石煤中含钒硅酸盐矿物微生物溶蚀浸钒作用机制研究

Vanadium is an imperative strategical material in the construction of national defense and economic. Vanadium-bearing stone coal is unique vanadium resources in China. The research on vanadium bioleaching technology is of great significance for the clean and efficient utilization of stone coal. Based on the characteristic that the vanadium bearing minerals in stone coal are mainly silicate minerals, a new idea of leaching vanadium by silicate bacteria (Bacillus mucilaginosus) is put forward in this project. It takes vanadium-bearing stone coal as the research object, and focus on the key scientific problems of the mechanism of vanadium bioleaching of vanadium-bearing silicate mineral in stone coal and mineral transformation mechanism under microbial actions. At first, the metabolism characteristics of the bioleaching bacteria and the bioleaching law of vanadium-bearing silicate minerals in the bioleaching system were investigated. On the basis of these, the key factors for controlling the vanadium leaching rate were obtained. After that, the adsorption behavior of bacteria on mineral surface was studied by means of microcosmic detection such as AFM and CLSM, and a kinetic model of adsorption was established. And then, the synergistic action of microbe and their metabolites on the bioleaching mechanism of vanadium-bearing silicate minerals were revealed by researching the interfacial effect of microbe and the indirect effect of the metabolites. Finally, the change rules of crystal structure, vanadium valence state and Si-Al coordination of vanadium-bearing silicate minerals before and after leaching were obtained by the micro-testing means of XRD, XAENS and nuclear magnetic resonance. Meanwhile, the transformation mechanism of mineral was revealed. The research results will provide theoretical basis and technical support for microorganism extraction of vanadium from stone coal.

钒是国防和经济建设的重要战略物资，石煤是我国独特的钒矿资源，开展微生物浸钒基础研究对于石煤的清洁、高效利用具有重要意义。本项目结合石煤中含钒矿物主要是硅酸盐矿物的特点，提出利用硅酸盐细菌（胶质芽孢杆菌）浸钒的新思路，重点研究石煤含钒硅酸盐矿物中钒的浸出机理以及矿物演变规律等关键科学问题。首先研究浸出体系中菌种代谢规律和含钒硅酸盐矿物中钒的浸出行为，获取调控浸钒效果的关键因素；采用AFM、CLSM等微观探测手段，研究菌种在矿物表面的吸附行为，建立吸附动力学模型；研究菌种与含钒硅酸盐矿物的直接界面作用以及菌种代谢产物与矿物的酸溶、络合等间接作用，揭示二者协同作用对石煤中含钒硅酸盐矿物的溶蚀浸钒机理；采用XRD、XAENS等测试手段，研究浸出过程中含钒硅酸盐矿物晶体结构、钒价态、硅铝配位、矿物成分等变化特征，揭示微生物浸钒过程中矿物演变规律。研究成果将为石煤微生物提钒提供理论基础和技术支持。

石煤是我国一种重要的钒资源，石煤提钒对丰富金属钒来源途径、促进石煤综合利用具有重要意义，生物浸出技术具有绿色经济等优势。基于石煤中钒赋存状态和硅酸盐细菌的代谢特点，本项目提出了采用硅酸盐细菌浸提石煤中钒的新思路，以课题组选育的诱变胶质芽孢杆菌作为浸钒菌种，系统开展了微生物浸钒行为和浸出机理研究。首先，研发出了适用于石煤钒矿微生物高效提钒的新方法：胶质芽孢杆菌经过ARTP-化学诱变处理后用于浸出空白焙烧预处理的含钒石煤，优化获得了诱变胶质芽孢杆菌对含钒石煤浸出的适宜工艺条件，同时发现空白焙烧预处理可大幅度提高钒浸出率的原因为石煤经焙烧后V3+含量降低，V4+、V5+含量增高，从而有利于钒的浸出。其次，研究发现诱变胶质芽孢杆菌在石煤表面的吸附受培养时间、pH、接种浓度等多种因素影响，当浸出体系的pH值为5.0时，菌体与含钒石煤之间的强静电引力可有效促进生物吸附作用，处于对数生长期的胶质芽孢杆菌更具有优良的生物吸附特性，生物吸附过程符合Freundlich等温吸附模型和准二级吸附动力学模型，该过程属于非均质的多层吸附，且主要受化学反应控制，菌体表面的–CH2、–CH3、–NH2等官能团参与了吸附过程，生物吸附作用改变了含钒石煤的表面性质，导致其等电点向菌种的等电点靠近。诱变胶质芽孢杆菌对石煤钒矿的浸出机制研究发现，浸出过程包括直接作用和代谢产物间接作用，且间接作用贡献率更大，代谢产物苹果酸、酒石酸等通过酸解和络合作用实现了钒的浸出。AFM结果表明细菌浸出后石煤表面腐蚀严重，腐蚀深度增大；通过XPS分析和钒形态测定发现，浸出后石煤表面钒相对含量有所减少，且钒形态由残渣态向可氧化态转化；XRD结果发现细菌能破坏钒云母晶体结构，使其结晶度下降，矿物溶解性增强。本项目研究成果可为微生物浸出含钒石煤过程调控及其作用机制研究提供理论指导。