Effects of fine–coarse particles interaction on flotation separation and interaction energy calculation

Interaction Behavior between Coarse and Fine Particles in the Reverse Flotation of Fluorapatite and Dolomite

The precondition for efficient flotation of middle- to low-grade phosphate ore is the dissociation of apatite from gangue minerals through fine grinding. However, fine gangue minerals, such as dolomite, have a lower hardness and are thus easily overground and converted into slime during the grinding stage. The effect of -10 μm dolomite fines (Dol-10μm) on the flotation of -75 + 25 μm dolomite (Dol-75+25μm) and -75 + 25 μm fluorapatite (FAp-75+25μm) from a detailed mechanism was investigated by microflotation tests, cryo-electron microscopy analysis, contact angle measurements, bubble-particle attachment test, and EDLVO theory. It was found that Dol-10μm significantly reduced the recovery of Dol-75+25μm and FAp-75+25μm. The Dol-10μm particles could decrease the flotation recovery of Dol-75+25μm particles by masking on their surfaces, thus reducing the hydrophobicity of mineral surfaces and preventing them from floating. Furthermore, Dol-10μm particles were easily adsorbed on the FAp-75+25μm surface and could not be effectively floated, which results in fine dolomite being mixed into the concentrate at the bottom of the tank, thereby reducing the selectivity of reverse flotation for phosphate ore. The interaction energy calculation showed that the presence of NaOL led to an attractive interaction force between Dol-10μm and Dol-75+25μm, as well as between Dol-10μm and FAp-75+25μm. As a result, Dol-10μm particles presented a nonselective aggregation with Dol-75+25μm and FAp-75+25μm particles, explaining the phenomenon of "slime coating" and the depressing effect of dolomite fines on phosphate reverse flotation.

Process Mineralogy Characteristics and Flotation Application of a Refractory Collophanite from Guizhou, China

A refractory phosphate ore obtained from Guizhou, China, contains high amounts of detrimental metal impurities (e.g., Fe, Al, and Mg) which affect the deep wet processing of phosphorus products before use. In this study, mineralogy parameters of the ore such as mineral composition, disseminated particle size, mineral liberation degree, and intergrowth relationship were investigated using X-ray fluorescence spectrometer (XRF), X-ray powder diffractometer (XRD), and advanced mineral identification and characterization system (AMICS). The mechanism for flotation separation was also discussed. The results showed that the ore was a fine-grained calcareous-siliceous collophanite with high P2O5 grade. The gangue minerals such as quartz, sericite (muscovite), pyrite, and dolomite were finely disseminated and encapsulated by fluoroapatite particles in a rather complex relationship. A double reverse flotation process was carried out based on the separation principle of less flotation and more inhibition. A phosphorous concentrate with a P2O5 grade of 35.53%, SiO2 content of 5.88%, MgO content of 0.91%, sesquioxide (Fe2O3 + Al2O3) content of 1.98%, MER value of 8.13%, and phosphorus recovery of 75.04% was obtained. Based on the flotation test results and the analysis of process mineralogy parameters, we concluded that the main causes of difficulty in separation of collophanite are fine disseminated particle size, poor mineral liberation degree, and serious argillization. The selection of foam-controlled collectors, efficient dispersing inhibitors and classified desliming process will be necessary for improving flotation index. These results provide a technical reference for subsequent development and utilization of collophanite resources.

Discrimination of Six Flotation Kinetic Models Used in the Conventional Flotation and Carrier Flotation of -74 μm Coal Fines

In this study, experimental results of conventional flotation and carrier flotation were characterized by six commonly used flotation kinetic models. Two statistical criteria (coefficient of determination, R ², and root mean square error, RMSE) were used for comparison of fitting performance of different models. All kinetic models tested gave good levels of goodness of fit, but the second-order model with rectangular distribution (model 6) provided the best fitting performance for the experimental data of conventional flotation and carrier flotation. On this basis, two parameters, that is, modified flotation rate constant (K _m) and selectivity index (SI), were used to evaluate the difference in flotation separation selectivity between conventional flotation and carrier flotation. Comparisons of K _m and SI values indicated that carrier flotation significantly improved the flotation rate constant of combustible materials and flotation separation selectivity of ultrafine coal (-74 μm). In addition, measurements of average bubble size and water recovery indicated that both the coalescence of bubbles and the drainage of liquid in the froth were promoted when coarse coal particles (contact angle >90°) were employed as the carrier to assist the flotation recovery of ultrafine particles, which in turn favored the inhibition effect of the entrainment of gangue materials in carrier flotation compared to conventional flotation.