Research On Magnesium Inhibition Mechanism Of Composite Adjustors In Flotation Of Copper And Nickel Sulfide Ore

Nickel is an extremely important strategic metal.In China,nickel ore resources mainly exist as low grade copper and nickel sulfide ore,which contains a lot of magnesium silicate minerals such as serpentine,chlorite and talc.These minerals seriously disturb the flotation of copper and nickel sulfide ore and increase MgO content of flotation concentrate and bring troubles to the subsequent smelting process.Flotation magnesium reduction has been a technical problem to the copper and nickel sulfide ore dressing foa longtime.It is of great theoretical guiding value for national nickel production practice to conduct research on effective inhibitors of magnesium silicate minerals in copper and nickel sulfide ore flotation.This paper took 3 kinds of copper and nickel sulfide minerals（pentlandite,chalcopyrite and pyrite）and 3 kinds of magnesium silicate minerals（serpentine,chlorite and talc）as research objects.The activation mechanism of Cu²⁺,Ni²⁺ ions to serpentine and chlorite and deactivation by complexing agent,the activation mechanism of complexing agent to sufide ores,the function of phosphate and silicate adjustors to flotation separation of serpentine and copper and nickel sulfide minerals and the depression mechanism of polysaccharide inhibitors with different structures to talc were systematically investigated through single mineral flotation,Zeta potential,IR,XPS and adsorption amount measurements.Based on these,the flotation experiments of artificial mixing minerals and Jinchuan real ores were carried out.The research results showed that complexing agent has a dual-function to the flotation of copper and nickel sulfide ore:Firstly,serpentine and chlorite had low natural floatabilities;however,they were easily activated by Cu²⁺,Ni²⁺ ions.Hydrophobic species such as CUX₂ and NiX₂ were formed on the surface of serpentine and chlorite,which made them more floatable;By reacted with complexing agent Cu²⁺,Ni²⁺ ions were transformed to stable soluble complex compounds,which would eliminate the activation effct of Cu²⁺,Ni²⁺ ions to flotation of serpentine and chlorite and make them depressed.Secondly,hydrophilic hydroxide film was formed on the surface of oxidized sulfide minerals,which decreased the floatability and flotation speed of sulfide minerals.The complexing agent was able to remove the hydrophilic hydroxide film,increase the surface hydrophobicity of sulfide minerals and activate their flotation.Serpentine had dual influences on the flotation of copper and nickel sulfide ore:Firstly,it decreased the flotation recovery of copper and nickel sulfide minerals;Secondly,it increased the MgO content of copper and nickel flotation concentrate.The reason was that during the flotation pH range,the surface charge of serpentine was positive whereas those of pentlandite and chalcopyrite were both negative.The interaction energies between serpentine and pentlandite,chalcopyrite were negative,which made them attracted to each other to form heterocoagulation.Consequencely serpentine was easily to form coverage on the surface of pentlandite and chalcopyrite.Small coverage would make serpentine float up with pentlandite and chalcopyrite to mix in the concentrate;heavy coverage would decrease the surface hydrophobicity of sulfide minerals and depress pentlandite and chalcopyrite.By treated with phosphate adjustors the Zeta potentials of serpentine and pentlandite,chalcopyrite were decreased to negative.The repulsive effect between the different minerals would eliminate the heterocoagulation,thus eliminate the adverse effect of serpentine to the flotation of copper and nickel sulfide ore.Guar gum had the strongest inhibiting effect to talc among the used polysaccharide inhibitors.Inhibitor/collector adding order had a great influence on the flotation separation between talc and copper and nickel sulfide minerals.Talc and copper and nickel sulfide minerals both could be depressed by adding inhibitor firstly and then collector;however,talc could be inhibited selectively;meanwhile the inhibiting effect to copper and nickel sulfide minerals could be reduced by adding collector firstly and then inhibitor,which was beneficial to the flotation separation between talc and copper and nickel sulfide minerals.The flotation result of artificial mixing minerals showed:When the magnesium silicate minerals in the feeding were mainly serpentine and chlorite and the content of talc was low,citric acid-sodium hexametaphosphate should be used as the composite adjustor;when the talc content was high,citric acid-sodium hexametaphosphate-guar gum should be used as the composite adjustor,additionally guar gum should be added after butyl xanthate.The flotation result of Jinchuan copper and nickel sulfide real ore showed:Compared with the flotation index using the plant reagent regime,the recoveries ofNi,Cu in the flotation concentrate could be increased by 1.52 and 1.77 percents,respectively,and the MgO content could be decreased by 1.34 percent by using citric acid-sodium hexametaphosphate as composite adjustor.The MgO content in flotation concentrate was decreased below 6.5%and met the quality requirement of smelting plant to the flotation concentrate.