Fabrication and application of palygorskite-based superhydrophobic antibacterial coatings for sandstone heritage conservation

Sandstone cultural heritage is vulnerable to acid rain and microbial colonization. This study develops a palygorskite-based multifunctional protective coating (Fluor@Ag + CuFePBA/Pal) for sandstone conservation. CuFePBA/Pal nanocomposites were synthesized via co-precipitation using palygorskite as a natural mineral carrier, followed by Ag⁺ introduction to yield light-colored Ag + CuFePBA/Pal with enhanced antibacterial activity through sustained release of metal ions and reactive oxygen species generation. Surface fluorination with PFDTES reduced surface energy while the nanofibrous microstructure created micro/nano-roughness, synergistically achieving superhydrophobicity (water contact angle 162°, sliding angle 18.1°, contact angle hysteresis 8.7°) and 99.9% bacterial anti-adhesion against both Staphylococcus aureus ( S. aureus ) and Escherichia coli ( E. coli ). Simulated sandstone showed no microbial growth after 30 days. Accelerated aging tests and 12-month indoor exposure confirmed the coating’s long-term stability and durability in real preservation environments, establishing an effective strategy for protecting sandstone cultural heritage.