Abstract
The effect of hydrofluoric acid (HF) pretreatment on flotation of feldspar and quartz using dodecylamine (DDA) as collector was investigated by micro-flotation, zeta potential, pyrene fluorescence spectroscopy, attenuated total reflection flourier transformed infrared spectroscopy (ATR-FTIR), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and bench scale flotation. The micro-flotation tests revealed that there was little difference in the flotation of feldspar and quartz at pH 2, using H2SO4 as pH regulator. After HF pretreatment, the floatability of feldspar significantly increased while the floatability of quartz showed no change. HF pretreatment resulted in leaching of SiO2 and enrichment of Na, K and Al on the feldspar surface. Consequently, the negative surface charge of feldspar increased at pH 2, which allowed for the flotation separation of the feasible minerals. This took place via an increased electrostatic adsorption between DDA and Na, K, Al on the feldspar surface, which effectively increased its hydrophobicity and as a result, improved the floatability of feldspar. An alternative process which exhibited effective separation of quartz and feldspar while recycling the tailwater from the flotation was proposed.
Highlights
Feldspar minerals (KAlSi3 O8, NaAlSi3 O8, CaAl2 Si2 O8 ) are the most abundant of aluminosilicate rock forming minerals, comprising 60% of the earth’s crust
After hydrofluoric acid (HF) pretreatment, and at pH < 2.5, the floatability of quartz showed little change while the floatability of feldspar increased substantially. This may be due to a partial dissolution of the feldspar surface as a result of HF pretreatment, which leads to an increased electrostatic adsorption of DDA at Al, Na, K sites
Vidyadhar et al [11,12,13] demonstrated that feldspar can be selectively floated from quartz at pH 2, where the doubly positively charged collector species was adsorbed on the feldspar surface but not on the quartz surface
Summary
Feldspar minerals (KAlSi3 O8 , NaAlSi3 O8 , CaAl2 Si2 O8 ) are the most abundant of aluminosilicate rock forming minerals, comprising 60% of the earth’s crust. Sulfuric acid (H2 SO4 ) or hydrochloric acid (HCl) was used to adjust the flotation pulp in a strong acidic environment (pH = 2), and HF or NaF was added to activate the feldspar surface, and, amine cationic was applied as a collector for the flotation separation of feldspar and quartz. There is a large amount of chemical activator (HF or NaF) in the flotation system, as the activator is added directly into the pulp These fluoride ions are severely harmful to the surrounding environment. The effectiveness of this separation method is worse than conventional fluorine-containing flotation It can generally only obtain a product of quartz sand (or feldspar), and is not applicable on an industrial scale [14]. An alternative method considering the above factors is to be developed, for effective separation of quartz and feldspar while recycling the tailwater
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