Inhibiting effect of citric acid on the floatability of serpentine activated by Cu(II) and Ni(II) ions

The laboratory researches about the inhibiting effect of citric acid on the flotation performance of serpentine activated by Cu²⁺ and Ni²⁺ were carried out through micro flotation tests, zeta potential measurements, collector adsorption capacity measurements and solution chemistry analysis. The flotation results showed that Cu²⁺ and Ni²⁺ could remarkably activate the flotation of serpentine when the pH value was more than 6, however, this activation could be effectively weakened by adding citric acid. Zeta potential measurement and adsorption capacity measurement indicated that the presence of citric acid could prevent the adsorption of Cu²⁺ and Ni²⁺, and therefore reduce the adsorption amount of potassium butyl xanthate on serpentine surface. Furthermore, solution chemical analysis of the flotation system showed that copper hydroxide Cu(OH)_2(s) and the nickel hydroxide Ni(OH)2(s) were the main component in the pH range of 9 to 10, which adsorbed onto serpentine surface and made it activated; while the citric acid could effectively prohibit the formation of these metal hydroxide in slurry so as to inhibit the activation impact.