关键词: 真菌, 黑曲霉, 有机酸, 浸铀, 影响因素

Abstract: Leaching uranium ores by fungi is a promising new bioleaching approach，and organic acids play key roles.However，little is known about the relationships between uranium leaching rate and organic acids produced by fungi.To explore the effects of medium types，culture temperature and pH value on uranium leaching by organic acids from Aspergillus niger，a strain of them was separated and purified from some water samples from a uranium mine.PSA and PCS medium were used for culture of Aspergillus niger，and mixed organic acids with different pH value produced by Aspergillus niger at diverse culture temperature were obtained and applied to tests of uranium leaching.The results show that leaching rate of uranium has statistically significant difference for these organic acids produced at different conditions，because there are different ingredients in these organic acids.All factors including of medium type，culture temperature and pH could influence composition and quantity of mixed organic acids.When Aspergillus niger was cultured in different medium，the composition of mixed organic acids is different，mainly oxalic acid and citric acid，and uranium leaching rates also different.Uranium leaching is better for the products obtained in PSA medium than in PCS one no matter different pH and culture temperature (p<0.05).For same medium，due to difference in pH value culture temperature uranium leaching rate is also different (p<0.05).For example，for PSA the best culture temperature and pH value are 25℃ and 2.3 respectively，and mean uranium leaching rate were 76.14% and 82.40% at these conditions.While for PCS，the best conditions were 30℃ and 2.0，and the mean uranium leaching rate were 56.60% and 67.91%，respectively. The results also show that there are interaction effects between culture temperature and pH value of mixed organic acids （p<0.05).Main factor influencing uranium leaching rate is pH value，and the second their interaction effects.Culture temperature has less effect on uranium leaching.So，the conclusion can be made：the mixed organic acids produced by Aspergillus niger is of ability of uranium leaching，and culture medium，temperature and pH value has effect on uranium leaching rate.The optimal parameters obtained are culture temperature 25℃and pH value 2.3 for PSA media，and 30℃ and 2.0 for PCS.PSA medium is better than PCS medium.

Key words: fungi, Aspergillus niger, organic acid, uranium leaching, influencing factor