Ultraviolet Light-Assisted Decontamination of Chemical Warfare Agent Simulant 2-Chloroethyl Phenyl Sulfide on Metal-Loaded TiO2/Ti Surfaces

Abstract

The application of ultraviolet (UV) light for the decontamination of chemical warfare agents (CWAs) has gained recognition as an effective method, especially for treating hard-to-reach areas where wet chemical methods are impractical. In this study, TiO₂/Ti was employed as a model catalyst, which was contaminated with 2-chloroethyl phenyl sulfide (CEPS), and subjected to photocatalytic decontamination using both UVB and UVC light. Additionally, photocatalytic decontamination efficiency by introducing Au, Pt, and Cu onto the TiO₂/Ti surface was explored. During the photodecomposition process under UVC light, at least eight distinct secondary byproducts were identified. It was observed that the introduction of overlayer metals did not significantly enhance the photodecomposition under UVC light instead overlaid Au exhibited substantially improved activity under UVB light. Whereas, photodecomposition process under UVB light, only five secondary products were detected, including novel compounds with sulfoxide and sulfone functional groups. This novel study offers valuable insights into the generation of secondary products and sheds light on the roles of overlayer metals and photon wavelength in the photodecontamination process of CWA.

Keywords: 2-chloroethyl phenyl sulfide; Chemical warfare agent; Overlaid Au; Secondary byproducts; TiO2/Ti; UV photodecontamination.

Figure 1

GC‐MS profiles of CEPS and after photocatalytic decontamination over bare TiO₂/Ti and Au/TiO₂/Ti with Au deposition time (a). Selected GC‐MS profile for Au_60s/TiO₂/Ti showing decontaminated byproducts (A to H), and inset shows CEPS showing plausible bond breakages (b). Relative intensity of the product compared with CEPS peak, I/I_CEPS×100 (%) (c to c7).

Scheme 1

Reaction mechanism for A (2,3‐dihydro benzothiophene).

Scheme 2

Reaction mechanism for B (2‐chloro‐1,1‐bis(2‐chloroethoxy)ethane).

Scheme 3

Reaction mechanism for C (diphenyl sulfide).

Scheme 4

Reaction mechanism for D ((phenylthio)acetic acid).

Scheme 5

Reaction mechanism for E (2‐chloroethyl phenyl sulfone).

Scheme 6

Reaction mechanism for F (diphenyl disulfide).

Scheme 7

Reaction mechanism for G (phenyl vinyl sulfide)

Scheme 8

Reaction mechanism for H (allyl phenyl sulfide).

Figure 2

GC‐MS profiles of CEPS after photocatalytic decontamination over bare TiO₂/Ti, Au_20s/TiO₂/Ti, Cu_30s/TiO₂/Ti, and Pt_30s/TiO₂/Ti (a). Relative intensities of the secondary byproducts compared with the CEPS peak, I/I_CEPS×100 (%) for the four different catalysts under UVC conditions (b to b7).

Figure 3

GC‐MS profiles of CEPS after photocatalytic decontamination over bare TiO₂/Ti and Au_20s/TiO₂/Ti under UVB condition (a). GC‐MS profiles of CEPS after photodecontamination over Au_20s/TiO₂/Ti under UVC and UVB conditions (b). Relative intensities of the secondary byproducts compared with the CEPS peak, I/I_CEPS×100 (%) over bare TiO₂/Ti and Au_20s/TiO₂/Ti under UVB condition (c and d, respectively).

Scheme 9

Reaction mechanism for I ((ethenylsulfinyl)benzene).

Scheme 10

Reaction mechanism for J (phenyl vinyl sulfone).

Figure 4

XRD pattern of TiO₂/Ti (a). Raman spectra and SEM image (in the inset) of TiO₂/Ti (b). UV–vis absorption spectra of CEPS before and after photocatalytic decontamination over bare TiO₂/Ti and Au_20s/TiO₂/Ti under UVC and UVB light conditions (c). Corresponding FT‐IR spectra of CEPS before and after photodecontamination over bare TiO₂/Ti and Au_20s/TiO₂/Ti under UVC and UVB light conditions (d).

Figure 5

Ti 2p (a), O 1s (b), C 1s (c), Cl 2p (d), S 2p (e), and Au 4f (f) XPS profiles of CEPS before (non‐contaminated and contaminated) and after photocatalytic decontamination over bare TiO₂/Ti and Au_20s/TiO₂/Ti under UVC light condition.

Figure 6

Secondary byproducts formed under UV light photocatalytic decontamination of CEPS. I and J were only produced under UVB light conditions.