基于镍铁渣基复合磷酸盐化学键合材料协同固化电解锰渣机理研究

Electrolytic manganese residue, a kind of acid waste generated from the process of the electrolytic metal manganese, contains pollutants such as manganese, ammonium nitrogen, lead, and cadmium. Solidification/stabilization method has been currently recognized as an effective way to deal with the toxic wastes. However, the traditional alkaline cement method for the solidification of the electrolytic manganese residue has some disadvantages, including high ammonia release and lower carbonization resistance. In the present study, we want to prepare chemically bonded composite magnesium-iron phosphate ceramics with higher strength and more suitable setting behavior, according to the acid-based reaction between magnesium- and iron-rich ferronickel slag and acid phosphates, and then use the as-obtained ceramics to enduringly and efficiently solidify/stabilize the electrolytic manganese residue through chemical bonding, physical encapsulation and adsorption. We will investigate the influence of various factors, e.g. physicochemical characteristics of ferronickel slag, and phosphate species, on the microstructures and mechanical properties of chemically bonded composite phosphate ceramics, and then propose the formation mechanism of chemically bonded phosphate ceramics. During the solidification process of the electrolytic manganese residue with the chemically bonded composite magnesium-iron phosphate ceramics, we will evaluate the leachability of pollutants, and characterize the micromorphology, structure group, and occurrence state of the manganese, ammonium nitrogen, and other associated heavy metals, and then deduce the possible solidification/stabilization mechanism of electrolytic manganese residue using ferronickel slag based chemically bonded composite phosphate ceramics. We believe that the present study will provide experimental and theoretical evidence for expanding the reutilization approaches of ferronickel slag, and controlling electrolytic manganese residue pollution with chemically bonded composite phosphate ceramics.

电解锰渣是电解锰生产过程中产生的酸性废渣，含锰、氨氮、铅、镉等污染物，固化/稳定化技术是治理有害固废的一种有效途径，但传统碱性水泥固化锰渣存在高氨释放率、易碳化等缺陷。本申请提出以富含镁、铁质的冶炼镍铁渣为原料与磷酸/酸式磷酸盐反应制备高强、凝固速度适中的复合(铁-镁)磷酸盐化学键合材料，并用作基体材料通过化学键合、物理吸附及物理包裹三重作用高效、持久固化锰渣。拟研究镍铁渣的理化特性、磷酸盐种类等因素对磷酸盐化学键合材料性能的影响，探索镍铁渣基复合磷酸盐化学键合材料的制备机理；拟利用镍铁渣基复合磷酸盐化学键合材料固化电解锰渣，测试固化体毒性浸出，分析锰渣中锰、氨氮以及伴生重金属在固化体中的微观形貌、结构基团及赋存状态，揭示磷酸盐化学键合材料固化电解锰渣机理。预期研究成果将为拓展冶炼镍铁渣的综合利用途径及磷酸盐化学键合材料治理电解锰渣污染提供实验及理论依据。

电解锰渣（EMR）是电解锰行业最大、最危险的污染源，含锰(Mn)和氨氮(NH4+-N)等污染物，需进行固化/稳定化处理。而磷酸镁化学键合材料是一种常温下通过金属氧化镁与酸式磷酸盐反应形成的具有快凝、高强的新型无机胶凝材料，可用于土木工程、重金属及危险废弃物固化等领域。鉴于传统镁系磷酸盐化学键合材料施工可操作性差、处理成本较高等缺陷，项目提出利用富含镁、铁质的镍铁渣（FS）替代氧化镁与磷酸二氢氨（ADP）反应制备镍铁渣基复合（镁、铁）磷酸盐化学键合材料（FSCBPCs），并用其固化EMR。根据任务书规定，开展了以下主要研究内容：（1）系统研究了FS/ADP质量比、氧化镁量（M%）、水胶质量比（W/B）和缓凝剂硼酸量（BA%）对材料性能的调控行为。当FS/ADP=4:1、M%=4%、W/B=0.17、BA%=0.3%时，净浆凝结时间为12 min，试样1、3、7、28 d的抗压强度分别为32.6、39.9、48.7和54.9 MPa。（2）FS与ADP通过酸碱水化反应产生结晶水化产物鸟粪石（MgNH4PO4·6H2O）、磷镁铵石（(NH4)2Mg(HPO4)2·4H2O）和无定型磷酸铁盐相，三者协同胶结未反应FS颗粒，最终形成镍铁渣基复合（镁、铁）磷酸盐化学键合材料。（3）在复合磷酸盐化学键合陶瓷化过程中，EMR中的NH4+-N和Mn分别以鸟粪石（NH4MgPO4·6H2O），羟锰矿（Mn(OH)2）和磷酸锰（MnPO4·H2O）形式被稳定化。当EMR固化量=40wt%，FS/磷源（FS/P）=4:1时，固化体自然养护28 d的抗压强度达6.7 MPa，满足中国高速公路标准；Mn的固化率高达99.9%以上，游离NH4+-N的固化率达91.63%。研究成果为拓展冶炼镍铁渣的综合利用途径及磷酸盐化学键合材料治理电解锰渣污染提供实验及理论依据。