Technology And Basic Research On Extracting Vanadium And Gold From Vanadium-bearing Carbonaceous Gold Ore By Chlorination Roasting Process

Carbonaceous gold ores account for an important proportion in China's gold reserves.In addition to high carbon content in the ores,the content of elements such as vanadium,calcium,lead,arsenic,potassium,gallium,phosphorus,sulfur,thallium and barium,is also relatively high.When carbonaceous gold ores are associate with valuable metals,conventional cyanide leaching process is difficult to achieve synchronous recovery of gold and associated valuable metals.In addition,after pretreatment,cyanidation,thiosulfate,thiourea and other Au extraction methods can realize the extraction of gold,but it is difficult to realize the simultaneous recovery of the associated metals.This paper took the vanadium-bearing carbonaceous gold ore as the research object,realized the simultaneous extraction of vanadium and gold using a chlorination roasting method through the addition of solid chlorination reagent.In the process,the metal element and chlorine element in the chlorinating reagent were used to volatilize gold in the form of gold chloride,the vanadium was converted into the corresponding soluble vanadate,and vanadium was enriched and recovered by leaching-extraction process.Thermodynamic studies showed that,the priority order of chlorination reaction of mineral components was ZnS>FeS2>ZnO>Au>Fe2O3>V2O3>V2O5.Compared with the chlorination reaction,FeS2 was more prone to oxidation reaction to produce SO2 and the corresponding iron oxide.Only with the participation of O2,the solid chlorinating reagent could not be directly heated to desorb Cl2,and simultaneously it could not directly react with gold.The chlorination reaction of gold required a solid chlorination reagent to react with the material components in the ore to produce Cl2.The sulfide and vanadium oxide in the ore could promote the decomposition of the chlorinating reagent and generated the corresponding sulfate,vanadate and chlorine gas.The mechanism of chlorination-volatilization process of gold was explained as follows.During low-temperature roasting(below 600?)stage,the chlorine-making reaction between sulfide ore and sodium chloride could be divided into two ways.One was that sulfide ore directly reacted with sodium chloride to generate Cl2.The other one was that sulfide ore undergone oxidation reaction to produce intermediate product-SO2,and SO2 and NaCl reacted to generate Cl2.The chlorination reaction occurred between Cl2 produced by the two and gold.The crystal structure of mica was not destroyed at the roasting temperature,and the vanadium in mica could not contact with NaCl to participate in the reaction.In the high-temperature roasting(above 600?)stage,the crystal structure of mica was destroyed,vanadium and NaCl were oxidized,and the high-value vanadium combined with sodium was converted into water-soluble sodium vanadate to generate Cl2 and complete the chlorination reaction.Through the optimization process comparison of different chlorinating additives(NaCl,CaCl2),the chlorinated roasting-water leaching process for extracting gold and vanadium with NaCl as the additive was determined.The optimal conditions of chlorination roasting process were NaCl dosage of 10 wt%,roasting temperature of 800?,roasting time of 4 h,and air flow rate of 1 L/min.The optimal conditions of water leaching were liquid-solid ratio of 10:1,stirring speed of 500 r/min,leaching temperature of 80? and leaching time of 4 h,and the volatilization ratio of gold and the leaching ratio of vanadium were 92.01%and 85.34%,respectively.The kinetic study of the chlorination-volatilization process of gold showed that the chlorination volatilization of gold was controlled by a chemical reaction,and the apparent activation energy was 40.61 kJ/mol.Chlorination roasting process could realize the synchronous volatilization of zinc and gold.The kinetic study of vanadium leaching process showed that the vanadium leaching process was controlled by solid film diffusion,and the apparent activation energy was 15.74 kJ/mol.Through the comparison experiments of the optimized process of different extractants,the optimal process for synergistic extracting vanadium with mixed extractants(P507-N235)was determined.Under the optimal conditions of extraction temperature of 25?,extraction time of 8 min,pH value of 2,extraction concentration of 20%(v/v),P235:P507=1:2(v/v)and O/A ratio of 2:1,the vanadium(V)-loaded organic phase was obtained after three stages of countercurrent extraction experiments.Under the conditions of H2SO4 dosage of 2 mol/L and O/A ratio of 2:1,a three-stage countercurrent extraction experiment of the vanadium(V)-loaded organic phase was carried out,which could achieve 98.56%vanadium(V)extraction.The maximum cooperative extraction coefficient(R)of P507-N235 mixed extractants was 2.21,namely that,the mixed extractants had a synergistic extraction effect on vanadium.Through process comparison and optimized condition experiments,the process of chlorinating roasting for extracting gold-water leaching-cooperative extraction of vanadium with sodium chloride as additive and P507-N235 as mixed extractants was finally determined,which effectively realized the separation and extraction of gold and vanadium.The volatilization ratio of gold was 92.01%and the recovery ratio of vanadium was 84.11%.Chlorination roasting method can overcome the shortcomings of conventional cyanidation leaching,thiourea method,thiosulfate method,carbon chloride method and so on.Compared with cyanidation method,this method can realize the comprehensive recovery of multi-metals and comprehensively utilize the anions and cations in chlorination reagent.The process of extracting vanadium and gold from vanadium-bearing carbonaceous gold ore by chlorination roasting provides a new technical reference for the recovery and utilization of such mineral resources.