Natural-sunlight-driven photocatalytic degradation of the organophosphorus nerve agent (GD) and sulfur mustard (HD) by TiO ₂

Titanium dioxide (TiO2)-mediated photocatalytic degradation of the organophosphorus nerve agent GD (soman) and sulfur mustard (HD) was examined under natural sunlight using authentic chemical warfare agents (CWAs). Experiments were performed in both liquid-phase and surface systems using n-hexane solutions and TiO2-coated paint substrates. After 6 h of sunlight exposure, the apparent parent-agent peak-area losses of GD and HD in solution were approximately 60% and 63%, respectively, while the corresponding apparent losses on TiO2-coated paint surfaces were 84% for GD and 86% for HD. In contrast, little parent-agent loss was observed in the dark or in the absence of TiO2, indicating that both solar irradiation and TiO2 were required for the observed decrease in GC/FPD response. All experiments were conducted with authentic CWAs in a laboratory designated under the Chemical Weapons Convention (CWC), following institutionally approved procedures for scheduled chemicals. These findings suggest that TiO2 can reduce detectable parent-agent residues under natural sunlight, and that TiO2-coated surfaces may provide a passive means of reducing residual contamination. Because the reported values were derived from relative GC/FPD peak-area changes without full external-calibration-based analytical validation, and because degradation products were not identified, the present results should be interpreted as representative proof-of-concept data rather than fully validated quantitative decontamination efficiencies.