Triphasic CoFe2O4/ ZnFe2O4 / CuFe2O4 nanocomposite for water treatment applications

Abstract

In the recent years, ferrites have been extending their application niche from the traditional field of soft magnetics to various other fields, including catalysis, gas sensors, energy, biomedicine, and water decontamination. Most of these applications are geared toward single-phase ferrites and their mixtures are rarely investigated. Here, we report on the first study of a triphasic spinel ferrite nanocomposite containing CoFe2O4, ZnFe2O4 and CuFe2O4 and synthesized using citrate auto-combustion. Detailed characterization of the composite in comparison with its three constitutive ferrites is provided. Interestingly, many of the physical properties of the triphasic nanocomposite are more conducive to adsorption of heavy metals than those of any of the three individual ferrites. These properties include experimental density, surface area and roughness, and microstrain, which were all highest in the nanocomposite. For example, the triphasic nanocomposite displayed a twice higher surface roughness and three times higher surface area than those of CuFe2O4. Further, due to heterogeneous structuring of grain boundaries, the band gap of the nanocomposite was at 2.21 eV lower than that of any individual ferrites comprising it (2.31 – 2.62 eV). Consequently, at 6 × 1010 S-1, the maximum of the optical conductivity versus photon energy dependence was higher and the dielectric constant was lower for the nanocomposite than for any of its constitutive ferrites. The suitability of the nanocomposite to act as an adsorbent of toxic heavy metals was tested on the lead ion. The adsorption of lead increased with pH due to the effects on terminal group configuration, dispersion stability and metal ion speciation. The sorption also increased with the contact time, reaching saturation at 89% of the removal efficiency after 50 min. Adsorption isotherm fitting demonstrated that the ions adsorbed as monolayers on the surface of the nanocomposite. The adsorption process also followed the pseudo-second order kinetic model, with chemisorption as the dominant form of surface binding. The study confirms the potential of the triphasic ferrite nanocomposite to serve as an adsorbent material, given the promising removal efficiencies exhibited under the ambient conditions. This opens the door to a wide range of applications, not restricted to wastewater treatments alone, but also extending to the fields of antimicrobials, dye removal, and photocatalysis.