Arsenic redistribution and transformation during Fe(II)-catalyzed recrystallization of As-adsorbed ferrihydrite under anaerobic conditions

Zhang, Guoqing; Yuan, Zidan; Lei, Lei; Lin, Jinru; Wang, Xin; Wang, Shaofeng; Jia, Yongfeng

doi:10.1016/j.chemgeo.2019.08.002

Cited by 55 publications

(22 citation statements)

References 69 publications

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“…Previous studies have reported that LP crystals formed from the catalytic transformation of 2-line FH by Fe(II) (aq) consist of tabular plate-like crystals. 13,21,28,29,60 Unfortunately, these reported LP particles have been well-crystallized and imaged aer long reaction times (e.g. 5.5, 9, and 30 days).…”

Section: Amorphous Phase Growth and Deposition On The Surface Of 2-limentioning

confidence: 99%

Further insights into the Fe(ii) reduction of 2-line ferrihydrite: a semi in situ and in situ TEM study

et al. 2020

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Section: Amorphous Phase Growth and Deposition On The Surface Of 2-limentioning

confidence: 99%

Further insights into the Fe(ii) reduction of 2-line ferrihydrite: a semi in situ and in situ TEM study

et al. 2020

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“…Transformation of the reacted solids in these experiments was not widespread, and is further inhibited by anionic ligands occupying surface Fe(III) binding sites, ,− thereby limiting potential for ET. ,, The lower pH and adsorbed MoO 4 tetrahedra in both pH 0 5.0 Ads-Mo-L and Ads-Mo-H experiments likely limited Fe(II) sorption and ET to structural Fe(III) and inhibited widespread mineral transformation as indicated by the lack of lepidocrocite, goethite, or bamfordite peaks in powder XRD, but the presence of these phases using TEM-SAED. Conversely, more extensive transformation is typically observed under higher pH conditions that are less favorable for anion sorption. ,,− Minimal ferrihydrite transformation in the pH 0 6.5 Ads-Mo experiments is attributed to limited Fe(II) availability in the presence of sorbed MoO 4 2– at this higher pH (Figure ).…”

Section: Discussionmentioning

confidence: 86%

Molybdenum(VI) Sequestration Mechanisms During Iron(II)-Induced Ferrihydrite Transformation

Schoepfer

Lum

Lindsay

2021

ACS Earth Space Chem.

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Adsorption and coprecipitation reactions with Fe(III) (oxyhydr)oxides contribute to Mo(VI) attenuation within geohydrologic systems. Redox transitions within these systems can promote transformation of metastable phases, including ferrihydrite, and repartitioning of associated Mo(VI). Recent studies show that Mo(VI) coordination shifts from tetrahedral to octahedral during Fe(II)-induced ferrihydrite transformation. However, effects of initial conditions including solution pH, the Mo(VI) uptake mechanism, and Mo(VI) loading on repartitioning are not known. We performed batch experiments using ferrihydrite suspensions prepared with adsorbed or coprecipitated Mo(VI) (0, 25, and 100 μmol g–1) at two initial pH values (pH0; 5.0 and 6.5). We catalyzed ferrihydrite transformation under anoxic conditions by adding Fe(II)(aq) (0.5 mM) and monitored pH, [Mo]T, and [Fe]T over time. After 168 h, we collected reacted solids for analysis by powder X-ray diffraction (XRD), transmission electron microscopy-selected area electron diffraction (TEM-SAED), and Mo K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy. XRD data indicate that bulk ferrihydrite transformation was limited in all but the pH0 6.5 coprecipitated Mo(VI) experiments. The TEM-SAED results reveal that nanoscale lepidocrocite and goethite formed at ferrihydrite surfaces in all experiments, whereas nanoscale bamfordite [FeMo2O6(OH)3·H2O] crystallites were observed in pH0 6.5 experiments. EXAFS models reveal changes in Mo(VI) coordination and bonding consistent with bamfordite precipitation combined with structural incorporation into neoformed goethite and lepidocrocite. Our results improve the understanding of Mo(VI) retention pathways in geohydrologic systems.

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“…High concentrations of Fe(II) (20 mM) led to some reduction of As(V) to As(III) in the Fe(II)–jarosite system with an Fe(II)/As(V) molar ratio of 125 . The majority of arsenic still existed in solid products by the end of all incubations via adsorption and incorporation. , …”

Section: Proposed Reaction Mechanismsmentioning

confidence: 99%

“…Previous studies have shown that schwertmannite can exist for years under oxic and acidic conditions, but its hydrolytic transformation to goethite is accelerated at higher pH. , Reduction-driven (including abiotic Fe(II)-introduced and microbially mediated Fe(III) and SO 4 2– reduction) metastable Fe(III) mineral transformations were also widespread under reducing conditions, , for example, acidic mining lake sediments and constructed wetland soils that are rich in organic matter (OM). , In reducing environments, the abiotic Fe(II)-induced Fe(III) mineral transformation has been well explored, involving electron transfer and atom exchange between the adsorbed Fe(II) and structured Fe(III) on the mineral surface. , It has been pointed out that the extent and rates of secondary mineral formation during Fe(II)-catalyzed transformation are determined by the transport rate of Fe(II) to the mineral surface and the concentration of adsorbed Fe(II) . Several studies have reported the influence of Fe(II)-induced Fe(III) mineral transformation on the fate of preadsorbed/coprecipitated trace metals/metalloids. , In the study of Fe(II)-catalyzed As(V)-adsorbed ferrihydrite recrystallization, 90% phosphate-extractable As incorporated into a more stable phase (e.g., lepidocrocite and goethite) and 70–80% adsorbed As(III) was oxidized to As(V) . Fe(II)-induced As(V)/Sb(V)-jarosite transformation processes enhanced As repartitioning to the phosphate-extractable phase when the product was lepidocrocite and Sb was released into the solution .…”

Section: Introductionmentioning

confidence: 99%

“…21,22 In the study of Fe(II)-catalyzed As(V)adsorbed ferrihydrite recrystallization, 90% phosphate-extractable As incorporated into a more stable phase (e.g., lepidocrocite and goethite) and 70−80% adsorbed As(III) was oxidized to As(V). 23 Fe(II)-induced As(V)/Sb(V)-jarosite transformation processes enhanced As repartitioning to the phosphateextractable phase when the product was lepidocrocite and Sb was released into the solution. 24 However, Fe(II)-catalyzed Fe(III) oxide transformation can be affected by a wide range of factors, including coexisting ions and natural organic matter (NOM).…”

Section: Introductionmentioning

confidence: 99%

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Arsenic Partitioning during Schwertmannite Dissolution and Recrystallization in the Presence of Fe(II) and Oxalic Acid

Jin

Guo

et al. 2021

ACS Earth Space Chem.

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Fe(II)-driven transformation of schwertmannite can strongly impact the transport and redistribution of coprecipitated As in reducing acid sulfate soil (ASS)/acid mine drainage (AMD)-contaminated environments. Oxalic acid is prevalent in the natural environment, but its influence on Fe(II)-induced schwertmannite conversion and the repartitioning behavior of coprecipitated As is poorly characterized. In the present study, we examined the impact of oxalic acid on Fe(II)-induced As(V)-coprecipitated schwertmannite transformation and As redistribution between dissolved, adsorbed, and incorporated phases during mineral transformation at a pH of 5.5 and in 1 mM Fe(II). According to Mossbauer analysis, in 1 mM Fe(II) without oxalic acid treatment, schwertmannite was converted into lepidocrocite (65%) and goethite (35%). In mixed Fe(II)−oxalic acid systems, oxalic acid played a synergistic role in the dissolution and transformation of Fe(II)-induced schwertmannite. In 1 mM Fe(II) with 0.1/0.5/1 mM oxalic acid reaction systems after 14 day incubation, the fractions of goethite were 68% (lepidocrocite occupied 32%), 100%, and 100%, respectively. In all treatments, the PO 4 3− -extractable fraction of As increased during mineral transformation, indicating that partially coprecipitated As of the original mineral transferred to the surface of the resulting products. Compared with mixed Fe(II)−oxalic acid systems, more adsorbed As formed in Fe(II) treatment without oxalic acid, which might correspond to the speciation of the resulting minerals. Although Fe(II) was a potential reductant for As(V), no As(III) was detected in any reaction system by the end of incubation. These findings have important implications for accurately predicting the geochemical behavior of As in AMD-contaminated areas.

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Arsenic redistribution and transformation during Fe(II)-catalyzed recrystallization of As-adsorbed ferrihydrite under anaerobic conditions

Cited by 55 publications

References 69 publications

Further insights into the Fe(ii) reduction of 2-line ferrihydrite: a semi in situ and in situ TEM study

Further insights into the Fe(ii) reduction of 2-line ferrihydrite: a semi in situ and in situ TEM study

Molybdenum(VI) Sequestration Mechanisms During Iron(II)-Induced Ferrihydrite Transformation

Arsenic Partitioning during Schwertmannite Dissolution and Recrystallization in the Presence of Fe(II) and Oxalic Acid

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