电解锰渣蒸压砖内源硫酸盐侵蚀行为及机理研究

Electrolytic manganese residues (EMR) are the largest and most dangerous pollution source of electrolytic manganese industry. One of the effective ways of realizing large utilization of EMR with high value-added is preparation for autoclaved bricks with EMR. The sulfate in EMR plays potential attack during the long-term service of autoclaved brick which hindered the industrial application and promotion of autoclaved brick produced from EMR. This project focuses sulfate attack in EMR. The factors such as pretreatment method of EMR, autoclave process and mineral admixtures will be studied, which will affect the existing form, reaction products and microstructure of sulfate in EMR. The sulfate attack state, expansive, quality and performance of autoclaved brick under the wet and dry cycle, water immersion and the actual working conditions will be discussed, and the structure and microscopic characteristics of the experimental bricks also revealed. Under the related theory such as physical chemistry, mechanics and materials science, and testing methods combining micro and macro, the correlations between the phase composition and microstructure and the sulfate attack in EMR will be analyzed, which will play an important role in the finding of sulfate attack mechanism on autoclaved brick, and also will be of great significance in extending the covering and mechanism of sulfate attack in building materials containing internal sulfate. Research results can supply theoretical guidance and experimental basis for harmless treatment and reutilization of EMR.

为了消减电解锰渣这一电解金属锰行业产生量最大、最危险的污染源，利用其制蒸压砖是大量消纳电解锰渣的有效途径之一。但电解锰渣内含40%左右的硫酸盐对蒸压砖的长期性能存在潜在侵蚀，这种侵蚀行为极大地阻碍了电解锰渣蒸压砖的产业化应用和推广。本项目拟研究电解锰渣预处理方法、蒸压工艺以及矿物掺合料对电解锰渣中内源硫酸盐存在形态、反应产物和微观形貌的影响；在干湿循环、水溶液浸泡和实际使用工况条件下，电解锰渣蒸压砖的侵蚀状态、膨胀、质量和性能等指标的变化规律，以及侵蚀后电解锰渣蒸压砖中硫酸盐的组织结构和微观特征。运用物理化学、力学、材料科学等相关理论，采用微观和宏观相结合的测试手段，探明内源硫酸盐在电解锰渣蒸压砖中的输运过程、转化形式、物相组成和微观结构，并揭示电解锰渣蒸压砖收内源硫酸盐侵蚀破坏过程及机理，丰富建筑材料内源硫酸盐破坏的作用机理。研究成果将为电解锰渣稳定化处理与资源化利用提供理论和实验依据。

针对电解锰渣制备蒸压砖过程硫酸盐存在的潜在侵蚀问题，项目研究了电解锰渣预处理、蒸压工艺以及矿物掺合料对电解锰渣蒸压砖的强度、反应产物、微观形貌和内源硫酸盐的存在形态的影响。提出锰渣中多种硫酸盐的系统测定方法，通过正交试验获得球磨12h、药剂用量12%、水渣比1:1、洗涤3次时，锰渣中可溶性硫酸盐含量达到最低。矿物掺合料制砖结果显示：随着掺合料用量的增加，砖的强度呈上升趋势，最高可达到49.30MPa。XRD显示砖中新生成了托贝莫来石、水化硅酸钙，水化铝硅酸钙等强度相。未加矿物掺合料砖样浸出液中硫酸根浓度达164.75mg/L，而添加矿物掺合料砖样的浸出液中未检出硫酸根。SEM-EDS结果表明这些强度相中间有一定量的含硫物质，这些组织越发达、互相密集搭接的强度相，在提高强度的同时，对硫酸盐类物质也起到了包裹作用，从而阻止硫酸盐发生溶出和侵蚀。通过项目研究初步明确了内源硫酸盐对电解锰渣蒸压砖侵蚀的作用途径和规律，研究发现锰渣制砖过程添加5-10%的掺合料能明显抑制电解锰渣中内源硫酸盐的侵蚀溶出，为电解锰渣蒸压砖产业化和大规模应用提供理论和技术支撑。