Modification of doped strontium hexaferrite by MWCNT and PANI for photocatalytic degradation of methylene blue dye

Abstract

Nanoparticles of doped strontium hexaferrite (SrZn0.1Co0.1Sn0.2Fe11.6O19) were synthesized by the sol–gel auto-combustion method as a salient magnetic photocatalyst. For enhancing photocatalytic properties, a nanocomposite of the SrZn0.1Co0.1Sn0.2Fe11.6O19/multiwall carbon nanotube (MWCNT) and SrZn0.1Co0.1Sn0.2Fe11.6O19/polyaniline (PANI) was prepared. Fourier transform infrared spectra confirmed the formation of tetrahedral and octahedral vibrating modes of the Fe–O on the hexaferrite structure. In x-ray diffraction (XRD) patterns of SrZn0.1Co0.1Sn0.2Fe11.6O19/MWCNT, both the MWCNT’s peak at 2θ = 26.4° and hexaferrite pattern confirmed the formation of the nanocomposite. XRD analysis of SrZn0.1Co0.1Sn0.2Fe11.6O19/PANI nanocomposite represented the amorphous peak belonging to PANI. Field emission scanning electron microscopy pictures of SrZn0.1Co0.1Sn0.2Fe11.6O19/MWCNT showed nanoparticles of hexaferrite on the surface of the MWCNT’s nanofibers. In the SrZn0.1Co0.1Sn0.2Fe11.6O19/PANI nanocomposite, the spherical PANI encompassed the hexaferrite structure. Vibrating sample magnetometer hysteresis loops revealed that the SrZn0.1Co0.1Sn0.2Fe11.6O19 can be classified as a soft magnetic material. By adding non-magnetic particles of MWCNTs and PANI, the saturation magnetizations of all nanocomposites decreased. Photocatalytic studies showed that by adding PANI as a conducting polymer and MWCNTs with a high surface area, the mechanism of dye degradation was accelerated in comparison to the pure SrZn0.1Co0.1Sn0.2Fe11.6O19 nanoparticles. The kinetics, rate and mechanism of photodegradation were studied for all samples. By fabricating PANI nanocomposites, the remarkable transfer of charge carriers facilitated the methylene blue decomposing process. On the other hand, due to the high surface area of MWCNTs and decreasing the electron–hole accumulation, the degradation process was enhanced.