Shao Ningning, Wei Xuankun, Monasterio Manuel, Dong Zhijun, Zhang Zuotai
Institute of Technology for Marine Civil Engineering, Shenzhen Institute of Information Technology, Shenzhen 518172, PR China.
School of Environmental Science and Engineering, Southern University of Science and Technology (SUSTech), Shenzhen 518055, PR China.
Waste Manag. 2021 May 1;126:747-753. doi: 10.1016/j.wasman.2021.04.003. Epub 2021 Apr 25.
The safe disposal of municipal solid waste incineration fly ash (MSWIFA) has become the weakest link of the circular economy of MSW due to its hazardous nature. In this study, we focused on the heavy metals solidification of MSWIFA by using alkali-activation technology and introducing a mold-pressing method. The influence of alkaline activator (AA) including alkali concentration and dosage of sodium silicate solution were well designed and studied. MSWIFA before and after alkali-activation, as well as the sample treated by commercial chelating agent (CA), were contrastively studied the performance of heavy metals solidification. The results show that the alkali-activated MSWIFA exhibits superior solidification for heavy metals than the blank control and the CA treated ones. With mold-pressing technology, the alkali-activated MSWIFA shows a core-shell structure, in which a thin layer that is composed of mainly N-A-S-H gel is as the shell and acts as a protective layer to inhibit the leaching of heavy metals. Besides, the introduced mold-pressing technology is beneficial for the improvement of materials strength and the reduction of AA dosage. The optimal AA composition is that the net concentration of NaOH is ∼4 M and sodium silicate dosage is ∼65 wt% in alkaline activator, and the total alkaline activator requirement is only 32 wt% of MSWIFA, yielding 7.9 MPa compressive strength at 10.2 MPa molding pressure. In summary, this work paves a potential new way for safe and recycling use of hazardous MSWIFA, which will be of great significance to environmental sustainability.
城市固体废弃物焚烧飞灰（MSWIFA）因其有害性质，已成为城市固体废弃物循环经济中最薄弱的环节。在本研究中，我们聚焦于利用碱激活技术并引入模压法对MSWIFA进行重金属固化。精心设计并研究了碱性活化剂（AA）的影响，包括碱浓度和硅酸钠溶液的用量。对碱激活前后的MSWIFA以及经商业螯合剂（CA）处理的样品进行了重金属固化性能的对比研究。结果表明，碱激活后的MSWIFA对重金属的固化性能优于空白对照和经CA处理的样品。采用模压技术，碱激活后的MSWIFA呈现核壳结构，其中主要由N-A-S-H凝胶组成的薄层作为壳层，起到抑制重金属浸出的保护层作用。此外，引入的模压技术有利于提高材料强度并减少AA用量。最佳的AA组成是，碱性活化剂中NaOH的净浓度约为4 M，硅酸钠用量约为65 wt%，碱性活化剂的总需求量仅为MSWIFA的32 wt%，在10.2 MPa的成型压力下可产生7.9 MPa的抗压强度。总之，这项工作为有害的MSWIFA的安全和循环利用开辟了一条潜在的新途径，这对环境可持续性具有重要意义。
