Improvement of flotation and suppression of pyrite oxidation using phosphate-enhanced galvanic microencapsulation (GME) in a ball mill with steel ball media

[Display omitted] •Galvanic microencapsulation treatment during ball milling process was proposed.•Iron phosphate coating were formed on pyrite surface after treatment.•Sufficient supply of oxygen was crucial for formation of iron phosphate coating.•Iron phosphate coating passivated pyrite oxidation.•Hydrophilic coating on pyrite improved separation efficiency of coal flotation. Acid mine drainage (AMD) is one of the biggest and most challenging environmental concerns of the mining and mineral processing industries. In our previous study, we reported a new and promising approach to passivate sulfide minerals and limit AMD formation called galvanic microencapsulation (GME), a technique that forms protective coatings via galvanic interactions between sulfide minerals (e.g., pyrite) and metal powders (e.g., zero-valent iron and aluminum). In this paper, the possible application of GME in a ball mill with steel ball media and phosphate to suppress pyrite floatability during coal cleaning and limit pyrite oxidation after disposal is proposed. The results showed that adding phosphate and maintaining sufficient oxygen supply during GME treatment in the ball mill passivated pyrite and suppressed its oxidation via the formation of protective iron phosphate coatings. Moreover, the iron phosphate coatings on pyrite made the mineral more hydrophilic, which improved the separation efficiency during coal flotation.