• Journal of the Mineralogical Society of Korea
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• v.19 no.4 s.50
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• pp.231-238
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• 2006

Transports of heterogeneously charged particles were investigated based on column experiments. Synthesized mono-dispersed ferrihydrite (${\sim}100nm$) and amorphous $SiO_2\;({\sim}40nm\;and\;{\sim}80nm)$ particles, of which surfaces are oppositely charged under pH < 9.0 (ferrihydrite, positive; amorphous silica, negative), were used. $177{\sim}250{\mu}m$ quartz sand was used as a stationary matrix. The results show that even favorable particles (i.e., ferrihydrite) can show a conservative transport through the oppositely charged media (i.e., quartz) when they coexist with humic acid or with much greater number of oppositely charged particles. These results imply that transports of both negatively and positively charged contaminants may be possible at the same time under a condition of heterogeneous colloidal system.

• Journal of the Mineralogical Society of Korea
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• v.24 no.2
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• pp.73-82
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• 2011

X-ray absorption spectroscopy (XAS) study was conducted using arsenite-sorbed two-line ferrihydrite to investigate the mechanism of surface interactions between two-line ferrihydrite and As(III) (arsenite) which are ubiquitous in nature. The two-line ferrihydrite used was synthesized in the laboratory and the study was undertaken at pHs 4 and 10 to compare the difference in mechanisms of surface interaction between acidic and alkaline environments. The effect of arsenite-adsorbed concentrations on surface complexation was investigated at each pH condition as well. From the results of XAS analyses, the structural parameters of arsenite in the EXAFS revealed that the coordination number and distanceof As-O were 3.1~3.3 and 1.74~1.79 ${\AA}$, respectively, which indicate that the unit structure of arsenite complex formed on the surface of two-line ferrihydrite is $AsO_3$. The dominant structures of As(III)-Fe complex were examined to be bidentate binuclear comer-sharing ($^2C$) and the mixture of bidentate mononuclear edge sharing ($^2E$) and $^2C$ appeared as well. At pH 4, arsenite complex showed different structures on the surface of two-line ferrihydrite, depending on the adsorbed concentrations. At pH 10, on the contrary, the surface structures of arsenite complexes were interpreted to be almost identical, irrespective of the adsorbed concentrations of arsenite. Consequently, this microscopic XAS results support the results of macroscopic adsorption experiments in which the surface interaction between arsenite and two-line ferrihydrite is significantly influenced by pH conditions as well as arsenite concentrations.

• Journal of the Mineralogical Society of Korea
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• v.24 no.2
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• pp.91-99
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• 2011

The turbidity in several wells of Samdong-myeon, Ulsan, exceeded potable groundwater standard (1 NTU). Mineralogical analysis showed that the fine suspended particles are ferrihydrite spheres with a size of less than $0.5\;{\mu}m$ and helical iron-oxidizing bacterial filaments, and their aggregates. Ferrihydrite was almost amorphous only showing two electron diffraction rings, and contained Si and P. Helical bacterial filaments were almost replaced by ferrihydrite. The helical bacteria have played an important role in the ferrihydrite formation by becoming the loci for ferrihydrite precipitation as well as oxidizing ferrous iron. The physicochemical conditions of low pH, low redox potential, high Ca concentration, and high alkalinity are consistent with the hydrogeochemical characteristics of carbonate groundwater, implicating that the inflow of deep ferriferous carbonate groundwater and its oxidation have caused the ferrihydrite turbidity in several wells of the study area.

• Journal of the Mineralogical Society of Korea
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• v.21 no.3
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• pp.227-237
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• 2008

Arsenic has recently become of the most serious environmental concerns, and the worldwide regulation of arsenic fur drinking water has been reinforced. Arsenic contaminated groundwater and soil have been frequently revealed as well, and arsenic contamination and its treatment and measures have been domestically raised as one of the most important environmental issues. Arsenic behavior in geo-environment is principally affected by oxides and clay minerals, and particularly iron (oxy)hydroxides have been well known to be most effective in controlling arsenic. Among a number of iron (oxy)hydroxides, for this reason, 2-line ferrihydrite was selected in this study to investigate its effect on arsenic behavior. Adsorption of 2-line ferrihydrite was characterized and compared between As(III) and As(V) which are known to be the most ubiquitous species among arsenic forms in natural environment. Two-line ferrihydrite synthesized in the lab as the adsorbent of arsenic had $10\sim200$ nm for diameter, $247m^{2}/g$ for specific surface area, and 8.2 for pH of zero charge, and those representative properties of 2-line ferrihydrite appeared to be greatly suitable to be used as adsorbent of arsenic. The experimental results on equilibrium adsorption indicate that As(III) showed much stronger adsorption affinity onto 2-line ferrihydrite than As(V). In addition, the maximum adsorptions of As(III) and As(V) were observed at pH 7.0 and 2.0, respectively. In particular, the adsorption of As(III) did not show any difference between pH conditions, except for pH 12.2. On the contrary, the As(V) adsorption was remarkably decreased with increase in pH. The results obtained from the detailed experiments investigating pH effect on arsenic adsorption show that As(III) adsorption increased up to pH 8.0 and dramatically decreased above pH 9.2. In case of As(V), its adsorption steadily decreased with increase in pH. The reason the adsorption characteristics became totally different depending on arsenic species is attributed to the fact that chemical speciation of arsenic and surface charge of 2-line ferrihydrite are significantly affected by pH, and it is speculated that those composite phenomena cause the difference in adsorption between As(III) and As(V). From the view point of adsorption kinetics, adsorption of arsenic species onto 2-line ferrihydrite was investigated to be mostly completed within the duration of 2 hours. Among the kinetic models proposed so for, power function and elovich model were evaluated to be the most suitable ones which can simulate adsorption kinetics of two kinds of arsenic species onto 2-line ferrihydrite.

• Journal of the Mineralogical Society of Korea
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• v.13 no.3
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• pp.115-120
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• 2000

Oxidation of pyrite has caused a serious environmental problem such as the acidification of soil and surface water. The mineralogical change of acid sulfate weathering of hydrothermally altered andesite which contained 11.8% of pyrite and was exposed in atmosphere by lay out works for a residential area and a golf course was studied using X-ray diffraction (XRD) and electronmicroscopes. Ferrihydrite, jarosite, and an unidentified water soluble phase were observed as weathering products of the andesite. Under electronmicroscopes, showed aggregate of platy microcrystals; jarosite was platy morphology: water soluble Phase was columnar. Morphology of fresh Pyrite in the andesite changed from pyritrohedron to cubic in its frequency with increasing its particle size. The drainage water was acidic (pH 3.5) and in an equilibrium state with both ferrihydrite and jarosite.

• Journal of the Mineralogical Society of Korea
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• v.16 no.2
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• pp.191-198
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• 2003

The ochreous precipitates, reddish brown and brownish yellow in color, are pre- cipitated in the stream bottom of acid mine drainage (AMD) in the Donghae coal mine area. X-ray diffraction analysis shows that the reddish brown precipitate consists mainly of ferrihydrite with small amount of goethite, while the brownish yellow precipitate of schwertmannite. Thermal experiments show that ferrihydrite and schwertmannite partially convert to poorly-crystallized hematite at $400^{\circ}C$ and to well-crystallized hematite at $700^{\circ}C$.

• Bulletin of the Korean Chemical Society
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• v.29 no.10
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• pp.1969-1972
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• 2008

In this study, horse spleen apoferritins were induced to form biominerals using up to 3000 Fe atoms per protein molecule. The morphology and crystallinity of the nanometer-sized biominerals formed in the ferritins were then analyzed using field emission-energy filtering-transmission electron microscopy (FE-TEM). The ferritins were found to have reconstitution yields of 60-70% in the experiments. The mean core size of the ferritins varied somewhat with protein concentrations, indicating that crystal growth in ferritins could be controlled via protein concentrations. The core mineral size increased with the amount of Fe used. Lattice fringes of the core, associated with good crystallinity, were found in all samples. The lattice fringe images of a single domain ferrihydrite mineral appeared frequently in the (011) planes (d-spacing of 0.246 nm) under [100] zone axis in all samples of this study. In addition, the lattice image occasionally revealed fringes corresponding to the (100) planes (d = 0.254 nm) from the [001] zone axis, indicating the characteristic pattern of hexagonal crystal lattice. Diffraction patterns in the minerals identified as ferrihydrite were fitted well into the space group of $P3_{1c}$.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1B
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• pp.107-111
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• 2006

The samples collected from two reactors are analyzed by X-ray diffraction and M$\ddot{o}$ssbauer spectroscopy in this study. It is concluded that the iron oxide crystal attached on anthracite media which possesses catalytic ability is identified to be Ferrihydrite, regardless of the value of pH from the analysis of the iron oxide. Iron oxide in Batch reactor is identified to be Microcrystalline goethite.

• Economic and Environmental Geology
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• v.56 no.3
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• pp.301-310
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• 2023

Ferrihydrite is an iron oxide mineral that is easily found in the natural environment, including acid mine drainage, and has a low crystallinity and high specific surface area, resulting in high reactivity with other ions, and can remove environmentally hazardous substances. However, because ferrihydrite is a metastable mineral, there is a possibility of releasing adsorbed ions by phase transformation to other minerals having low surface area and high crystallinity. In this study, the adsorption characteristics of arsenate, chromate, and selenate on ferrihydrite and the oxyanion removal efficiency of ferrihydrite were studied considering mineral phase transformation. At both pH 4 and 8, the adsorption of oxyanions used in the study were in good agreement with both Langmuir and Freundlich adsorption models except for selenate at pH 8. Due to the difference in surface charge according to pH, at pH 4 a higher amount of ions were adsorbed than at pH 8. The adsorption amount were in the order of arsenate, chromate, and selenate. These different adsorption models and adsorption amounts were due to different adsorption mechanisms for each oxyanions on the surface of ferrihydrite. These adsorption characteristics were closely related to changes in the mineral phase. At pH 4, a phase transformation to goethite or hematite was observed, but only a phase transformation to hematite was observed at pH 8. Among the oxyanion species on ferrihydrite, arsenate showed the highest adsorption capacity and hardly caused phase transformation during the experimental period after adsorption. Contrary to this, chromate and selenate showed faster mineral phase transformation than arsenate, and selenate had the lowest retardation effect among the three oxyanions. Ferrihydrite can effectively remove arsenate due to its high adsorption capacity and low phase transformation rate. However, the removal efficiency for other two oxyanions were low by the low adsorption amount and additional mineral phase transformation. For chromate, the efficient removal is expected only at low concentrations in low pH environments.

• Economic and Environmental Geology
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• v.54 no.2
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• pp.299-308
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• 2021

Fe(II) released from mining activities is precipitated as various Fe(III)-oxyhydroxides when exposed to an oxidizing environment including mine drainage. Ferrihydrite, one of the representative precipitated Fe(III) minerals, is easy to adsorb heavy metals and other pollutants due to the large specific surface area caused by very low crystallinity. Ferrihydrite is transformed to thermodynamically more stable goethite in the natural environment. Hence, information on the transformation of ferrihydrite to goethite and the related mobility of heavy metals in the acid mine drainage is important to predict the behaviors of those elements during ferrihydrite to goethite transition. The behaviors of heavy metals during the transformation of ferrihydrite to goethite were investigated for core samples collected from an AMD treatment system in the Heungjin-Taemaek coal mine by using X-ray diffraction (XRD), chemical analysis, and statistical analysis. XRD results showed that ferrihydrite gradually transformed to goethite from the top to the bottom of the core samples. Chemical analysis showed that the relative concentration of As was significantly high in the core samples compared with that in the drainage, indicating that As was likely to be adsorbed strongly on or coprecipitated with iron oxyhydroxide. Correlation analysis also indicated that As can be easily removed from mine drainage during iron mineral precipitation due to its high affinity to Fe. The concentration ratio of As, Cd, Co, Ni, and Zn to Fe generally decreased with depth in the core samples, suggesting that mineral transformation can increase those concentrations in the drainage. In contrast, the concentration ratio of Cr to Fe increased with depth, which can be explained by the chemical bond of iron oxide and chromate, and surface charge of ferrihydrite and goethite.