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Mineralogy of precipitates formed from mine effluents in Finland
Published in A.A. Balkema, Tailings and Mine Waste 2000, 2022
Liisa Carlson, Sirpa Kumpulainen
Sulfide minerals, such as pyrite and pyrrhotite, are weathered in tailings impoundments and waste rock piles exposed to air and rain, and acid mine effluents gather in pools and ditches. Depending on local conditions, such as the type of bedrock and soils, the acid waters can be neutralized. In Finland, however, the bedrock and therefore also soils have low acid neutralization capacity because carbonate rocks are rare and the proportion of mafic rocks is low. Oxidation and hydrolysis of iron, which is the most common metallic cation in waters, leads to the formation of ochreous precipitate. At low pH bacteria such as Thiobacillus ferrooxidans calalyze the oxidation which abiotically would be much too slow. The mineral species formed depend on the conditions, such as pH and dissolved compounds other than iron. Jarosite (KFe3(SO4)2(OH)6) and goethite (α-FeOOH) have been known for a long time to occur in mine drainage precipitates. Ferrihydrite (Fe5HO8•4H2O) was first described from natural milieu by Chukhrov et al. in 1972, but was formerly known, e.g., as amorphous ferric hydroxide. This mineral is typical of environments with neutral pH and with dissolved silica in solution. Therefore, it is not a mineral to be expected in acid mine effluents, unless they are neutralized. Schwertmannite (Fe8O8(OH)6SO4) which was accepted in 1992 (Bigham et al., 1994), is a typical mine drainage mineral formed from low-pH waters high in dissolved iron and sulfate.
Reciprocal influence of arsenic and iron on the long-term immobilization of arsenic in contaminated soils
Published in Yong-Guan Zhu, Huaming Guo, Prosun Bhattacharya, Jochen Bundschuh, Arslan Ahmad, Ravi Naidu, Environmental Arsenic in a Changing World, 2019
Y. Sun, J. Antelo, J. Lezama-Pacheco, S. Fiol, S. Fendorf, J. Kumpiene
Iron secondary minerals initially sequester large amounts of trace elements (TE), such as arsenic. However, the long-term immobilization of TE in these mineral phases will be defined by the stability of these minerals. Schwertmannite is a metastable mineral, transforming eventually into more stable phases such as hematite and goethite (Bigham & Nordstrom, 2000). Jarosite is stable under acidic conditions while it dissolves at natural pH (Smith et al., 2006). Interestingly, certain cations have been observed to increase the stability of secondary minerals related to AMD. For instance, the presence of Cu significantly enhances the stability of schwertmannite (Antelo et al., 2013) and some results show evidences pointing towards arsenate stabilizing schwertmannite (Regenspurg & Peiffer, 2005). Yet, the number of studies assessing the effect of TE on the stability and reactivity of iron oxyhydroxysulfates is limited. Summarizing, the bonding mechanism of sequestration and the effect of TE on the reactivity and stability of iron oxyhydroxy sulfates are under studied and can be considered key knowledge to better understand the mobility of TE in AMD systems.
Mines: Acidic Drainage Water
Published in Brian D. Fath, Sven E. Jørgensen, Megan Cole, Managing Water Resources and Hydrological Systems, 2020
Wendy B. Gagliano, Jerry M. Bigham
Goethite is a crystalline oxyhydroxide that occurs over a wide pH range, is relatively stable, and may represent a final transformation product of other mine drainage minerals.[8] Ferrihydrite is a poorly crystalline ferric oxide that forms in higher pH (>6.5) environments. Schwertmannite is commonly found in drainage waters with pH ranging from 2.8 to 4.5, and with moderate to high sulfate contents. It may be the dominant phase controlling major and minor element activities in most acid mine drainage. Jarosite group minerals form in more extreme environments with pH < 3, very high sulfate concentrations, and in the presence of appropriate cations like Na and K.
Effect of pH regulation on the formation of biogenic schwertmannite driven by Acidithiobacillus ferrooxidans and its arsenic removal ability
Published in Environmental Technology, 2022
Jia-Xing Zhou, Yu-Jun Zhou, Jian Zhang, Yan Dong, Fen-Wu Liu, Zhi-Hui Wu, Wen-Long Bi, Jun-Mei Qin
Adsorption is considered to be a promising treatment method for As-containing groundwater due to its easy and simple performance, as well as its low cost [20,21]. Schwertmannite is a poorly crystallized oxyhydroxysulfate of iron often formed in acidic, iron- and sulfate-rich environments such as acid mine drainage (AMD), sediments impacted by AMD, or coastal lowland acid sulfate soils [22–24]. Schwertmannite has a tunnel structure akin to akaganéite in which Cl- is replaced with that is suggested to share oxygen with two adjacent Fe-chains of the type –Fe–O–SO2–O–Fe– in the tunnels, which leads to distortion in the structure and the poor crystalloid [22,23], and its chemical formula can be expressed as Fe8O8(OH)8-2x(SO4)x (1≤x≤1.75) [23]. Schwertmannite has been studied widely to remove As(III) and As(V) from As-contaminated water [10,12,25]. Liao et al. [12] reported that the optimum pH for As(III) adsorption from As-contaminated groundwater by bio-schwertmannite is in the range of 7.00–10.00. In addition, As(III) can be incorporated into the schwertmannite structure by exchanging for the structural , ionic-exchange between As(III) and the surface OH- and groups of schwertmannite, or the formation of amorphous As(III)-Fe(III)-, which may be responsible for As(III) attenuation by schwertmannite [10,12,25]. Fukushi et al. [26] reported that the As(V) can be adsorbed by schwertmannite and released at pH=3.30.
Effects of Fe(II) concentration on the biosynthesis of schwertmannite by Acidithiobacillus ferrooxidans and the As(III) removal capacity of schwertmannite
Published in Environmental Technology, 2022
Jian Zhang, Jiaxing Zhou, Yanpeng Ji, Wenlong Bi, Fenwu Liu
The SO42- and TOC content in bioschwertmannite were determined. The measured content of sulphur elements or carbon elements represents the content of SO42- and TOC in the minerals because no other sulphur or carbon elements were introduced during the experiment. As shown in Figure 6, the content of SO42- in schwertmannite across the three treatments was 144.5 mg/g (50 mmol/L), 160.3 mg/g (200 mmol/L), and 167.9 mg/g (400 mmol/L), respectively. The chemical formula of schwertmannite was Fe8O8(OH)5.64(SO4)1.18, Fe8O8(OH)5.34(SO4)1.33, and Fe8O8(OH)5.20(SO4)1.40, respectively. The SO42- content compared with previous studies is relatively low but within a reasonable range [31,32]. The bioschwertmannite synthesised through a 50 mmol/L FeSO4 solution has the largest OH- content, showing that higher OH- content is more conducive to As(III) adsorption. As(III) adsorption by schwertmannite increases with solution pH from pH 3–9 [5,15]. Meng et al. [33] results suggested that schwertmannite had a high efficiency in As(III) adsorption because of the much higher OH- proportion. Liu et al. [17] studied the effect of adding H2O2 into the FeSO4·7H2O solution at different supply rates during schwertmannite synthesis. Fe(II) oxidation slowly led to the schwertmannite having a large SSA and OH- content. The As(III) removal capacity of schwertmannite also improved. In this study, the treatment system with a Fe(II) concentration of 400 mmol/L oxidised efficiency slowly. The schwertmannite harvested from this treatment had the largest SSA, but the lowest OH- content, which may have lead to its having the worst As(III) removal adsorption.
Differential and mechanism analysis of sulfate influence on the degradation of 1,1,2- trichloroethane by nano- and micron-size zero-valent iron
Published in Environmental Technology, 2023
Yi Li, Naijin Wu, Jiuhao Song, Zhenxia Wang, Peizhong Li, Yun Song
The influence mechanism of sulfate on dechlorination of 1,1,2-TCA by ZVI was summarised below (conceptual diagram is shown in Figure 7). Under our experimental conditions, SO42− formed bidentate complexes on the mZVI surface, which weakened the Fe-O bond and promoted the dissolution of iron oxides, allowing the active part of mZVI to react better with 1,1,2-TCA, thus, accelerating its degradation. However, SO42− formed monodentate complexes on the nZVI surface, which slowed down the dissolution of iron oxides by blocking the adsorption sites of the protons. As a result, this inhibited the degradation of the contaminants, and the previous interpretation regarding the pH value increase was verified. The iron-sulfate complexes on the nZVI surface further hindered the H+ production by Fe2+ mineralisation, resulting in the accumulation of OH− in the solution. In addition, for the different inhibition phenomena in the N80 group, among the nZVI groups, we presumed that the possible reasons were as follows. In addition to the formation of monodentate complexes, nZVI could form schwertmannite (Fe8O8(OH)8-2x(SO4)x·nH2O, where 1 ≤ x ≤ 1.75 [58]) on its surface after long-term aging in very high concentration SO42− solutions (i.e. 80 mM). Schwertmannite is a nanocrystalline hydroxy sulfate iron mineral commonly found in sulfate-rich acidic environments such as acid mine wastewater and has been shown to play an essential role in many environmental geochemical processes. Reinsch et al. [59] showed that the pH of nZVI aged in unbuffered deionised water containing 10 mN SO42− increased to 9.0–11.8 after 6 months, with additional schwertmannite minerals forming on the nZVI surface. Meanwhile, Wang et al. [60] found the presence of bidentate-binuclear sulfate inner-sphere complexes in schwertmannite minerals. Combined with the characteristic peak corresponding to C2v at 1010 cm−1 in the N80 group, it speculated that both complexes were likely to be present on its surface. In summary, the N80 group possibly exhibited decreased inhibition of TCA degradation under the combined influence of two different types of complexes on the surface.