Abstract
The effects of Ca2+ ions on the flotation of sillimanite using dodecylammonium chloride as a collector were investigated by micro-flotation tests, zeta potential measurements, solution chemistry analysis and molecular dynamics (MD) simulation. The micro-flotation results indicated that Ca2+ ions remarkably inhibit the flotation of sillimanite in the pH range of 2.0–9.0. The point of zero charge (PZC) of sillimanite changed from 5.4 to 6.1 with the addition of Ca2+ ions. Meanwhile, the calculated concentration of RNH3+ in the sillimanite interface layer decreased in the presence of Ca2+ ions. The results of MD simulation revealed that Ca2+ ions have strong binding energy with the sillimanite (010) surface, and the binding energy of RNH3+ with sillimanite (010) surface reduced in the presence of Ca2+ ions. The conclusions drawn from the computations are in good agreement with the experimental results.
Highlights
Sillimanite is an alumino-silicate mineral with a chain structure, which shares the same chemical formula Al2 SiO5 with kyanite and andalusite
Micro-flotation tests achieved flotation recoveries of sillimanite in the presence of dodecylammonium chloride (DAC), where the floatability of sillimanite was inhibited by adding Ca2+ ions
The maximum flotation recovery of sillimanite decreased from 87.25% to 30.36% at pH = 9.0 with Ca2+ ions
Summary
Sillimanite is an alumino-silicate mineral with a chain structure, which shares the same chemical formula Al2 SiO5 with kyanite and andalusite. Previous research has showed that the unavoidable metal ions in process water, such as Ca2+ and Mg2+ ions, affect the flotation of silicate minerals significantly [9,10,11,12,13,14]. Lu et al [15] described the depression effects of Ca2+ ions on andalusite, and the results showed that both Ca2+ ions and [CaOH]+ could depress the flotation of andalusite. Liu et al [13] investigated the effects of Ca2+ and Mg2+ ions on the flotation of spodumene with sodium oleate as the collector. They found that the hydroxy complexes ([CaOH]+ and [MgOH]+ ) and precipitates (Ca(OH) and Mg(OH)2 )
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