Ionic Crosslinked Hydrogel Films for Immediate Decontamination of Chemical Warfare Agents

Abstract

This study describes the development of hydrogel formulations with ionic crosslinking capacity and photocatalytic characteristics. The objective of this research is to provide an effective, accessible, “green”, and facile route for the decontamination of chemical warfare agents (CWAs, namely the blistering agent—mustard gas/sulfur mustard (HD)) from contaminated surfaces, by decomposition and entrapment of CWAs and their degradation products inside the hydrogel films generated “on-site”. The decontamination of the notorious warfare agent HD was successfully achieved through a dual hydrolytic–photocatalytic degradation process. Subsequently, the post-decontamination residues were encapsulated within a hydrogel membrane film produced via an ionic crosslinking mechanism. Polyvinyl alcohol (PVA) and sodium alginate (ALG) are the primary constituents of the decontaminating formulations. These polymeric components were chosen for this application due to their cost-effectiveness, versatility, and their ability to form hydrogen bonds, facilitating hydrogel formation. In the presence of divalent metallic ions, ALG undergoes ionic crosslinking, resulting in rapid gelation. This facilitated prompt PVA-ALG film curing and allowed for immediate decontamination of targeted surfaces. Additionally, bentonite nanoclay, titanium nanoparticles, and a tetrasulfonated nickel phthalocyanine (NiPc) derivative were incorporated into the formulations to enhance absorption capacity, improve mechanical properties, and confer photocatalytic activity to the hydrogels obtained via Zn2+—mediated ionic crosslinking. The resulting hydrogels underwent characterization using a variety of analytical techniques, including scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), viscometry, and mechanical analysis (shear, tensile, and compression tests), as well as swelling investigations, to establish the optimal formulations for CWA decontamination applications. The introduction of the fillers led to an increase in the maximum strain up to 0.14 MPa (maximum tensile resistance) and 0.39 MPa (maximum compressive stress). The UV-Vis characterization of the hydrogels allowed the determination of the band-gap value and absorption domain. A gas chromatography–mass spectrometry assay was employed to evaluate the decontamination efficacy for a chemical warfare agent (sulfur mustard—HD) and confirmed that the ionic crosslinked hydrogel films achieved decontamination efficiencies of up to 92.3%. Furthermore, the presence of the photocatalytic species can facilitate the degradation of up to 90% of the HD removed from the surface and entrapped inside the hydrogel matrix, which renders the post-decontamination residue significantly less dangerous.

Keywords

• hydrogels
• mustard gas decontamination
• photocatalytic degradation
• mechanical properties of hydrogels
• ionic crosslinking