Stabilization/solidification mechanisms of tin tailings and fuming slag-based geopolymers for different heavy metals

IF 6.1 2区 环境科学与生态学 Q2 ENGINEERING, ENVIRONMENTAL
Xian Zhou, Zhengfu Zhang, Hui Yang
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Abstract

Tin mine tailings (TMT) and fuming slag (FS) contain many heavy metals (As, Cr, Cu, Zn and Mn) that cause severe pollution to the environment. Herein, geopolymers were prepared using TMT, FS and flue gas desulfurization gypsum (FGDG) to immobilize heavy metals, and their compressive strength and heavy metal leaching toxicity were investigated. It was first determined that T4F5 (TMT:FS = 4:5) sample exhibited the highest compressive strength (7.83 MPa). T4F5 achieved 95% immobilization efficiency for As and Cr, and nearly 100% for Cu, Zn and Mn, showing good immobilization performance. A series of characterization analyses showed that heavy metal cations can balance the charge in the geopolymer and replace Al in the geopolymer structure to form covalent bonds. In addition, about 2%–20% of heavy metal Fe was immobilized in hydration products, heavy metal hydroxides and non-bridging Si–O and Al–O coordination with silica-aluminate matrices. AsO33− was oxidized into AsO43−, which may form Ca–As or Fe–As precipitates. Cr2O72− was converted to CrO42− under alkaline environment and then combined with OH to form Cr(OH)3 precipitates. Mn2+ may react directly with dissolved silicate to form Mn2SiO4 and also form Mn(OH)2 precipitates. The unstable Mn(OH)2 can be further oxidized to MnO2. The heavy metal cations were immobilized in the silicoaluminate lattice, while the anions tended to form insoluble precipitates. These results may benefit the industry and government for better handling of TMT, FS and solid wastes containing the abovementioned five heavy metals.

Abstract Image

锡尾矿和发火矿渣基土工聚合物对不同重金属的稳定/固化机制
锡矿尾矿(TMT)和发炉渣(FS)含有多种重金属(砷、铬、铜、锌和锰),对环境造成严重污染。本文利用 TMT、FS 和烟气脱硫石膏(FGDG)制备了固定重金属的土工聚合物,并对其抗压强度和重金属浸出毒性进行了研究。首先确定 T4F5(TMT:FS = 4:5)样品的抗压强度最高(7.83 兆帕)。T4F5 对砷和铬的固定化效率达到 95%,对铜、锌和锰的固定化效率接近 100%,显示出良好的固定化性能。一系列表征分析表明,重金属阳离子可以平衡土工聚合物中的电荷,并取代土工聚合物结构中的 Al 形成共价键。此外,约 2%-20% 的重金属 Fe 被固定在硅铝酸盐基质的水化产物、重金属氢氧化物以及非桥接的 Si-O 和 Al-O 配位中。AsO33- 被氧化成 AsO43-,可能形成 Ca-As 或 Fe-As 沉淀。Cr2O72- 在碱性环境下转化为 CrO42-,然后与 OH- 结合形成 Cr(OH)3 沉淀。Mn2+ 可直接与溶解的硅酸盐反应生成 Mn2SiO4,也可生成 Mn(OH)2 沉淀。不稳定的 Mn(OH)2 可进一步氧化成 MnO2。重金属阳离子被固定在硅铝酸盐晶格中,而阴离子则倾向于形成不溶性沉淀。这些结果将有助于工业界和政府更好地处理含有上述五种重金属的 TMT、FS 和固体废物。
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来源期刊
Frontiers of Environmental Science & Engineering
Frontiers of Environmental Science & Engineering ENGINEERING, ENVIRONMENTAL-ENVIRONMENTAL SCIENCES
CiteScore
10.90
自引率
12.50%
发文量
988
审稿时长
6.1 months
期刊介绍: Frontiers of Environmental Science & Engineering (FESE) is an international journal for researchers interested in a wide range of environmental disciplines. The journal''s aim is to advance and disseminate knowledge in all main branches of environmental science & engineering. The journal emphasizes papers in developing fields, as well as papers showing the interaction between environmental disciplines and other disciplines. FESE is a bi-monthly journal. Its peer-reviewed contents consist of a broad blend of reviews, research papers, policy analyses, short communications, and opinions. Nonscheduled “special issue” and "hot topic", including a review article followed by a couple of related research articles, are organized to publish novel contributions and breaking results on all aspects of environmental field.
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