铀矿生物浸出过程中沥青铀矿-微生物溶浸液相互作用机理

Uranium bioleaching is a resource-saving and environment-friendly technique with a promising future for uranium recovery from low grade refractory uranium ores. However，the interaction mechanisms between microorganisms and uranium minerals in the process of bioleaching are still unclear today. Especially, it is a mystery that if microorganisms oxidize uranium minerals directly. In this project, pitchblende, one of the main uranium minerals, is taken as the target mineral and 4 strains of acidophiles isolated and purified in our previous work is used as bacteria source. The Imaging and micro-analytical technologies as EPMA and SEM, microbial molecular ecology method as Fluorescence In-situ Hybridization (FISH) and Real Time Q-PCR, interface analysis methods as Fourier Transform Infrared Spectrometry (FTIR) and Confocal Laser Scanning Microscope (CLSM) will be applied to study the interaction mechanisms between pitchblende and sulfuric acid, to analyze the biochemical and physicochemical characteristics of extracellular polymeric substances (EPS) of different strains, to search for the interaction mechanisms between microorganisms and pitchblende during the bioleaching with and without ferrous iron added, and to explore the direct-indirect mechanisms of pitchblende dissolution and oxidation of uranium IV compared on the physical and chemical characteristics at the interface between mineral and microorganisms in different leaching systems including bioleaching kinetics, morphological characteristics and their change rules. This project has important theoretical and practical significance to uranium bioleaching. It will also be highlight for uranium extracting efficiently from low grade refractory uranium ores.

铀矿生物浸出是一种节约资源且环境友好，对低品位难浸铀矿最具前景的应用技术,但生物浸出过程中微生物与铀矿的相互作用机制及关键影响因素尚待明确，特别是微生物对铀的氧化是否存在直接作用机制仍是未解之谜。本项目以沥青铀矿为目标矿物，以前期工作筛选的4种特效浸矿菌株为菌源，采用EPMA、SEM等显微成像与显微分析技术，FISH、Q-PCR等微生物分子生态学定量化技术，综合运用FTIR、CLSM等多种界面分析技术，分析沥青铀矿与硫酸溶浸液界面间的作用特征，考察不同菌种胞外聚合物生物化学和物理化学特征，研究有/无铁能源微生物浸出体系中沥青铀矿-微生物作用机制，对比不同浸出体系矿石-微生物两者的界面物理化学、生物浸铀动力学、形貌特征及其变化规律，探索微生物对沥青铀矿的间接作用机制和直接作用机制以及U(IV)的氧化本质。这对完善铀矿生物浸出理论，指导低品位复杂难处理铀资源高效开发具有重要的理论与实际意义。

铀矿生物浸出是一种资源节约且环境友好，对低品位难浸铀矿最具前景的应用技术，然而生物浸出过程中微生物与铀矿之间相互作用机制及关键影响因素尚待明确，尤其是微生物对铀的氧化是否存在直接作用机制仍需要进一步探索。本项目以沥青铀矿为目标矿物，以前期工作筛选的特效自养型浸铀菌株和新选育的嗜酸异养型菌株为菌源，综合运用XRD、XFAS、XPS、EPMA、AFM、TEM、SEM、FTIR、XRD、Raman等表征技术，MPN、FISH、Q-PCR等微生物分子生态学定量化技术及ICP-OES、IC等浸出液阴阳离子测定技术，分析原始沥青铀矿矿物学、表面形貌特征，探究沥青铀矿与纯硫酸溶浸液界面间作用特征，考察目标浸铀菌胞外聚合物生物化学和物理化学性质，研究有/无铁能源微生物浸出体系中沥青铀矿-微生物作用特征，对比不同浸出体系沥青铀矿-微生物溶浸液界面物理化学、生物浸铀动力学、形貌特征变化规律，探索微生物对沥青铀矿作用机制。研究结果表明，原始沥青铀矿已部分蚀变为铀石，Ca、Si、Fe等杂质元素在蚀变作用下掺杂到沥青铀矿晶格之中，导致U、Pb丢失。浸铀菌最佳组合比例为2：9：9，胞外聚合物官能团-OH、-COOH和-NH2显著影响浸铀菌物化性质从而对微生物浸铀起着重要作用。沥青铀矿铀酸法浸出和生物浸出动力学机制均符合Avrami方程，生物作用浸出率相对纯酸法浸出率显著提高。在微生物溶浸液作用下，矿物杂质元素相对铀元素更为快速地浸出，导致矿渣表面铀元素百分含量平均数相对原始矿物逐渐升高；矿物颗粒表面在浸出过程中逐渐变得粗糙，并形成越来越多不规则孔洞。生物浸出过程中，可见吸附菌通过胞外聚合物紧密附着于矿物颗粒上，沥青铀矿表面铀价态逐渐升高且局域几何结构也发生明显变化。本项目研究成果对完善铀矿生物浸出理论，指导低品位复杂难处理铀资源高效开发具有重要的理论与实际意义。