Evaluation of photocatalytic nanoparticle release to the aquatic environment

Nanotechnology creates possibilities to produce new products with novel functionalities and improved characteristics. Therefore the incorporation of engineered nanoparticles (ENP) in commercial products is progressively increasing and so is the potential for release of these novel materials into the environment. In fact, the occurrence and release of titanium nanomaterials in a wastewater treatment plant has already been proven. This implies that nanomaterials will reach the aquatic environment and that they could represent a risk to aquatic organisms and humans. We have studied the discharge of nano-TiO₂ (nTiO₂) to water for two case studies related to photocatalytic nanomaterials: A- The release of nTiO₂ from two photocatalytic coatings under accelerated aging under a water flow and B- The release of nTiO₂ though a filtration pilot plant from tap water containing 2 mg/L nanoparticles. Case A. The influence of environmental parameters (water matrix, UV-light) was investigated while the consequences of aging were evaluated under different endpoints, among them, the release of TiO₂ nanoparticles. Despite that TiO₂ emissions were observed for both coatings, only one of them presented mechanical damages. TiO₂ concentrations up to 150.5 μg/L were detected in the aging water. Case B. Preliminary experiments were conducted at laboratory scale to determine optimum polymeric material as well as pore size. Among the common commercial materials PVDF showed the best performance. Two different industrial hollow fiber cartridges were tested with a pore size of 0.45 μm (microfiltration) and 0.03 μm (ultrafiltration). TiO₂ was detected at an average concentration of 51 μg/L in the filtered water.