Enhancing flotation recovery of phosphate ores using nonionic surfactants

The beneficial effect of nonylphenol polyethylene glycol ether and various PEO/PPOPEO type triblock copolymer surfactants were investigated to enhance the flotation of Central Florida phosphate ores. Pure sodium oleate and dodecane were used as model reagents for fatty acids and fuel oil, respectively. In order to elucidate ore flotation results equilibrium and dynamic surface tension, emulsification, adsorption, contact angle, and microflotation experiments were carried out.; Equilibrium and dynamic surface tensions of single and binary surfactant solutions of sodium oleate and nonionic surfactant were carried out to determine synergistic effect of surfactant mixtures. Interaction parameter between sodium oleate and nonionic surfactant was calculated from equilibrium surface tension data by using suitable thermodynamic model. The dynamic surface tension results were analyzed by using a model in which surfactant adsorption is considered to follow the Langmuir isotherm. Kinetics of emulsification of dodecane with nonionic surfactants was studied by droplet size distribution of dodecane as a function of time. The results showed that droplet size of dodecane became finer in the presence of nonionic surfactants. A phenomenological model was used to analyze the kinetics of emulsification of dodecane.; The presence of nonionic surfactants decreased the adsorption of sodium oleate on pure apatite mineral possibly due to competition for surface sites. The nonionic surfactants increased the contact angle of oleate on apatite at low surfactant concentrations but decreased at high concentrations. Effect of presence of Ca2+ ions on adsorption and contact angle of surfactants on apatite was investigated. It was found that the detrimental effect of dissolved Ca2+ ions on sodium oleate could be reduced in the presence of nonionic surfactants. It is considered that nonionic surfactants forms mixed micelles with sodium oleate and hence protects the collector from hard ions (e.g. Ca2+) to be consumed as an insoluble calcium oleate.; Microflotation of pure apatite and calcite minerals showed that the recovery of pure minerals depends on the PEO groups in the nonylphenol and PEO/PPO/PEO type surfactants. It was seen that flotation recovery decreased with higher ethoxylation in the structure. Presence of Ca2+ ions was found very detrimental to the flotation of pure minerals by sodium oleate alone. But, presence of nonionic surfactants enhanced the flotation of minerals significantly and the detrimental effect of Ca2+ ions was compensated.; The performance of surfactants was tested in batch flotation of three different size fractions of phosphate ores, namely coarse (−16+35 mesh), fine (−35+150 mesh), and very fine (−150+400 mesh) sizes. Flotation of phosphate ores was conducted in distilled and tap water. Presence of nonionic surfactant increased the recovery of fine and very fine size phosphate ores. The beneficial effect of nonionic surfactant was more significant when tap water was used in the experiments. In the flotation of coarse size phosphate ore the nonionic surfactant was beneficial only at high dosages of sodium oleate and dodecane.