Abstract
This paper focuses on the synthesis of cobalt ferrite nanoparticles by the sol–gel method and their photocatalytic activity to eliminate bacteria in aqueous media at two different scales: in a laboratory reactor and a solar pilot plant. Cobalt ferrite nanoparticles were prepared using Co(II) and Fe(II) salts as precursors and cetyltrimethyl ammonium bromide as a surfactant. The obtained nanoparticles were characterized by X-ray diffraction, scanning and transmission electron microscopy. Escherichia coli (E. coli) strain ATCC 22922 was used as model bacteria for contact biocidal analysis carried out by disk diffusion method and photocatalysis under an ultraviolet A (UV-A) lamp for laboratory analysis and solar radiation (radiation below 350 W/m2 in a typical cloudy day) for the pilot plant analysis. The results showed that cobalt ferrite nanoparticles have an average diameter of (36 ± 20) nm and the X-ray diffraction pattern shows a cubic spinel structure. Using the disk diffusion technique, it was obtained inhibition zones of (17 ± 2) mm diameter. Results confirm the photocatalytic elimination of E. coli in water samples with remaining bacteria below 1% of the initial concentration during the experiment time (30 min for laboratory tests and 1.5 h for pilot plant tests).
Highlights
One of the most important problems in developing cities around the world is the microbiological contamination of drinking water
Wastewater discharges in fresh water and coast seawater are the major sources of fecal microorganisms
A semiconductor under solar radiation could promote an electron from the valence band to the conduction band, generating an electron-hole pair
Summary
One of the most important problems in developing cities around the world is the microbiological contamination of drinking water. There is a harmful impact on water quality with huge consequences in human health [1] Traditional wastewater methods, such as UV radiation, and ozonolysis, are not commonly used due to the high operation costs, their low yield, and the production of intermediate species that could be more harmful for human intake [2,3]. A semiconductor under solar radiation could promote an electron from the valence band to the conduction band, generating an electron-hole pair. These charge carriers could drive redox reactions and possible degradation reaction of contaminants and microorganisms in water.
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