Abstract The influence on fine particle aggregation and flotation behavior induced by high intensity conditioning (HIC) from saturated of the slurry with CO 2 saturation was investigated. Bubble size measurements were conducted. The effect of dissolved gas, xanthate addition and agitation speed on fine sphalerite particle aggregation- and flotation-behavior were studied. The results show that during HIC in air or CO 2 saturated water xanthate acts as a frother. The dissolved gas content in the pulp and HIC play a synergistic role in promoting fine particle aggregation and hence flotation; a significantly enhanced aggregation of fine sphalerite particles in a CO 2 saturated slurry by HIC is observed. The aggregate size increased when the agitation speed was increased from 700 r/min to 1500 r/min. Increasing the HIC speed to 1500 r/min caused a positive impact on flotation kinetics. Further increasing the speed to 2000 r/min resulted in an adverse effect on flotation kinetics.