Innovative floatable O-g-C3N4 alginate spheres for water remediation under solar light

In the last decades, the attention to environmental issues and the race to develop eco-friendly processes, has further attracted the field of research towards an inexpensive, simple, and reliable technology. A concerning global issue is freshwater scarcity mainly caused by leaking landfills, industrial waste, and sewage. In this regard, heterogeneous photocatalysis could offer a feasible solution to this problem aiming at the development of photoactive devices suitable for water remediation. Although TiO2 is still the most used semiconductor due to its chemical and physical stability, good photoactivity and low cost, researchers are willing to replace it with new smart materials because of its suspected carcinogenic nature and limited activity under solar light[1]. Among them, g-C3N4 has promising features as photocatalyst for water-remediation considering its visible-light response, simple synthetic pathway, and peculiar layered structure and cheap production cost[2]. To overcome problems related to the use of slurry systems for water purification, new floating substrates were employed to immobilize the photocatalyst. Since their closeness to water-surface, these devices can be fully irradiated by light source, better oxygenated, and easily recovered and reused[3]. Within this framework, synthetic polymers are commonly used as support, however their non-degradability has raised ecological concerns. Instead, an eco-friendly alternative can be the use of natural polymers, such as alginate, which derives from brown seaweeds and can be used for the immobilization of photocatalysts under safe and mild conditions[4]. In the present study, different methods were applied in order to synthesize floating alginates as support for O-doped g-C3N4 catalysts, whose activity was improved under visible light by doping with oxygen. These materials were deeply studied for photodegradation of rhodamine B, sodium diclofenac and isoproturon in water under solar light irradiation. Furthermore, floating photocatalyst were subjected to recycle test, in order to verify their activity and stability after several experiments. [1] D. Meroni, M.Jiménez-Salcedo, E. Falletta, B. M. Bresolin, C. Fai Kait, D. C. Boffito, C. L. Bianchi, C. Pirola, Ultrason. Sonochem. 2020, 67, 105. [2] J. Fu, J. Yu, C. Jiang, B. Cheng, Adv. Energy Mater. 2018, 8, 1. [3] Z. Xing, J. Zhang, J. Cui, J. Yin, T. Zhao, J. Kuang, Z. Xiu, Appl. Catal. B Environ. 2018, 225, 452. [4] I. Dalponte, B. C. de Sousa, A. L. Mathias, R. M. M. Jorge, Int. J. Biol. Macromol. 2019, 137, 992.