National Engineering Research Center of Coal Preparation and Purification, China University of Mining and Technology, Xuzhou, 221116, China; Department of Earth Resources Engineering, Kyushu University, Fukuoka, 819-0395, Japan.
National Engineering Research Center of Coal Preparation and Purification, China University of Mining and Technology, Xuzhou, 221116, China; School of Chemical Engineering and Technology, China University of Mining and Technology, Xuzhou, 221116, China.
Environ Pollut. 2021 Apr 1;274:116509. doi: 10.1016/j.envpol.2021.116509. Epub 2021 Jan 15.
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 N 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 (Na(OH)(HO))(AsO) 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.
通过浸出实验和 XRD、FTIR、TG、NMR、XAFS、N2 吸附-脱附等温线等固体特性分析，研究了地质聚合物的 Si/Al 摩尔比对 Se 和 As 氧阴离子固定化的影响。总的来说，随着地质聚合物 Si/Al 摩尔比的增加，Se 和 As 氧阴离子的浸出率也随之增加。线性组合拟合证实，大部分亚硒酸盐、硒酸盐和砷酸盐离子通过静电相互作用存在于地质聚合物中。因此，地质聚合物结构中的四配位铝原子在很大程度上控制了这些氧阴离子的电荷稳定性。不同的是，对于砷酸盐离子，它们在地质聚合物中重新结晶为砷酸盐化合物(Na(OH)(HO))(AsO)。这些污染物的添加对地质聚合物的致密性有不利影响，从而影响浸出性能。然而，浸出结果的变化并不遵循不同 Si/Al 比地质聚合物比表面积和孔体积的变化趋势。四配位铝原子的数量和分布以及地质聚合物的致密性对这些氧阴离子的固定化具有协同作用。此外，地质聚合物样品的抗压强度始终高于 20 MPa，满足危险废物安全处置的要求。
