Separation And Extraction Of Gold From Pyrite Concentrate

Pyrite is a typical mineral containing gold. In nonferrous metal concentrators,pyrite concentrate is usually called as sulphur concentrate. The gold contained insulphur concentrate performs as microscopic gold, submicroscopic gold and latticegold. The separation and recovery of gold from sulphur concentrate become more andmore important in gold processing, although it is difficult to get a satisfactory result.The sulphur concentrate sample used in the tests of this paper was obtainedfrom a nonferrous metal company in Chenzhou city, Hunan Province. The grade of Au,S and Fe in the sample are3.65g/t,35.68%and29.24%, respectively. XRD analysisshows that the gold minerals are mainly composed of gold sulfide, gold oxide, andsilicate gold. For the extraction of the gold in the sample, it is necessary to destroy thecrystal structure of the pyrite, so that the gold minerals can be fully liberated from thegangue. Three pretreatment methods are investigated, including oxidizingroasting-acid dissolution, acid oxidation, and alkali oxidation with aeration. After thepretreatment of the sulphur concentrate, the leaching of gold can be carried out usingsome leaching agents.The optimum parameters of the oxidizing roasting-acid dissolution technique areas follows: roasting temperature700℃, roasting time3h, dissolution at roomtemperature, liquid to solid ratio2mL/g, sulfuric acid dosage20%of the roastedmineral, dissolution time8h. Under this condition, a gold concentrate is obtainedwith the gold grade of6.79g/t, the concentrate yield and gold recovery are52.4%and100.0%, repectively. Then, gold leaching is carried out with the roasted goldconcentrate as a sample under the following condition: room temperature, leachingagent0.04%, leaching time12h, liquid to solid ratio3mL/g, pulp pH value11,stirring speed400r/min. The leaching efficiency of gold is89.6%.The optimum parameters of the acid oxidation technique are as follows:grinding fineness95%-200mesh, reaction temperature95℃, reaction time8h,liquid to solid ratio6mL/g, stirring speed400r/min, the dosages of Fe3+, hydrogenperoxide and sulfuric acid are50%,120%and100%of the theoretical amount,repectively. Under this condition, a gold concentrate is obtained with the gold gradeof9g/t. Then, gold leaching is carried out, the leaching efficiency of gold is87.4%.The optimum parameters of the alkali oxidation with aeration technique are asfollows: stirring and aeration reaction at room temperature, reaction time7d, grinding fineness95%-200mesh, the dosage of NaOH is100%of the theoretical amount,liquid to solid ratio3mL/g. Under this condition, a gold concentrate is obtained withthe gold grade of6.71g/t, the gold recovery is96.35%. Then, gold leaching is carriedout, the leaching efficiency of gold is82.2%.