• The Fe³⁺-Cu²⁺-BX process effectively separates sphalerite from pyrite without lime, achieving pyrite recovery below 16% and sphalerite recovery above 47% at pH 5.0-10.0.
• Zeta potential and wettability analyses reveal that ferric ions selectively adsorb on pyrite, while copper ions activate sphalerite, enhancing its hydrophobicity.
• XPS analysis confirms the formation of Cu—S bonds on sphalerite and hydrophilic ferric hydroxide on pyrite, facilitating selective flotation.
• This lime-free process offers an environmentally friendly alternative to the conventional lime-Cu²⁺-xanthate method, reducing pipeline scaling and improving recovery of associated precious metals.