Water overflow rate and bubble surface area flux in flotation

One of the most important factors that determines the concentrate grade in flotation is water recovery. Water recovery is influenced by frother through control of bubble size and possibly a frother-related chemical effect. A frother mass balance approach is presented for determining an equivalent water film thickness associated with bubble surface area flux exiting via the froth overflow to represent the chemistry effect.;A closed loop mini flotation cell setup is used to achieve steady state in continuous tests. Four frothers are evaluated to reveal the dependence of water overflow velocity (JwO) on frother type and concentration. Using Total Organic Carbon analysis, frother partitioning between overflow and underflow is measured, showing a remarkable preferential distribution to the overflow at low frother dosage. From surface tension measurements the Gibbs excess adsorption density (Gamma) is estimated and used in the mass balance approach to estimate bubble surface area flux to overflow (S bO). Estimations from this approach are compared with bubble surface area flux into and on top of froth obtained from bubble size data using image analysis. A correlation is shown between JwO and S bO permitting an equivalent water film thickness carried by the bubble into the overflow (deltaO) to be estimated. The delta O reflects the frother type: a stronger frother creates a larger delta O and a weaker frother creates a smaller deltaO. Possible implications in flotation are discussed.