功能矿物协同条件下铀尾矿—水淬渣地聚物充填体中铀的滞留特性及机理研究

Cement-solidified underground cemented filling is an effective way to solve the environmental problems of uranium tailings stacking on the surface, but the characteristics of uranium tailings seriously affect the mechanical strength, chemical stability and leaching resistance of the filling body. Paste can effectively control the diffusion of harmful elements in groundwater, polymer cement has good stability in alkali metal and sulfate environment, and other functional minerals such as zeolite have good adsorption capacity for uranium. Therefore, the synergistic effect of functional minerals-uranium tailings-water quenched slag geo-polymer system has become an important idea to improve the solidification performance of filling body..The scientific assumption of functional mineral adsorption-geo-polymer segmentation and encapsulation-paste stabilization and synergistic solidification is proposed in this paper. By simulating the filling system preparation and leaching resistance test of the functional mineral - uranium tailings - water quashing slag in the mine environment, the phase evolution law of the backfill will be studied to reveal its reaction mechanism under specific physical-chemical conditions. The occurrence state of uranium in backfill will be analyzed to explore the influence of phase evolution and microstructure evolution on uranium retention characteristics. Taking uranium leaching resistance and mechanical strength of backfill as the evaluation indexes of curing effect, the filling material proportion in the case of reasonable capacity increasing ratio will be proposed. And the solution of this scientific problem is helpful to build a new type of underground filling technology system of uranium tailings - water quenching slag - functional mineral compound paste.

基于水泥固化的井下胶结充填是解决铀尾矿地表堆置环境问题的有效途径，但铀尾矿的特性严重影响充填体的机械强度、化学稳定性和抗浸出性。膏体可有效控制有害成分在地下水中的扩散，地聚物水泥在碱金属和硫酸环境中均具有良好的稳定性，沸石等功能矿物对铀有较好的吸附能力，因此，功能矿物—铀尾矿—水淬渣地聚物复合体系协同作用成为改善充填体固化性能的重要思路。.课题提出功能矿物吸附—地聚物分割包裹—膏体稳固协同固化的科学设想。通过模拟矿井环境的功能矿物—铀尾矿—水淬渣地聚物充填体制备及抗浸出性试验，研究充填体的物相演化规律，揭示其在特定物理—化学条件下的反应机理；分析铀在充填体中的赋存状态，探究物相演化和微观结构演化对铀滞留特性的影响；以铀的抗浸出性和充填体的机械强度作为固化效果的评价指标，提出合理增容比时的充填物料配比。该科学问题的解决，有助于构建新型的铀尾矿—水淬渣—功能矿物复合地聚物膏体井下充填技术体系。

井下胶结充填是实现铀尾矿安全高效处置的重要途径之一，而抗浸出性是铀尾矿骨料充填体的关键指标。围绕铀尾矿充填体抗浸出性关键目标及其影响因素，提出了功能矿物协同条件下铀尾矿—水淬矿渣井下胶结充填处置体系；基于铀矿水冶尾砂、粒化高炉矿渣以及沸石、海泡石、硅灰、蛭石和凹凸棒土等五种功能矿物，研究了掺加功能矿物粒化高炉矿渣的胶凝特性及机理，研究了铀尾矿—水淬矿渣井下胶结充填体的制备方法；研究了掺加功能矿物铀尾矿充填体的抗压、抗拉、抗冻融、抗冲击、抗浸泡和抗浸出特性；揭示了铀尾矿—水淬渣—功能矿物复合体系的物相和微观结构特征；阐释了其对铀固化滞留的协同作用机制。研究表明：掺加功能矿物粒化高炉矿渣的胶凝产物主要为C-(A)-S-H凝胶，掺加功能矿物可提高高聚合度产物的含量，但降低了低聚合度产物的含量，并导致其结构疏松或者产生裂隙；粒化高炉矿渣是铀尾矿骨料充填体系的有效胶凝材料，生石灰是该体系的有效复配材料之一，掺加功能矿物不会显著降低铀尾矿充填体的力学性能，能够满足低、中水平放射性废物水泥固化体等国家标准及充填开采对充填体的强度要求；铀尾矿充填体对铀具有良好的固化滞留效果，42 d内不同浸出周期的浸出液铀的浓度、浸出率Rn、累积浸出分数Pt均远低于相应的国家标准限值，掺加功能矿物可显著增强铀尾矿充填体的抗铀浸出性；铀尾矿充填体中的孔隙包括界面孔隙和胶凝材料内部裂隙孔隙，适量的功能矿物掺加可降低充填体孔隙率；铀尾矿对掺加功能矿物粒化高炉矿渣的胶凝反应并无明显影响，铀尾矿充填体对铀的固化滞留是固封—吸附—交换—沉淀等多重效应的协同作用。本项目提出的铀尾矿充填处置方法对于绿色生态铀矿采冶具有重要的理论价值和实际意义，并为含放射性或重金属固体废物处置提供了新方法。