Plasma-activated water induced vacancy engineering for selective separation of arsenopyrite and pyrite

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Abstract

Selective separation of minerals with similar surface properties remains challenging. This study introduces a green surface modification strategy that leverages grinding-induced vacancy defects and their subsequent selective passivation with plasma-activated water (PAW). 

The results demonstrate that the type and density of vacancies generated by mechanical treatment differ distinctly between pyrite and arsenopyrite. After PAW treatment, pyrite flotation recovery remained as high as 75.21%, while arsenopyrite dropped to 14.67%. 

Reactive oxygen species (ROS), particularly ·OH, preferentially interact with As vacancy sites on arsenopyrite, inducing deep surface reconstruction and the formation of a stable hydrophilic As(V)‒O overlayer (increasing from 5.70% to 11.36% of surface As species). 

In contrast, the more stable Fe‒S lattice of pyrite undergoes only superficial oxidation and vacancy passivation, largely preserving its intrinsic floatability. This work establishes a vacancy-mediated, ROS-driven surface reconstruction mechanism, offering a novel paradigm for the selective separation of sulfide mineral systems with significant environmental benefits, eliminating the use of toxic chemical depressants and the generation of hazardous wastewater.

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