Removal Of Thallium From Lead Sulfide Concentrate

Thallium is a kind of toxic and scattered heavy metal,often embedded in galena,sphalerite,pyrite,stibnite,chalcopyrite,cinnabar,and other sulfideminerals.In the process of beneficiation,a part of thallium in lead-zinc sulfide ore will be enriched in lead concentrate,and release from lead concentrate in smelting process,causing environment pollution.Therefore,finding technologies to remove thallium from lead concentrate is clearly an important issue in non-ferrous metals industry.However,to the best of our knowledge,thallium removal technology for lead concentrate has not been reported to date.In this study,lead sulfide concentrate from Hunan Baoshan non-ferrous metals industry was selected as research object,the grade of thallium was 48.75 g/t.BCR shows that about 72.6% thallium are occurrence in oxidation states of ore samples.According to different combination of thalliumin lead concentrate,this paper introduced three kinds of technologiesto remove thallium: direct acid leaching,oxidant-acid leaching and Alkaline oxidation pretreatment-acid leaching technology,the feasibility and optimum conditions were discussed.(1)Direct acid leaching technology is not optimal for thallium removal.The experiment results show that removal rate were fairly low,with only 18.5% in optimum condition: particle size-0.074 mm 90%,dosage of sulfuric acid 5%,leaching temperature 60 ?,leaching time 8 h.Adding NaCl to leaching system could shorten leaching time and improveremoval rate to 23.1%,but couldn't meet the requirements of the smelter.(2)In the experimental study onoxidant-acid leaching technology,sodium hypochlorite,sodium chlorate,ferric sulfate and ferric chloride were selected as oxidants,according to the results,removal rate of thallium were 36.1%?50.2%?22.2% and 27.4%,respectively,under best experimental conditions.Using sodium chlorate as pretreatment oxidant could obtain better removal rate,but the recovery of lead is reduced,about 79.8%.(3)However,through Alkaline oxidation pretreatment-acid leaching processes,the removal rate of thallium could reach up to 83.4%.The best experimental conditions: particle size-0.074 mm 90%,NaOH dosage 5%,inflation rate 1.25 L/min,pulp concentration 20%,oxidation temperature 50 ?,basic oxidation 32 h,dosage of sulfuric acid 12%,leaching temperature 40 ? and leaching time 3.5 h.The thallium grade in thallium removed sulfide concentrates is 8.06 g/t,the grade and recovery of lead are 61.9% and 96.9%,respectively,which are fully meet the requirements of the smelter.