Comparative study on the effect of chitosan, chitosan nanoparticles, and SiO2 loaded chitosan for the consolidation of the painted stone

The mural paintings are prone to deterioration due to surface powdering, cracking, and loss of painted layers, so coating the mural paintings with eco-friendly benign materials is urgent for consolidation and restoration purposes. Minimizing particle size to the nanoscale results in better properties compared to their bulk equivalents. This paper discussed the utilization of chitosan (Cs), chitosan nanoparticles (CsNPs), and silica-loaded chitosan (SiO₂@CsNPs) to improve the consolidation of the painting surfaces on the facade of Neb-Maat-Ra's palace gate, which is a monument to King Ramesses IX (1125–1107 BC) in Egypt. Biopolymers are eco-friendly materials and considered an effective alternatives to synthetic coatings in the consolidation of cultural heritage. Cs has the potential to be a substitute for conserving well-painted paintings and stone, the presence of amino groups in chitosan's structure confers high biological activity and reactivity. CsNPs are more attractive compared to bulk chitosan, moreover, the incorporation of silica (SiO₂) into CsNPs created good hydrophilic/hydrophobic balance and enhanced the mechanical scrub resistance. Digital Microscope, Scanning Electron Microscopy (SEM), Portable X-Ray Fluorescence Spectrometer (pXRF), (FTIR ATR), and Colorimetric measurements were used in performing the study. X-ray fluorescence was utilized to determine the compounds used in the facade of Neb-Maat-Ra's palace gate. Limestone served as the support, and hematite was used to create red pigment. The results showed that CsNPs and SiO₂@CsNPs were superior to traditional Cs, however, the best result was observed for SiO₂@CsNPs. Our study revealed the potential of CsNPs and SiO₂@CsNPs in the protection of the facade of Neb-Maat-Ra, the son of King Ramesses.