Floating Photocatalysts as a Sustainable Solution for Water Harvesting in Vulnerable Communities

The exponential growth of the global population, projected to exceed 9 billion people by 2050, combined with increasing water scarcity driven by climate change, is placing unprecedented pressure on the world's water resources [1]. This issue is even more pronounced in developing countries, where water scarcity is a key factor behind numerous public health crises, during which unsanitary conditions expose both patients and doctors to risks of disease transmission [2]. In this challenging scenario, treating the tons of wastewater generated every day offers a promising solution. By transforming wastewater into a viable alternative water source, this approach addresses both resource scarcity and environmental sustainability. Although various technologies have been developed for water depollution (e.g., filtration, chemical or biological treatments) [3], they generally fail to remove contaminants of emerging concern (CECs) due to their high chemical stability, so developing efficient technologies for wastewater purification is crucial to mitigating water scarcity and ensuring access to safe water for all. In this framework, photocatalysis plays a pivotal role; indeed, the use of sunlight, an extremely powerful and abundant energy source, represents a vital resource in light of the current energy crisis. However, developing photocatalytic materials capable of exploiting the entire solar spectrum for pollutant photodegradation is challenging. Additionally, the most advanced materials reported in the literature are typically used as dispersed powders. Even if working with fine powders offers several benefits (e.g., high dispersion and impressive photoactivity), it also presents critical challenges, such as the difficulty of recovering them from the reaction mixture, which leads to contamination issues and additional costs [4]. For this reason, immobilizing photocatalysts strikes a balance between their advantages and the need for practical application by enhancing stability and enabling easier handling. In this context, floating photocatalysts offer the advantage of maximizing both light utilization and surface aeration, as they can remain at the air-water interface. Their use also reduces post-treatment costs. These foundations inspired the development of the project “Water Decontamination by Sunlight-Driven Floating Photocatalytic Systems” (SUNFLOAT). Within the SUNFLOAT project, various safe, cost-effective, and highly efficient photocatalysts designed to operate under solar irradiation were successfully fabricated and immobilized on different synthetic and natural floating supports [5-6]. The resulting materials were rigorously tested for the photodegradation of various CECs under both simulated and real sunlight conditions. The innovation introduced by the SUNFLOAT project highlights the practical viability of floating photocatalysts under natural solar conditions. The project underscores the effectiveness of these novel materials in harnessing solar energy for sustainable water purification. By proving their functionality under real sunlight, this initiative represents a significant advancement, offering an eco-friendly and scalable solution to improve water quality for remote communities facing water scarcity. References: [1]: He, C., Liu, Z., Wu, J., Pan, X., Fang, Z., Li, J., Brett, A.B., Nat. Commun.12, 4667 (2021). [2]: https://www.cdc.gov [3] Galloni, M.G., Ferrara, E., Falletta, E., Bianchi, C.L., Catalyst 12(8), 923, (2022). [4] Djellabi, R., Giannantonio, R., Falletta, E., Bianchi, C.L., Curr. Opin. Chem. Eng.33, 100696 (2021). [5] Galloni, M.G., Falletta, E., Mahdi, M., Giordana, A., Cerrato, G., Boffito, D.C., Bianchi, C.L., Adv. Sus. Syst. 2300565 (2024). [6] Galloni, M.G., Nikonova, V., Cerrato, G., Giordana, A., Pleva, P., Humpolicek, P., Falletta, E., Bianchi, C.L., J. Environ. Man., 369, 122365, (2024).