| Under current economic and technological conditions,the main copper oxide minerals with industrial value are malachite,chrysocolla,and cuprite.Among these,cuprite has the highest theoretical copper content,and it is often associated with malachite and other copper-bearing minerals.Conventional sulfidization flotation is not an ideal method for the collection of chrysocolla and cuprite,and it is difficult to ensure that effective recovery of copper mineral resources is achieved.This causes serious obstacles in the efficient comprehensive recovery and utilization of copper oxide resources.For cuprite-containing copper oxide ores,the lack of effective methods for cuprite recovery leads to loss of a large amount of cuprite in the tailings.This results in a significant decrease in the recovery of copper concentrate,which decreases the economic viability of such processes.To overcome the difficulties associated with cuprite sulfidization and recovery in industrial production,a technique that can be described as enhanced sulfidization–xanthate flotation of cuprite by pre-oxidation and sulfidization is proposed.Cuprite was the subject of this study.The techniques used were quantum chemical calculations,inductively coupled plasma-mass spectrometry,zeta potential measurements,surface adsorption measurements,infrared spectroscopy,X-ray photoelectron spectroscopy,and micro-flotation tests.The characteristics of the adsorption of sulfide species and collectors on the cuprite surface,the crystal and surface electronic structural properties of ideal cuprite,the form of sulfide products present on the cuprite surface in the direct sulfidization system,the rules for attenuation of sulfide ions in the cuprite pulp,the effect of sulfidization on xanthate adsorption on the cuprite surface,the sulfidization characteristics and flotation mechanism of cuprite in the direct sulfidization system,and the effect of oxidation on the surface properties of cuprite were investigated.The effects of the oxidant type and concentration on the flotation behavior of cuprite,the effect of pre-oxidation on the surface sulfidization of cuprite,and the effect of pre-oxidation–sulfidization on xanthate adsorption on the cuprite surface were also investigated.The results of this innovative research are as follows.A higher cuprite recovery was achieved with sulfidization–xanthate flotation than with direct xanthate flotation.Surface sulfidization enhanced xanthate adsorption on the cuprite surface.Under conditions similar to those used for flotation recovery of cuprite,the amount of collector required after sulfidization was lower.After sulfidization,various sulfur species were detected on the cuprite surface.The copper sulfide species present on the cuprite surface were mainly responsible for promoting subsequent collector adsorption on the cuprite surface.The results of quantum chemical calculations showed that HS~-could spontaneously react with Cu atoms on the(111)surface of cuprite,and HS~-could interact with the(111)surface of cuprite via chemical adsorption.However,nearly 40%of the cuprite was still lost in the tailings in the direct sulfidization–xanthate flotation system.Pre-oxidation treatment with sodium hypochlorite as the oxidant greatly improved the flotation recovery of cuprite compared with that achieved by direct sulfidization–xanthate flotation.When the same concentrations of sodium sulfide and xanthate were used,the flotation recovery of cuprite in the pre-oxidation–sulfidization–xanthate flotation system was greater than 85%.The pre-oxidation–sulfidization technique significantly improved the flotation behavior of cuprite,and the flotation recovery increased by 24.97%compared with that achieved by direct sulfidization–xanthate flotation.The cuprite surface is composed of Cu(Ⅰ)species and oxygen species.The concentration of copper atoms on the cuprite surface is higher than those on malachite and chrysocolla surfaces.However,the affinity between the Cu(Ⅰ)species on the cuprite surface and sulfide ions is weaker than those between sulfide ions and the Cu(Ⅱ)species on the surfaces of malachite and chrysocolla.Sufficient sulfidization of the cuprite surface is therefore difficult.The density of states near the Fermi level of the Cu atom clearly increased after oxidation of the Cu(Ⅰ)species on the(111)surface of cuprite,and the Cu atom reactivity was enhanced.After pre-oxidation,the proportion of Cu(Ⅱ)species on the cuprite surface increased from 46.92%to 64.77%.The newly generated Cu(Ⅱ)species have a stronger ability to lose electrons and are more likely to interact with sulfide ions in the pulp through oxidation–reduction reactions.This creates favorable conditions for subsequent adsorption of sulfide ions and generation of copper sulfide species on the cuprite surface.Pre-oxidation and sulfidization treatments increased the amount of copper sulfide particles on the cuprite surface,and the copper sulfide particles were compact and uniform.The results of semi-quantitative elemental analysis showed that the atomic concentration of sulfur on the cuprite surface increased from 15.96%to 19.54%,i.e.,the newly generated Cu(Ⅱ)species showed a stronger chemical affinity for sulfide ions in the pulp,and this promoted the formation of copper sulfide species on the cuprite surface.In addition,quantum chemical calculations showed that the Cu(Ⅰ)species on the(1 1 1)surface of cuprite were oxidized to Cu(Ⅱ)species,the adsorption energy of HS~-on the(1 1 1)surface of cuprite decreased from-117.91 to-465.36 k J/mol,and the Cu–S bond length changed from 2.34 to 2.27(?),i.e.,the stability of the Cu–S structures on the cuprite surface was effectively enhanced.Pre-oxidation–sulfidization treatment increased the amount of copper sulfide on the cuprite surface,and the amount of xanthate species also increased.The characteristic absorption peak for xanthate appeared in the infrared spectrum of the cuprite surface was more obvious.This shows that the adsorption of xanthate species on the cuprite surface was improved.This effectively enhanced the hydrophobicity of the cuprite surface,and a more ideal flotation recovery of cuprite was achieved.Pre-oxidation treatment therefore promoted the conversion of Cu(Ⅰ)species to Cu(Ⅱ)species on the cuprite surface and enhanced the reactivity of copper species and sulfide ions.This led to enhanced sulfidization flotation of cuprite.In the conventional cuprite sulfidization–xanthate flotation system,surface sulfidization of cuprite is insufficient,and effective interaction between the collector and the mineral surface is difficult.However,in the pre-oxidation–sulfidization–xanthate flotation of cuprite,the cuprite surface can be fully sulfidized.This enhances xanthate adsorption on the cuprite surface,which greatly improves the flotation behavior of cuprite.These results provide a theoretical and technical basis for achieving efficient flotation recovery of copper from cuprite-containing copper oxide resources. |
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