Study On Passivation Performance And Mechanism Of Pyrite By Passivators Based On Tannic Acid And Organosilane

Acid mine drainage(AMD)is a multi-factor pollutant formed by complex chemical,physical and biological interactions between pyrite and other metal sulfide minerals as well as external oxidation media,whose formation process usually occurs in abandoned or active mines.As a sustainable and cost-effective prevention technology,surface passivation can effectively inhibit the oxidation of pyrite by using passivator to form a protective passivation film on the surface of pyrite,so as to control the generation of AMD at the source.Although great progress has been made in the research of surface passivators,most of passivators will still expose the disadvantages of high toxicity and complex preparation process,which limit their further use in practice.Therefore,in order to comply with today’s green and sustainable mine development concept,the surface passivation treatment of pyrite should be carried out in the direction of low cost,simple,efficient and environment-friendly.Focusing on the central idea of developing and looking for new green passivators,this paper adopted two different low-cost and simple passivation methods to treat pyrite under mild environmental conditions,so as to achieve the good passivation effect of pyrite and meet the requirements of practical application as much as possible.Firstly,inspired by mussel adhesion protein,an eco-friendly natural green polyphenol tannic acid(TA)was utilized as the passivator to inhibit pyrite oxidation in this study.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,whose 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.In order to further enhance the hydrophobic and passivation ability of TA passivation coating as well as improve the coating process of organosilane passivation method,γ-mercaptopropyltrimethoxysilane(Prop S-SH)and TA were introduced to synergistically passivate pyrite in this paper.Electrochemical measurements and chemical leaching tests confirmed that the Prop S-SH-TA composite passivated pyrite had better passivation performance than raw pyrite and single TA or Prop S-SH passivated pyrite.Furthermore,the results of SEM and static water contact angle tests showed that the flake coatings were formed on the surface of the composite passivated pyrite,which may be the reason for the significant improvement of its surface hydrophobicity.The passivation mechanism of Prop S-SH-TA composite passivator for pyrite was discussed by FTIR and XPS.The analysis results indicated that the benzoquinone derivative oxidized by TA under weak alkaline conditions could be copolymerized with hydrolyzed and condensed sulfhydryl silane Prop S-SH through Michael addition or Schiff base reactions.The copolymer could strongly interact with pyrite as well as deposit and adhere to the mineral surface,thereby constructing a dense hydrophobic passivation coating,which further provided better oxidation barrier for pyrite on the basis of TA passivation coating.