Decontamination of sarin in water by designed oxime-clay composites

The hydrolysis of the organophosphate nerve agent sarin (GB), is prone to rapid catalytic hydrolysis by oximes. In this study, an oxime-clay composite, based on the adsorption of 2-pyridinealdoxime (2-PAM) to montmorillonite (MMT), was designed as a delivery system of oxime for GB degradation in water. 2-PAM adsorption reached a plateau at ~0.5 mmol/g; however, the degree of 2-PAM desorption from composites in water (with and without GB) was not constant and increased with an increase in its initial added concentration. The composites were characterized by SEM, XRD, FTIR-ATR and TGA measurements. We suggest 2-PAM adsorbs in three modes; in a planar orientation while 1. intercalated or 2. directly adsorbed on the external surface, and 3. “weakly adsorbed”, as a multilayer on the external surface. The removal of GB (40 μg/ml) in the presence of MMT-PAM composites enhanced dramatically compared to its spontaneous hydrolysis in distilled-, tap- or buffered water e.g., from a half-life time of 2.5 h in tap-water to 0.3 h in a composite suspension (6.4 g clay/l). GB removal was attributed, not to adsorption, but rather to catalytic hydrolysis by released oxime, forming non-toxic compounds. The rate of GB removal was further enhanced by applying composites designed to release higher concentrations of 2-PAM.