Kitamura Hiroki, Sawada Takaya, Shimaoka Takayuki, Takahashi Fumitake
Department of Environmental Science and Technology, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, 4259, Nagatsuta, Midori-ku, Yokohama, 226-8503, Japan.
Faculty of Urban and Environmental Engineering, Graduate School of Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, 819-0395, Japan.
Environ Sci Pollut Res Int. 2016 Jan;23(1):734-43. doi: 10.1007/s11356-015-5229-5. Epub 2015 Sep 4.
Leaching behaviors of heavy metals contained in municipal solid waste incineration (MSWI) fly ash have been studied well. However, micro-characteristics of MSWI fly ash particles are still uncertain and might be non-negligible to describe their leaching behaviors. Therefore, this study investigated micro-characteristics of MSWI fly ash particles, especially their structural properties and impacts of chelate treatment on surface characteristics. According to SEM observations, raw fly ash particles could be categorized into four types based on their shapes. Because chelate treatment changed the surface of fly ash particles dramatically owing to secondary mineral formations like ettringite, two more types could be categorized for chelate-treated fly ash particles. Acid extraction experiments suggest that fly ash particles, tested in this study, consist of Si-base insoluble core structure, Al/Ca/Si-base semi-soluble matrices inside the body, and KCl/NaCl-base soluble aggregates on the surface. Scanning electron microscope (SEM) observations of the same fly ash particles during twice moistening treatments showed that KCl/NaCl moved under wet condition and concentrated at different places on the particle surface. However, element mobility depended on secondary mineral formations. When insoluble mineral like gypsum was generated and covered the particle surface, it inhibited element transfer under wet condition. Surface characteristics including secondary mineral formation of MSWI fly ash particles are likely non-negligible to describe trace element leaching behaviors.
城市固体废弃物焚烧（MSWI）飞灰中重金属的浸出行为已得到充分研究。然而，MSWI飞灰颗粒的微观特征仍不明确，且对于描述其浸出行为可能不可忽视。因此，本研究调查了MSWI飞灰颗粒的微观特征，特别是其结构特性以及螯合处理对表面特性的影响。根据扫描电子显微镜（SEM）观察结果，原生飞灰颗粒可根据其形状分为四种类型。由于螯合处理因钙矾石等次生矿物的形成而显著改变了飞灰颗粒的表面，因此螯合处理后的飞灰颗粒又可分为另外两种类型。酸提取实验表明，本研究中测试的飞灰颗粒由硅基不溶性核心结构、体内的铝/钙/硅基半溶性基质以及表面的氯化钾/氯化钠基可溶性聚集体组成。对同一飞灰颗粒在两次湿润处理过程中的扫描电子显微镜（SEM）观察表明，氯化钾/氯化钠在潮湿条件下移动并集中在颗粒表面的不同位置。然而，元素迁移取决于次生矿物的形成。当生成像石膏这样的不溶性矿物并覆盖颗粒表面时，它会抑制潮湿条件下的元素转移。MSWI飞灰颗粒的表面特征（包括次生矿物的形成）对于描述微量元素的浸出行为可能不可忽视。
