Two-step Process Of Aspergillus Niger Combined With Chemical Oxidation To Leach Granite Uranium Ore

Due to the advantages of low cost,low energy consumption,high recovery,environmental protection and so on,microbial leaching technology has a wide application prospect in the field of mineral resource recovery.Granite-type uranium ore is one of the four major uranium deposits in China.Its main uranium mineral is Uraninite,of which tetravalent uranium has a relatively high proportion and low solubility.In order to efficiently recover uranium resources,this paper uses two-step method of Aspergillus niger combined with chemical oxidation to leach granite uranium ore.The research results are as follows:(1)Two-step leaching experiments using Aspergillus niger were carried out,and the effects of three main factors,such as pre-culture time of A.niger,uranium ore particle size and leaching time on the uranium extraction were investigated.The results showed that under the condition of A.niger pre-culture of 36 h,uranium ore particle size of-200 mesh and leaching time of 72 h,the leaching effect of two-step method was the best,and the uranium recovery was 59.34%.(2)Two-step process of A.niger combined with chemical oxidation leaching experiments were carried out.The addition of four oxidants such as manganese dioxide,ferric chloride,sodium chlorate and hydrogen peroxide all resulted in an increase in uranium extraction.At a dosage of 2.5% manganese dioxide,the highest uranium recovery reached to 74.09%.(3)Scanning electron microscope(SEM)and energy dispersive spectroscopy(EDS)were used to characterize the surface morphology and element composition of the raw ore sample,the two-step leaching residue and the combined leaching residue.The results showed that the surface of the ore particles after leaching was obviously corroded,and combined leaching led to a more pronounced fissure-pit structure with a deeper corrosion damage.This indicates that adding oxidant can promote the corrosion of A.niger to the ore and improve uranium extraction.(4)Using the mineral dissolution / precipitation plate of Visual MINTEQ software simulated the reaction of uranium minerals and main gangues in the ore used with organic acids.The results show that oxalic acid has a stronger ability of leaching uranium than citric acid and malic acid.When oxalic acid and citric acid are combined for leaching,it is more favorable for leaching of uranium.