黑曲霉浸铀过程中生物矿石颗粒的形成及其浸出机理

There are many types of uranium ore in China, of which more than 30% cannot be treated in heap leaching, conventional agitation leaching and bioleaching by chemoautotrophic bacteria such as Acidithiobacillus ferrooxidans due to high carbonate concentration or high clay content. Although fungal leaching is an effective method for the extraction of uranium from these types of ore, fungal morphological form present in the leaching solution has significant effect on the recovery of uranium. For this purpose, we propose a new method of bio-ore pellets for uranium leaching. By controlling the leaching conditions, the bio-ore pellets would be obtained. And the bio-ore pellets have a core-shell structure，in which uranium ore particles as core will be inclosed by a porous webbed mycelia layer. According to the new idea, two key scientific issues need to be solved: the mechanism for formation of bio-ore pellets and the mechanism for uranium leaching using bio-ore pellets. To elucidate the mechanism for formation of bio-ore pellets, the conditions for their formation, the effects of physical, chemical and biological factors on the morphological and structural characters of bio-ore pellets, the interfacial interaction, the electrochemical effect and the biological action in the process of bio-ore pellets formation would be studied. Regarding the mechanism for uranium leaching using bio-ore pellets, the effects of the characters of the morphology and structure of bio-ore pellets on the solution system and the behavior of components, the alternations of technological mineralogy characters of uranium ore，and the adsorption and precipitation of uranium by the hyphae of Aspergillus niger would be studied. Then the method for uranium leaching using bio-ores pellets would be established. This research is of great significance for enriching the theory of bioleaching and recoverying uranium with high efficency from the refractory uranium ore and mill tailings.

我国30%以上的铀矿资源由于碳酸盐含量高或含泥量大，不适于堆浸、常规搅拌浸出和氧化亚铁硫杆菌等自养菌浸出。虽然真菌浸出是一种有效浸出方法，但真菌的形态会直接影响浸出效果。为此，提出了生物矿石颗粒浸铀方法：通过控制浸出条件，使黑曲霉多孔的网状菌丝将铀矿石包裹起来，形成以铀矿石为内核，黑曲霉菌丝为外壳的核-壳结构的生物矿石颗粒。拟围绕生物矿石颗粒的形成机制及浸铀机理两个关键科学问题，研究生物矿石颗粒的形成条件，物理、化学和生物因素对生物矿石颗粒的形态特征和结构特征的影响，生物矿石颗粒形成过程中的界面作用、电化学作用及生物学作用，阐明生物矿石颗粒的形成机制；研究生物矿石颗粒的形态和结构特征对溶液体系及组元行为的影响，生物矿石颗粒对铀矿石工艺矿物学特性的改变及黑曲霉菌丝对铀的吸附和沉淀，揭示其浸铀机理，建立生物矿石颗粒浸铀方法。该研究对丰富微生物浸矿理论，实现难浸铀矿资源的高效利用及铀尾矿资源的二次回收具有重要意义。

碳酸盐含量高或含泥量大的低品位铀矿资源的高效开发是亟待解决的难题。围绕黑曲霉浸铀过程中生物矿石颗粒的形成机制及其浸铀机理两个关键科学问题，采用X射线断层扫描与3D重构、原子力显微镜立体成像、工艺矿物学分析系统、微区X射线光谱分析等方法，研究了黑曲霉-铀矿石颗粒的形成条件，物理、化学和生物因素对黑曲霉-铀矿石颗粒的形态特征和结构特征的影响，黑曲霉-铀矿石颗粒形成的电化学、生物学和界面作用，确定了黑曲霉-铀矿石颗粒的形成条件，探明了黑曲霉-铀矿石颗粒形态特征与影响因素间的关系，阐明了黑曲霉-铀矿石颗粒的形成机制；研究了物理、化学和生物因素对铀浸出、黑曲霉代谢产酸种类和浓度、钙铁铝镁溶解的影响，浸出前后铀矿石工艺矿物学特征变化，探明了黑曲霉-铀矿石颗粒结构特征与铀浸出的关系，构建了生物矿石颗粒浸矿机理模型，阐明了其浸铀机理。研究发现，生物矿石颗粒具有三种结构，内层为空心、外层为菌丝包裹矿粉的两层结构利于铀浸出；黑曲霉菌丝生长过程中消耗碳氮源、分泌胞外产物及有机酸，改变体系的pH、Zeta电位，并在静电引力、胞外聚合物的粘附力、菌丝“锚固”力和水流剪切力作用下形成生物矿石颗粒；黑曲霉代谢产生的有机酸通过酸化、络合等作用溶解铀矿物，菌丝对矿粉的吸附和包裹产生机械力，加剧矿石风化，促进铀的溶解；矿石中铁铝铀的溶解对黑曲霉产生毒害，影响其代谢产酸，抑制铀浸出；浸出之后，矿石主要矿物组成不变，但元素组成发生改变，且U（IV）含量降低。本项目提出的生物颗粒浸铀方法对碳酸盐含量高或含泥量大的低品位铀矿资源的高效开发具有重要的理论价值和实际意义。