Effect Of Sphalerite Iron Content On Its Flotation And Separation From Pyrite

Zinc sulfide minerals are the main raw materials for extracting zinc metal resources in the industry,among which marmatite resources occupy an important position.China is rich in marmatite resources and a large number of rare and precious metals are associated with it,so it is of great significance to carry out research on its separation and recovery.When iron atoms replace some of the zinc atoms in the crystal lattice of sphalerite,its physical and chemical properties are significantly affected,and the surface properties and flotation behavior also change.The marmatite is difficult to be activated by copper,poor in adsorption activity with xanthate,severely depressed under alkaline conditions,and difficult to be efficiently separated from pyrite.However,these problems have not yet been systematically and effectively solved.Therefore,this paper takes sphalerite with different iron content as research object.Firstly,influence of the iron content of sphalerite on its flotation behavior and reagent adsorption under copper activation and butyl xanthate collection have been investigated through pure mineral flotation research and reagent adsorption measurement.On this basis,the effect of iron content on the surface oxidation of sphalerite,the selectivity of copper activation in the mixed minerals system,and the selectivity of depression under high alkali and high calcium environment have been investigated through contact angle measurement,dissolution measurement,EDTA selective extraction,XPS analysis,FESEM-EDS analysis,TOF-SIMS analysis,electrochemical research,etc.Three exploration directions to improve the flotation separation of sphalerite and pyrite are proposed: developing processes under non-high alkali environment,improving the selectivity of copper activation,and achieving selective depression of pyrite.Finally,studies are carried out to optimize the separation of sphalerite and pyrite by regulating the selectivity of copper activation through ammonium chloride under low alkalinity and realizing selective depression of pyrite under non-high alkalinity,and which achieved good results.Pure mineral flotation and reagent adsorption studies show that iron substitution reduces the natural floatability of sphalerite,the floatability of sphalerite under butyl xanthate collection and the floatability of sphalerite under copper activation and butyl xanthate collection.The hindering effect of iron substitution on the xanthate adsorption process of sphalerite is the reason for the deterioration of its flotation.The increase in alkalinity and the use of calcium oxide highlight the adverse effects of iron substitution on the xanthate adsorption and flotation of sphalerite.The flotation of high-iron sphalerite is severely depressed under a high-alkali environment adjusted by calcium oxide.Studies on the surface oxidation of sphalerite show that sphalerite oxidizes slowly in the air and oxidizes to a certain extent in the slurry,and the activity and degree of oxidation of sphalerite increase with its iron content.The increase in the iron content of sphalerite leads to aggravation of its surface oxidation,which brings about differences in surface dissolution,composition and morphology of surface oxidation product,surface hydrophobicity and flotation behavior.Under acidic conditions,a greater degree of oxidation of sphalerite is manifested by increased surface dissolution,higher surface sulfur enrichment,and increased surface natural hydrophobicity after oxidation.Under high alkalinity,as the iron content increases,the surface dissolution of sphalerite increases,more metal oxides/hydroxides and metal hydroxylases anions are adsorbed on the sphalerite surface,the morphology of surface oxidation products changes significantly,the natural hydrophobicity decreases and the decline in flotation recovery after oxidation has increased.The mixed mineral flotation test shows that copper activation and butyl xanthate collection can only achieve flotation separation of sphalerite and pyrite under high alkalinity,and as the iron content of sphalerite increases,the separation effect decreases significantly.The environment adjusted by calcium oxide significantly depresses the flotation of marmatite,and further reduces the separation effect of marmatite and pyrite.Under high alkaline conditions,the marmatite cannot be separated from pyrite through flotation.The adsorption of copper on the surface of sphalerite and pyrite is selective in acidity and neutrality,and unselective in alkaline conditions.The adsorption of butyl xanthate on the surface of copper-activated sphalerite and copper-activated pyrite has certain selectivity,and the selectivity decreases with the increase of the iron content of the sphalerite.There are two essential differences in the copper activation process between sphalerite and pyrite: regardless of acid or alkali,regardless of the level of iron content,the copper activation process of sphalerite follows the ion exchange mechanism between copper and zinc,while the copper activation process of pyrite does not undergo copper-iron ion exchange;copper ions can penetrate into the interior of sphalerite crystal lattice,while copper is only adsorbed on the surface of pyrite.Iron substitution has a certain impact on the copper activation process of marmatite: the iron atoms on the surface of sphalerite cannot be exchanged with copper ions,and iron substitution promotes the process of copper ions infiltrating into the sphalerite crystals.The essential difference in the copper activation process between sphalerite and pyrite reflects the significant difference in the adsorption strength of copper ions on the surface of the two minerals,which creates good conditions for regulating the selectivity of copper activation of the two minerals.Under high alkalinity,the adsorption of calcium and iron hydroxide on the surface of sphalerite and pyrite has certain selectivity.However,as the iron content of sphalerite increases,the surface adsorption selectivity of the two substances decreases significantly,which is the essential reason for the insufficient selectivity in depression under the high alkali and high calcium environment.The increase in the iron content of sphalerite leads to a decrease in the selectivity of copper activation,calcium depression and surface iron hydroxide adsorption,resulting in a decrease in the separation effect of sphalerite and pyrite under high alkali and high calcium environment.Based on this,the exploration direction to improve the flotation separation effect of sphalerite,especially high-iron sphalerite and pyrite under the copper activation and xanthate collection is proposed: developing separation process under low-alkalinity,improving selectivity of copper activation,and achieving selective depression of pyrite.Studies on the regulation of selectivity of copper activation by ammonium chloride show that under p H=9,ammonium chloride can strengthen the copper activation of sphalerite and weaken the copper activation of pyrite,thereby improving the separation effect of sphalerite and pyrite,but the separation effect still shows a downward trend as the iron content of sphalerite increases.Under low alkalinity,ammonium chloride mainly strengthens the copper activation of sphalerite through three ways: dissolving zinc hydroxide and promoting copper-zinc exchange through zinc-ammonia complexing,maintaining copper ion concentration through "storing","releasing" and "carrying" copper ion by copper ammonia complex ions.Ammonium chloride weakens copper activation of pyrite by maintaining the hydroxylation of the pyrite surface and ammonia molecules desorbing copper on the pyrite surface.Studies on the selective depression of pyrite under non-high alkalinity conditions show that calcium hypochlorite has good depression selectivity at p H=9/10.5,which can realize the flotation separation of sphalerite and pyrite.Combining the selective depression of calcium hypochlorite with the selective copper activation in the copper ammonia system can achieve a better flotation separation of sphalerite and pyrite under low alkalinity,but the adverse effect of the iron substitution of sphalerite on separation effect cannot be avoided.The difference in the degree of surface oxidation,the adsorption of zinc and iron hydroxides and the selectivity of calcium adsorption are the basis for the selective depression of calcium hypochlorite in the mixed minerals system of sphalerite and pyrite.Selectivity reduction in oxidation dissolution,zinc/iron hydroxide adsorption and calcium adsorption brought by the iron substitution of sphalerite are the essential cause of the decreased selectivity of depression of calcium hypochlorite.The research in this paper has proved the influence law and mechanism of the iron substitution of sphalerite on flotation separation of sphalerite and pyrite under copper activation and xanthate collection.This article clarifies the breakthrough direction to improve the flotation separation effect of sphalerite and pyrite,and conducts in-depth and effective research from two directions: regulating selectivity of copper activation and achieving selective depression of pyrite under non-high alkali environment.It has laid a theoretical foundation for systematically solving the problem of flotation separation of marmatite and pyrite.