Ferrihydrite mineral transformations in the presence of Fe(II) and organic ligands

2020 ◽  
Author(s):  
Laurel K. ThomasArrigo ◽  
Ruben Kretzschmar
Keyword(s):  
Trace Elements ◽  
High Surface ◽  
Dynamic Environments ◽  
Organic Ligands ◽  
Mineral Transformation ◽  
Iron Minerals ◽  
Molar Ratios ◽  
Reducing Conditions ◽  
Soils And Sediments ◽  
Mineral Transformations

<p>In soils and sediments, poorly-crystalline, short-range order (SRO) iron minerals constitute one of the most abundant and reactive components. With high surface areas, SRO minerals like ferrihydrite (Fe<sub>10</sub>O<sub>14</sub>(OH)<sub>2</sub>+mH<sub>2</sub>O) influence the biogeochemical cycling of trace elements and nutrients, particularly in redox dynamic environments. While under oxic conditions SRO iron mineral adsorption capacity is high, in the absence of O<sub>2</sub>, Fe<sup>III</sup> acts as an electron acceptor during microbial respiration. Electron transfer induces transformations in pure iron minerals, impacting the release and re-distribution of SRO-associated trace elements and nutrients.</p><p>In nature, however, pure SRO iron minerals rarely form. Rather, the ubiquitous presence of natural organic matter (OM) in soils and sediments promotes the formation mineral-organic associations. Coprecipitation of ferrihydrite with OM decreases particle size and alters the mineral susceptibility towards microbial reduction. Thus, under reducing conditions, an increased rate and extent of mineral transformation could be expected for OM-associated ferrihydrite. However, in the presence of abiotic reductants, mineral transformation rates and extents in OM-associated ferrihydrite are markedly inhibited when compared to that of a pure ferrihydrite. Using polygalacturonic acid (PGA) as a proxy for acid carbohydrate fraction found in exopolymeric substances, we reacted ferrihydrite-PGA coprecipitates of varying C:Fe molar ratios (0-2.5) with ferrous Fe (Fe(II), 0.5-5.0 mM) at neutral pH for up to 5 weeks. Through a combination of XRD and <sup>57</sup>Fe Mössbauer spectroscopy, we showed that at all Fe(II) concentrations, the kinetics and extent of mineral transformation decreased with increasing C content of the coprecipitates. Similarly, ferrihydrite-OM coprecipitates comprising PGA, citric acid (CA), or galacturonic acid (GA) of similar C:Fe molar ratios (~0.6) also showed inhibited mineral transformations compared to a pure ferrihydrite, whereby the extent of inhibition of mineral transformations followed the order GA>>CA>PGA. In addition, electron microscopy imaging showed that the crystal morphology of the secondary mineral phases varied with the varying chemical structure of the coprecipitating organic ligands. Despite this, applications of stable Fe isotope tracers revealed that all OM-associated ferrihydrite actively partook in iron atom exchange, suggesting that the presence of OM inhibited crystal growth of more crystalline phases, therefore again leading to SRO phases during iron atom exchange. Collectively, the stabilization of high surface-area ferrihydrite under reducing conditions via recrystallization has implications for the release and re-distribution of ferrihydrite-associated trace elements and nutrients in redox-dynamic environments.</p>

scholarly journals Sulfidization of ferrihydrite in the presence of organic ligands

2021 ◽  
Author(s):  
Laurel K. ThomasArrigo ◽  
Sylvain Bouchet ◽  
Ralf Kaegi ◽  
Ruben Kretzschmar
Keyword(s):  
Trace Elements ◽  
High Surface ◽  
Organic Ligand ◽  
Organic Ligands ◽  
Molar Ratios ◽  
Iron Mineral ◽  
Surface Areas ◽  
Secondary Reactions ◽  
Mineral Components ◽  
The Impact

<p>In soils and sediments, short-range order (SRO) iron minerals constitute one of the most abundant and reactive mineral components. With high surface areas and points of zero charge near pH 7-8, SRO minerals like ferrihydrite (Fe<sub>10</sub>O<sub>14</sub>(OH)<sub>2</sub>+mH<sub>2</sub>O) are often linked to high adsorption of nutrients (C, N, P, S) and trace elements (e.g. As, Zn). However, under oxygen-limiting conditions, microbially derived sulfide (S(−II)) may cause the rapid reductive dissolution of ferrihydrite and the release of associated nutrients and trace elements, thus influencing the biogeochemical cycling of trace elements and nutrients, particularly in redox dynamic environments.</p><p>Sulfidization of ferrihydrite occurs rapidly, whereby electron transfer between surface complexed sulfide and the ferrihydrite surface results in (partially) oxidized sulfur species and Fe(II). Depending on the S(-II):Fe molar ratios, secondary reactions then lead to mackinawite (FeS) or pyrite (FeS<sub>2</sub>) precipitation. In nature, however, ferrihydrite is often found associated with natural organic matter (NOM). Because coprecipitation of ferrihydrite with NOM decreases particle size, alters the surface charge, and may block surface sorption sites, we speculated that kinetics and pathways of sulfidization of organic-associated ferrihydrite may differ from those of the pure mineral. Therefore, in this study, we followed iron mineral transformations and sulfur speciation during sulfidization of a pure ferrihydrite over one year and compared this to ferrihydrite coprecipitated with model organic ligands (polygalacturonic acid, galacturonic acid, and citric acid). Using a combination of solid- and aqueous phase Fe and S speciation techniques, we show that the impact of OM on ferrihydrite sulfidization kinetics and pathways varies with the chemical structure of the organic ligand, and that secondary reactions continue well past the initial rapid consumption of S(-II).</p>

The influence of highly dispersed preparations on metabolism and productivity of young cattle

2020 ◽  
pp. 22-33
Author(s):  
E. A. Sizova ◽  
A. M. Makaeva
Keyword(s):  
Trace Elements ◽  
High Surface ◽  
Live Weight ◽  
Animal Husbandry ◽  
Control Group ◽  
Dispersed Particles ◽  
Highly Dispersed ◽  
Young Cattle ◽  
Experimental Group ◽  
Highly Dispersed Particles

Preparations of highly dispersed particles of trace elements are increasingly used in animal husbandry. This is determined by their extraordinary biological properties such as the ability to penetrate into tissues and organs, a high surface area, and so on. One of the promising directions for using highly dispersed particles both in the post-embryonic and embryonic periods of animal development is the use of trace elements as sources. This is determined by the relatively lower toxicity, higher bioavailability of elements from preparations of highly dispersed particles, which reduces the load on the environment and allows you to produce products enriched with minerals. The purpose of the research was to study the effect of highly dispersed drugs on rumen digestion, the composition of the rumen microbiome, metabolism and productivity of young cattle. A comprehensive assessment of the use of highly dispersed SiO2 and FeCo preparations in cattle nutrition has been provided in the paper. The digestibility of feed, metabolism, and productivity of young cattle when feeding highly dispersed particles have been studied. An unusual fact of increasing bacterial biomass when using highly dispersed particles of silicon dioxide in animal feeding has been described. A method for increasing the digestibility of feed components by ruminants through the use of highly dispersed FeCo alloy particles has been proposed. As follows from the data obtained the use of highly dispersed particles allowed to increase the live weight of experimental young animals to 413 kg in the 1st experimental group and 416 kg in the 2nd experimental group, which was by 11 (P ≤ 0,01) and 14 kg (P ≤ 0,01) higher than the control indicator. As follows from the analysis of the data obtained, the profitability of rearing young animals in the 1st and 2nd experimental groups was by 2,4 and 2,2 % higher than the same indicator calculated for the control group.

scholarly journals Green and facile synthesis of cerium doped Ni3Fe electrocatalyst for efficient oxygen evolution reaction

2020 ◽  
Vol 34 (2) ◽  
pp. 353-363
Author(s):  
F. Kanwal ◽  
A. Batool ◽  
R. Akbar ◽  
S. Asim ◽  
M. Saleem
Keyword(s):  
Oxygen Evolution ◽  
Oxygen Evolution Reaction ◽  
Large Scale ◽  
Low Cost ◽  
High Surface ◽  
High Surface Area ◽  
Three Dimensional ◽  
Alkaline Electrolyte ◽  
Hydrogen Electrode ◽  
Molar Ratios

Electrochemical water splitting is the most promising pathway to produce high-purity hydrogen to alleviate global energy crisis. This reaction demands inexpensive, efficient and robust electrocatalyst for its commercial use. Herein, we demonstrate an effective, facile and scalable method for the synthesis of cerium doped Ni3Fe nanostructures as an electrocatalyst for oxygen evolution reaction (OER) by following simple chemical bath deposition route. The different molar ratios (3, 6 and 12 mM) of cerium in the chemical bath were used to study its effect on the structural and the electrochemical properties of the Ni3Fe nanostructured films. Doping of cerium contents induced variations in the morphology of deposited Ni3Fe nanostructures. The optimized electrocatalyst Ni3Fe/Ce-6 yielded high surface area catalyst nanosheets uniformly deposited on three-dimensional conductive scaffold to ensure increase in the exposure of doped Ni3Fe catalytic sites with high electrical conductivity. As a result, this earth-abundant electrocatalyst affords high OER performance with a small overpotential of 310 mV versus reversible hydrogen electrode (RHE) at 10 mA cm-2 and retains good stability up to ~ 10 h in alkaline electrolyte. This scalable strategy has great potential in future advancement of efficient and low-cost electrocatalysts for their large-scale application in energy conversion systems.                     KEY WORDS: Oxygen evolution, Electrocatalyst, Ni3Fe nanostructures, Cerium, Alkaline electrolyte   Bull. Chem. Soc. Ethiop. 2020, 34(2), 353-363 DOI: https://dx.doi.org/10.4314/bcse.v34i2.12

Behavior of trace elements and mineral transformations in the super-high organic sulfur Ganhe coal during gasification

2018 ◽  
Vol 177 ◽  
pp. 140-151 ◽  
Author(s):  
Yafeng Wang ◽  
Yuegang Tang ◽  
Shuqin Liu ◽  
Yonggang Wang ◽  
Robert B. Finkelman ◽  
...  
Keyword(s):  
Trace Elements ◽  
Organic Sulfur ◽  
Mineral Transformations

Synthesis of Nanoporous Materials Al-MCM-41 from Natural Halloysite

NANO ◽  
2015 ◽  
Vol 10 (01) ◽  
pp. 1550005 ◽  
Author(s):  
Yaling Xie ◽  
Aidong Tang ◽  
Huaming Yang
Keyword(s):  
Surface Area ◽  
High Surface ◽  
High Surface Area ◽  
Halloysite Nanotubes ◽  
Nanoporous Materials ◽  
Molar Ratio ◽  
Molar Ratios ◽  
Naoh Solution ◽  
The One ◽  
Mcm 41

Nanoporous materials Al -MCM-41 with varying Si / Al molar ratios have been successfully synthesized from natural clay mineral halloysite nanotubes (HNTs). Hydrothermal treatment of acid-pretreated HNTs and NaOH solution resulted in the one-step synthesis of final nanoporous products by using surfactant. The effects of Si / Al molar ratios (7.7, 61.0 and 176.5) on the surface area, porosity and degree of structural order of Al -MCM-41 materials have been investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), N 2 adsorption–desorption measurements and Fourier transform infrared (FTIR) spectra techniques. The results indicated that Si / Al molar ratio had important effect on the characteristics of nanoporous materials, and Al -MCM-41 with an intermediate Si / Al molar ratio of 61.0 exhibited excellent characteristics with high degree of order, high surface area (S BET ) of 1033 m2/g and pore volume of 0.92 mL/g.

Detection of High-Organic-Carbon Features in Sediments by Direct-Push Color Logging

2020 ◽  
Author(s):  
Stefan Klingler ◽  
Ulrike Werban ◽  
Carsten Leven ◽  
Peter Dietrich ◽  
Olaf A. Cirpka
Keyword(s):  
Organic Carbon ◽  
Color Space ◽  
Gaussian Mixture Models ◽  
Gaussian Mixture ◽  
Horizontal Resolution ◽  
Flow Paths ◽  
Direct Push ◽  
Reducing Conditions ◽  
Soils And Sediments ◽  
Floodplain Sediments

<p>A biogeochemical site characterization aims at delineating zones of reducing and oxidizing conditions in the subsurface to infer their influence on solute and contaminant turnover processes along groundwater flow paths. Hereby, large values of the total organic carbon (TOC) content mark reducing conditions in soils and sediments. Dark sediment colors are good predictors for high-TOC zones and thus indicate hotspots of biogeochemical turnover and microbial activity. Traditionally, obtaining the sediment color requires costly sampling, resulting in poor horizontal resolution and related uncertainty caused by interpolation. We suggest using a direct-push soil color optical screening tool to acquire multiple high-resolution vertical color profiles and demonstrate its applicability in floodplain sediments down to 12 m depth. We use Gaussian mixture models for a cluster analysis of the color logs in the CIE L*a*b* color space to identify color-facies, determine facies-specific relationships between the L*a*b* color-values and the TOC content of the sediments, and to construct the 3-D distributions of three distinct facies and organic matter. Direct-push color-logging may also be used for in-situ mapping of redox-zonation, iron content, or sedimentary structures.</p>

Determination of trace elements in iron minerals by instrumental and radiochemical neutron activation analysis

2008 ◽  
Vol 96 (12) ◽  
Author(s):  
Petre Makreski ◽  
Radojko Jacimovic ◽  
Vekoslava Stibilj ◽  
Trajče Stafilov ◽  
Gligor Jovanovski
Keyword(s):  
Trace Elements ◽  
Neutron Activation Analysis ◽  
Iron Oxide ◽  
Activation Analysis ◽  
Neutron Activation ◽  
Major And Trace Elements ◽  
Radiochemical Neutron Activation Analysis ◽  
Iron Minerals

AbstractThe method for determination of major and trace elements in iron oxide [hematite (Fe

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