The accelerated deterioration of carbonate stone artifacts under climate change has long been an urgent issue. Inspired by biomineralization, we developed carboxymethyl chitosan-diammonium hydrogen phosphate (CD) composite and investigated the conservation effectiveness of the CD composite compared to diammonium hydrogen phosphate (DAP) on limestone. The morphologies and microstructures were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FT-IR). The consolidating effectiveness was investigated through a compressive strength test. The protective ability was assessed by disintegration resistance test, acid attack resistance test, salt attack resistance test, and freeze–thaw aging cycle test. SEM observations revealed that carboxymethyl chitosan (CMCS) served as an effective template, inducing the in situ formation of a uniform and continuous calcium phosphate coating on both the surface and interior of the stone. The tests indicated that the CD composite further enhanced the consolidating effectiveness and improved resistance to disintegration and freeze–thaw cycles. Notably, as an amphiphilic polyelectrolyte, CMCS functioned as a pH buffer and a protective barrier against sodium sulfate salts, which improved the resistance to acid and salt attacks. Additionally, the CD composite did not cause significant variations in the esthetic appearance or water vapor permeability. We then applied the CD composite at an actual carbonate stone cultural heritage site, successfully demonstrating the feasibility of CD application and the reversibility of CMCS in a real-world setting. Based on the study’s results, our approach provides a new perspective for developing multifunctional and sustainable conservation materials for carbonate stone artifacts.

中文翻译：

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羧甲基壳聚糖作为磷酸钙的可逆模板，用于碳酸盐石的多功能保护


长期以来，气候变化下碳酸盐岩文物的加速恶化一直是一个紧迫的问题。受生物矿化作用的启发，我们开发了羧甲基壳聚糖-磷酸氢二铵 （CD） 复合材料，并研究了 CD 复合材料与磷酸氢二铵 （DAP） 相比在石灰石上的保护效果。使用扫描电子显微镜 （SEM） 、 X 射线衍射 （XRD） 和傅里叶变换红外光谱 （FT-IR） 对形貌和微观结构进行了表征。通过抗压强度测试研究了固结效果。通过抗崩解性试验、抗酸性试验、抗盐侵蚀性试验和冻融老化循环试验评价保护能力。SEM 观察显示，羧甲基壳聚糖 （CMCS） 是一种有效的模板，可在宝石的表面和内部诱导原位形成均匀连续的磷酸钙涂层。结果表明，CD 复合材料进一步增强了固结效果，提高了对崩解和冻融循环的抵抗力。值得注意的是，作为一种两亲性聚电解质，CMCS 起到 pH 缓冲剂和对抗硫酸钠盐的保护屏障的作用，从而提高了对酸和盐侵蚀的抵抗力。此外，CD 复合材料不会引起美学外观或水蒸气渗透性的显着变化。然后，我们在实际的碳酸盐岩文化遗产地应用了 CD 复合材料，成功地证明了 CD 应用的可行性和 CMCS 在现实世界中的可逆性。 根据研究结果，我们的方法为开发多功能和可持续的碳酸盐石文物保护材料提供了新的视角。