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Topic: Ferrihydrite

	ARS \| Publication request: Modeling the Impact of Ferrihydrite on Adsorption-Desorption of Soil Phosphorus (Site not responding. Last check: 2007-10-18)
		Ferrihydrite is a form of iron that is so common in groundwater in the southeastern United States that it is available in large quantitites from water treatments plants.
		Application of ferrihydrite increased the rapid P adsorption but equilibrium between the amount in solution and the amount sorbed was not reached after 1440 h due to the highly time-dependent nature of P sorption.
		Modeling the P adsorption and desorption mechanisms of soil amended with ferrihydrite is necessary to predict the movement of dissolved and sediment-bound P. The objective of this study was to model the multi-reaction P sorption properties of soil amended with ferrihydrite.
	www.ars.usda.gov /research/publications/publications.htm?SEQ_NO_115=135070 (573 words)

	Department of Energy Information Bridge - full-text scientific and technical reports (gray literature)
		Four ferrihydrite suspensions were aged at pH 12 and 50 Â°C with or without Ba in 0.01 M KN03 for 68 h or in 0.17 M KN03 for 3424 h.
		Two ferrihydrite suspensions were aged with and without Sr at pH 8 in 0.1 M KN03 at 70Â°C. Barium or Sr sorption, or resorption, was measured by periodically centrifuging suspension subsamples, filtering, and analyzing the filtrate for Ba or Sr.
		The percent transformation of ferrihydrite to goethite/hematite was estimated from the ratio of oxalate and HC1 extractable Fe.
	www.osti.gov /bridge/product.biblio.jsp?osti_id=7261 (672 words)

	OhioLINK ETD: Beak, Douglas
		Arsenate or lead sorbed to ferrihydrite, corundum, and birnessite model oxide minerals were used to simulate possible effects of ingestion of soil contaminated with As(V) or Pb(II).
		The sorption maximum was found to be 2.13 g kg-1 for corundum, 38.6 g kg-1 for ferrihydrite, and 127 g kg-1 for birnessite.
		Ferrihydrite and corundum usefulness in Pb remediation would be limited when risk of incidental ingestion is of major concern.
	www.ohiolink.edu /etd/view.cgi?osu1131933545 (387 words)

	ARS \| Publication request: Ferrihydrite Influence on Infiltration, Runoff and Soil Loss (Site not responding. Last check: 2007-10-18)
		Ferrihydrite, a naturally occurring iron oxide byproduct of water treatment plants, was added as an amendment to several soils to evaluate its ability to improve aggregation.
		Ferrihydrite was added in slurry form to five different soils with textures ranging from clay loam to loamy fine sand.
		As ferrihydrite increased from 0 to 16.80 Mg ha-1 on the acid soils, infiltration increased an average of 21.5% while runoff and soil loss decreased 20 and 40%, respectively.
	www.ars.usda.gov /research/publications/publications.htm?SEQ_NO_115=134757 (437 words)

	ARS \| Publication request: Modeling the Impact of Ferrihydrite on Adsorption-Desorption of Soil Phosphorus (Site not responding. Last check: 2007-10-18)
		Ferrihydrite is a form of iron that is so common in groundwater in the southeastern United States that it is available in large quantitites from water treatments plants.
		Application of ferrihydrite increased the rapid P adsorption but equilibrium between the amount in solution and the amount sorbed was not reached after 1440 h due to the highly time-dependent nature of P sorption.
		Modeling the P adsorption and desorption mechanisms of soil amended with ferrihydrite is necessary to predict the movement of dissolved and sediment-bound P. The objective of this study was to model the multi-reaction P sorption properties of soil amended with ferrihydrite.
	ars.usda.gov /research/publications/publications.htm?SEQ_NO_115=135070 (573 words)

	Jarosite, schwertmannite, goethite, ferrihydrite and lepidocrocite: the legacy of coal and sulfide ore mining
		Oxalate extraction in the dark, which leads to a complete dissolution of schwertmannite and ferrihydrite (in contrast to goethite and jarosite), enables an estimate of the relative proportions of the former minerals to be made in samples of complex mineralogy.
		Ferrihydrite, which often forms under the participation of bacteria that live at near-neutral pH, was observed at less acid (pH > 5) conditions, generally in the presence of dissolved silica or organic matter.
		Both ferrihydrite and lepidocrocite typically form by rapid oxidation of Fe -bearing solutions, but the presence of lepidocrocite, which is less common in mine drainage environments, and the absence of goethite indicate the crusts to have formed in an environment that is low in CO (Schwertmann 1985).
	www.regional.org.au /au/asssi/supersoil2004/s1/oral/1088_murade.htm (3589 words)

	Ferrihydrite Influence on Infiltration, Runoff, and Soil Loss -- Rhoton et al. 67 (4): 1220 -- Soil Science Society of ... (Site not responding. Last check: 2007-10-18)
		Ferrihydrite Influence on Infiltration, Runoff, and Soil Loss -- Rhoton et al.
		Ferrihydrite is abundant in ground water seeps and ephemeral
		Amarillo, Gomez, and Olton soils, infiltration decreased and
	soil.scijournals.org /cgi/content/full/67/4/1220 (3446 words)

	Full Text - Preliminary results of using ESR to examine biofilms
		Thirdly the iron support clips for the plastic sheet rusted surprisingly fast underwater to ferrihydrite and created a localised yellow-brown rust stain whose most prominent ESR peak (in an intense ESR spectrum) was similarly at g=2.12 and showed the peak at g=4.3 in the usual proportion, and the usual intensity of the organic radical.
		Ferrihydrite is rust coloured so the amounts in young biofilms must be very small and calculation by comparison with a Mn standard shows they must be fractions of a microgram, not more than a few percent of total dry weight.
		However the corresponding ratio of ferrihydrite for the top points in the two figures is about 1:2, which is significantly less, and shows change in the relative biotic composition at the two sites.
	www.ejbiotechnology.info /content/vol7/issue3/full/1/index.html (3772 words)

	Adsorption of Arsenate and Arsenite on Ferrihydrite in the Presence and Absence of Dissolved Organic Carbon -- Grafe et ...
		Adsorption of Arsenate and Arsenite on Ferrihydrite in the Presence and Absence of Dissolved Organic Carbon -- Grafe et al.
		The adsorption of As(V) and As(III) on synthetic two-line ferrihydrite
		The adsorption of As(V) and As(III) on ferrihydrite in the presence
	jeq.scijournals.org /cgi/content/full/31/4/1115 (5412 words)

	Kristina L. Straub 2004 5744
		Observations in enrichment cultures of ferric iron-reducing bacteria indicated that ferrihydrite was reduced to ferrous iron minerals via sulfur cycling with sulfide as the reductant.
		Enrichment cultures were supplied with ferrihydrite (5 to 10 mM) as an electron acceptor; a mixture of acetate (5 to 10 mM), propionate (1 to 2 mM), and butyrate (1 to 2 mM) as possible electron donors and carbon sources; and ferrous chloride (2 mM) as a reducing agent.
		The electron acceptor 2-line ferrihydrite was generated by allowing a lithotrophic, nitrate-reducing enrichment culture to oxidize ferrous iron (18, 19).
	www.bionewsonline.com /9/n/kristina_l_straub_2004_5744.htm (4077 words)

	Reduction of crystalline iron(III) oxyhydroxides using hydroquinone: Influence of phase and particle size
		Furthermore, the surface-area-normalized rates for 4 nm ferrihydrite nanoparticles are up to 20 times faster than the rates for 6 nm ferrihydrite nanoparticles, and the surface-area-normalized rates for 5 × 64 nm goethite nanoparticles are up to two times faster than the rates for 22 × 367 nm goethite nanoparticles.
		The justification for drying the particles is that previous results have shown that the six-line ferrihydrite nanoparticles prepared using this method are not stable in aqueous suspension because they grow by oriented aggregation accompanied by phase transformation to goethite in a relatively short period of time, even at room temperature (i.e., within a few weeks).
		It is likely that surface energy varies as a function of size,2 and such an effect could be a consequence of the relative number of atoms at kinks versus facets and the relative number of atoms contained at or near the surface in comparison to the bulk.
	www.geochemicaltransactions.com /content/xml/1467-4866-6-60.xml (4182 words)

	Chromatographic, Spectroscopic and Microscopic Analyses Reveal the Impact of Iron Oxides and Electron Shuttles on the ...
		in the presence of ferrihydrite and the electron shuttle anthraquinone-2,6-disulfonate (AQDS) were conducted to reveal biotic and abiotic mechanisms contributing to the degradation of TNT.
		Strain ES6 was found to reduce TNT and ferrihydrite with enhanced reduction in the presence of AQDS.
		Ferrihydrite underwent reductive dissolution with the formation of secondary hematite.
	www.erc.montana.edu /Res-Lib99-SW/pubs/Theses/2003/Thesis03_Borch.htm (448 words)

	Environmental Soil Chemistry - Borch
		Phosphate sorption or sequestration is increased upon ferrihydrite bioreduction despite a concurrent decrease in specific surface area of the solid phases.
		The reduction of ferrihydrite is diminishing with increased phosphate surface coverage which is to some extent a result of phosphate-induced surface stabilization.
		Ferrihydrite biomineralization in the presence of phosphate results in formation of vivianite (ferrous phosphate) and green rust-like phases while inhibiting goethite and lepidocrocite production.
	www.colostate.edu /Depts/SoilCrop/additional_homes/borchweb/borch_researchprojects.htm (1093 words)

	Title page for ETD etd-10032003-114015
		Phosphate was sorbed in single-mineral aqueous suspensions of ferrihydrite (ferric hydroxide), boehmite (aluminum oxyhydroxide), goethite (iron oxyhydroxide), or non-crystalline (non-xl) Al-hydroxide, and mixtures of ferrihydrite/boehmite, goethite/boehmite, and ferrihydrite/non-xl Al-hydroxide at pH 6.
		Phosphorus K-XANES spectra for phosphate on Fe- vs. Al-oxide minerals differed in that a weak doublet peak was observed for Fe-oxides on the low-energy side of the P K-edge, i.e., in the pre-edge region.
		The quantitative distribution of phosphate between ferrihydrite and boehmite in mixtures of these minerals was determined using linear combination fitting (LCF) analysis of the XANES pre-edge region.
	www.lib.ncsu.edu /theses/available/etd-10032003-114015 (473 words)

	Arsenic Retention on Ferrihydrite: Stability under Aerobic and Anaerobic Conditions. (Site not responding. Last check: 2007-10-18)
		Ferrihydrite is one of the dominant phases regulating the dissolved concentration and transport of arsenic.
		Under anaerobic conditions, reductive dissolution of ferrihydrite, and other ferric (hydr)oxides, is generally perceived to liberate arsenic from the solid to the solution phase.
		Thus, despite the current paradigm of arsenic release under anaerobic conditions, biomineralization of ferrihydrite may stabilize arsenic relative to its transport under aerobic conditions.
	crops.confex.com /crops/2005am/techprogram/P7051.HTM (215 words)

	CIM Bulletin - Abstract of paper [field:ArkNumb] (Site not responding. Last check: 2007-10-18)
		Ferrihydrite is often the initial precipitate resulting from the rapid neutralization of Fe(III) sulphate solutions, and it seems to be a major constituent of zinc plant neutral leach residues.
		Low temperatures and rapid neutralization rates yield poorly filterable ferrihydrite, whereas higher temperatures and slower neutralization rates produce readily filterable precipitates; in all instances, however, the precipitates are two-line ferrihydrite.
		Generally, the sulphate contents of the precipitates decrease as the Zn contents increase, and this may indicate that the Zn is adsorbed on the ferrihydrite.
	www.cim.org /bulletin/abstract.cfm?Tech_Paper_Ark_Number=91-1019-94 (201 words)

	Infotrieve Online (Site not responding. Last check: 2007-10-18)
		The adsorption of As(V) and As(III) on synthetic two-line ferrihydrite in the presence and absence of a peat humic acid (HAp), Suwannee River fulvic acid (FA), or citric acid (CA) was investigated.
		The observed differences between this study and the earlier study on goethite are believed to be an intricate function of ferrihydrite's surface characteristics, which affect the mechanisms of adsorption and hence the affinity of organic acids such as HAp, FA, and CA for the ferrihydrite surface.
		As such, the adsorption of DOCs to ferrihydrite are assumed to be less favorable and to occur with a fewer number of ligands, resulting in lower surface coverage of weaker bond strength.
	www4.infotrieve.com /newmedline/detail.asp?NameID=12175028&Session=&searchQuery=Arsenites&count=1374 (330 words)

	Modified Ferrihydrite for Enhanced Removal of Arsenic from Mine Wastewater \| Annual Report 2005 \| Mine Waste Technology ...
		The main objective of this project was to investigate the adsorption characteristics of ferrihydrite and aluminum modified ferrihydrite for removing both arsenate and arsenite species as well as investigating the relative stability of the products that will be most effective in removing arsenic from mine wastewaters.
		Arsenic removal by adsorption on a ferrihydrite surface is used throughout the world for removing arsenic from wastewaters; however, long-term stability of ferrihydrite, especially in outdoor storage ponds, is questionable.
		Previous investigations have demonstrated that aluminum modification of the precipitated ferrihydrite changes the adsorptive properties of the solid so that it is much more effective for adsorbing arsenic than is unmodified ferrihydrite.
	www.epa.gov /hardrockmining/annual/annual2005/tmr/ferrihydrite.htm (386 words)

	Montana Tech \| Mine Waste Technology Program
		Should it be necessary to decrease arsenic concentrations in waste streams, facilities using ferrihydrite may need to increase ferric iron addition, which would in turn increase the amount of sludge produced.
		The objectives were to investigate adsorption characteristics of ferrihydrite and AMF for removing both arsenate and arsenite species and to investigate the long-term stability of AMF compared to ferrihyrdrite.
		Ferrihydrite and AMF were held at pH 7, and aged for up to 500 days at both room temperature and 70°C. The conversion rates for ferrihydrite and AMF were similar, however, the presence of As(V) in the solids significantly decreased the conversion rate, especially for AMF/As.
	www.mtech.edu /mwtp/activity%20IV/proj31.html (381 words)

	Elemental Sulfur and Thiosulfate Disproportionation by Desulfocapsa sulfoexigens sp. nov., a New Anaerobic Bacterium ...
		grown with elemental sulfur in the presence of ferrihydrite.
		Black spots in the reddish brown ferrihydrite, indicating the formation of iron sulfide, were observed in the first dilution
		Most ferrihydrite and iron sulfide precipitates were dissolved by dithionite-citrate-acetic acid extraction.
	aem.asm.org /cgi/content/full/64/1/119 (4770 words)

	Dr. Thomas Pichler, Univeristy of South Florida (Site not responding. Last check: 2007-10-18)
		The pXRD patterns show systematic differences with patterns for 2-line ferrihydrite, that are interpreted as evidence for significant populations of oxygen-coordinated Fe-As pairs.
		The loss on ignition (LOI) is quantitatively consistent with OH + H2O, measured by GC, which, in turn, is consistent with ~ 1 nm diameter primary particles having all their surface cations (Fe3+, As5+, Si4+, C4+) being coordinated on the free surface side by OH and OH2.
		Complexation of arsenate onto the HFO core was found to significantly increased the average quadrupole splitting (QS) obtained from Mössbauer spectroscopy by an amount that could not be explained by other chemical differences and that is consistent with an ~ 1 nm diameter particle size and somewhat smaller HFO core.
	chuma.cas.usf.edu /~pichler/papers/abstract7.htm (411 words)

	As Poison Flowing Through the Ground (Site not responding. Last check: 2007-10-18)
		Their results showed that when fulvic acid is present, As adsorption onto ferrihydrite is reduced by up to 50%.
		Perhaps it was related to the presence of iron in the ferrihydrite.
		Only 0.5% of ferrihydrite was reduced in the laboratory during that time, certainly not enough to explain the 50% difference seen in As concentrations.
	www.mq.edu.au /scienceresearch/mcrae.htm (436 words)

	Competing Fe(II)-Induced Mineralization Pathways of Ferrihydrite
		Owing to its high surface area and intrinsic reactivity, ferrihydrite serves as a dominant sink for numerous metals and nutrients in surface environments and is a potentially important terminal electron acceptor for microbial respiration.
		While Fe(II) concentration is the master variable dictating secondary mineralization pathways of ferrihydrite, here we reveal that the kinetics of conversion and ultimate mineral assemblage are a function of competing mineralization pathways influenced by pH and stabilizing ligands.
		In the absence of magnetite nucleation, lepidocrocite and goethite continue to precipitate at the expense of ferrihydrite with near complete conversion within hours, the relative proportions of the two hydroxides dependent upon the ligand present.
	pubs.acs.org /cgi-bin/abstract.cgi/esthag/2005/39/i18/abs/es050666z.html (324 words)

	Research (Site not responding. Last check: 2007-10-18)
		Abstract: Ferrihydrite is a common constituent of soils and sediments, and an important phase due to its high chemical reactivity, sorption capacity and role in dissimilatory iron reduction.
		Studies have shown rapid conversion of pristine ferrihydrite-coated quartz to secondary iron phases due to biotic and abiotic mediated reduction processes; however, inorganic/organic sorbates and support materials other than quartz may impact microbial reduction of ferrihydrite and thus the extent, nature, and rate of secondary iron phase formation.
		Batch studies with ferrous iron illustrate that the “host” substrate influences the transformation of ferrihydrite due to competing redox reactions, Fe(II) retention, or conformational changes.
	soils.stanford.edu /new/presentations/PresDetail.asp?id=32 (192 words)

	[No title]
		The goal of the long-term stability study is to determine the relative distribution of heavy metals between three phases: a solution phase, a ferrihydrite x-ray amorphous phase and a crystalline hematite phase.
		The conversion from amorphous ferrihydrite (surface area ~300 m2/gram) to a crystalline structure results in a tremendous decrease in the solid phase surface area (to ~90 m2/gram).
		It may be necessary, therefore, to use both the oxalate leach (for the iron content from which the amount of ferrihydrite can be determined) and the hydrochloric leach for determining the amount of heavy metals present in the amorphous ferrihydrite.
	www.mtech.edu /research/images/proposal_prep_help_pages.doc (2065 words)

	Hydrothermal Deposits - 1999 Cruise Report (Site not responding. Last check: 2007-10-18)
		Analyses of Fe-oxyhydroxide samples taken from Steve Mound, Gollum Vent and south of ASHES in 1998 show the material to be silica poor ferrihydrite (nominally Fe together with amorphous silica.
		Ferrihydrite is commonly found in soils, oxidized mine wastes and other iron-rich environments, and now also on the deep seafloor (Boyd and Scott, 1999, Can.
		During NeMO 99, ferrihydrite deposits were sampled at Oxide Vent (inactive); at Naaz, south of ASHES (inactive); and, at the west wall of the caldera near ASHES (active).
	www.pmel.noaa.gov /vents/nemo1999/cruise-report/deposits.html (522 words)

	About clays
		Ferrihydrite is the brown rusty scum visible at springs, where water seeps from cracks in rocks, or as an "oil slick" on some swamp water.
		Ferrihydrite transforms to a more stable oxyhydroxide (goethite, usually) over a period of a few years.
		Most ferrihydrite is associated with bacteria (Gallionella and Leptothrix) which gain their energy from the oxidation reaction Fe = Fe + e
	www.clays.org.au /mins.htm (1051 words)

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