| Many lead and zinc tailings contain a certain amount of useful metal elements,such as lead,silver,zinc,iron,copper,iron,etc.With the social development and resource consumption,more and more tailings will be produced.We can achieve better environmental and economic benefit,if recycling these valuable metals in the tailings.For these lead and zinc mines which are depleted,the development and utilization of those mine tailings is also an important channel to extricate from the situationThe Lead and Zinc mine tailings from Yunnan Huize has been analyzed,its main components included FeS2,ZnS,CaCO3,CaMg(CO3)2,KHSO4,PbS.The tailings contained a certain amount of substances which consumed acid easily.It has been found that the content of iron was 24.11%in the tailings,the content of zinc and lead was 2.4%and 2.01%,respectively,by the result of multi-element analysis.The content of zinc and lead both met the minimum industrial grade.This paper studied that leaching valuable metal Fe and Zn from lead and zinc tailings using chemical and microbial leaching method.The test on chemical static leaching of lead and zinc mine tailings was conducted with low concentration of sulfuric acid,the reaction of acid leaching was very severe in the beginning,the reaction of carbonate and sulfuric acid generated a lot of small bubbles,that consumed some acid.This paper studied the different particle size and different temperatures on the leaching rate.The lead and zinc mine tailings leaching test has been done for five particle grade including 60 mesh,80 mesh,100 mesh,140 mesh and 180mesh.It found that the leaching of tailings powder which was 60 mesh had the highest leaching rate of Zn and Fe after 7 hours,the leaching rate of Zn and Fe was 96%and 6.8%,respectively,the two metals leaching rate was lower as the particle size was bigger.Five different temperature leaching test showed that the influence of temperature on leaching rate of Zn was not obvious,the influence of temperature on leaching rate of Fe expressed as the leaching rate of Fe increased with the temperature rose.The result of chemical static leaching test with low concentration of sulfuric acid showed Zn was easy to leach from the lead and Zinc mine tailings and the leaching rate was quite high compared to Fe.The first step of bioleaching was to isolate the bioleaching bacteria from the original strains.The bioleaching bacteria was isolated and purified from sulfide ore acid mine drainage in the laboratory,the morphological and physiological characteristics of the bacteria had been studied,and the bioleaching bacteria has been identified.The tests results showed that the bioleaching bacteria been isolated was Acidithiobacillus thiooxidans,it was gram-negative bacteria and obligate autotroph.The size of bacteria was 0.5?m × 1.2?m,its optimum growth temperature was 30?and optimum initial pH was 2.0.It has been acclimatied the isolated bacteria,gradually reduced the S powder content in the culture medium,and increasd the amount of tailings,cultured and passaged for three times,in order to make the bacteria adapt to the leaching environment.The oxidation activity of domesticated bacteria has been studied when the domestication completed.The results showed that the adaptability and acid production of the bacteria increased capacity.After 7 days of culture,the pH decreased from 2.0 to 1.62.In order to improve the efficiency of microbial leaching,ultra-violet ray mutation breeding was used to Thiobacillus thiooxidans isolated.It was found that the strains which had been radiated in different times has significant differences in the oxidation activity to the sulfur under the same conditions.The strains which was radiated 120s had the highest oxidation activity to the sulfur and the fastest decline in pH,it has the lowest pH after 7 days,in the seventh day the pH was 1.5.The strains which was radiated 120s had been used to the leaching of lead and zinc tailings,after 15 days bioleaching,the leaching rate of zinc and iron was increased by 7%and 6%,respectively,than the strains which was not radiated.It showed that the strains radiated by ultra-violet had a higher oxidation activity.The results of chemical leaching and bioleaching showed the leaching rates of Zn were both high in the two ways.The leaching rate of Fe was very low in the low concentration of sulfuric,the Fe leaching rate was greatly increased by using leaching bacteria. |
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