Seawater Flotation Separation Mechanisms Of Chalcopyrite And Pyrite

Chalcopyrite（hosting about 70%of the copper resources on the earth）is a copper-bearing mineral,often associated with pyrite.Flotation is commonly used in industry to achieve copper-sulfur separation.Due to the gradual scarcity of freshwater resources and the increasing discharge standards of mineral processing wastewater,many mineral processing plants use industrial circulating water containing a large number of ions,groundwater and seawater with complex components as flotation media.However,the Ca²⁺and Mg²⁺ions contained in these high brines generate a large amount of hydroxide precipitates on the surface of the minerals in an alkaline environment,which are indiscriminately adsorbed on the surface of minerals through electrostatic attraction,inhibiting chalcopyrite and pyrite flotation.The recovery decreases,reducing the selectivity and worsening the beneficiation efficiency.Although researchers have tried to use new inhibitors to prevent pyrite flotation,the agents used are normally in large amounts in seawater and highly toxic,harm to environmental safety and human health.In this study,chalcopyrite and pyrite are taken as the research objects,and the oxidant H₂O₂ is used as a new inhibitor to investigate the separation efficient and mechanism for chalcopyrite and pyrite in pure water and seawater.Combined with FTIR,contact angle,X-ray photoelectron spectroscopy（XPS）,UV-Vis spectroscopy,microcalorimetry and density functional theory calculations（DFT）,the changes in the surface properties of minerals in pure water and seawater were investigated.Therefore,the influencing mechanism of oxidant H₂O₂ and seawater ions on the floatability of chalcopyrite and pyrite was revealed.Therefore,this study provides a theoretical basis for realizing the separation of chalcopyrite and pyrite in seawater.The results show:In seawater,both chalcopyrite and pyrite showed high flotation recovery under acidic and neutral conditions,which however decreased under alkaline conditions.The higher the p H,the lower the flotation recovery of either chalcopyrite or pyrite.Therefore,chalcopyrite and pyrite have poor flotation separation selectivity in seawater.When 0.05 vol.%H₂O₂ was used as the inhibitor,the flotation recovery of chalcopyrite in seawater changed insignificantly,but the flotation recovery of pyrite in seawater was greatly reduced.The recovery of pyrite under these three conditions was in the order of pure water>sea water>sea water+0.05 vol.%H₂O₂.The flotation recovery of chalcopyrite did not change much under these conditions,showing a good selectivity,mainly due to the different sensitivity of chalcopyrite and pyrite to oxidation reaction.The experimental results showed that the oxidant H₂O₂ can effectively achieve the flotation separation of chalcopyrite and pyrite.In addition,the seawater environment can promote the oxidation of pyrite by H₂O₂,which is beneficial to improve the separation efficiency of the agent and reduce the dosage of the agent.The contact angle analysis shows that the contact angle of pyrite is significantly reduced after being oxidized by seawater and H₂O₂,suggesting that the surface hydrophobicity of oxidized pyrite is greatly reduced.Based on the FTIR and UV-Vis spectroscopy analyses,the adsorption of xanthate on the surface of pyrite decreased significantly after oxidation,while the adsorption of xanthate on the surface of chalcopyrite decreased insignificantly,indicating that H₂O₂ can selectively hinder the adsorption of xanthate on pyrite surface.The microcalorimetric analysis shows that the reaction rate（k）of the reaction between H₂O₂ and pyrite is larger than that of chalcopyrite,indicating a higher reaction rate on pyrite due to H₂O₂.The apparent activation energy（E_a）,activation free energy（ΔG_≠^θ）and apparent activation enthalpy（ΔH_≠^θ）of the reaction of H₂O₂ with pyrite are smaller than those of chalcopyrite,indicating that H₂O₂ is more likely to react with pyrite.Based on XPS and DFT results,H₂O₂ was more likely to react with Fe sites on the surface of pyrite to form hydrophilic Fe₂O₃,Fe（OH）₃,Fe OOH and Fe₂（SO₄）₃.However,Fe on chalcopyrite surface was slightly dissolved,leaving a large number of hydrophobic S₂^2-,S_n^2-,and S⁰,which improved the recovery.Since xanthate was mainly adsorbed on Cu on chalcopyrite surface and Fe on pyrite surface,H₂O₂ oxidation can form hydrophilic O^2-,OH^-,SO₃^2-and SO₄^2-groups,hindering the adsorption of xanthate on Fe sites.In contrast,the adsorption of xanthate at Cu sites on chalcopyrite surface was not hindered.Therefore,the selective flotation separation of chalcopyrite and pyrite was realized.