Research On The Effect And Regulation Mechanism Of Pyrite And Arsenic, Nickel And Lead On Thiosulfate Gold Leaching

With the continuing decline of reserves of easily-processed gold mine and the increasingly strict environmental protection requirements,it is imperative to research and develop non-toxic and eco-friendly gold extraction technology suitable for complex ore.The gold extraction method of thiosulfate is considered as the green gold extraction technology with the most industrialized application prospect due to being non-toxic,efficient,eco-friendly,and suitable for processing complex ore.However,both the high consumption of thiosulfate and the passivation of gold severely restrict the industrialization pace of the gold extraction process.The"Cu²⁺-en-S₂O₃^2-"gold leaching system established in our previous research significantly reduced the reagent consumption.But the mechanism of action of associated minerals and metal impurities in oxygenolysis of leaching reagents and oxidation dissolution of gold in this system is still unknown,so it is difficult to achieve effective control.In this paper,for"Cu²⁺-en-S₂O₃^2-"system,the influence of the pyrite containing single impurity such as arsenic,nickel or lead single impurity component and nickel-lead impurity element on the gold leaching process and its mechanism were researched.Firstly,pure-phase cube pyrite,nickel-bearing pyrite and lead-bearing pyrite with high purity were synthesized by hydrothermal method.The nickeliferous pyrite and lead-bearing pyrite form by controlling the doping contents of nickel or lead in synthetic process,and the absorption spectrum,forbidden bandwidth and photocatalytic degradation nature of pure phase pyrite and nickeliferous pyrite are discussed.The discussion results show that absorption spectrum and forbidden bandwidth of pure phase pyrite have little difference with those of natural pyrite,which indicates that the semi-conductive property of synthetic pure phase pyrite is close to that of natural pyrite.With the increase of impurity contents,the light-induced catalytic action and light absorption performance of the nickeliferous pyrite and lead-bearing pyrite enhance.Secondly,in the gold leaching experiment of"Cu²⁺-en-S₂O₃^2-"gold leaching system,natural arsenic bearing pyrite plays a passivation role in the gold dissolution,and plays a catalytic degradation role in the thiosulfate.The natural arsenic bearing pyrite's particle size,system's oxygenation capacity,light,etc.are changed for the specific research of the rules between arsenic bearing pyrite and gold dissolution and of the absorption action of Au(S₂O₃)₂^3-.The research results show that the pyrite with fraction size between-0.106 mm and+0.074 mm plays a minimum role in passivation of dissolved gold and absorption of Au(S₂O₃)₂^3-;In the continuous oxygenation or illumination condition,natural arsenic bearing pyrite would accelerate the decomposition of thiosulfate and inhibit the dissolution of gold.Then the influence of the impurities in nickeliferous pyrite and lead-bearing pyrite in this system on the catalytic degradation property of light is explored,based on which the influence of above two kinds of impure pyrite on the dissolution of gold,oxygenolysis of thiosulfate and absorption of Au(S₂O₃)₂^3-is researched.The research results indicate that,with the increase of contents of nickel and lead impurities in pyrite,its inhibiting effect of gold dissolution,catalytic degradation of thiosulfate and absorption of Au(S₂O₃)₂^3-would increase.With the increase of the nickel doping content,the nickeliferous pyrite's forbidden bandwidth will gradually decrease.As a result,more electron hole pairs generate on the surface of nickeliferous pyrite,which promotes great decomposition of thiosulfate.Besides,with the decrease of forbidden bandwidth,the photocatalytic degradation rate of nickeliferous pyrite increases,which certifies that catalytic degradation of thiosulfate is related to the semiconductor property of pyrite,especially the light-induced catalytic action.The influence of nickel ion,lead ion and pyrite on"Cu²⁺-en-S₂O₃^2-"system gold leaching is researched.The research results indicate that in this system,nickel ion will inhibit the dissolution of gold and increase the consumption of thiosulfate.Nickel ion inhibits gold leaching mainly because the nickel ion can form stable Ni(en)₂²⁺with en complexation,promote Cu(II)to transform into Cu(?),and consume lots of thiosulfates.The nickel ion with different concentrations is added to this system containing natural arsenic bearing pyrite,which can effectively eliminate the passivation of arsenic bearing pyrite in gold dissolution and promote the dissolution of gold with concentration increasing to 22.5mg/L.The reason is that the nickel ion weakens even eliminates the pyrite's role in acceleration of copper-bearing sulfide layer on the surface of gold,then copper-bearing sulfide layer is mostly absorbed on the surface of pyrite.The lead ion with appropriate concentration is added to"Cu²⁺-en-S₂O₃^2-"system,then the lead dioxide spots and part of gold exposed would form Pb O₂/Au micro-battery,thus promoting the dissolution of gold and inhibiting the consumption of extra thiosulfate.The lead ion with different concentration is added to the system containing natural arsenic bearing pyrite,which can effectively eliminate the arsenic bearing pyrite's role in passivation of gold dissolution and promote the dissolution of gold with concentration increasing to 21.75mg/L,and promote the catalytic decomposition of thiosulfate.Eventually,the role of hole-electronic clearing agent in the hole-electron pairs concentration caused by impurity level on the surface of arsenic bearing pyrite,is researched to screen the electron and hole scavenger which can effectively reduce the pyrite's role in catalytic decomposition of thiosulfate,such as potassium chloride,potassium acetate,potassium chloride,sodium oxalate,methanol,etc.The above hole and electron scavenger conduct gold leaching after preprocessing of pyrite,which can obviously reduce the pyrite's role in inhibition of gold dissolution and in catalytic degradation of thiosulfate.The above conclusions provide the reference about theoretical and experimental methods for researching the influence of pyrite on semi-stable gold leaching reagent and eliminating the pyrite role in passivation of gold.