Modelling of bubble formation in reactive flotation Part 1 – Active site approach

Abstract

Reactive flotation is an innovative process to separate dolomite from phosphate rock. It mainly depends on the generation of CO₂ gas due to reaction of dolomite as a carbonate mineral with acidic media. The presence of a coating polymer is mandatory to form CO₂ bubbles at the dolomite particle surface. In this study, polyvinyl alcohol (PVA) was used as a coating polymer. The kinetics of bubble formation that arises due to dissolution of dolomite in sulphuric acid has been studied using narrow sized particles under constant conditions of temperature and acid concentration to determine the rate of dissolution and the effect of coating and particle size. The results show that the dissolution rate increases by decreasing the particle size. Also, it was found that the presence of coating is very effective in forming bubbles, floating the particle, as well as reducing the reaction activity. Based on the kinetic data for coated and uncoated particles, a model was developed and used to explain the tests results, elucidate the controlling mechanism and predict the time needed to float a particle of a certain size. The suggested controlling mechanism mainly depend on the number of the reactant (active) sites at the particle surface as well as the presence of the reaction products that in turn either prevent the acid diffusion or hide the active sites.