Insight into the structural, optical, adsorptive, and photocatalytic properties of MgFe2O4-bentonite nanocomposites

Abstract

Nanofabrication of magnesium ferrite nanoparticles (MgFe2O4 NPs) and bentonite clay offers a new class of nanocomposites with environmentally safe and non-toxic components. In the present study, MgFe2O4-bentonite clay nanocomposites with four different w/w ratios have been synthesized by a sol–gel auto-combustion method. Their structural, morphological, and magnetic properties have been comparatively analyzed by means of SEM-EDS, TEM, XRD, BET, FTIR, and VSM techniques. The intensity of the FTIR band corresponding to Si-Al-O framework vibration increased linearly with increasing bentonite content, thus confirming successful nanofabrication with different bentonite contents. Magnetization values decreased from 11.4 to 3.7 emu/g with increasing bentonite content. Specific surface areas of the nanocomposites were in the range 48.9–87.0 m2/g, with the highest value for MgFe2O4-bentonite nanocomposite with 1:0.05 (w/w). The synthesized nanocomposites have been used as adsorbents for the sequestration of heavy metal ions from aqueous solution spiked with Pb(II), Ni(II), Zn(II), and Cd(II). Inductively coupled argon plasma-optical emission spectroscopy confirmed NC-I, having the composition 1:0.05, to be the best adsorbent among the synthesized nanocomposites and pristine MgFe2O4 NPs. Maximum removal was observed for Pb(II) ions, followed by Zn(II), Cd(II), and Ni(II) ions, which can be correlated to the radii of the hydrated ions. At optimized adsorbent dose, the removal of heavy metal ions was in the range 92.5–95.2%. NC-I also acted as the best photocatalyst, fully degrading para-nitrophenol within 180 min. The optical band gap of MgFe2O4 NPs is 2.58 eV, and this decreases to 2.26 eV in the NCs. Effective charge separation and a low band gap lead to higher photocatalytic performance. The results correlated with specific surface area. The present studies highlight the immense potential of nanofabrication in tuning the properties of composite materials for environmental applications.