Study Of Inhibition Property And Mechanism Of Props-SH On Pyrite Biological Oxidation

As the most common metal sulfide mineral, pyrite is widely present in tailings, waste rocks and metal-associated minerals. In natural conditions, pyrite is susceptible to oxidation by microorganisms and various oxides under atmospheric precipitation and surface runoff, and the resulting acid mine drainage (AMD) can lead to a serious threat to the human survival environment. In this paper, aiming to control the pollution of AMD at source, y-mercaptopropyltrimethoxysilane (Props-SH) was used to inhibit pyrite biological oxidation, in which the passivation efficiency for PropS-SH coating was evaluated by electrochemical techniques and biological leaching test.The mechanism of microbial pyrite oxidation was investigated, in which cultivated Thiobacillus ferrooxidans (A.f) was used as pyrite-oxidizing bacteria to simulate pyrite biological oxidation under natural conditions. The results show that both of direct oxidation and indirect oxidation are existing in the process of microbial pyrite oxidation.The electrochemical behavior of pyrite before and after coated by Props-SH in bioleaching system was studied by using electrochemical techniques. The cyclic voltammetry curves show that Props-SH can significantly decrease the redox peaks of pyrite electrode and the redox peaks is decreased with an increase in PropS-SH. When 5% of PropS-SH was adopted in the coating treatment, the anodic and cathodic current peaks were too weak to be detected. Similarly, The results of Tafel polarization curves and electrochemical impedance spectra also demonstrate that Props-SH can effectively inhibit the electrochemical behavior of the pyrite. In the bioleaching experiments, the total Fe released from pyrite coated with 1%,3% and 5% PropS-SH is decreased by 49.1%,87.6% and 96.0%, respectively, and the SO42-concentration in corresponding solution is reduced by 49.3%,73.9% and 93.2% respectively, confirming that the inhibition efficiency increases with increasing PropS-SH concentration.At the end of the paper, the film formation mechanism of PropS-SH on pyrite surface was analyzed with Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy (Raman). The results show that Fe-O-Si bonds are formed through cross-linking reaction of Props-SH and a resulting dense protection film is generated on the pyrite surface. Additionally, Contact angle measurements suggest that the PropS-SH coating increases the hydrophobicity of pyrite surface. When 5% of PropS-SH was adopted in the coating treatment, the property of the pyrite surface changed from hydrophilic to hydrophobic. The morphology characteristics of pyrite surface observed by scanning electron microscopy (SEM) show that the pyrite surface is smooth after Props-SH passivation and the formed Props-SH coating can effectively limit the contact of Acidithiobacillus ferrooxidans cells with pyrite.