compositions and methods for destroying chemical and biological agents such as toxins and bacteria are provided wherein the substance to be destroyed is contacted with finely divided metal oxide nanoparticles . the metal oxide nanoparticles are coated with a material selected from the group consisting of surfactants , waxes , oils , silyls , synthetic and natural polymers , resins , and mixtures thereof . the coatings are selected for their tendency to exclude water while not excluding the target compound or adsorbates . the desired metal oxide nanoparticles can be pressed into pellets for use when a powder is not feasible . preferred metal oxides for the methods include mgo , sro , bao , cao , tio 2 , zro 2 , feo , v 2 o 3 , v 2 o 5 , mn 2 o 3 , fe 2 o 3 , nio , cuo , al 2 o 3 , sio 2 , zno , ag 2 o , the corresponding hydroxides of the foregoing , and mixtures thereof .