Adsorption and photodegradation of dimethyl methylphosphonate on mineral surfaces: A comparative study of titania and kaolin

• Investigated the adsorption and photodegradation of a chemical warfare agent simulant (DMMP) on titania and anhydrous and natural kaolin. • Results for DMMP on titania show strong interactions and photodegradation and are consistent with previous literature reports. • Results for DMMP on kaolin show significantly weaker interactions and photodegradation, with some reactions being reversible. The environmental persistence and surface interactions of chemical warfare agents (CWAs) and their simulants are of critical importance for understanding contamination dynamics and informing decontamination strategies. In this study, we investigated the adsorption and photo-induced decomposition of dimethyl methylphosphonate (DMMP), a widely used CWA simulant, on three mineral substrates: titania (TiO 2 ), anhydrous kaolin, and natural kaolin. Using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), we monitored the chemical transformations of DMMP under controlled dosing and UV photoirradiation conditions. On titania, DMMP exhibited strong surface interactions and underwent significant photo-decomposition, forming transient products such as formic acid and CO 2 . In contrast, both anhydrous and natural kaolin showed weaker interactions, with fewer and largely reversible spectral changes. Notably, natural kaolin exhibited additional features associated with its inherent water content but lacked evidence of the carbonyl-containing photoproducts observed on titania. These findings demonstrate that mineral surface composition and structure significantly influence the fate of organophosphorus compounds under environmental conditions. The results contribute to a deeper understanding of CWA behavior on mineral dust surfaces and may support the development of passive remediation strategies.