Effect of Si/Al molar ratio on the immobilization of selenium and arsenic oxyanions in geopolymer. (1st April 2021)

• Record Type: Journal Article
• Authors: Tian, Quanzhi; Chen, Changshuai; Wang, MengMeng; Guo, Binglin; Zhang, Haijun; Sasaki, Keiko
• Is Part Of: Environmental pollution. Volume 274(2021)
• Publication Date: 2021-04-01
• Subjects: Geopolymer -- Si/Al ratio -- Se and As oxyanions -- Immobilization; Pollution -- Periodicals; Pollution -- Environmental aspects -- Periodicals; Environmental Pollution -- Periodicals; Pollution -- Périodiques; Pollution -- Aspect de l'environnement -- Périodiques; Pollution -- Effets physiologiques -- Périodiques; Pollution; Pollution -- Environmental aspects; Periodicals; Electronic journals; 363.73
• DOI: 10.1016/j.envpol.2021.116509
• Languages: English
• ISSNs: 0269-7491

Abstract

Abstract: The effect of Si/Al molar ratio of geopolymer on the immobilization of Se and As oxyanions was studied through leaching test and solid characterizations including XRD, FTIR, TG, NMR, XAFS, and N2 adsorption-desorption isotherm. As a whole, the leaching percentages of Se and As oxyanions increased with the increase of the Si/Al molar ratio of geopolymer. Linear combination fitting confirmed that most of selenite, selenate and arsenate ions existed in geopolymers through electrostatic interaction. Thus, Al tetrahedrons in geopolymer structure control the charge stability for these oxyanions to a large extent. Differently, as for arsenate ions, they were recrystallized into an arsenate compound (Na3.25 (OH)0.25 (H2 O)12 )(AsO4 ) in geopolymers. The additive of these pollutants has an adverse effect on the compactness of geopolymer, then influencing the leaching performance in turn. However, the changes in leaching results did not follow the variation trend of specific surface areas and pore volumes of geopolymers with different Si/Al ratios. The number and distribution of Al tetrahedron and compactness of geopolymer have a synergistic effect on the immobilization of these oxyanions. Besides, the compressive strengths of geopolymer samples are always higher than 20 MPa, which meets the requirement of safe disposal of hazardous waste. Graphical abstract: Image 1 Highlights: The percentages of Se and As leaching increased with the increase of the Si/Al ratio. Selenite, selenate and arsenite existed in geopolymer by electrostatic interaction. Arsenate ions were crystallized into an arsenate compound in geopolymer. Al distribution and compactness have a synergistic effect on the S/S process. Abstract : The number and distribution of Al tetrahedron largely determine the stabilities of Se and As oxyanions in geopolymers.