Study On Selection And Cultivation Of Efficient Phosphorus Leaching Bacteria

The resource of phosphorus in our country is very rich but with low grade and imbalance in distribution. It's difficult to separate the phosphorus from the ore with the traditional methods of mill run, which is high cost and unfriendly to our environment at the same time. Therefore, experts are searching for other better options. The microbe hydrometallurgy has become more and more popular as its economic and sanitary. Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans can utilize the oxygen in the ari to oxidize the reductive Fe and S, and they can get the ATP they need to breed and leach out the useful materials. So they have become the main bacteria used in bioleaching. However, reseach relating to the bacteria was mainly in the field of metal mine, leaving the usage in nonmetal unexplored, especially in phosphorus ore.The selection and cultivation of choiceness At.f and At.t have been investigated in this issue as well as the process of purification, domestication, inducement and bioleaching. After that there is a discussion on the mechanism of phosphorus bioleaching. We aimed to improve the leaching rate while phosphorus bioleaching and we got the following results:1. While cultivated in liquid, the pH of At.t can be simulated with multinomial with R² =0.9847 and the lowest pH can be around 1.80; the dosage of S can be optimized to 7.5 g/L, and the SEM of S showed the coarse surface corraded by At.t. The pH of At.f can be simulated by multinomial too and the R² is 0.986 while the lowest point is 1.60; while cultivated in medium with phosphorus, At.f can get lower pH with both Fe²⁺ and S in the medium, and only with S in the non-phosphorus medium that At.f can get lower pH. While cultivated in medium with FeS₂ as the unique energy source, At.f grow slowly and the pH didn't show any evidence of downtrend.2. After domesticated by phosphorite step by step, the two bacteria have better growth activity. When used in bioleaching, the domesticated bacteria can adapt the phosphorite more quickly and the pH of the lixivium declined obviously with the leaching rate in 30 days improved.3. We can get the following results after applying physical inducement on the bacteria: At.t can grow better after induced by non-continuous microwave within 10 s to 20 s; while At.f should be induced by continuous microwave if we want to get better bacteria; the average pH of At.t dropped obviously and the bioleaching rate doubled after the At.t induced by ultraviolet radiation, and there was no evidence of similar effect on At.f; the bioleaching rate can be enhanced if the At.t is induced by microwave in 10 s and then induced by ultraviolet radiation in 12 min.4. After comparing the bacteria with cultivation in leaching phosphorus, we can find that the phosphate (K₂HPO₄ or KH₂PO₄) in the medium will combine with Ca, Mg in the ore and create indissoluble phosphate (such as Brushite ), but the bacteria can help to restrict the process; the leaching rate will be improved if we use At.t and At.f together at one certain proportion.