Federico Giuffrida

An improvement of water supply and sanitation and better management of water resources, especially in terms of water reuse, is one of the priorities of the European Green Deal. In this context, it is crucial to find new strategies to recycle wastewater efficiently in a low-cost and eco-friendly manner. The immobilization of inorganic nanomaterials on polymeric matrices has been drawing a lot of attention in recent years due to the extraordinary properties characterizing the as-obtained nanocomposites. The hybrid materials, indeed, combine the properties of the polymers, such as flexibility, low cost, mechanical stability, high durability, and ease of availability, with the properties of the inorganic counterpart. In particular, if the inorganic fillers are nanostructured photocatalysts, the materials will be able to utilize the energy delivered by light to catalyze chemical reactions for efficient wastewater treatment. Additionally, with the anchoring of the nanomaterials to the polymers, the dispersion of the nanomaterials in the environment is prevented, thus overcoming one of the main limits that impede the application of nanostructured photocatalysts on a large scale. In this work, we will present nanocomposites made of polymers, i.e., polymethyl methacrylate (PMMA), and photocatalytic semiconductors, i.e., TiO₂ nanoparticles (Evonik). MoS₂ nanoflakes were also added as co-catalysts to improve the photocatalytic performance of the TiO₂. The hybrid materials were prepared using the sonication and solution casting method. The nanocomposites were deeply characterized, and their remarkable photocatalytic abilities were evaluated by the degradation of two common water pollutants: methyl orange and diclofenac. The relevance of the obtained results will be discussed, opening the route for the application of these materials in photocatalysis and especially for novel wastewater remediation.

The photocatalytic proprieties of TiO₂/FeO₃ and TiO₂/WO₃ nanocomposites have been investigated using methylene blue as a pollutant. We propose a non-conventional approach for material preparation, i.e., the Doctor Blade technique, which is an easy and inexpensive method for coating materials. Several drawbacks related to the use of powders can be alleviated by using solid substrates, and this deposition method allows us to take advantage of the high surface area of nanoparticles, avoiding dispersion in the solution. The possibility of coating a material with a photoactive molecule with an easy and inexpensive method leads to the use of photocatalysis in the real world. The structural, optical, and textural characterizations of these materials were carried out using UV-vis. Diffuse Reflectance Spectroscopy (DRS) was used to calculate the energy band gap with the Kubelka-Munk method, and N₂ absorption-desorption measurements were used to study the exposed surface area (S_BET). The photocatalytic activity was evaluated in nanocomposites containing 0.1/0.2/0.3/0.5 wt.% of Fe₂O₃ or WO₃ or both Fe₂O₃ and WO₃. An enhancement of about 60% was achieved by adding 0.2% wt. of WO₃ after 2 h of exposure to UV light. The TiO₂@Fe₂O₃ and TiO₂@WO₃/Fe₂O₃ mixtures showed the same behavior as the TiO₂@WO₃ mixture. Therefore, the photoactivity of these photocatalysts is not related to the oxide itself. These solid results are due to the energy band structure of the materials. In fact, there is an important band matching among TiO₂, WO₃, and Fe₂O₃, which gives these nanocomposites a substantial improvement in photodegradation. The pH evaluated was neutral pH both at the beginning and at the end of the experiment, which is consistent with the well-known photodegradation pathway of methylene blue.