Effect of the Water Hardness Level on Chalcopyrite Flotation Inhibition by the Disodium Carboxymethyl Trithiocarbonate

Disodium carboxymethyl trithiocarbonate (DCMT) is considered to have the potential to replace sulfide and cyanide as a new chalcopyrite inhibitor. However, the effect of its application in the industrial field is often not ideal, mainly because the flotation involves solid, liquid and gas three-phase flotation systems, leading to many influencing factors, especially the chemical changes in pulp caused by the liquid phase. In order to promote the industrial application DCMT, we studied the effect of water quality in the flotation liquid phase on the inhibition of DCMT on chalcopyrite. Water quality generally involves the physical, chemical and biological characteristics of water bodies. The water for beneficiation belongs to industrial water, and the main indicator of its water quality is the water hardness level. Flotation and contact angle studies showed that higher water hardness levels suppressed chalcopyrite inhibition by DCMT. Infrared and Raman spectra revealed that the free CO32− and Ca2+ in water coordinated with the residual organic chains on the surface of the pretreated chalcopyrite and was subsequently adsorbed onto the chalcopyrite surface. Moreover, the addition of DCMT dislodged the captured CO32− and Ca2+. X-ray photoelectron spectroscopy indicated that DCMT could adsorb on the chalcopyrite surface and compete with the Ca2+. When Ca2+ was trapped on the chalcopyrite surface, there were fewer adsorption sites available to the DCMT, resulting in a lower inhibition capacity. Simultaneously, the presence of DCMT promoted the release of Ca2+ from the chalcopyrite surface. Therefore, the influence of water quality must be considered when designing a flotation reagent system, and the water hardness level should be reduced to optimize the flotation process.