroscopy (XAS), and kinetic experiments, to study the MnOx formed by the sheathed <italic>Leptothrix discophora</italic> SP-6 (SP6-MnOx). TEM of unstained thin sections of SP6-MnOx embedded in hydrophilic resin show that they are primarily formed by layers associated to fibrillar structures (50–100 nm size). X-ray absorption near edge structure (XANES) at the MnK-edge shows octahedral Mn coordination, with an oxidation state of 3.8 ± 0.3, similar to the family of MnO2 polymorphs. The inspection of the radial distance function of the extended X-ray absorption fine structure (EXAFS) suggests similarity with todorokite (3 x 3 tunnel structure) and chalcophanite (layer structure coordinated to extra-layer Zn). A mathematical model of the EXAFS contribution of the first three coordination shells around Mn was calibrated and validated using big tunnel (2 x 2, 2 x 3, and 3 x 3) and layered MnO 2 minerals. The estimated radial distances and coordination numbers suggest that the SP6-MnOx are formed by layers with fewer vacancies than chalcophanite, which are coordinated to extra-layer Mn<super>2+</super> or Mn<super>3+</super>. This finding is consistent with the layer morphology observed in the TEM micrographs. Kinetic experiments show that at circumneutral pH the formation of the SP6-MnOx is governed by a purely biological process. The rate of autocatalytic MnOx formation was estimated to be lower than 5% of the biological rate. XANES shows that the SP6-MnOx oxidation state increases during the oxidation process, suggesting a preliminary sorption of Mn(II) on the active sites, followed by the oxidation step. The MnOx formation rate is inhibited by 25 μM Zn<super>2+</super>, Co<super>2+</super>, or Zn<super>2+</super>. For pH > 7.2, the MnOx formation is faster, but it is controlled abiotically, resulting in reduced forms of oxy-hydroxides with different morphology compared to the SP6-MnOx formed at circumneutral pH. Besides pH, other environmental variables do not affect significantly the SP6-MnOx structure.

ISBN: 0493651810Subjects--Topical Terms:

545717
Biogeochemistry.

Structure and formation kinetics of manganese oxides by Leptothrix discophora SP-6.
LDR:03301nam 2200277 a 45 001 928267
005 20110426
008 110426s2002 eng d
020 $a 0493651810
035 $a (UnM)AAI3050570
035 $a AAI3050570
040 $a UnM $c UnM
100 1 $a Pasten, Pablo A. $3 1251730
245 1 0 $a Structure and formation kinetics of manganese oxides by Leptothrix discophora SP-6.
300 $a 285 p.
500 $a Adviser: Jean-Francois Gaillard.
500 $a Source: Dissertation Abstracts International, Volume: 63-04, Section: B, page: 2008.
502 $a Thesis (Ph.D.)--Northwestern University, 2002.
520 $a Manganese oxides (MnOx) are very reactive species in natural and engineered systems. Many bacterial species catalyze the formation of MnOx, but their structure and formation kinetics is poorly understood. This work uses a multi-method approach, including transmission electron microscopy (TEM), X-ray absorption spectroscopy (XAS), and kinetic experiments, to study the MnOx formed by the sheathed <italic>Leptothrix discophora</italic> SP-6 (SP6-MnOx). TEM of unstained thin sections of SP6-MnOx embedded in hydrophilic resin show that they are primarily formed by layers associated to fibrillar structures (50–100 nm size). X-ray absorption near edge structure (XANES) at the MnK-edge shows octahedral Mn coordination, with an oxidation state of 3.8 ± 0.3, similar to the family of MnO2 polymorphs. The inspection of the radial distance function of the extended X-ray absorption fine structure (EXAFS) suggests similarity with todorokite (3 x 3 tunnel structure) and chalcophanite (layer structure coordinated to extra-layer Zn). A mathematical model of the EXAFS contribution of the first three coordination shells around Mn was calibrated and validated using big tunnel (2 x 2, 2 x 3, and 3 x 3) and layered MnO 2 minerals. The estimated radial distances and coordination numbers suggest that the SP6-MnOx are formed by layers with fewer vacancies than chalcophanite, which are coordinated to extra-layer Mn<super>2+</super> or Mn<super>3+</super>. This finding is consistent with the layer morphology observed in the TEM micrographs. Kinetic experiments show that at circumneutral pH the formation of the SP6-MnOx is governed by a purely biological process. The rate of autocatalytic MnOx formation was estimated to be lower than 5% of the biological rate. XANES shows that the SP6-MnOx oxidation state increases during the oxidation process, suggesting a preliminary sorption of Mn(II) on the active sites, followed by the oxidation step. The MnOx formation rate is inhibited by 25 μM Zn<super>2+</super>, Co<super>2+</super>, or Zn<super>2+</super>. For pH > 7.2, the MnOx formation is faster, but it is controlled abiotically, resulting in reduced forms of oxy-hydroxides with different morphology compared to the SP6-MnOx formed at circumneutral pH. Besides pH, other environmental variables do not affect significantly the SP6-MnOx structure.
590 $a School code: 0163.
650 4 $a Biogeochemistry. $3 545717
650 4 $a Engineering, Environmental. $3 783782
690 $a 0425
690 $a 0775
710 2 0 $a Northwestern University. $3 1018161
773 0 $t Dissertation Abstracts International $g 63-04B.
790 $a 0163
790 1 0 $a Gaillard, Jean-Francois, $e advisor
791 $a Ph.D.
792 $a 2002
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3050570