A method for preparing highly stabilized and dispersible zero valent iron nanoparticles and using the nanoparticles as a remediation technology against inorganic chemical toxins in contaminated sites. The method employs a composition containing select polysaccharides (starch or cellulose) as a stabilizer for the iron nanoparticles in a liquid carrier, and results in suspensions of iron nanoparticles of desired size and mobility in water, brine, soils or sediments. The stabilizer facilitates controlling the dispersibility of the iron nanoparticles in the liquid carrier. An effective amount of the composition is delivered to a contaminated site so that the zero valent iron nanoparticles can remediate one or more toxins such as an arsenate, a nitrate, a chromate, or a perchlorate in the contaminated site.