Study On Resource Recovery From Tailings With Efficient Acidophilic Iron-oxidizing Bacteria

With the continuous development and utilization of mineral resources in China,high-grade mineral resources continue to decrease,so poor mineral resources such as low-grade ore and tailings need to be developed and utilized to solve the problem of resource shortage.Bioleaching has a great potential to recover valuable metals from low grade,polymetallic and complex sulfide ores due to relative simplicity,environmentally eco-friendly process and low capital and operational cost requirements.Acidophilic bacteria which is widespread in acid mine drainage is one of the main bacterium uesd in bioleaching,especially Acidithiobacillus ferrooxidans,Acidithiobacillus thiooxidans,and Leptospirillum ferrooxidans.They play an important role in bioleaching because they can bear low pH and oxide Fe2+ and S0 to Fe3+and H2SO4 which dissolving minerals.Based on the characteristics of different mine drainages,this study carried out the enrichment,isolation and identification of acidophilic iron-oxidizing bacteria from different mine drainages,and studied the leaching ability of the isolated acidophilic iron-oxidizing bacteria,which provided a theoretical basis for the efficient screening of leaching microorganisms.In this study,acidophilic iron-oxidizing bacteria were enriched from four different mine drainages,including coal mine drainage with pH of 2.71,coal mine drainage with pH of 3.17,gold mine drainage with pH of 2.72 and coal mine drainage with pH of 8.21.By changing the initial pH of 9K enrichment medium,the optimal pH range for bacterial growth was investigated.When the mine wastewater is acidic,the target bacteria can be enriched under the conditions of pH 2.0,2.5 and 3.0,and the growth activity of bacteria in different mine drainages is also different.When the pH too low(pH 1.0)or too high(pH 3.5,pH 4.0),the target bacteria can not be enriched.However,there is no enrichment of acidophilic bacteria in the alkaline mine wastewater(pH>7.0).The microbial community structure of the raw mine drainage and the enriched bacterial solution was analyzed by high-throughput sequencing.It was found that the microbial community structure of different mine drainage had significant differences,and the microbial diversity of the enriched bacterial solution was affected by the characteristics and the microbial community structure of the raw mine drainage,and the initial pH of the medium.The study adopted streak plate method screening six strains of acidophilic iron-oxidizing bacteria from the enriched bacterial solution.Based on phylogenetic analysis named Acidithiobacillus ferriphilus WT1-1,Acidithiobacillus ferrooxidans WT1-2,Acidithiobacillus ferriphilus WT2-1,Acidithiobacillus ferrooxidans WT2-2,Leptospirillum ferrooxidans WT3-1 and Acidithiobacillus ferrooxidans WT3-2.Study on the oxidation capacity of six strains was carried out.Acidithiobacillus ferriphilus WT1-1,Acidithiobacillus ferrooxidans WT2-2 and Leptospirillum ferrooxidans WT3-1 with better oxidation capacity were studied on leaching tailings.Under the condition of bacterial column 15%,pulp density 100 g/L,temperature 30℃,pH 2.5,agitation speed 140 rpm,the three strains have the ability to leaching Cu,Zn,Mg and Al from polymetallic sulfide tailings.The leaching rates with strain WT1-1 are 58.37%,76.95%,80.09%and 53.14%,respectively.The leaching rates with strain WT2-2 were 55.23%,72.09%,77.44%and 43.55%,respectively.The leaching rates with strain WT3-1 were 53.14%,70.14%,78.00%and 44.50%,respectively.In this paper,three strains(WT1-1,WT2-2,WT3-1)with leaching ore function with a ratio of 1:1:1 for leaching ore experiment One-step leaching and two-step leaching experiments were adopted.Cu has the highest leaching efficiency in the two-step leaching group,with a leaching rate of 66.3 7%,while Zn,Mg and Al have the highest leaching efficiency in the one-step leaching group,with leaching rates of 77.67%,84.68%,and 64.50%,respectively.Compared with the two-step leaching,the one-step leaching has a stronger direct contact effect with bacteria.Under the premise that the metal content in the tailings does noe affect the growth of bacteria,the one-step leaching method can more effectively leach the metal from the tailings,and is more in line with the practical operation.