黑曲霉产有机酸浸出铀矿石的影响因素

Factors influencing leaching of uranium ore by organic acids from Aspergillus niger

为了解培养基种类、培养温度和pH值等因素对黑曲霉产生的混合有机酸浸出铀矿石的影响,从铀矿山水样中分离、纯化得到了一株真菌——黑曲霉,应用马铃薯-蔗糖培养基(potato sucrose agar,PSA)和葡萄糖-玉米浆培养基(dextrose corn syrup,PCS)进行黑曲霉培养,获得了不同培养温度下产生的pH值不同的黑曲霉产混合有机酸,并将之作为浸出剂用于浸铀实验研究。研究表明,黑曲霉产生的有机酸的主要组分为草酸和柠檬酸等有机酸,培养基种类的不同会影响黑曲霉所产有机酸的浸铀效果,采用PSA培养基培养的黑曲霉产生的有机酸浸铀效果更好(p<0.05)。培养温度和混合有机酸的pH值也会对黑曲霉代谢产物的铀浸出率有显著性影响(p<0.05),且二者具有交互效应,pH值对铀浸出率的影响相对较大。应用PSA培养基时,最佳培养温度为25℃,最佳代谢产物pH值为2.3;应用PCS培养基时,最佳培养温度为30℃,最佳混合有机酸pH值为2.0。培养基种类、温度和pH值主要通过改变黑曲霉产生的有机酸的成分和含量对铀浸出率产生影响。

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.