Passivation performance and mechanism of a novel self-healing composite passivator on pyrite

Abstract

Acid mine drainage (AMD) is a harmful effluent from mining activities. Surface passivation technology can prevent AMD production by coating minerals with passivation films. Previous study reported a composite passivator comprising γ-mercaptopropyltrimethoxysilane (PropS-SH) and halloysite loaded with benzotriazole (BTA). However, two issues persist in this work: the organosilane-based passivator requires passivating pyrite at 50–100 °C, and the encapsulation method for the guest passivator in halloysite is limited. To address these challenges, a novel self-healing composite passivator (PLHP passivator) was synthesized, using PropS-SH and lawsone as the main passivation agents and halloysite loaded with 8-HQ as the nanofiller. Polyelectrolytes were employed as encapsulants within the nanofillers. The formation of a hydrophobic coating on the PLHP coated pyrite surface was revealed by SEM and contact angle tests. The enhanced oxidation resistance of PLHP coated pyrite over raw pyrite and other coated pyrite was verified by electrochemical measurements and chemical leaching tests. Notably, the PLHP coatings could passivate pyrite at room temperature, exhibiting excellent long-term stability and self-healing ability. Furthermore, the incorporation of polyelectrolytes expanded the application range of the guest passivator. This paper provides new insights into overcoming the limitations of organosilane-based passivation and self-healing methods in current technology.