Green-engineered clay- and carbon-based composite materials for the adsorption of benzene from air

Benzene is a carcinogenic volatile organic compound (VOC) that is ubiquitously detected in enclosed spaces due to emissions from cooking activities, building materials, and cleaning products. To remove benzene and other VOCs from indoor air and protect public health, traditional fabric filters have been modified to contain activated carbons to enhance the filtration efficacy. In this study, composites derived from natural clay minerals and activated carbon were individually green-engineered with chlorophylls and were attached to the surface of filter materials. These systems were assessed for their adsorption of benzene from air using in vitro and in silico methods. Isothermal, thermodynamic, and kinetic experiments indicated that all green-engineered composites had improved binding profiles for benzene, as demonstrated by increased binding affinities (K_f ≥ 900 vs 472) and lower values of Gibbs free energy (ΔG = -16.8 vs -15.2) compared to activated carbon. Adsorption of benzene to all composites was achieved quickly (< 30 min), and the green-engineered composites also showed low levels of desorption (≤ 25%). While free chlorophyll is known to be photosensitive, chlorophylls in the green-engineered composites showed photostability and maintained high binding rates (≥ 70%). Additionally, the in silico simulations demonstrated the significant contribution of chlorophyll for the overall binding of benzene in clay systems and that chlorophyll could contribute to benzene binding in the carbon-based systems. Together, these studies indicated that novel, green-engineered composite materials can be effective filter sorbents to enhance the removal of benzene from air.