Interesting makeover of strontium hexaferrites for environment remediation from excellent photocatalysts to outstanding adsorbents via inclusion of Mn3+into the lattice

Manganese incorporated strontium hexaferrites with composition SrMnxFe12-xO19 (x=0.0, 0.4, 0.8, 1.2, 1.6, 2.0, 3.0, 4.0 and 5.0) were fabricated via chemical co-precipitation methodology. Various characterization techniques were employed to investigate the physical properties of the synthesized hexaferrites. Powder X-Ray Diffraction (XRD) patterns revealed the formation of hexagonal phase with P63/mmc space group. FE-SEM micrographs exhibited hexagonal morphology of the synthesized materials; particle size of 125-150 nm range was observed. EDX spectra unveiled the presence of desired elements. The lattice interplanar fringe width from HR-TEM images was observed to be 0.22 nm, 0.26 nm and 0.27 nm indexed to (114), (107) and (203) planes of the manganese doped strontium hexaferrite. Surface area of the synthesized hexaferrites was found to be in the range of similar to 7.8-similar to 8.4 m(2)/g, scrutinized by Brunauer-Emmet-Teller (BET) plots. Saturation magnetization values were found to decrease with increase in Mn content from 38.7 to 11.7 emu/g, albeit retaining sufficient magnetic strength to be recovered using an external magnet. Absorption edge for all the hexaferrites was found to lie in the visible region of the spectrum. The oxidation state of different elements present in synthesized hexaferrites was scrutinized using X-ray Photoelectron Spectroscopy (XPS). To explore the catalytic efficiency of the synthesized hexaferrites, photo-fenton degradation of methyl orange (MO), remazol deep red (RDR) and p-nitrophenol (PNP) was employed. All the synthesized hexaferrites were found to be highly proficient, degrading the pollutants upto similar to 98%. Interestingly, astonishing adsorption of similar to 92.7% was showcased by SrMn5Fe7O19, prior to the addition of oxidizing agent indicating the symptomatic transformation from excellent photocatalyst to outstanding adsorbents via incorporation of Mn3+ into the lattice. The maximum adsorption capacity of 56.20 and 112.35 mg/g was observed for MO and RDR, respectively. (C) 2019 Elsevier B.V. All rights reserved.