Hydrothermal synthesis of magnetic CoFe2O4 nanoparticles and CoFe2O4/MWCNTs nanocomposites for U and Pb removal from aqueous solutions

Sensing the invisible: Ultra-low-level electrochemical detection of the microbe (Pseudomonas aeruginosa) on cobalt ferrite-doped silver nanocomposite (CoFe2O4/AgNPs) surfaces

This study introduces an efficient electrochemical method for rapidly identifying the pathogen Pseudomonas aeruginosa (P. aeruginosa), which poses threats to individuals with compromised immune systems and cystic fibrosis. Unlike conventional techniques such as polymerase chain reaction, which fails to detect modifications in the resistant properties of microbes due to environmental stress, our proposed electrochemical approach offers a promising alternative. The characterisation analyses, involving microscopic and spectroscopic methods, reveal that the nanocomposite exhibits a crystalline structure, specific atomic vibrational patterns, a cubic surface shape, and distinct elemental compositions. This sensor demonstrates exceptional detection capabilities for P. aeruginosa, with a linear range of 1-23 CFU mL-1 and a low detection limit of 4.0 × 10-3 CFU mL-1. This research not only explores novel electrochemical techniques and the CoFe2O4/AgNPs nanocomposite but also their practical implications in food science, highlighting their relevance across various food samples, water, and soil.

Molten salt synthesis of disordered spinel CoFe2O4 with improved electrochemical performance for sodium-ion batteries

Sodium-ion (Na-ion) batteries are currently being investigated as an attractive substitute for lithium-ion (Li-ion) batteries in large energy storage systems because of the more abundant and less expensive supply of Na than Li. However, the reversible capacity of Na-ions is limited because Na possesses a large ionic radius and has a higher standard electrode potential than that of Li, making it challenging to obtain electrode materials that are capable of storing large quantities of Na-ions. This study investigates the potential of CoFe2O4 synthesised via the molten salt method as an anode for Na-ion batteries. The obtained phase structure, morphology and charge and discharge properties of CoFe2O4 are thoroughly assessed. The synthesised CoFe2O4 has an octahedron morphology, with a particle size in the range of 1.1-3.6 μm and a crystallite size of ∼26 nm. Moreover, the CoFe2O4 (M800) electrodes can deliver a high discharge capacity of 839 mA h g-1 in the first cycle at a current density of 0.1 A g-1, reasonable cyclability of 98 mA h g-1 after 100 cycles and coulombic efficiency of ∼99%. The improved electrochemical performances of CoFe2O4 can be due to Na-ion-pathway shortening, wherein the homogeneity and small size of CoFe2O4 particles may enhance the Na-ion transportation. Therefore, this simple synthetic approach using molten salt favours the Na-ion diffusion and electron transport to a great extent and maximises the utilisation of CoFe2O4 as a potential anode material for Na-ion batteries.

Preparation of melon peel biochar/CoFe2O4 as a new adsorbent for the separation and preconcentration of Cu(II), Cd(II), and Pb(II) ions by solid-phase extraction in water and vegetable samples

The present research describes the successful preparation of melon peel biochar modified with CoFe₂O₄ (MPBC/CoFe₂O₄) followed by its usage as a new sorbent to separate, preconcentrate, and determine the toxic heavy metal ions by magnetic solid-phase extraction. The metal ion desorption was performed by 0.1 M HCl solution with a volume of 5.0 mL. Flame atomic absorption spectrometry (FAAS) was utilized for detection of the analyte levels. SEM-EDX, TEM, XRD, and FTIR techniques were carried out to illuminate the structure of MPBC/CoFe₂O₄. The fundamental variables affecting the adsorption and elution efficiencies of the analyte ions including solution pH, MPBC/CoFe₂O₄ amount, type and concentration of eluent, adsorption and desorption equilibrium time, and sample volume were optimized. The detection limits were calculated as 0.41, 1.82, and 3.16 µg L^-1 for Cu²⁺, Cd²⁺, and Pb²⁺ ions, respectively, with the relative standard deviation of lower than 4.2%. There were no substantial interference effects on the analyte ion recovery due to the presence of foreign ions at high levels. Five minutes of contact time was adequate to attain the adsorption equilibrium. The adsorption capacity of MPBC/CoFe₂O₄ was obtained as 106.4, 65.4, and 188.7 mg g^-1 for Cu²⁺, Cd²⁺, and Pb²⁺ ions, respectively, by utilizing Langmuir isotherm model. The pseudo-second order model is favorable to identify the adsorption kinetics. The method was validated by spike/recovery test, and then, it was successfully implemented to determine the aforementioned analyte levels in sea and stream water, pepper, black cabbage, eggplant, and tomato samples.

Fast and efficient removal of Pb(II) ion and malachite green dye from wastewater by using magnetic activated carbon-cobalt nanoparticles

A high-surface-area and inexpensive activated carbon has been produced from lemon peel using chemical activation with H₃PO₄ at 500 °C in a N₂ atmosphere. Afterwards, the synthesized cobalt nanoparticles using coprecipitation method were adsorbed on the activated carbon surface, and as a result magnetic activated carbon was obtained. Sample characterization has been assessed via X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, nitrogen adsorption-desorption and magnetic properties. It was found that magnetic activated carbon-cobalt nanoparticles (MAC/Co) synthesized had a high saturation magnetization. The MAC/Co revealed super-paramagnetic behaviors at room temperature, and have been readily isolated from solution by using an exterior magnet. Next, adsorption behavior of malachite green and Pb(II) onto the generated MAC/Co has been examined. Sorption kinetics and equilibrium have been studied using batch procedure. The kinetic and isothermal adsorption results were matched completely with the Elovich and Langmuir models, respectively. Based on the Langmuir model, the highest adsorption capacities of malachite green dye and Pb(II) ion respectively were 263.2 and 312.5 mg g^-1 at room temperature. Based on the results, the MAC/Co is a probable economic and effective adsorbent that can be employed as a new adsorbent to remove malachite green dye and Pb(II) from wastewater.