Synthesis, characterization and environmental remediation applications of polyoxometalates-based magnetic zinc oxide nanocomposites (Fe3O4@ZnO/PMOs)

Abstract

In the present work, the photocatalytic performance of synthesized magnetic nanocatalysts composed of two polyoxometalates (PMOs) namely, phosphomolybdic acid (PMo) and phosphotungstic acid (PW), immobilized individually on ZnO coated magnetic core/shell nanoparticles (Fe3O4@ZnO/PMOs) has been investigated. Several characterization methods including XRD, FE-SEM, VSM, BET and UV–vis absorption spectra were employed to characterize the synthesized nanocomposites. Fe3O4@ZnO/PMo and Fe3O4@ZnO/PW nanocomposites were efficiently investigated for photocatalytic degradation of azo dye methyl orange (MO) in aqueous solutions. Relatively, all synthesized nanocomposites relieved high photocatalytic degradation activity. Fe3O4@ZnO/PMo photocatalysts revealed higher MO degradation efficiency (98.2 %) than Fe3O4@ZnO/PW (92.3 %) at specific conditions. The stability study showed a little decrease in the degradation activity of the nanocatalysts on reuse. The photocatalytic activity of Fe3O4@ZnO/PMo nanocomposite in the sixth reaction cycle (82.8 %) is only 6.4 % lower than the first cycle (98.2 %). Generally, the results proved that integration of PMo and PW with the Fe3O4@ZnO core/shell nanocomposite leads to an improve in photocatalytic degradation due to reduced recombination of electron-hole pair generated and electron drop performance of Fe3O4@ZnO for electrons photogenerated of PMo and PW. Furthermore, antibacterial activity of both nanocomposites was investigated against E. coli and they revealed efficient antimicrobial properties. Fe3O4@ZnO/PMo and Fe3O4@ZnO/PW nanocomposites revealed 91.2 % and 89.3 % of bacterial growth inhibition, respectively when using a dosage equal to 1600 μg/l.