Inhibition of pyrite oxidation using PropS-SH/sepiolite composite coatings for the source control of acid mine drainage

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 gamma-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 (SiNMR)-Si-29 measurements, which indicated that sepiolite particles could be embedded in PropS-SH network through oxygen bridges, thus improving the stability of the composite coatings.

Automated summary

A new composite passivator named PSPT was fabricated in this study, and appropriate addition of sepiolite particles significantly improved its inhibition ability against pyrite oxidation. However, excessive addition of sepiolite weakened the passivation performance of the coatings. The mechanism of sepiolite particles embedding in PropS-SH network through oxygen bridges was proposed based on characterization results.