Sodium insertion/extraction investigations into zinc ferrite nanospheres as a high performance anode material

Arabic Gum-Grafted-Hydrolyzed Polyacrylonitrile@ZnFe2O4 as a Magnetic Adsorbent for Remediation of Levofloxacin Antibiotic from Aqueous Solutions

The Arabic gum-grafted-hydrolyzed polyacrylonitrile/ZnFe₂O₄ (AG-g-HPAN@ZnFe₂O₄) as organic/inorganic adsorbent was obtained in three steps using grafted PAN onto Arabic gum in the presence of ZnFe₂O₄ magnetic nanoparticles and then hydrolysis by alkaline solution. Fourier transform infrared (FT-IR), energy-dispersive X-ray analysis (EDX), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), and the Brunauer-Emmett-Teller (BET) analysis analyses were used to characterize the chemical, morphological, thermal, magnetic, and textural properties of the hydrogel nanocomposite. The obtained result demonstrated that the AG-g-HPAN@ZnFe₂O₄ adsorbent showed acceptable thermal stability with 58% char yields and superparamagnetic property with magnetic saturation (Ms) of 24 emu g^-1. The XRD pattern showed that the semicrystalline structure with the presence of ZnFe₂O₄ has distinct peaks which displayed that the addition of zinc ferrite nanospheres to amorphous AG-g-HPAN increased its crystallinity. The AG-g-HPAN@ZnFe₂O₄ surface morphology exhibits uniform dispersion of zinc ferrite nanospheres throughout the smooth surface of the hydrogel matrix, and its BET surface area was measured at 6.86 m²/g, which was higher than that of AG-g-HPAN as a result of zinc ferrite nanosphere incorporation. The adsorption effectiveness of AG-g-HPAN@ZnFe₂O₄ for eliminating a quinolone antibiotic (levofloxacin) from aqueous solutions was investigated. The effectiveness of adsorption was assessed under several experimental conditions, including solution pH (2-10), adsorbent dose (0.0015-0.02 g) contact duration (10-60 min), and initial concentration (50-500 mg/L). The maximum adsorption capacity (Q _max) of the produced adsorbent for levofloxacin was found to be 1428.57 mg/g (at 298 k), and the experimental adsorption data were well explained by the Freundlich isotherm model. The pseudo-second-order model satisfactorily described the adsorption kinetic data. The levofloxacin was mostly adsorbed onto the AG-g-HPAN@ZnFe₂O₄ adsorbent via electrostatic contact and hydrogen bonding. Adsorption-desorption studies demonstrated that the adsorbent could be efficiently recovered and reused after four consecutive runs with no significant loss in adsorption performance.

Reducing the resistance for the use of electrochemical impedance spectroscopy analysis in materials chemistry

Electrochemical impedance spectroscopy (EIS) is a highly applicable electrochemical, analytical, and non-invasive technique for materials characterization, which allows the user to evaluate the impact, efficiency, and magnitude of different components within an electrical circuit at a higher resolution than other common electrochemical techniques such as cyclic voltammetry (CV) or chronoamperometry. EIS can be used to study mechanisms of surface reactions, evaluate kinetics and mass transport, and study the level of corrosion on conductive materials, just to name a few. Therefore, this review demonstrates the scope of physical properties of the materials that can be studied using EIS, such as for characterization of supercapacitors, dye-sensitized solar cells (DSSCs), conductive coatings, sensors, self-assembled monolayers (SAMs), and other materials. This guide was created to support beginner and intermediate level researchers in EIS studies to inspire a wider application of this technique for materials characterization. In this work, we provide a summary of the essential background theory of EIS, including experimental design, signal responses, and instrumentation. Then, we discuss the main graphical representations for EIS data, including a scope of the foundation principles of Nyquist, Bode phase angle, Bode magnitude, capacitance and Randles plots, followed by detailed step-by-step explanations of the corresponding calculations that evolve from these graphs and direct examples from the literature highlighting practical applications of EIS for characterization of different types of materials. In addition, we discuss various applications of EIS technique for materials research.