CuO nanoparticles decorated on hydroxyapatite/ferrite magnetic support: photocatalysis, cytotoxicity, and antimicrobial response.

Photocatalysts supported in magnetic nanocomposites for application in environmental remediation processes have been evaluated for removing contaminants due to easy recovery and low toxicity to the ecosystem. In this work, copper oxide (CuO) nanoparticles with photocatalytic properties were decorated on magnetic support constituted by hydroxyapatite (HAP) and ferrite to achieve efficiency in contaminated water remediation under visible light irradiation. First, nanomaterials were obtained by precipitation route, allowing fast and straightforward synthesis. Then, CuO nanoparticles with 6 nm diameter were efficiently decorated on magnetic support (25 nm), showing a high ability to absorb visible light irradiation (bandgap) to promote electronic transition and charge separation. Under visible irradiation, CuO promotes the H2O2 reduction in the conduction band (BC) to form hydroxyl radicals (•OH), which are responsible for rhodamine B (RhB) dye degradation (> 90% in 60 min). Magnetic hysteresis assays confirmed the magnetic properties of HAP/ferrite support, which enabled the recovery and reuse of the magnetic photocatalyst efficiently up to 3 cycles. Due to low Cu2+ leaching after the photocatalytic application stage, cytotoxicity assay for the Allium cepa seeds did not exhibit abnormal cells other than those commonly found. Furthermore, the CuO-decorated nanoparticles showed bactericidal activity against S. aureus (Gram-positive) and E. coli (Gram-negative) microorganisms, being more significant for the first one. Thus, the developed nanocomposite of CuO nanoparticles decorated on the magnetic support surface showed to be a complete system for water remediation, acting in contaminant degradation under visible light irradiation and bactericidal control with environmentally friendly characteristics.Graphical abstract CuO nanoparticles decorated on hydroxyapatite/ferrite magnetic support acting as a photocatalytic and bactericidal system.

Nb2O5 nanoparticles decorated with magnetic ferrites for wastewater photocatalytic remediation.

Nanotechnology has been studied on environmental remediation processes to foster greater photocatalysts efficiency and reuse in wastewater. This study investigated the photocatalytic efficiency and viability of niobium pentoxide (Nb2O5) nanoparticles decorated with magnetic ferrite (cobalt ferrite (CoFe2O4) or magnesium ferrite (MgFe2O4)) for atrazine photodegradation. Thus, the decorated Nb2O5 was synthesized by the polymeric precursor method, forming nanoparticles with sizes ranging from 25 to 50 nm. Nanocomposite elementary analyses showed a homogeneous distribution of elements on all particles surface. Efficient magnetic saturation was observed for pure CoFe2O4 (53 emu g-1) and MgFe2O4 (19 emu g-1) nanoparticles, promoting the magnetic removal of Nb2O5:CoFe2O4 and Nb2O5:MgFe2O4 nanocomposites. Photocatalytic assays showed 88% efficiency for atrazine photodegradation with all nanomaterials, which represented a 21% increase compared to photolysis in the 1st cycle. The magnetic nanocomposites when applied to a 5th cycle maintained the atrazine photodegradation activity. In this way, magnetic Nb2O5-based nanocomposites decorated with ferrite nanoparticles showed an efficient photocatalytic response, in addition to posterior magnetic removal from the aqueous medium. Therefore, the evaluated magnetic Nb2O5 nanocomposites may be an alternative to enhance the wastewater removal process and foster the reuse in advanced oxidative processes.