Radioactive borate waste containing a high concentration of boron (B) is problematic to be solidified using cement because soluble borate such as boric acid hinders the hydration reaction. In this study, borate waste was used as a raw material for metakaolin-based geopolymer according to the characteristic that B replaces a part of Si. Geopolymers using KOH alkaline activator (K-geopolymers) showed higher compressive strength than geopolymers using NaOH alkaline activator (Na-geopolymer). In addition, the compressive strength increased proportionally to the Si/(Al+B) ratio regardless of the alkaline cation species. These variations in compressive strength might be due to the viscosity of the geopolymer mixture, atomic size of alkaline cations, and the increase in Si content. The characteristic analyses (XRD, FT-IR, and solid state ¹¹B MAS NMR) indicated that B was incorporated into the geopolymer structure. Thus, the K-geopolymer has a dense and homogeneous microstructure. In a semi-dynamic leaching test, less B leached from the geopolymers compared to the cement waste form. Consequently, borate waste can be solidified using metakaolin-based geopolymer, and the use of a KOH alkaline activator is advantageous in terms of mechanical property and structural durability.

含有高浓度硼 (B) 的放射性硼酸盐废物在使用水泥固化时存在问题，因为硼酸等可溶性硼酸盐会阻碍水合反应。本研究利用硼酸盐废料作为偏高岭土基地质聚合物的原料，根据 B 替代部分 Si 的特性。使用 KOH 碱性活化剂的地质聚合物（K-地质聚合物）显示出比使用 NaOH 碱性活化剂（Na-地质聚合物）的地质聚合物更高的抗压强度。此外，无论碱性阳离子种类如何，抗压强度均与 Si/(Al+B) 比成比例增加。抗压强度的这些变化可能是由于地质聚合物混合物的粘度、碱性阳离子的原子大小和硅含量的增加。特征分析（XRD、FT-IR 和固态¹¹ B MAS NMR) 表明 B 被结合到地质聚合物结构中。因此，K-地质聚合物具有致密且均匀的微观结构。在半动态浸出试验中，与水泥废物形式相比，从地质聚合物中浸出的 B 较少。因此，可以使用偏高岭土基地质聚合物固化硼酸盐废物，并且使用 KOH 碱性活化剂在机械性能和结构耐久性方面是有利的。