Effects of salinity on xanthate adsorption on sphalerite and bubble–sphalerite interactions

• High ion concentration inhibits the xanthate adsorption process.
• High ion concentration facilitates the attachment of sphalerite and air bubble.
• Ca2+ and Mg2+ ions play an important role in bubble–sphalerite interaction.

The adsorption of amyl xanthate on sphalerite in NaCl solutions of different concentrations and in saline water (viz. simulated sea water) and the surface properties of treated minerals were investigated. The interactions between xanthate treated sphalerite particles and air bubbles were examined using induction time measurement, which revealed that the salt ions could inhibit the adsorption of xanthate on sphalerite due to the competitive adsorption, but also could compress the electrical double layer at mineral/water interface. The induction time of sphalerite treated in potassium amyl xanthate (PAX) with saline water was shorter than that of sphalerite treated in PAX with NaCl of the same ion concentration, which implies that the water composition (e.g. Ca2+, Mg2+) could play an important role in the bubble–particle interaction. The hydrophobicity, chemical composition, and charge property of PAX treated sphalerite surfaces were characterized using contact angle measurement, Cryo-X-ray photoelectron spectroscopy (Cryo-XPS) and zeta potential determination, respectively, which support the inhibition effect of salt ions on the xanthate adsorption on sphalerite. In the case of saline water, the xanthate decomposition products were confirmed by XPS, which could further lower the hydrophobicity of the treated sphalerite. Our results provide insights into the basic understanding of the salinity effects on the xanthate adsorption on sphalerite and the bubble–mineral interactions in flotation.

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