Hydrophobic flocculation of sphalerite fines in aqueous suspensions induced by ethyl and amyl xanthates

The hydrophobic flocculation of sphalerite fines in aqueous suspensions induced by ethyl and amyl xanthates has been investigated using laser diffraction, electrophoretic light scattering and contact angle measurements. The investigation includes studying the effects of various parameters, namely hydrocarbon chain length of xanthate ions, xanthate concentration, pH, original particle size and stirring strength, and approaching the mechanisms of the hydrophobic flocculation. The experimental results have demonstrated that the hydrophobic flocculation arises as a result of the adsorption of ethyl and amyl xanthate ions on sphalerite, which imparts hydrophobicity to the particles, and thereby hydrophobic interaction between the particles. It closely correlates with sphalerite particle hydrophobicity and original particles sizes. The more hydrophobic and the smaller the particles, the stronger is the hydrophobic flocculation. There are critical ethyl and amyl xanthate concentrations at which the hydrophobic flocculation start to increase sharply, which well accords with the contact angle and negative ζ potential of sphalerite. The hydrophobic flocculation increased with increasing xanthate concentration despite an simultaneous increase in the negative ζ potential of sphalerite, meaning that hydrophobic interaction between the particles increased much more strongly than electric double layer repulsion from the adsorption of the xanthate ions. Also, it has been found that there is a direct relationship between particle hydrophobicity and stirring strength for the hydrophobic flocculation.