Silver nanoparticles are used in the Manufacture of more than 200 consumer products which include clothing and cosmetics, because of their antibacterial properties. As reported by researchers silver leaching from these consumer products transforms into silver sulfide nanoparticles in wastewater treatment plants. This finding is important to get information about the life cycle of these nanomaterials and to know how they move from manufactured products into the environment and what their impact is.
Virginia Polytechnic Institute & State University researchers found silver in the Sludge from a typical wastewater treatment plant using x-ray transmission electron microscopy, an extremely sensitive technique that can identify both composition and structure. With micrographs of sludge they identified nanoparticles 5 to 20 nm in diameter and determined that the particles had a 2-to-1 silver-to-sulfur ratio. The scientists also obtained a crystal structure to confirm that the particles were Ag2S. This is because wastewater plants contain high concentrations of sulfide and so silver readily binds to sulfur. The conversion of silver to silver sulfide within waste treatment plants may be good for the environment, but it is feared that these materials could still enter the ecosystem via animals who consume particles in the sludge, clearly giving a warning signal on the excessive use of silver nanoparticles.