Elsevier

Chemosphere

Volume 209, October 2018, Pages 381-391
Chemosphere

Dissolution of realgar by Acidithiobacillus ferrooxidans in the presence and absence of zerovalent iron: Implications for remediation of iron-deficient realgar tailings

https://doi.org/10.1016/j.chemosphere.2018.05.192Get rights and content

Highlights

  • Realgar dissolution by A. ferrooxidans with and without zerovalent iron studied.

  • Arsenic released to solution due to realgar oxidation.

  • Low aqueous arsenic observed in ZVI-added systems.

  • Arsenic attenuation due to formation of As-bearing Fe oxyhydr-oxides and –sulfates.

  • Zerovalent iron and A. ferrooxidans could be used to remediate realgar tailings.

Abstract

Realgar (As4S4)-rich tailings are iron-deficient arsenical mine wastes. The mechanisms and products of the dissolution of realgar by Acidithiobacillus ferrooxidans (A. ferrooxidans) in the presence (0.2 g and 2 g) and absence of zerovalent iron (ZVI) are investigated for three stages (each of 7 d with fresh A. ferrooxidans medium addition between the stages). SEM-EDX, FTIR, XPS and selective extraction analysis are used to characterize the solid-phase during the experiments. ZVI addition causes the systems to become more acid-generating, although pH increases are observed in the first day due to ZVI dissolution. Arsenic is released to solution due to realgar oxidation (∼30 mg L−1 in the 0 g ZVI system in Stage I), but low concentrations are observed in the ZVI-added systems (<5 mg L−1) and in Stages II and III of the 0 g ZVI system. As(III) dominates the released As(T) at day 1 (83–89% of As(T)), but is largely oxidized to As(V) at day 7 of each stage (53–98% of As(T)). Arsenic attenuation is attributed to the formation of mixed As-Fe oxyhydroxides and oxyhydroxy sulfates that take up released arsenic and are abundant in the 2.0 g ZVI system, and to passivation of the realgar surface. Consequently, a new strategy that combines A. ferrooxidans and exogenous ZVI addition for treating in-situ iron-deficient realgar-rich tailings is proposed, although its long-term effects need to be monitored.

Introduction

Arsenic (As) is a ubiquitous concern worldwide because of its toxic, carcinogenic and teratogenic properties on human health (Smith et al., 1992; Nordstrom and Alpers, 1999; Smedley and Kinniburgh, 2002). Dissolution of As-rich tailings is one of main causes of As contamination in water, soil and diverse ecosystems (Macur et al., 2001; Mkandawire and Dudel, 2005; Shi et al., 2017). The behavior of As in tailings and soils is strongly influenced by the oxidative and reductive microbial dissolution of As-bearing sulfides and Fe oxyhydroxides (Johnston et al., 2011; Lu and Wang, 2012; Burton et al., 2013). Arsenopyrite (FeAsS) and arsenian pyrite (Fe(S, As)2) are common iron-rich As sulfides that can incorporate gold, silver, etc., but mining and hydrometallurgy operations involving them can result in significant release of As to the environment (Reich et al., 2005; Corkhill and Vaughan, 2009). Microbial techniques can be used to treat these mine wastes by enhancing As immobilization (Gonzalezcontreras et al., 2010, 2012; Okibe et al., 2017). For example, Egal et al. (2009) found that various Acidithiobacillus ferrooxidans (A. ferrooxidans) strains can help the formation of kinds of ferric oxyhydroxy sulfates (e.g. tooeleite, schwertmannite and jarosite) that are able to incorporate As within their structure or adsorb them at their surface during microbial Fe(II) oxidation. Gonzalezcontreras et al. (2010) have shown that Acidianus sulfidivorans can promote the formation of scorodite (FeAsO4·2H2O), which has low solubility and is a good mineral trap for As.

Arsenian pyrite can contain up to 10 wt.% As (Qiu et al., 2017). The microbial dissolution of pyrite involving organisms such as A. ferrooxidans has been studied for more than forty years (Singer and Stumm, 1970; Percak-Dennett et al., 2017). A. ferrooxidans is an acidophilic iron-oxidizing bacteria which oxidizes Fe(II) to Fe(III) at pH 1.5–7.0 to obtain energy for growth (Meruane and Vargas, 2003; Ko et al., 2013). The released Fe(III) can also oxidize pyrite and increase its dissolution rate. The oxidative dissolution of arsenopyrite, leading to the release of As(III) and As(V), has also been extensively studied (Barrett et al., 1993; Corkhill and Vaughan, 2009). It has been shown that addition of excess Fe(III) can trigger electron transfer between Fe(III) and Fe(II) in arsenian pyrite and arsenopyrite dissolution, resulting in higher oxidative dissolution rates and production of secondary phases such as iron oxyhydroxides (Chen et al., 2014; Neil and Jun, 2016). These newly-formed iron oxyhydroxides can in turn sequester As via sorption or co-precipitation reactions (Dixit and Hering, 2003; Root et al., 2009; Johnston et al., 2012).

Realgar (As4S4) is another common As sulfide (containing mainly As(II)) (Lengke and Tempel, 2003; Wu et al., 2017), but compared to arsenopyrite and pyrite, is iron-deficient. Like the other As-bearing sulfides, realgar dissolution can be affected by physical, chemical and biological factors including pH, Eh, oxygen, light, solution composition/speciation and microorganism activity (Cullen and Reimer, 1989; Kyono et al., 2005). A. ferrooxidans, for example, has been shown to oxidize realgar (Zhang et al., 2007; Chen et al., 2011; Yan et al., 2017). Zhang et al. (2007) showed that the oxidation of realgar in acidic conditions was significantly accelerated in the presence of dissolved Fe(II) and mixed cultures of A. ferrooxidans and A. thiooxidans, compared to single culture experiments. By contrast, Chen et al. (2011) found that microbially-generated Fe(III) can prevent the oxidation of realgar. These studies have mainly focused on the effects of aqueous iron ions (e.g. Fe(II), Fe(III)) and no studies to date have been carried out to investigate the effect of exogenous solid zerovalent iron (ZVI) on the dissolution of realgar. ZVI is a wide and effective commercial remediation agent used to remove As and other contaminants from groundwater and soils (Kuijae et al., 2009; Tuček et al., 2017; Xie et al., 2017). Recently, Liang et al. (2017) used ZVI to stabilize As-containing sludge, and showed that the extent of ZVI oxidation was closely related to its As sorption capacity. These findings raise important questions. What will happen when ZVI is added to iron-deficient As sulfides such as realgar? What are the mechanisms of As release during microbial realgar dissolution with and without ZVI? An understanding of the mechanisms and products of realgar dissolution by A. ferrooxidans with ZVI would answer these questions. If the process is effective, exogenous ZVI combined with A. ferrooxidans might be an efficient remediation strategy for in-situ realgar-containing tailings.

Therefore, the aim of this study was to determine the mechanisms and products of realgar dissolution by A. ferrooxidans with and without ZVI. We used A. ferrooxidans since it is a common bacterium in AMD system and it is tolerant to, but does not metabolize, As (Jones et al., 2003; Yan et al., 2017). The specific objectives of the study were to (i) investigate the behavior and speciation of As during realgar dissolution; (ii) determine the character and stability of the secondary products; (iii) identify the mechanisms involved. This knowledge will be beneficial for developing remediation schemes for in-situ iron-deficient realgar-rich tailings.

Section snippets

Sample preparation

The raw realgar used in this study was obtained from the Shimen Realgar Mine (Hunan Province, China), the largest former As supplier in Asia (Chen et al., 2017; Fan et al., 2018). The realgar was ground, sieved to less than 100 mesh (<180 μm) and without any other treatment to represent typical realgar tailings. X-ray diffraction (XRD) analysis confirmed that realgar was the dominant phase with no distinct diffraction peaks of other minerals observed (Fig. S1). X-ray fluorescence (XRF) analysis

Dynamics of As and Fe release during realgar dissolution with and without ZVI

pH and Eh variations are important indices for understanding mineral dissolution mechanisms in environmental systems (Burlo et al., 1999; Yamaguchi et al., 2011). Changes in pH and Eh as a function of time and ZVI presence and absence are shown in Fig. 1. The pH and Eh values in the control at every stage were relatively stable at ∼2.4 and ∼250–350 mV, respectively. In Stages I and II, dramatic increases in pH to ∼3.5–4.0 and Eh decreases to ∼180 mV were observed in the first day of the 2.0 g

Conclusions

This study examined gradient levels (0 g, 0.2 g, 2 g) of exogenous zerovalent iron (ZVI) addition on the realgar dissolution by A. ferrooxidans. Our major findings are depicted schematically in Fig. 8 and are summarized as follows:

  • 1)

    Realgar dissolution by A. ferrooxidans results in decreases in solution pH and increases in Eh. However, high amounts of ZVI (2.0 g) addition initially causes increases in pH and decreases in Eh due to ZVI dissolution at first. As realgar oxidation proceeds, these

Acknowledgements

This study was supported by the National Natural Science Foundation of China (Grant No. 4177236) and National Key R&D Program of China (2016YFC0502204).

References (70)

  • R.A. Jones et al.

    Surface alteration of arsenopyrite (FeAsS) by Thiobacillus ferrooxidans

    Geochim. Cosmochim. Acta

    (2003)
  • M.F. Lengke et al.

    Natural realgar and amorphous AsS oxidation kinetics

    Geochim. Cosmochim. Acta

    (2003)
  • M.F. Lengke et al.

    Geochemical modeling of arsenic sulfide oxidation kinetics in a mining environment

    Geochim. Cosmochim. Acta

    (2005)
  • Y. Liang et al.

    Stabilization of arsenic sludge with mechanochemically modified zero valent iron

    Chemosphere

    (2017)
  • Z. Liu et al.

    Microwave-assisted arsenic removal and the magnetic effects of typical arsenopyrite-bearing mine tailings

    Chem. Eng. J.

    (2015)
  • G. Meruane et al.

    Bacterial oxidation of ferrous iron by Acidithiobacillus ferrooxidans in the pH range 2.5–7.0

    Hydrometallurgy

    (2003)
  • M. Mkandawire et al.

    Accumulation of arsenic in Lemna gibba L. (duckweed) in tailing waters of two abandoned uranium mining sites in Saxony, Germany

    Sci. Total Environ.

    (2005)
  • N. Okibe et al.

    Bioscorodite crystallization using Acidianus brierleyi: effects caused by Cu(II) present in As(III)-bearing copper refinery wastewaters

    Hydrometallurgy

    (2017)
  • G. Qiu et al.

    Mechanisms of arsenic-containing pyrite oxidation by aqueous arsenate under anoxic conditions

    Geochim. Cosmochim. Acta

    (2017)
  • M. Reich et al.

    Solubility of gold in arsenian pyrite

    Geochim. Cosmochim. Acta

    (2005)
  • P.L. Smedley et al.

    A review of the source, behaviour and distribution of arsenic in natural waters

    Appl. Geochem.

    (2002)
  • R.N. Tempel et al.

    Geochemical modeling approach to predicting arsenic concentrations in a mine pit lake

    Appl. Geochem.

    (2000)
  • W.W. Wenzel et al.

    Arsenic fractionation in soils using an improved sequential extraction procedure

    Anal. Chim. Acta

    (2001)
  • Y. Wu et al.

    Migration and transformation of arsenic: contamination control and remediation in realgar mining areas

    Appl. Geochem.

    (2017)
  • Y. Xie et al.

    The interactions between nanoscale zero-valent iron and microbes in the subsurface environment: a review

    J. Hazard Mater.

    (2017)
  • N. Yamaguchi et al.

    Arsenic release from flooded paddy soils is influenced by speciation, Eh, pH, and iron dissolution

    Chemosphere

    (2011)
  • L. Yan et al.

    Arsenic tolerance and bioleaching from realgar based on response surface methodology by Acidithiobacillus ferrooxidans isolated from Wudalianchi volcanic lake, northeast China

    Electron. J. Biotechnol.

    (2017)
  • J. Zhang et al.

    Bioleaching of arsenic from medicinal realgar by pure and mixed cultures

    Process Biochem.

    (2007)
  • A. Adamescu et al.

    Insights into the surface complexation of dimethylarsinic acid on iron (oxyhydr)oxides from ATR-FTIR studies and quantum chemical calculations

    Environ. Sci. Technol.

    (2010)
  • S.D. And et al.

    Comparison of arsenic(V) and arsenic(III) sorption onto iron oxide minerals:  Implications for arsenic mobility

    Environ. Sci. Technol.

    (2003)
  • I. Ardelean et al.

    Structural study of the Fe2O3–B2O3–BaO glass system by FTIR spectroscopy

    Mod. Phys. Lett. B

    (2008)
  • J.M. Bigham et al.

    Iron and aluminum hydroxysulfates from acid sulfate waters

    Rev. Mineral. Geochem.

    (2000)
  • F. Burlo et al.

    The influence of redox chemistry and pH on chemically active forms of arsenic in sewage sludge-amended soil

    Environ. Int.

    (1999)
  • A. Burnol et al.

    Decoupling of arsenic and iron release from ferrihydrite suspension under reducing conditions: a biogeochemical model

    Geochem. Trans.

    (2007)
  • E.D. Burton et al.

    Sulfate availability drives divergent evolution of arsenic speciation during microbially mediated reductive transformation of schwertmannite

    Environ. Sci. Technol.

    (2013)
  • Cited by (21)

    • Mechanism of arsenic release from realgar oxidation in the presence of dissolved oxygen: Effect of reactive oxygen species and light-induced transformation

      2022, Geochimica et Cosmochimica Acta
      Citation Excerpt :

      For example, iron oxyhydroxides/oxides formed during the oxidation of iron sulfide minerals have high affinity for As, which can alleviate the As pollution to a certain extent (Hong et al., 2021; Qiu et al., 2018). As for realgar, due to the lack of iron in its crystal structure, the As(III)/As(V) generated from As(II) oxidation easily pollutes soils, rivers and groundwaters through surface runoff or infiltration (Fan et al., 2018; Wu et al., 2017). Recently, serious As pollution events have been reported in some realgar mining areas of China (Wang et al., 2019).

    View all citing articles on Scopus
    View full text