Research on Preparation of Coal Waste-Based Geopolymer and Its Stabilization/Solidification of Heavy Metals
Zifang Xu, Ye Dongdong, Tao Dai, Yan Dai
Abstract
The limitation of silica–alumina raw materials of traditional geopolymers has restricted the development of the immobilization technology of heavy metals. Therefore, the performance and mechanism of stabilization/solidification of heavy metals by coal-waste-based geopolymer on were investigated in this article. Low-calcium fly ash and metakaolin were substituted by coal waste, activated by alkali, the geopolymer with high performance was prepared, and its immobilization of various heavy metals (Co2+, Cr3+,Zn2+ and Ni2+）were studied. The results showed that with room temperature of 20 °C∼25 °C and the relative humidity of 90%∼95%, the optimized ratio of raw materials was that: the ratio of activated coal gangue to high-calcium fly ash was 7:4, mixed with 6.8% of micro-silica fume. The gangue and fly ash were closely surrounded by amorphous polymers. Plenty of scaly products were formed upon the surface of solidified matrix, interlaced with one layer to another, which makes the structure more dense. Synthesizes the compressive strength and the leaching toxicity, the optimum immobilization amounts of Co2+, Cr3+, Zn2+ and Ni2+ were 1.6%, 2.6%, 2.3% and 1.8%, respectively, with effective immobilization, good stability and long-term safety.