3D printed floating photocatalysts for wastewater treatment

Abstract

Organic contaminants, specifically contaminants of emerging concern (CECs), have a great environmental impact, since the removal of these pollutants is of great difficulty by conventional treatments and the presence of these pollutants in the aquatic medium, even at low concentrations, is extremely hazardous to human health. Advanced oxidation processes and, specifically, TiO₂-photocatalytic process is considered an option with positive results for an efficient treatment. However, the photocatalyst must be accessible to the UV radiation, for the activation of the TiO₂. For this reason, it is recommendable to use a floating photocatalyst (with lower density than water) if the UV light comes from the solar radiation, because it will be on the water surface. In addition, this characteristic of the catalyst can entail an increase of the process efficiency if the pollutant is mainly located on the surface of water. In this context, the goal of this work is the preparation of floating photocatalysts for the removal of CECs from wastewater. TiO₂ is deposited in low-density-polyethylene (LDPE), support with lower density than water and high stability and resistance to degradation. LDPE-TiO₂ mixtures were prepared by different methods: mixing TiO₂ and LDPE in a hot-cylinder-mixer or using o-xylene or an anionic surfactant as dispersing agent, in order to increase the dispersion of TiO₂ before extrusion. Filaments obtained were printed as meshes in a Fused-Deposition-Modelling 3D-printer. The printed photocatalysts improved the activity in comparison with the plate obtained in the cylinder, used as benchmark. Thus, this study opens the doors to the in-situ treatment of CECs, using floating photocatalysts and solar radiation as the sole reagent, a very economical, efficient, easily implantable and environmentally compatible process.