M-Type Strontium Hexaferrite Nanoestructures Derived from the Pechini Method as Magnetically Hard Adsorbents for Cadmium Removal in Aqueous Solution

This study investigates the removal of Cd2+ ions from aqueous solutions using hard magnetic strontium hexaferrite (SrFe12O19) nanoparticles synthesized via the Pechini method, with an average particle size of 116 nm. The material was successfully obtained at a relatively low calcination temperature of 900 °C. The crystalline structure of the hexaferrite particles was investigated by X-ray diffraction, confirming SrFe12O19 crystalline structure. The powder samples were also characterized by Fourier transform infrared spectroscopy (FTIR). The morphology and size distribution were studied using scanning electron microscopy (SEM). Furthermore, the magnetic properties of strontium hexaferrite contribute significantly to adsorption and removal processes, primarily by acting as a recoverable magnetic adsorbent. The ferromagnetic material, with its high saturation magnetization and coercivity, responds rapidly to external magnets, facilitating the removal of contaminants and maintaining its magnetic characteristics even in complex chemical environments. For this purpose, its magnetic behavior was also studied using vibrating sample magnetometry (VSM). The experimental adsorption results were successfully modeled using PFO (pseudo—first—order) and PSO (pseudo—second—order) along with Freundlich and Langmuir isotherms, to fit the experimental adsorption data of the Cd(II) salt from the 0.1 and 0.2 mg samples at room temperature for two quantities of strontium hexaferrite at times ranging from 2.5 to 60 min. The results indicate that the strontium hexaferrite nanoparticles exhibited a 90% removal efficiency, which was the highest value. Additionally, the strontium hexaferrite can be magnetically recovered along with the adsorbed cadmium, representing a more efficient way to remediate water.