Realizing Nanolime Aqueous Dispersion via Ionic Liquid Surface Modification to Consolidate Stone Relics

After decades of research in the conservation of cultural heritage, nanolime (NL) has emerged as a potential alternative inorganic material to the frequently used organic materials. However, its poor kinetic stability in water has been a major challenge that restricted its penetration depth through cultural relics and resulted in unsatisfactory conservation outcomes. Here, for the first time, we realize NL water dispersion by modification of ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate) via a sample aqueous solution deposit method. Our findings indicate that the cation of the ionic liquid (IL) binds strongly to the surface of NL particles (IL-NL) by forming hydrogen bonds with Ca(OH)₂ facets. The absorption of IL causes an unexpected significant alteration in the morphology of NL particles and results in a drastic reduction in NL's size. More importantly, this absorption endows NL excellent kinetic stability dispersed into water and implements NL water dispersion, which makes a breakthrough in terms of extreme poor kinetic stability of as-synthesized NL and commercial NL in water. The mechanism driving IL-NL water dispersion is explained by Stern theory. In the context of consolidating weathered stone, the presence of IL may delay carbonation of NL but the penetration depth of IL-NL through stone samples is three times deeper than that of as-synthesized and commercial NLs. Additionally, the consolidation strength of IL-NL is similar to that of as-synthesized NL and commercial NL. Moreover, IL-NL has no significant impact on the permeability, pore size, and microstructure of consolidated stone relics. Our research contributes to the field of NL-related materials and will enhance the dissemination and utilization of NL-based materials in the preservation of water-insensitive cultural heritage.