Surface modification of hemimorphite via double-complexation by ammonium fluoride and copper ion to promote sulfidation

Abstract

The effects of NH4F and Cu2+ ion on hemimorphite corrosion modification were studied. The recovery of hemimorphite in the presence of NH4F was 33.58% higher than that in the absence of NH4F. AFM and SEM-EDS imaging showed that the surface of hemimorphite after treatment in NH4F and Cu2+ solution than when treated with Cu2+ solution. This showed that the F− ions reacted with Si ions on the mineral surface and corroded the mineral surface. NH3 reacted with Cu2+ ions to form Cu(NH3)i2+ (i = 1, 2, 3, 4), which adsorbed onto the mineral surface. XPS analysis revealed that the −O−Si− bonds of the hemimorphite surface were damaged by NH4F, and Cu(NH3)i2+ (i = 1, 2, 3, 4) promoted CuS film formation via catalytic sulfidation to obtain hydrophobic hemimorphite. DFT calculations and ICP analysis showed that the dissociative adsorption of H2O molecule on hemimorphite surface were observed, which hindered the further adsorption of HS on the surface. The strength of the chemical bond between S−Cu−O− hemimorphite was the key to ensuring the stability of the sulfide layer after Cu(NH3)−HS adsorption. The double-complexation of NH4F and Cu2+ ensured the satisfactory sulfidation flotation separation of hemimorphite and quartz.