添加剂对地质聚合物固化Se(Ⅵ)与Cr(Ⅵ)的作用机制

Effect of Additives on Immobilization of Se(Ⅵ)and Cr(Ⅵ)in Geopolymer

针对地质聚合物固化Se(Ⅵ)、Cr(Ⅵ)等含氧阴离子效率低的问题,研究了Ca、Mg、Fe(Ⅱ)盐对地质聚合物固化Se(Ⅵ)、Cr(Ⅵ)的作用机制。结果表明:无添加剂作用的地质聚合物固化体Se或Cr浸出量可高达60%以上,CaO或Fe(Ⅱ)盐对Se或Cr浸出有一定的抑制作用,但浸出量仍高达40%以上,效果均有限,而Mg O作用下Se或Cr浸出量可降至10%以下。LCF分析结果显示Cr(Ⅵ)与Se(Ⅵ)在地质聚合物三维网状结构中均以静电力的结合方式存在。此外,Mg O或CaO的水化过程可促使Fe(Ⅱ)还原性的释放,约15%的Cr(Ⅵ)可被还原为Cr(Ⅲ);而针对Se(Ⅵ),Ca与Se(Ⅵ)可发生键合作用,Fe(Ⅱ)并没有起到还原性的作用;Mg O、CaO、Fe(Ⅱ)盐对固化体中Se(Ⅵ)或Cr(Ⅵ)的浸出起着一定的协同效应。此外,Mg O、CaO、Fe(Ⅱ)盐作用的地质聚合物固化体强度均满足工业填埋最低要求。

Geopolymers have a low immobilization efficiency to oxyanions,such as Se(Ⅵ)and Cr(Ⅵ).Effects of Ca,Mg and Fe(Ⅱ)additives on the immobilization of Se(Ⅵ)and Cr(Ⅵ)in geopolymer were thus investigated.The results indicate that the leaching amount of Se or Cr ions is greater than 60%for the geopolymers without any additives.CaO or Fe(Ⅱ)has a limited depressive effect on Se(Ⅵ)or Cr(Ⅵ)leaching from geopolymers,and the corresponding leaching amount of Se(Ⅵ)or Cr(Ⅵ)is still greater than 40%.However,the leaching amount of Se(Ⅵ)or Cr(Ⅵ)is lower than 10%for the geopolymers with the addition of MgO.According to the LCF fitting results,Cr(Ⅵ)can also exist in the geopolymer network through electrostatic interaction as Se(Ⅵ).Besides,MgO or CaO can promote Fe(Ⅱ)to release its reducibility,thereby reducing approximately 15%of Cr(Ⅵ)to Cr(Ⅲ).Se(Ⅵ)can have a bonding interaction with Ca.Fe(Ⅱ)does not present its reducibility during the solidification of Se(Ⅵ).To some extent,MgO,CaO and Fe(Ⅱ)have a synergistic effect on the leaching of Se(Ⅵ)and Cr(Ⅵ)from geopolymers.In addition,the mechanical strength of geopolymers with or without these additives can satisfy a requirement for industrial landfill.