Pyrite oxidation inhibition by organosilane coatings for acid mine drainage control

• The inhibition efficiencies were evaluated by electrochemical techniques.
• Organosilane agents were used as passivants to suppress pyrite oxidation.
• The inhibition efficiency of coatings follows the sequence of PropS-SH > VTMS > APS.
• The coated pyrite samples were characterized by FT-IR and XPS.
• The mechanism of pyrite oxidation suppression by studied coatings was determined.

By using electrochemical techniques and conventional chemical leaching approach, the potential of organosilane coatings to suppress the pyrite oxidation under acidic conditions was investigated, including γ-mercaptopropyltrimethoxysilane (PropS-SH), γ-aminopropyltrimethoxysilane (APS) and vinyltrimethoxysilane (VTMS). The coated pyrite samples were analyzed by Fourier transforms infrared reflection (FT-IR) spectroscopy and X-ray photoelectron spectrometer (XPS). The results from electrochemical tests have indicated that all the studied coatings could suppress the oxidation of pyrite and the inhibition efficiency should follow the sequence of PropS-SH > VTMS > APS. The results of chemical leaching experiments have showed that pyrite oxidation was decreased by 49.4%, 71.4% and 89.2% (based on Fe release) respectively by using APS, VTMS and PropS-SH coatings. The mechanism of inhibition action could possibly be the formation of a cross-linking network of Si–O–Si and Si–O–Fe bonds on the pyrite surface which could restrain the permeation of aggressive species.