Tannic acid as an eco-friendly natural passivator for the inhibition of pyrite oxidation to prevent acid mine drainage at the source

In this study, an eco-friendly natural green polyphenol tannic acid (TA) was utilized as the passivator to inhibit pyrite oxidation. The strong coordination of phenolic hydroxyl groups in TA to Fe ions on pyrite makes TA have the characteristics of simple coating process on pyrite surface. Electrochemical measurements and chemical leaching tests were used to study the inhibition performance of TA on pyrite oxidation. The experimental results indicated that TA passivation coating could provide good antioxidant protection for pyrite and the inhibition ability of TA on pyrite oxidation raised with the increase of TA concentration. Additionally, the morphological changes of pyrite surface before and after TA passivation were further observed by Scanning electron microscopy (SEM). Finally, Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) were applied to probe the interaction mechanism of TA with pyrite in detail. The results of surface analyses verified that TA was capable of forming TA-Fe complexes with Fe ions on pyrite through chelation reaction, so as to be chemically deposited on the surface of pyrite that could effectively protect pyrite from oxidation. It is believed that this work can provide a new low-cost and simple way for acid mine drainage (AMD) control.