Spinel inorganic compounds promising materials in the preparation of capacitive deionization electrodes

Magnetic nanoparticles are increasingly considered for research applications in the field of water purification, computer memory and sensors due to their many features. Among many pseudocapacitive materials, metal oxides with spinel structure are widely spread minerals. Particularly those compounds with a general formula AB۲O۴ offer a suitable crystalline architecture with three-dimensional lattice network that can be served as pseudocapacitive materials for electro- sorption process and capacitive deionization of water.Although a number of oxide spinel crystals have been investigated as electrode materials in energy storage, the spinel mixed metal oxide with two cations (A, B) are rarely studied. In spinel- type mixed metal oxide, the divalent ions A are in the tetrahedral and the trivalent ions B are in the octahedral arrangement.Among spinel mixed metal oxide, spinel ferrite nanoparticles are widely studied because of their excellent magnetic and electrical properties. Spinel ferrite nanoparticles have a general formula MFe۲O۴, where M can be metal cations such as Mg, Ba, Cd, Zn, Fe, Mg, Co, Ni, Mn, etc [۱-۲]. Due to their high surface area, high electrochemical activity, natural abundance and low cost, spinel ferrite nanoparticles have been known as an ideal material for use in capacitive deionization. Several studies report that the electrodes consisting of spinel ferrite nanoparticles can increase the salt absorption capacity of capacitive deionization cells due to the stability of the electrode and the speed of ion diffusion. Jie et al [۳] used the capacitive deionization technique to remove NaCl from water by a zinc iron oxide (ZFO) nanoparticle electrode. The desalination capacity reached ۱۳۶.۶ mg/g of NaCl of ZFO under optimized conditions, a voltage range of −۱.۴ to ۱.۴ V and an initial concentration of ۱۰۰ mM. The mixed ferrite Co۰.۵Ni۰.۵Fe۲O۴ was employed as an electrode in a CDI system. The electrode was used to treat ۲۵۰ mg/L NaCl solution at ۱.۲ V and a feed flow rate of ۱۰ mL/min. Under optimized experimental conditions, the highest specific salt adsorption capacity was ۲۱.۸۴ mg/g [۴]. Younes et al (۲۰۲۲) [۵] reported a one-step hydrothermal synthesis of cobalt iron oxide (CFO) high-performance nanocomposites such as CFO-graphene, CFO-CNTs, and CFO-۳DrGO. The results have demonstrated that the surface adsorption capacity of CFO-۳DrGO/CFO (۶۴.۵ mg/g) is greater than that of the CFO-graphene/CFO (۵۵.۱۶ mg/g) and CFO-CNTs/CFO (۲۱.۵ mg/g) due to the better surface area of the CFO-۳DrGO nanocomposite (۳۳۰ m۲/g). Recently, Jiang et al [۶]. reported spinel LiMn۲O۴ as the cathode and activated carbon as the anode in the CDI cell. An ultrahigh deionization capacity of ۱۵۹.۴۹ mg/g was obtained at ۱.۰ V with an initial salinity of ۲۰ mM. Spinel LiMn۲O۴ could not only enhanced the ion transfer during deionization, but also offer hope for resolving the conflict between electrode material production and CDI performance in the desalination industry. In continue of our previous work [۷], in this project, spinel like of magnesium and aluminum oxide was synthesized via facile synthesis method and characterized by Field Emission Scanning Electron Microscopy (FE-SEM), Energy Dispersive Spectroscopy (EDX), X-ray Diffraction Spectroscopy (XRD), and Fourier-Transform Infrared Spectroscopy (FT-IR). The as-prepared spinel like MgAl۲O۴ was successfully applied in a capacitive deionization cell.

کلیدواژه ها:

Capacitive deionization ، Spinel ، Electrosorption ، Mixed metal oxide