Inhibition of pyrite oxidation using PropS-SH/sepiolite composite coatings for the source control of acid mine drainage
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RESEARCH ARTICLE
Inhibition of pyrite oxidation using PropS-SH/sepiolite composite coatings for the source control of acid mine drainage Baolin Gong 1 & Dejian Li 1 & Zheng Niu 1 & Yun Liu 1 & Zhi Dang 2 Received: 12 July 2020 / Accepted: 18 October 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Pyrite, as one of the most abundant sulfide minerals, can be easily oxidized to generate acid mine drainage (AMD). In the present study, a new composite passivator named PropS-SH/sepiolite (PSPT) using γ-mercaptopropyltrimethoxysilane (PropS-SH) as the main passivator and natural sepiolite particles as filler was fabricated and used to suppress the oxidation of pyrite. Electrochemical tests and chemical leaching experiments were carried out to evaluate the passivation performance of PSPT coatings with different amount of sepiolite particles on pyrite oxidation. The results showed that the addition of appropriate sepiolite could significantly improve the inhibition ability of PropS-SH against pyrite oxidation. However, excessive addition of sepiolite particles weakened the inhibition ability of the PSPT coatings owing to aggregations of sepiolite. Additionally, the coating mechanism of PSPT on pyrite was also proposed based on the characterization of FTIR, XPS, and 29SiNMR measurements, which indicated that sepiolite particles could be embedded in PropS-SH network through oxygen bridges, thus improving the stability of the composite coatings. Keywords Acid mine drainage . Pyrite . Composite coatings . Sepiolite
Introduction As a common sulfide mineral, pyrite extensively exists in tailing dams and waste rocks. When exposed to water and oxygen, pyrite will undergo a series of chemical reactions and eventually be oxidized to form acid mine drainage (AMD), which is accompanied by strong acidity and a large number of heavy metal ions (such as Cu, Pb, Zn, Cd, As, and Se) (Akcil and Koldas 2006; Tabelin et al. 2018; Valente et al. 2013). In this process, pyrite can be dissolved rapidly under the attack of oxidants such as dissolved O2 (DO) and Fe3+ (Li et al. 2016; Tabelin et al. 2017b). In particular, this oxidation process can be maintained and enhanced under the catalysis of
Responsible Editor: Ioannis A. Katsoyiannis * Yun Liu [email protected] 1
Present address: Department of Environmental Science and Engineering, College of Environment and Resources, Xiangtan University, Xiangtan 411105, China
2
School of Environment and Energy, South China University of Technology, Guangzhou 510006, China
oxidizing bacteria (especially acidophiles such as Thiobacillus ferrooxians). The formation process of AMD can be presented by the following equations (Tabelin et al. 2017a): FeS2 ðsÞ þ 3:5O2 ðaqÞ þ H2 O→Fe2þ þ 2Hþ þ 2SO2− 4
ð1Þ
FeS2 ðsÞ þ 14Fe3þ þ 8H2 O→15Fe2þ þ 16Hþ þ 2SO2− 4 ð2Þ Fe2þ þ 0:25O2 ðaqÞ þ Hþ → Fe3þ þ 0:5H2 O
ð3Þ
After the closure or abandonment of mines, the generation of AMD in old mine workings and pit lakes may last for hundreds or thousands years (Tomiyama et al. 2019, 2020). If AM
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