Hazard and Life Cycle Assessment of Titanium Dioxide Nanoparticles when Applied as Antimicrobial Coatings in Textiles

Abstract

Different methods have been developed to incorporate photocatalytic molecules like titanium dioxide onto cotton fabrics. The process chemicals used to fabricate three types of titanium dioxide coatings (nano-particle titanium dioxide, nitrogen doped titanium dioxide and nitrogen-plus-silver iodide doped titanium dioxide) were evaluated by utilizing two hazard assessment tools along with a life cycle assessment. Results from the GreenScreen and NanoRiskCat assessments illustrate that the hazard traits of the three coatings were very similar and thus there is no tradeoff between the efficiency and toxicity. The chemicals all obtained a GreenScreen benchmark score of 2 or 1, which represents chemicals to be avoided. The NRC ratings for the exposure-effects and hazardous-potential categories were the same of each of the three coatings. The life cycle assessment (LCA) provided insight into the potential environmental effects from the production process. Introduction. One of the unique properties of titanium dioxide is that it can act as an antimicrobial under particular conditions. When exposed to certain wavelengths of light, the titanium dioxide reacts and forms superoxide ions and hydroxyl radicals that can oxidize/ destroy various organic compounds - (i.e., pollutants, bacteria, dyes, stains, etc.) to form carbon dioxide and water. Because of this property, there are many practical applications for titanium dioxide coatings, such as incorporating the coatings onto fabrics to make the fabric self cleaning. Furthermore, the incorporation of different chemicals into the coating changes the range of radiation frequencies that can be absorbed, thus the antibacterial efficiency of titanium dioxide coatings differs depending on other incorporated chemicals. Nitrogen doping decreases the band gap of titanium dioxide, which makes the coating more reactive and photocatalytic. The energy gap for titanium dioxide is 3.2 eV, but with nitrogen added, it becomes 2.93 eV, (2). The addition of silver iodide induces visible light activity and the energy gap becomes 2.86 eV, (2). A review of the literature indicates that there is limited information on the toxicity of the coatings themselves and on the process chemicals. Thus, the main focus of the current investigation was to evaluate the hazard traits of the process chemicals used to fabricate three different coatings with variable efficiencies: pure nano-particle titanium dioxide, nitrogen doped titanium dioxide and nitrogen-plus-silver iodide doped titanium dioxide. Proceedings of the International Symposium on Sustainable Systems and Technologies (ISSN 2329-9169) is published annually by the Sustainable Conoscente Network. Melissa Bilec and Jun-Ki Choi, co-editors.