High intensity conditioning and the carrier flotation of gold fine particles

Abstract

The effect of high intensity conditioning (HIC) on carrier flotation of gold was studied at laboratory scale by keeping the degree of turbulence constant and by varying the energy transferred to the pulp. Best results were obtained after pulp HIC and showed a 24% increase in the recovery of gold, 50% in concentrate grade and higher flotation rates (at least 3–4 times faster). The fines adhere better to the surface of coarse particles (gold or pyrite) at low shear energy values, 0.5–2 kWh/m 3 pulp, and between 2 and 3 kWh/m 3 pulp they detach from the coarse ones due to the shear forces operating at the contact surface. At about 3–4 kWh/m 3 pulp they aggregate themselves, yielding more floatable species, and at 4 kWh/m 3 pulp inter-particle attrition rules again, and no aggregates are formed. Thus, gold fines recovery proceeds through carrier and/or autogenous carrier flotation. Differences in response are mainly due to the residence time of particle in the shear conditioning, particle size, hydrophobicity and size distribution of values. These phenomena are demonstrated by higher separatin parameters (recovery-grade curves) and by the ‘true’ flotation values and their degree of entrainment. Alternatives for practical HIC, mechanisms involved and the effect of frothers are discussed.