The Size Effect Of Galena And Its Influence Mechanism On Lead-sulfur Flotation Separation

Yiliang lead-zinc mine is a representative deposit with a high content of pyrite,which has more than 85.66%sulfide mineral,and 52.75%is pyrite.The efficiency of the selective flotation between galena and pyrite can be affected by not only the high content of pyrite and closely embedded minerals,but also the interactions between sulfide minerals.In addition,most galena particles that lost in the pyrite concentrate are fine size grains due to the closely embedded minerals and the overgrinding of galena.Therefore,the present study was focused on the causes of fine galena particles loss and the effect of particle sizes on the separation between pyrite and galena,which can provide theoretical support to the efficient separation between pyrite and galena.The differences of flotation behavior,surface characteristics and collector sorption between coarse(-0.074+0.038mm),intermediate(-0.038+0.025mm)and fine(-0.025mm)size fractions of galena particles,and the effect of pyrite on the flotation behavior,surface characteristics and reagent adsorption of fine galena particles were conducted by flotation tests,dissolution tests,XPS analysis,sorption measurements and electrochemical measurements.Based on those studies,a reasonable process was adopted to achieve the efficient separation between pyrite and fine galena particles by adjusting the flotation flowsheet and reagent regime.The effect of particle size on the flotation behavior,surface oxidation and collectors sorption was investigated.Overall,smaller size of galena particle would be influenced easily by the pH of the pulp.Comparing with coarse and intermediate galena particles,the flotation recovery and flotation rate of fine galena particles was the lowest under the same conditions.Dissolution tests demonstrated that the amount of oxidation products increased with the decrease of particle sizes.The surface oxidization of galena was influenced by pH values,for low pH conditioning values(pH=7.3 and 9),the lead oxidation species on the galena surface were lead hydroxides.while for high conditioning pH values(pH=12),lead hydroxides and lead thiosulfates were formed in products of galena oxidation.Sorption measurement of ethyl xanthate and diethyldithiocarbamate illustrated that the sorption rate of collectors was the highest on the fine galena surface.The decreasing of particle sizes increases both the sorption rate of collector and the dissolution of galena,while the generation of hydrophilic product caused by dissolution is dominant,which rendering the fine galena particles hydrophilic.The effect of pyrite on the flotation behavior,surface oxidation and collector sorption was also conducted.Flotation recovery and flotation rate of three size fractions of galena particles decreased with the reduction of galena particles in the presence of pyrite,especially for the fine galena particles.Besides,the effect of pyrite on the flotation recovery of galena was enhanced by the reduction of particle sizes of pyrite.The electrochemical interaction between galena and pyrite enhanced the dissolution amount and Zeta potentials of galena particles.Although,there was no new product formed on the galena surface in the presence of pyrite,the addition of pyrite promoted the sorption and adsorption of lead hydroxides on the galena surface,which result in the decreasing sorption amount and sorption rate of collectors on the galena surface.The effect of pyrite on the flotation behavior,surface oxidation and collector sorption of fine galena particles was the greatest,which would enhance the difficulty of the separation between pyrite and fine galena particles.The effect of pyrite on the three size fractions of galena particles was conducted by electrochemical measurements.The results of the open circuit potential(OCP)indicated that the OCP difference was the greatest between pyrite and fine galena particles under the same condition,which indicated that the galvanic couple between pyrite and fine galena particles can be formed more easily.The galvanic interaction between pyrite and galena increased the corrosion current density of galena surface,but decreased the corrosion current density of pyrite surface through measurements of polarization curves.The cyclic voltammetry curves illustrated that the galvanic interaction between pyrite and galena decreased the sorption of collectors on the surface of fine galena particles in the presence of collectors.Moreover,comparing with using sodium hydroxide as pH regulator,the addition of lime increased the dissolution amount of Pb2+ and decreased the sorption amount and sorption rate of collectors on the galena surface.Employing lime as pH regulator also enhanced the galvanic interaction between pyrite and galena,which resulted in the decreasing the difference of floatability between galena and pyrite.Furthermore,in the presence of diethyldithiocarbamate,using lime was effective in separating pyrite and coarse and intermediate galena particles under high alkaline condition,but was unfavorable for the separation between pyrite and fine galena particles.The flotation tests of Pb-S bulk concentrate indicated that the method of asynchronous flotation was adopted,i.e.the flotation separation between pyrite and coarse and intermediate size fractions of galena particles through conventional flotation flowsheet,while the separation between pyrite and fine galena particles through employing oxidizing agent as the depressant of fine galena particles,to improve the total recovery of galena and achieve the successful separation between galena and pyrite,which would provide theoretical basis on recovering fine galena particles in high pyrite-bearing lead-zinc deposit.