| Pyrite is the carrier mineral of non-leached gold in cyanide tailings,which can be enriched and recovered by flotation of pyrite.However,pyrite has been deeply depressed by cyanide,and it’s difficult to obtain ideal technical indexes by using conventional flotation process and reagent system.The effects of cyanide leaching on the surface properties of pyrite were analyzed by using single mineral flotation and four electrochemical testing techniques,including cyclic voltammetry,steady-state polarization,open-circuit potential and electrochemical impedance spectroscopy.Similarly,The effects of CN-and[Fe(CN)6]4-,[Fe(CN)6]3-which are the reaction products of CN and pyrite on the flotability and electrochemical behavior of pyrite were further studied in the condition of actual flotation pulp of cyanide leaching residue.Eventually,the surface reaction products of CN-and pyrite were characterized by Raman spectroscopy and XPS.The main reasons for the depression of pyrite flotation in cyanide-containing solution system were clarified.A combined reagent which can remove the strong depression of cyanide on pyrite was selected and a undepressing activation flotation process was developed.It can provide theoretical basis and technical reference for the recovery of pyrite from cyanide tailings by flotation.The flotability of pyrite can be strongly depressed by cyanide leaching process.And the flotation recovery rate of pyrite was only 0.46%when concentration of NaCN was 0.1 wt.%and leaching time was 36 h.The order of depression effect of CN-,[Fe(CN)6]3-and[Fe(CN)6]4-on pyrite flotation is CN->[Fe(CN)6]3->[Fe(CN)6]4-and deep depression of pyrite can be achieved by CN-at very low concentration of 4.0 × 10-5 mo1·L-1.CN-can reduce the spontaneity and reaction rate of oxidation on the surface of pyrite and increase the reaction resistance of interface electrochemistry during cyanide leaching.There are differences in the mechanism of cyanide species depressing xanthate adsorption and oxidation on pyrite surface.CN-reduces the oxidation rate of xanthate by inhibiting the reduction reaction of oxygen on mineral surface,[Fe(CN)6]3-directly depresses the oxidation of xanthate to dixanthate and[Fe(CN)6]4-has no significant effect on the oxidation of xanthate.It indicates that the[Fe(CN)6]3-and[Fe(CN)6]4-produced by the reaction of CN-with pyrite are not the main reasons for the deep depression of pyrite in cyanide-containing solution.The results of Raman spectrum and XPS analysis showed that hydrophilic Prussian blue generally considered to be the cause of strong inhibition of xanthate flotation was not detected on the surface of pyrite,which was related to the easy desorption from the surface of pyrite and its solubility in alkaline solution.Therefore,Prussian blue is difficult to hinder the adsorption and oxidation of xanthate on mineral surface and make pyrite hydrophilic.Free cyanide should be responsible for the depression of pyrite flotation using xanthate as collector.An undepressing activation flotation process was developed.Destroying the depression effect of pyrite flotation by cyanide was the best when FeCl2 and FeCl3 were used together as undepressor and the molar concentration ratio of actual addition to theoretical calculation was 2.6,the recovery rate of pyrite was increased from 4.73%to 56.72%.Furthermore,the recovery rate of pyrite can be increased to 70.06%with copper sulfate and ammonium oxalate used as activators,whose addition respectively were 2.0×10-4 mol-L-1,3.0×10-4 mol·L-1.Furthermore,the recovery rate of pyrite flotation is increased by 30.06 percentage points compared with the traditional process of sulfuric acid removing cyanide&copper sulfate activating pyrite and the flotation recovery of pyrite under alkaline pulp conditions was realized successfully. |
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