Sodium Trithiocarbonate as a Promising Sulfidizing Agent for Efficient and Green Recovery of Azurite: Flotation Properties and Interaction Mechanism

The sulfidization-xanthate flotation process has been used commercially with some success in recovering azurite, but it remains unsatisfactory in terms of the environmental impact and flotation index. To remediate these deficiencies, this study evaluated the flotation performance of sodium trithiocarbonate (Na₂CS₃) as a green sulfidizing agent for azurite. Flotation test results demonstrated that Na₂CS₃ has the same efficacy as sodium sulfide but markedly superior activation performance. At one-fifth the dose, the maximum flotation recovery for Na₂CS₃ is about 20 percentage points higher than that observed for sodium sulfide. Contact angle measurements and field emission scanning electron microscopy analysis revealed that Na₂CS₃ modifies the pristine azurite surface by forming a relatively uniform sulfur-rich layer composed of nanoparticles, which in turn increases the collector efficacy and thus improves flotation recovery. The results of X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry further suggest that this sulfur-rich hydrophobic layer could be cuprous trithiocarbonate. The reduction of Cu(II) in the azurite lattice is considered a key step in forming the sulfur-rich layer, and the resultant Cu(I) interacts with Na₂CS₃ through the latter’s carbon–sulfur bonds. The results of this study will facilitate the development of better technologies to process copper oxide ores.