Short CommunicationRemoval of antimony (Sb(V)) from Sb mine drainage: Biological sulfate reduction and sulfide oxidation–precipitation
Introduction
Antimony (Sb) is a metalloid element widely used in production of flame retardants, textiles, papers, adhesives, tires, brake linings and plastics. Sb and its chemical compounds were listed as priority pollutants by USEPA and EU due to their toxicity to humans, plants and microorganisms (Zhang et al., 2010). China has more than half of the world’s reserve of Sb (1.5 × 105 tons). The ever-increasing global demand for Sb leads to excess exploitation of Sb ores in China (He et al., 2012). The Sb mine drainage (SMD) and wastewaters from mines and smelting factories, carrying high levels of Sb(V) (Liu et al., 2010, Wu et al., 2011), have usually been discharged into receiving waters without proper treatment (He et al., 2012). Direct discharge of SMD imposes a threat to life forms in the receiving waters and the human health via drinking water and food chain.
Precipitation, electrochemical methods and adsorption were proposed to remove Sb from waters (Solozhenkin and Lyalikova-Medvedeva, 2011, Leuz et al., 2006). Physicochemical technologies on SMD suffer the shortages of their high cost and possible secondary pollution. Additionally, adsorption of Sb(V) on adsorbents’ surface was poor in comparison with other heavy metals (Filella et al., 2007, Zhang et al., 2011). Current treatment technologies for SMD are generally not cost-effective. A recent report has shown that dissolved sulfide can react with aqueous Sb(V) to form insoluble Sb(III) minerals (Sb2S3) under anoxic conditions (Polack et al., 2009). The microbial remediation of acid mine drainage (AMD) by SRB had been studied (Bilek and Wagner, 2012, Bai et al., 2013). The SRB-precipitation process comprises reduction of sulfate by SRB to sulfide and subsequent formation of sulfide precipitates with heavy metal ions from waters (Wang et al., 2012). Production of bio-sulfide by sulfate-reducing bacteria (SRB) is low in operational cost and can be achieved by applying sulfate-reducing activated sludge to the wastewater streams. High levels of sulfate ions in the SMD are essential for SRB growth (Wu et al., 2011).
The mechanisms involved in Sb(V) removal from water by SRB has been rarely reported. This study conducted SRB-precipitation tests for treating synthetic SMD, with focus on the bio-reduction of Sb(V) to Sb(III) and the subsequent precipitate yield. Since the pH of SMD reported ranged 3.48–9.88 (Wu et al., 2011), whcih could markedly affect the activities of SRB in bioreactor (Lopes et al., 2010, Pagnanelli et al., 2010), effects of SMD pH on the performance of the studied SRB reactor were also examined.
Section snippets
Enrichment of SRB
The SRB consortium was enriched from anaerobic sludge collected from Hedong Sewage Treatment Plant in Urumqi, China. The collected sludge sample was added with 5 g l−1 anhydrous Na2SO4 and anaerobically incubated at 30 °C for one week (Whitley DG250, England). To enrich SRB for treatment, 10 ml of inoculum were repeatedly incubated for five times (seven days each) in 100 ml of modified Postgate B medium (pH 7.5; K2HPO4, 0.5 g l−1; NH4Cl 1 g l−1; CaCl2·6H2O 0.1 g l−1; MgSO4·7H2O 2 g l−1; Na2SO4 1 g l−1; FeSO4
Sulfate reducing activity and pH changes
The optimal growth pH for SRB was 7, followed by pH 9 and pH 5 (Fig. S1(a)). SRB grew slowly at pH 5. SRB in the present inoculum showed strong sulfate-reducing activities at various pH’s (Fig. S1(b)). On the day 5, the sulfate concentrations at pH 5, 7 and 9 were reduced from 1.25 g l−1 to 1.11, 0.98, and 1.01 g l−1, respectively. The sulfide concentration was higher at alkaline pH than at acidic pH (Fig. S1(c)). This observation was correlating with the consumption rates of sulfide noted for
Conclusion
This study for the first time demonstrated the feasibility of applying sulfate-reduction + sulfide-oxidization and precipitation process to remove Sb(V) from synthetic SMD. Sb was readily removed from neutral and weakly alkaline solutions in the form of stibnite (Sb2S3). Sb(V) was firstly reduced to Sb(III) by the formed sulfide and then Sb(III) was precipitated with excess sulfide. This process can also effectively remove As from SMD as orpiment (As2S3). This process is claimed a
Acknowledgements
This work was supported by Knowledge Innovation Program of Chinese Academy of Sciences (KZCX2-YW-335), Program of 100 Distinguished Young Scientists of the Chinese Academy of Sciences and National Natural Science Foundation of China (U1120302 and 41150110154).
References (21)
- et al.
Remediation of copper-contaminated soil by Kocuria flava CR1, based on microbially induced calcite precipitation
Ecol. Eng.
(2011) - et al.
Treatment of acid mine drainage by sulfate reducing bacteria with iron in bench scale run
Bioresour. Technol.
(2013) - et al.
Long term performance of an AMD treatment bioreactor using chemolithoautrophic sulfate reduction and ferrous iron precipitation under in situ groundwater conditions
Bioresour. Technol.
(2012) - et al.
Toxic effects of dissolved heavy metals on Desulfovibrio vulgaris and Desulfovibrio sp. strains
J. Hazard. Mater.
(2006) - et al.
Antimony speciation at ultra trace levels using hydride generation atomic fluorescence spectrometry and 8-hydroxyquinoline as an efficient masking agent
Anal. Chim. Acta.
(2001) - et al.
Antimony in the environment: a review focused on natural waters III. Microbiota relevant interactions
Earth-Sci. Rev.
(2007) - et al.
Antimony pollution in China
Sci. Total Environ.
(2012) Solubility of stibnite in hydrogen-sulfide solutions, speciation, and equilibrium-constants, from 25 to 350-degrees-C
Geochim. Cosmochim. Acta
(1988)- et al.
Sulfate reduction during the acidification of sucrose at pH 5 under thermophilic (55 °C) conditions. I: effect of trace metals
Bioresour. Technol.
(2010) - et al.
Isolation and quantification of cadmium removal mechanisms in batch reactors inoculated by sulphate reducing bacteria: biosorption versus bioprecipitation
Bioresour. Technol.
(2010)