Life Cycle Assessment of the Sustainability of Enhancing the Photodegradation Activity of TiO₂ with Metal-Doping

• Main Authors: Sónia Fernandes, Joaquim C.G. Esteves da Silva, Luís Pinto da Silva
• Format: Article
• Language: English
• Published: MDPI AG 2020-03-01
• Series: Materials
• Subjects: life cycle assessment; tio₂ photocatalysts; photodegradation; metal-doping; engineered nanomaterials
• Online Access: https://www.mdpi.com/1996-1944/13/7/1487

While TiO₂ nanoparticles have shown potential as photocatalysts in the degradation of organic contaminants, their inability to absorb efficiently visible light has limited their industrial application. One strategy for solving this problem is monodoping TiO₂ photocatalysts with transition metals, which has worked in the degradation of several pollutants. However, it is not clear if this improvement is enough to offset the potential environmental impacts of adding metal ions to the synthesis of TiO₂. Herein, we have used Life Cycle Assessment (LCA) to determine the sustainability of monodoping TiO₂ with transition metals (Fe, Co, Mn and Ni, with a 1% weight ratio) to enhance the photocatalytic properties of the photocatalyst toward the degradation of Carbamazepine and Methyl Orange, under UV-A and visible light irradiation. We found that the addition of transition-metals has no significant effect on the environmental impacts associated with the synthesis of TiO₂, when a weight-based functional unit was considered. However, when photocatalytic activity was considered, major differences were found. Thus, our results demonstrate that the sustainability of monodoping with different transition metals is solely determined by their ability to enhance (or not) the photocatalytic activity of TiO₂. Our data also demonstrated that isopropyl alcohol constitutes a critical point in the synthesis of TiO₂ photocatalysts, with ethanol being a potential substitute.