For the geological repository of high-level radioactive waste (HLW) built in granitic host rock，the control of buffer material (compacted bentonite) erosion and subsequent loss caused by groundwater in granite fissures is an unresolved problem of major concern. We propose here new insight into enhancing the erosion resistance of compacted bentonite by means of its electrostatic interaction with oppositely-charged layered double hydroxide (LDH). The interaction between bentonite and LDH was studied by dropwise addition of colloidal LDH into colloidal bentonite suspension, during which the variation in electrical conductivity, zeta potential and particle size proved a strong interaction between these two materials. Interestingly, in addition to their aggregation, intercalated structures of LDH and montmorillonite were found in the composite (BEN@LDH) by a combined characterization of X-ray diffraction (XRD) and high resolution transmission electron microscopy (HR-TEM), and were confirmed by density functional theory (DFT) calculation. Colloid generation of compacted BEN@LDH under ultrasonic conditions is negligible comparing with that of compacted bentonite, indicating a significantly higher erosion resistance. Besides, a small amount of LDH by mechanically mixing with bentonite (mass ratio 1:99) can also effectively improve the erosion resistance of compacted bentonite. Moreover, BEN@LDH displayed stronger retention performance towards U(VI) and Se(IV) than bentonite under near-neutral/weakly alkaline conditions. Our results indicate that LDH is a promising additive in compacted bentonite, and this approach may be extended to common geotechnical structures built with clays and soils.

对于建在花岗岩母岩中的高放废物地质处置库，控制缓冲材料（压实膨润土）在花岗岩裂隙中的冲刷和地下水流失是一个亟待解决的重大问题。我们在这里提出了通过与带相反电荷的层状双氢氧化物 (LDH) 的静电相互作用来增强压实膨润土的耐腐蚀性的新见解。通过将胶体LDH滴加到胶体膨润土悬浮液中研究了膨润土与LDH之间的相互作用，在此期间电导率、zeta电位和粒径的变化证明了这两种材料之间的强相互作用。有趣的是，除了它们的聚合，通过X射线衍射（XRD）和高分辨率透射电子显微镜（HR-TEM）的组合表征，在复合材料（BEN@LDH）中发现了LDH和蒙脱石的插层结构，并通过密度泛函理论（DFT）证实计算。与压实膨润土相比，超声波条件下压实 BEN@LDH 的胶体生成可忽略不计，表明其抗腐蚀性能显着提高。此外，少量LDH与膨润土机械混合（质量比1：99）也能有效提高压实膨润土的抗冲刷性。此外，在近中性/弱碱性条件下，BEN@LDH 对 U(VI) 和 Se(IV) 的保留性能比膨润土强。我们的研究结果表明，LDH 是一种很有前途的膨润土添加剂，