晶相析出对不锈钢渣矿相组成及Cr淋溶影响机理

The comprohensive utilization and final disposition of stainless steel slag are mainly limited by its mineralogical composition and leaching toxicity of chromium. The slag cooling condition, such as chemical composition, initial cooling temperature, cooling rate, etc. will be strategically controlled according to the analysis of state diagrams on the molten slags with FactSage software, during the remelting and reconstructing experiments. Next, by using various modern analyzing methods including SEM-EDX, metallographic microscope and XANES etc., the thermodynamic and dynamic analysis on the crystalization of crystal phases (spinal and C2S) and the formation of amorphous phase (glass) will be investigated in this project. Combined with the leaching properties of chromium in different leahates with disimmilar electrochemical characteristics, the chromium leaching model from stainless steel slag will be established, the quantitative relationship between the leaching amount of chromium and the mineralogical compositions of stainless steel slag will be determined, and the quantitative distribution of chromium in different phases and its transfermation mechanism during leaching will be elucidated..In this project, by means of the theories and technologies of thermodynamic of molten slag, mineralography, solution electrochemistry and environmental chemistry, etc., the influencing mechanism of cooling conditions on the minerlogical compositon, quantitative distribution of chromium and its transfermation mechanism during leaching will be investigated. It will potentially enrich the connotation of themodynamic of molten slag and chromium valence transfermation during leaching, and provide theoretical supports for utilization of steel slag and ecological risk assessment of typical toxic elements, which is of academic signifance.

矿相组成及Cr淋溶毒性是不锈钢渣资源化利用与处置的关键制约因素。通过重熔和重构实验中不锈钢渣组分、淬冷温度、冷却速度等成渣条件的控制和熔渣热力学参数状态图分析，采用SEM-EDX、矿相显微镜、XANES等现代分析方法，研究尖晶石与C2S等晶相析出和玻璃质生成的热力学与动力学；结合不同电化学特性淋溶液作用下,不锈钢渣中Cr的淋溶性能，构建不锈钢渣中Cr的淋溶模型，确定Cr淋溶量与不锈钢渣矿相组成间的定量关系，阐释不锈钢渣Cr在不同矿相中定量分布规律及其淋溶转化机理。.本研究运用熔渣热力学、矿相学、溶液电化学和环境化学等学科知识，研究成渣条件对不锈钢渣矿相组成和Cr定量分布与淋溶转化的影响机理，将极大丰富熔渣热力学与Cr淋溶形态转化过程的有关内涵，并为不锈钢渣的资源化再用及典型有毒元素的生态风险评价提供理论支撑，具有重要的学术价值。

采用重熔重构实验方法，研究了AOD原渣及重熔重构渣矿相组成及铬存在形态和定量分布规律；结合淋溶实验，明晰了AOD渣中铬淋溶机理，阐释了AOD中铬淋溶特性与不锈钢渣初相溶解和二次相生成间的关系；基于淋溶实验和矿相组成，构建了AOD渣中铬淋溶动力学模型，为不锈钢渣资源化再用及典型有毒元素的生态风险评价奠定理论和实验基础。项目研究过程中，共培养硕士研究生7名，申请发明专利4项，已发表学术论文13篇，其中SCI索引3篇、EI索引1篇、中文核心5篇，并获得以下理论成果：.AOD渣为碱性渣，铬主要以铬镁尖晶石为主要富集相；结合XRD与SEM/EDX对AOD渣矿相组成的定性分析，确定了绝热法为定量分析AOD渣矿相组成的适宜方法；静态淋溶、连续淋溶和动态淋溶证实AOD渣淋溶液呈碱性、还原性，固体废弃物毒性标准测试方法会过低评价AOD渣的淋溶毒性，尤其是长期动态淋溶中，渣中Cr的淋溶风险不容忽视；无论是连续淋溶还是动态淋溶，AOD渣中硅酸二钙、方镁石等碱性矿物快速溶解，而镁硅钙石含量有所升高，同时生成C-S-H等二次相；冷却速率对AOD重熔渣矿相组成影响显著，随着冷却速率增加，矿相种类有所增加，但矿相基本以普通辉石和透辉石为主；随着冷却强度增加（缓冷<空冷<水冷），矿相晶粒度降低、活性矿物含量增加，淋溶液中Cr3+、Cr6+和总铬浓度显著增加；Al2O3在一定程度上促进了重熔渣中铬的溶出，而Fe2O3在一定程度上能够抑制重熔渣中铬的淋溶；基于收缩核模型的铬淋溶动力学模型表明，AOD渣中铬溶出分为快速和慢速淋溶两个阶段，快速淋溶阶段受固膜扩散限速，而慢速淋溶阶段受固膜扩散和化学反应共同限速；连续淋溶动力学模型结果表明，抛物线模型能更好地反映AOD渣中铬的溶出特征，从而评价AOD渣中铬的淋溶毒性；基于PHREEQC的动力学模型表明，AOD渣淋溶液呈现碱性，Cr以Cr(OH)4-离子形式存在，三价铬离子很难向六价铬离子转化，Cr浓度受到二次相Cr(OH)3的热力学溶解平衡控制。