Characterization of silver release from commercially available functional (nano)textiles.

Silver, both in the nano as well as in other forms, is used in many applications including antimicrobial textiles. Washing of such textiles has already been identified as an important process that results in the release of silver into wastewater. This study thus investigated the release of silver from eight different commercially available silver-textiles during a washing and rinsing cycle. The silver released was size-fractionated and characterized using electron microscopy. In addition, the antimicrobial functionality of the textiles was tested before and after washing. Three of the textiles contained nanosized silver (labeled or confirmed by manufacturers' information), another used a metallic silver wire and four contained silver in undeclared form. The initial silver content of the textiles was between 1.5 and 2925mg Ag/kg. Only four of the investigated textiles leached detectable amounts of silver, of which 34-80% was in the form of particles larger than 450nm. Microscopic analysis of the particles released in the washing solutions identified Ti/Si-AgCl nanocomposites, AgCl nanoparticles, large AgCl particles, nanosilver sulfide and metallic nano-Ag, respectively. The nanoparticles were mainly found in highly agglomerated form. The identified nanotextiles showed the highest antimicrobial activity, whereas some of the other textiles, e.g. the one with a silver wire and the one with the lowest silver content, did not reduce the growth of bacteria at all. The results show that different silver textiles release different forms of silver during washing and that among the textiles investigated AgCl was the most frequently observed chemical form in the washwater.