耐酸抗氟冶金菌的固定化连续培养方法及快速浸铀机制研究

This project is based on the ability of metallurgical bacteria to maintain high efficient oxidation of ferrous ion at higher acidity, higher fluoride ion concentration and lower temperature conditions, will be studied continuous culture method of immobilized bacteria and mechanism of rapid bioleaching uranium. In the aspect of bacterial culture, will be focused on research of the optimal method of bacteria immobilization on the carrier and be determined the optimal parameters (liquid infusion mode, aeration mode and aeration volume, relationship between aeration volume and height of carrier column, resistance of bacteria to acid, fluoride ion and temperature, the best carrier suitable for bioleaching uranium, etc.) of oxidation of ferrous ion by immobilized bacteria. It is the first proposed that the oxidation rate per unit weight is used to characterize the ability of immobilized bacteria to oxidation of ferrous ion, and is used as the technical index to evaluate the advantages and disadvantages of various methods of immobilized bacteria. In the aspect of study on mechanism of bioleaching uranium, using the simulation software to compare the oxidative ability of iron sulfate and bacterial synthetic oxidants from the point of view of molecular quantum chemistry, will be ascertained that the essential difference between bioleaching uranium and chemical leaching uranium . The mode of leaching uranium will be modified from traditional intermittent spray mode into two modes, including submerged continuous flow under saturated condition and continuous spray under unsaturated condition. The law of the variation of solution movement rate and solute migration rate and their coupling relationship were studied in this mode. Will be made clear the change method about process parameters of bioleaching uranium and be constructed cycle system of rapid bioleaching uranium, to provide theoretical evidence for the practice of bioleaching uranium.

本项目以在较高酸度、较高氟离子浓度和较低温度条件下，细菌仍能保持高效氧化二价铁的能力为出发点，开展细菌固定化连续培养方法和快速浸铀机制研究。在细菌培养方面，重点研究将细菌固定在载体上的最佳方法，确定固定化细菌氧化二价铁的最优参数（进液方式、充气方式和充气量、充气量与载体柱高度的关系、细菌对酸、氟离子及温度的耐受性、适用于细菌浸铀的最佳载体等）。首次提出采用单位重量氧化速率表征固定化细菌氧化二价铁的能力，作为评价各种固定方法优劣的技术指标。在浸铀机制研究方面，使用模拟软件从分子的量子化学角度对比硫酸铁与细菌合成氧化剂的氧化能力，明确生物浸铀与化学浸铀的本质区别。将传统的间断喷淋浸铀模式改变为淹没式连续流动和包气式连续喷淋相结合的浸铀模式，研究在此模式下溶液运移速率与溶质迁移速率的变化规律及其耦合关系，掌握调变浸铀工艺参数的方法，构建快速浸铀循环系统，为细菌浸铀生产实践提供理论依据。

微生物浸铀技术在工业应用中存在细菌对不利因素的耐受性不强，导致成熟菌液供应不足的现象。为此，本项目针对性地研究了将细菌快速固定在载体上的方法，通过固定化细菌连续培养技术提高细菌对酸、氟离子、温度等的耐受性，实现成熟菌液的高效连续培养，并将其应用于生物快速浸铀。该项目研究了固定化细菌在连续培养阶段时载体种类、载体柱高度、初始溶液pH值、充气方式及充气量、进液方式及速率等优化参数，研究了细菌生成氧化剂与无菌Fe2(SO4)3化学氧化剂氧化能力的差别及其原因，研究了细菌固定化连续培养技术的快速浸铀机制，构建了快速浸铀循环系统。研究成果可为微生物浸铀的工业推广应用提供理论依据和技术支持。.项目研究成果表明：（1）氧化亚铁硫杆菌作用生成的生物试剂分子的结构式为Fe(С6H9O7)3，与无菌Fe2(SO4)3化学氧化剂相比，二者的分子构象明显不同，且Fe(С6H9O7)3比Fe2(SO4)3具有更强的氧化能力，证实细菌浸铀比纯化学浸铀更具优势；（2）采用50%接种率并逐次降低接种率循环回流培养的方法，可以在较短时间内实现氧化亚铁硫杆菌的固定。固定化细胞的循环培养生长曲线没有停滞期，在同等条件下，固定化细胞对亚铁的平均氧化速率是游离细胞20%接种率时的5倍，40%接种率时的4倍；（3）固定化氧化亚铁硫杆菌可在pH=1.4、温度4~14 ℃、F-浓度1057.78 mg/L条件下保持较高活性，在流量0.1 L/h、进液方式为下进上出、充气量1 L/min的55 cm高沸石载体柱中连续培养，能够满足12.74 L/(h·m2)喷淋强度，24 h不间断喷淋的柱浸试验对溶浸液的要求；（4）采用上进下出连续滴淋酸化、下进上出连续淹没式培养细菌，上进下出连续滴淋式的浸铀机制浸矿可以在总耗酸率6.75%条件下，77天内渣计浸出91.16%的铀矿，据此初步构建了快速浸铀循环系统。