Antimicrobial release from cleaning poultices for the conservation and disinfection of stone surfaces

Poultices, predominantly based on clays or silica powders, are commonly used by restorers for cleaning operations and disinfection of stone surfaces. However, operators often use poultices without paying particular attention to kinetics of release of the used antimicrobial agent from different types of supporting material. Cleaning procedures with poultices generally require fast and nearly complete release of the active agent. In this paper, releases of a commonly used antimicrobial ammonium salt (i.e. N-alkyl-N-benzyl-N,N-dimethylammonium chloride, shortly known as benzalkonium chloride, BAC) from poultices based on a sepiolite clay (Sep) or on a silica fume (SiO2), are studied by different techniques (WAXD, TGA, FT-IR, UV–Vis). Cation release from these poultices in aqueous media has been compared with those observed from intercalated compounds with a smectite clay (montmorillonite, Mt). Our results show that, for cleaning and disinfecting operations that require fast ammonium salt release, silica-based poultices would be preferred.