Advanced photocatalysts for wastewater remediation: the fascinating world of bismuth oxyhalides supported on eco-friendly floating devices

Nowadays, the water crisis caused by insufficient water supply and pollution leads to several problems related to drought, famine, and death. In particular, about 1.1 billion people worldwide suffer from poor access to water and ca. 2.7 billion experience water scarcity for at least one month each year [1]. In this drastic scenario, treating wastewater contaminated by different pollutants is of pivotal environmental and commercial importance and urgently requires fast and efficient solutions. Among all the possible strategies exploitable in this field, in the last decades, heterogeneous photocatalysis has emerged as an interesting strategy, operating under mild conditions, and degrading many pollutants without adding chemical oxidants [2-4]. In this perspective, photocatalytic floating devices can be exploited with the final aim of overcoming issues related to the use of catalyst-based slurry systems and maximizing light utilization and photocatalyst aeration. [5] In addition, another unavoidable challenge is to be able to develop alternative and efficient photocatalytic systems for TiO2. Herein, we present a selection of interesting results recently collected in our laboratories in the frame of the development and optimization of photoactive materials obtained by immobilizing visible light responsive catalysts, i.e., bismuth oxyhalides, on floating supports characterized by environmentally friendly features (e.g., Lightweight Expanded Clay Aggregate, LECA, alginates’ spheres). Targeted studies on the photocatalytic activity towards different classes of pollutants (i.e., dyes, drugs, polyphenols) after exposure to solar or visible light irradiation will be described with a special focus on the effect of water matrix (ultrapure or simulated drinking water), catalyst dosage and recycling tests in the view of a real application. All the fabricated samples were able to almost fully degrade the selected model pollutant under irradiation. The discussed results are very encouraging and open the view towards the future use of the innovative studied systems in real applications, satisfying the environmental protection and sustainable development goals.