• Xanthan gum serves as a non-toxic and biodegradable depressant for talc, olivine, and serpentine in copper-nickel sulfide flotation.
• XG shifts the aggregation among the three gangue minerals from talc-serpentine to olivine-serpentine, selectively depressing talc.
• Hydroxyl groups of XG chemically bond with Mg sites on olivine, causing a significant negative surface charge shift.
• Enhanced electrostatic attraction between serpentine and olivine promotes their aggregation, improving separation efficiency.