Self-assembly of TiO2/Fe3O4/SiO2 microbeads: A green approach to produce magnetic photocatalysts

Hypothesis: A green approach for producing magnetic photocatalysts via direct agglomeration of commercial nanoparticles in emulsion is shown. Aggregation is attributed to charge screening by salt addition which reduces stabilising repulsive forces between particles, and different nanoparticles (TiO2, Fe3O4 and SiO2) serve to imbue the final agglomerates with desired adsorption, photodegradation and magnetic properties. Experiment: Titania doped magnetic silica microbeads (TiO2/Fe3O4/SiO2) were produced at room temperature by CaCl2-induced aggregation of nanoparticles in a reverse emulsion template. The beads were characterized using optical microscopy, SEM, STEM, EDX and zeta potential measurements. The adsorption and photocatalytic properties of the system as well as its reusability were investigated using Rhodamine B and Methylene Blue as model pollutants. Results: Magnetically responsive beads approximately 3-9 mm in diameter incorporating SiO2, TiO2 and Fe3O4 nanoparticles were produced. Adsorption and photodegradation properties of the beads were confirmed by bleaching solutions of Rhodamine B, Methylene Blue as well as mixtures of both dyes. Reusability of the beads after magnetic separation was demonstrated, exhibiting a dye removal efficiency greater than 93% per cycle for three consecutive cycles of UV-light irradiation. This method is simpler than conventional sol-gel methods and offers a green and easy to implement approach for producing structured functional materials. (C) 2020 Elsevier Inc. All rights reserved.

Automated summary

A green approach for producing magnetic photocatalysts via direct agglomeration of commercial nanoparticles in emulsion was successfully demonstrated in this study. The aggregation was attributed to charge screening by salt addition. The experiment resulted in magnetically responsive beads with good adsorption and photodegradation properties, and they could be reused after magnetic separation.