Synthesis of CoFe₂O₄–Zeolite Materials and Application to the Adsorption of Gallium and Indium

Abstract

Magnetic cobalt ferrite (CoFe 2 O 4 )-coated zeolite was prepared with a hydrothermal method and used for the adsorption of gallium and indium. The magnetic zeolite was characterized with X-ray diffraction, X-ray photoelectric spectroscopy, Fourier-transformed infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy to determine its crystal structure, element valence, chemical bond, morphology, and grain size, respectively. Gallium and indium were determined with graphite furnace atomic absorption spectrometry. Effects of experimental parameters, including solution pH and adsorption time, were discussed. The experimental data were studied by employing various isotherm and kinetic models, such as Langmuir/Freundlich and pseudofirst-order/pseudo-second-order models. Furthermore, thermodynamic functions, such as changes of enthalpy (ΔH o ), entropy (ΔS o ), and Gibbs energy (ΔG o ), were obtained.

Diverse Surface Chemistry of Cobalt Ferrite Nanoparticles to Optimize Copper(II) Removal from Aqueous Media

“…However, the silica layer-mediated surface functionalization approach is complex, time consuming, and not favorable in large-scale applications. Importantly, the incorporation of silica into magnetic nanoparticles decreases the magnetic responsiveness of the nanocomposites due to the large total organic shell, which in some cases, has been found to reach a thickness of35 nm [31][32][33]. In addition, Si-O-Si bonds are prone to hydrolysis when exposed to harsh environments such as highly-saline conditions that are encountered in biological media [34][35][36].…”

Recovery of Gallium from Bauxite Residue Using Combined Oxalic Acid Leaching with Adsorption onto Zeolite HY

“…Adsorption as a separation process is also available as another possibility due to its apparent lower environmental impact, high efficiency, easy operation and low price in comparison to conventionally used solvents [60]. In recent years, zeolites have been investigated for the adsorption of metals owing to their net negative charge in the polymeric network and to the fact that zeolite exchangeable ions are relatively innocuous [61][62][63].…”

“…The net negative charge is balanced by the exchangeable cation (Na + , K + , NH + 4 or Ca 2+ ), and these cations are exchangeable with certain cations [61]. In Zhao et al [60], a magnetic cobalt ferrite (CoFe 2 O 4 )-coated zeolite was prepared using a hydrothermal method and was used for the adsorption of Ga and In. They investigated the effects of pH and adsorption time as the adsorption capacity was influenced by these parameters.…”

“…In their experiments, the adsorption equilibria of Ga and In on CoFe 2 O 4 −zeolite could be achieved very quickly. The optimum pH was chosen as 5.0 because at lower pH, more hydrogen ions exist, which can compete more effectively with Ga and In for active bonding sites, leading to lower adsorption capacity [60]. However, high pH also can lead to lower adsorption capacity, which is attributed to the formation of Ga(OH) 3 and In(OH) 3 [60].…”

“…The optimum pH was chosen as 5.0 because at lower pH, more hydrogen ions exist, which can compete more effectively with Ga and In for active bonding sites, leading to lower adsorption capacity [60]. However, high pH also can lead to lower adsorption capacity, which is attributed to the formation of Ga(OH) 3 and In(OH) 3 [60]. According to Zhao et al [60], the rapid and high adsorption efficiency was attributed to the presence of active sites on the adsorbent's surface in a large scale.…”