{"title":"Stabilization/solidification mechanisms of tin tailings and fuming slag-based geopolymers for different heavy metals","authors":"Xian Zhou, Zhengfu Zhang, Hui Yang","doi":"10.1007/s11783-024-1816-3","DOIUrl":null,"url":null,"abstract":"<p>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. AsO<sub>3</sub><sup>3−</sup> was oxidized into AsO<sub>4</sub><sup>3−</sup>, which may form Ca–As or Fe–As precipitates. Cr<sub>2</sub>O<sub>7</sub><sup>2−</sup> was converted to CrO<sub>4</sub><sup>2−</sup> under alkaline environment and then combined with OH<sup>−</sup> to form Cr(OH)<sub>3</sub> precipitates. Mn<sup>2+</sup> may react directly with dissolved silicate to form Mn<sub>2</sub>SiO<sub>4</sub> and also form Mn(OH)<sub>2</sub> precipitates. The unstable Mn(OH)<sub>2</sub> can be further oxidized to MnO<sub>2</sub>. 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.\n</p>","PeriodicalId":12720,"journal":{"name":"Frontiers of Environmental Science & Engineering","volume":"144 1","pages":""},"PeriodicalIF":6.1000,"publicationDate":"2024-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Frontiers of Environmental Science & Engineering","FirstCategoryId":"93","ListUrlMain":"https://doi.org/10.1007/s11783-024-1816-3","RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"ENGINEERING, ENVIRONMENTAL","Score":null,"Total":0}
引用次数: 0
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.
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.