Organophosphates (OP) represent a major class of pesticides as well as a number of chemical warfare agents. In addition to current remediation approaches, catalytic hydrolysis of these toxic environmental contaminants by recyclable particulates is emerging as a promising alternative. We have developed a catalytic system based on magnetic nanoparticles functionalized with appropriate reactive groups for catalytic decomposition of OP compounds; these particles can be recycled and reused repeatedly.

Magnetite (Fe3O4) nanoparticle clusters with an average size of approximate 100 nm were successfully functionalized by Ą-nucleophilic groups, such as oximes and iodo-benzoates, through both water- and organic solvent-based reactions. These modified magnetite nanoparticle colloidal suspensions were electro-statically stabilized over a wide pH range. The particles significantly accelerated the hydrolysis reaction of a model compound, p-nitrophenyl acetate, and a real pesticide, paraoxon, and were readily recovered from the aqueous milieu for reuse by high-gradient magnetic separation methods with no loss of catalytic activity. A pseudo-phase model incorporating both surface adsorption of the substrate and the subsequent catalytic reaction by the functional groups on the particle surface captured well the experimentally observed trends.