Ji Haiyan, Mi Xue, Tian Qiangkun, Liu Chunli, Yao Junxia, Ma Shuhua, Zeng Guisheng
Key Laboratory of Jiangxi Province for Persistent Pollutants Control and Resources Recycle, School of Environment and Chemical Engineering, Nanchang Hangkong University, Nanchang 330063, PR China.
ChuXiong DianZhong Non-ferrous Metals CO., LTD, Chuxiong 675000, PR China.
Sci Total Environ. 2021 Aug 25;784:147100. doi: 10.1016/j.scitotenv.2021.147100. Epub 2021 Apr 15.
High-alumina coal fly ash (HAFA) is a special solid waste since its alumina content can reach 40-50 wt%, which is seen as a potential resource for mullite material production. However, obtaining an ideal mullite material from HAFA is difficult because of its low AlO/SiO mass ratio. In this work, the microstructure characteristics of HAFA were systematically analyzed by combining multiple characterization techniques. It was found that HAFA had a core-shell structure with a mullite/corundum crystal core and a silica-rich amorphous phase shell. The novel mechanochemical activation-desilication process was used to remove amorphous phase from HAFA and elevate the AlO/SiO mass ratio. In particular, the effect of particle size after mechanical treatment and mechanism of the desilication process were extensively investigated. On decreasing the particle size, a high leaching rate of alumina was achieved during mechanochemical activation, thus generating a hydroxysodalite coating layer as desilication was suppressed, and the amorphous phase was effectively removed. The mineralogical phase of the desilicated HAFA is mainly mullite and corundum, and the AlO/SiO mass ratio was elevated from 1.29 to 3.02. Mullite refractory obtained from the desilicated HAFA exhibited excellent physical properties. This study provides insights into further high-valued utilization of HAFA.
高铝粉煤灰（HAFA）是一种特殊的固体废弃物，因为其氧化铝含量可达40 - 50 wt%，被视为生产莫来石材料的潜在资源。然而，由于其AlO/SiO质量比低，从HAFA中获得理想的莫来石材料很困难。在这项工作中，通过结合多种表征技术系统地分析了HAFA的微观结构特征。发现HAFA具有核壳结构，其核心为莫来石/刚玉晶体，外壳为富含二氧化硅的非晶相。采用新型机械化学活化 - 脱硅工艺从HAFA中去除非晶相并提高AlO/SiO质量比。特别地，广泛研究了机械处理后粒度的影响以及脱硅过程的机理。随着粒度减小，在机械化学活化过程中氧化铝的浸出率很高，从而在抑制脱硅的情况下生成了羟基方钠石涂层，有效去除了非晶相。脱硅后的HAFA的矿物相主要是莫来石和刚玉，AlO/SiO质量比从1.29提高到3.02。由脱硅后的HAFA获得的莫来石耐火材料表现出优异的物理性能。本研究为HAFA的进一步高值利用提供了见解。
