生活垃圾焚烧飞灰矿物学特性及重金属分布

生活垃圾焚烧飞灰的矿物学特性是飞灰中重金属赋存环境的直观反映,与重金属在处置环境中的释放和迁移行为密切相关.为掌握重金属在生活垃圾焚烧飞灰中的分布规律,结合X射线衍射、扫描电镜等常规矿物学研究工具及矿物解离分析系统对飞灰的矿物学宏观属性和微观属性进行全面测试.结果表明,飞灰是由矿物相和非矿物相组成,两者之间紧密连生,主要矿物相包括氯盐和方解石、氢氧钙石等多种含钙矿物.重金属元素在飞灰中主要以3种形式存在:均匀分布在无定形的非矿物组分中,以同晶置换赋存在方解石等矿物中以及吸附在特殊矿物如石英、赤铁矿等表面.难挥发性重金属Cu和Cr绝大部分分布在非矿物相中;半挥发性重金属Zn和Cd各有43.92%和60.61%的含量分布在矿物相中,其中,方解石对Cd、赤铁矿对Cr及硅酸盐对Zn存在较强的富集作用.

Mineralogy Characteristics and Heavy Metal Distribution of MSWI Fly Ash

Fly ash from municipal solid waste incineration (MSWI) plants can be categorized as a highly toxic mineral material due to the potential for leaching heavy metals. The mineralogical properties of MSWI fly ash visually reflect the heavy metals distribution in the ash, and are closely related to the release and migration behaviors of heavy metals in fly ash disposal or utilization scenarios. In order to understand the distribution of heavy metals in MSWI fly ash and provide support for heavy metals control technology, comprehensive tests on the macroscopic and microscopic mineralogical characteristics of the fly ash were conducted using X-ray diffraction (XRD), scanning electron microscope, a mineral liberation analysis system, and other methods. The results showed that MSWI fly ash was a heterogeneous material of closely combined mineral and non-mineral phases. The main mineral phases identified by XRD included chlorides and calcium-bearing minerals, mainly calcite and portlandite. The element distribution analysis, conducted with a mineral liberation analyzer, revealed that heavy metals of MSWI fly ash were mainly present in three forms:uniform distribution in the non-mineral amorphous phase, isomorphism in calcite and other minerals, and adsorption on the surfaces of quartz and hematite. Most content of Cu and Cr were distributed in the non-mineral phase due to their lower volatility, while most of semi-volatile heavy metals (43.92% of Zn and 60.61% of Cd) were present in mineral phases. In particular, Cd, Cr and Zn were mainly present in calcite, hematite and silicates respectively.