Mineral transformations and textural evolution during roasting of bog iron ores

Rzepa, Grzegorz; Bajda, Tomasz; Gaweł, Adam; Debiec, Klaudia; Drewniak, Łukasz

doi:10.1007/s10973-015-4925-1

Cited by 38 publications

(24 citation statements)

References 83 publications

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“…Natural BIOs are composed mainly of iron oxyhydroxides: ferrihydrite and goethite as well as quartz and organic matter (Rzepa et al, 2009 , 2016 ). The granulation process, however, seriously affects the ore composition–according to XRD and FTIR analyses (Figures 2 , 3 ), gypsum and calcite predominate in the gBIOs, accompanied by quartz, iron oxyhydroxides and traces of clay minerals and dolomite.…”

Section: Resultsmentioning

confidence: 99%

Granulated Bog Iron Ores as Sorbents in Passive (Bio)Remediation Systems for Arsenic Removal

et al. 2018

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The main element of PbRS (passive (bio)remediation systems) are sorbents, which act as natural filters retaining heavy metals and carriers of microorganisms involved in water treatment. Thus, the effectiveness of PbRS is determined by the quality of the (ad)sorbents, which should be stable under various environmental conditions, have a wide range of applications and be non-toxic to (micro)organisms used in these systems. Our previous studies showed that bog iron ores (BIOs) meet these requirements. However, further investigation of the physical and chemical parameters of BIOs under environmental conditions is required before their large-scale application in PbRS. The aim of this study was (i) to investigate the ability of granulated BIOs (gBIOs) to remove arsenic from various types of contaminated waters, and (ii) to estimate the application potential of gBIOs in technologies dedicated to water treatment. These studies were conducted on synthetic solutions of arsenic and environmental samples of arsenic contaminated water using a set of adsorption columns filled with gBIOs. The experiments performed in a static system revealed that gBIOs are appropriate arsenic and zinc adsorbent. Dynamic adsorption studies confirmed these results and showed, that the actual sorption efficiency of gBIOs depends on the adsorbate concentration and is directly proportional to them. Desorption analysis showed that As-loaded gBIOs are characterized by high chemical stability and they may be reused for the (ad)sorption of other elements, i.e., zinc. It was also shown that gBIOs may be used for remediation of both highly oxygenated waters and groundwater or settling ponds, where the oxygen level is low, as both forms of inorganic arsenic (arsenate and arsenite) were effectively removed. Arsenic concentration after treatment was <100 μg/L, which is below the limit for industrial water.

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Section: Resultsmentioning

confidence: 99%

Granulated Bog Iron Ores as Sorbents in Passive (Bio)Remediation Systems for Arsenic Removal

et al. 2018

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“…Thermal transformation processes are controlled by many factors, such as temperature, atmosphere, presence of impurities, and substitutions, all of which affect the reaction rate and mechanism. Previous studies have shown that iron(III) oxyhydroxides transform thermally into hematite [ 32 , 33 ]. This transformation path is strongly affected by the presence of phosphate adsorbed onto ferrihydrite during or after its precipitation [ 34 ].…”

Section: Introductionmentioning

confidence: 99%

Thermal Stability and Decomposition Products of P-Doped Ferrihydrite

et al. 2020

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This work aimed to determine the effect of various amounts of P admixtures in synthetic ferrihydrite on its thermal stability, transformation processes, and the properties of the products, at a broad range of temperatures up to 1000 °C. A detailed study was conducted using a series of synthetic ferrihydrites Fe5HO8·4H2O doped with phosphates at P/Fe molar ratios of 0.2, 0.5, and 1.0. Ferrihydrite was synthesized by a reaction of Fe2(SO4)3 with 1 M KOH at room temperature in the presence of K2HPO4 at pH 8.2. The products of the synthesis and the products of heating were characterized at various stages of transformation by using differential thermal analysis accompanied with X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy-energy dispersive X-ray spectroscopy. Coprecipitation of P with ferrihydrite results in the formation of P-doped 2-line ferrihydrite. A high P content reduces crystallinity. Phosphate significantly inhibits the thermal transformation processes. The temperature of thermal transformation increases from below 550 to 710–750 °C. Formation of intermediate maghemite and Fe-phosphates, is observed. The product of heating up to 1000 °C contains hematite associated with rodolicoite FePO4 and grattarolaite Fe3PO7. Higher P content greatly increases the thermal stability and transformation temperature of rodolicoite as well.

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“…At higher temperature, the Si was ejected from the structure [40]. Besides hematite, amorphous silica, which recrystallizes to cristobalite at higher temperature, has been often reported as a product of annealing of Si-ferrihydrite-rich materials [e.g., 16,42,43].…”

Section: Introductionmentioning

confidence: 99%

The influence of silicate on transformation pathways of synthetic 2-line ferrihydrite

Rzepa

Pieczara

Gaweł

et al. 2016

J Therm Anal Calorim

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In this study, a series of synthetic ferrihydrite samples of Si/Fe molar ratios ranging from zero to 1.5 were heated up to 1000°C using simultaneous TG-DTA equipment. The XRD, FTIR, SEM-EDS and magnetic susceptibility measurements were carried out prior to and after heating. It has been found that silicate retards ferrihydrite transformation to hematite and affects crystallinity of the product. Low Si admixture in the precursor reduces hematite crystal size severely, but the increase in average crystal dimensions with increasing Si/Fe molar ratio was observed. High Si content results in the formation of hematite which exhibits a wide range of crystal habits. The conversion of pure ferrihydrite to hematite proceeds without any intermediate phase, whereas the increasing silicate content in the pristine oxyhydroxide strongly affects the transformation pathway. During annealing of high-Si ferrihydrites, the presence of two or three intermediate Fe 2 O 3 polymorphs (gamma, epsilon and beta) was demonstrated prior to the crystallization of final a-Fe 2 O 3 . The conditions favoring crystallization of intermediate phases result from progressive silica polymerization which forms separate matrix-type phase and impedes the aggregation of iron oxide nanoparticles.

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Mineral transformations and textural evolution during roasting of bog iron ores

Cited by 38 publications

References 83 publications

Granulated Bog Iron Ores as Sorbents in Passive (Bio)Remediation Systems for Arsenic Removal

Granulated Bog Iron Ores as Sorbents in Passive (Bio)Remediation Systems for Arsenic Removal

Thermal Stability and Decomposition Products of P-Doped Ferrihydrite

The influence of silicate on transformation pathways of synthetic 2-line ferrihydrite

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