Adsorbent media for the sustainable removal of organic air pollutants from museum display cases

Abstract

The application of adsorbents in museum display cases appears auspicious, as the selection of low-emitting building and decoration materials does not necessarily ensure low pollution levels. Furthermore, historical furnishings may form an integral part of a museum and consequently cannot be substituted. Therefore, comprehensive experiments regarding the filtration efficiency of 37 different adsorbent media, both under active and passive conditions, have been conducted in order to simulate conditions in display cases with/without forced air exchange. The adsorbent media comprised pure and impregnated activated charcoal, charcoal foams and cloths, zeolites, molecular sieves and materials specially designed for museum purposes, such as archival cardboard, textiles and silica gels. Formaldehyde, formic acid, acetic acid, toluene and alpha-pinene were chosen as ubiquitous airborne pollutants in the museum environment. Tests were performed in environmental test chambers. The air exchange rate during active-mode tests was 0.5 h−1. The concentrations of single substances in the chamber air ranged between 0.3 mg m−3 and 6 mg m−3. For the passive-mode experiments, the chamber air was doped with 432 µg m−3 to 1371 µg m−3 of the target compounds. Under active conditions, most of the pure and impregnated charcoals were able to reduce pollutant levels quickly. The lowest adsorption efficiency was found for charcoal foam and cloths, zeolites, molecular sieves and special products designed for museum purposes. However, these materials also removed pollutants very efficiently within a short time under passive conditions with no forced air circulation. As pure activated charcoals performed best in both experiments, there is no need to use impregnated or cost-intensive sorbents in museum display cases. However, regular monitoring during application is recommended, as it was found that some adsorbent media might act as emission sources themselves by releasing volatile organics both before and after exposure to pollutants. It was also shown that emissions might be generated due to fragmentation reactions or pollutant-adsorber interactions; the selection and application of sorbents should therefore be performed with caution.