Zeinab Farouk Akl

The radioactive and hazardous nature of thorium demands the fabrication of efficient electrodes for its sensitive and selective monitoring in aqueous environments. The present paper reports the construction and characterization of a new carbon paste electrode (CPE) chemically modified by octyl phenyl acid phosphate (OPAP) as a selective recognition agent for the potentiometric assay of thorium(IV) ions. Improved sensitivity, electrical conductivity, and selectivity were achieved by incorporating oxidized multi-walled carbon nanotubes (o-MWCNTs) into the carbon paste composition. The electrochemical performance of the developed electrode was evaluated regarding the paste ingredients, response time, and working pH range. The standard CPE potentials, E°, were determined at various temperatures and the isothermal temperature coefficient was calculated. The optimized CPE showed a Nernstian slope of 14.65 ± 0.38 mV decade⁻¹ over the concentration range of 4.82 × 10^–7–1.00 × 10^–1 mol L⁻¹. The electrode possessed a short response time (9 s), independence of the solution pH over the range of 2.5–5.5, and a relatively long operational lifetime (˃ 3 months). The selectivity coefficients indicated the good discrimination ability of the developed CPE towards thorium(IV) ion compared to various common ions. Aiming to judge the practical utility of the developed CPE, it was successfully used for the potentiometric analysis of thorium(IV) ions in various real aqueous matrices with sensible results.

The significance of reliable monitoring of uranium levels in water recourses calls for the development of time-saving, robust, and accurate methods for its estimation. In this view, the current study describes the design and analytical parameters of a potentiometric membrane sensor for uranium(VI) ions. The sensor is based on a new Schiff base derivative, as an ionophore, that was synthesized and structurally characterized by elemental, FTIR, and ¹HNMR analyses. The impact of the membrane constituents was studied and the membrane composition of PVC (32.50) : o-NPOE (65.00) : ionophore (2.00) : KTpClPB (0.50) (%, w/w) achieved the optimal performance. A Nernestian response was observed for uranium(VI) ions within the concentration range 1.00 × 10⁻⁶ to 1.00 × 10⁻¹ mol L⁻¹. The sensor revealed a low detection limit of 3.90 × 10⁻⁷ mol L⁻¹ with satisfactory reproducibility. Stable and reproducible potentials were obtained within a short time (9 s) over the pH range 2.10–4.21. The impact of possible competing ions was investigated and the selectivity coefficients revealed appropriate selectivity for uranium(VI) ions over various cations without significant interference. The sensor's performance was examined by determining the amount of uranium(VI) in water samples and the results showed no significant differences from those obtained by the ICP-OES method.

This work focuses on investigating the feasibility of using a crosslinked amidoximated copolymeric hydrogel as a potential adsorbent to recover uranium and thorium ions from aqueous media. The hydrogel was synthesized via gamma-irradiation copolymerization and characterized through FTIR, TGA, and SEM. The medium acidity notably affected the adsorption capacity of both ions. The adsorption data was in line with the pseudo-1st-order equation and the Freundlich isothermal model. The thermodynamics analysis showed that the temperature rise promoted the adsorption capacity. The reusability studies highlighted the good performance of the hydrogel up to five regeneration rounds.

Uranium is the backbone of the nuclear fuel used for energy production but is still a hazardous environmental contaminant; thus, its removal and recovery are important for energy security and environmental protection. So far, the development of biocompatible, efficient, economical, and reusable adsorbents for uranium is still a challenge. In this work, a new orange peel biochar-based hydrogel composite was prepared by graft polymerization using guar gum and acrylamide. The composite’s structural, morphological, and thermal characteristics were investigated via Fourier transform infrared (FTIR), scanning electron microscope (SEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA) methods. The composite’s water absorption properties were investigated in different media. The performance of the prepared composite in adsorbing uranium (VI) ions from aqueous media was systematically investigated under varying conditions including solution’s acidity and temperature, composite dose, contact time, and starting amount of uranium. The adsorption efficiency increased with solution pH from 2 to 5.5 and composite dose from 15 to 50 mg. The adsorption kinetics, isotherms, and thermodynamics parameters were analyzed to get insights into the process’s feasibility and viability. The equilibrium data were better described through a pseudo-second-order mechanism and a Langmuir isotherm model, indicating a homogeneous composite surface with the maximum uranium (VI) adsorption capacity of 263.2 mg/g. The calculated thermodynamic parameters suggested that a spontaneous and endothermic process prevailed. Interference studies showed high selectivity toward uranium (VI) against other competing cations. Desorption and recyclability studies indicated the good recycling performance of the prepared composite. The adsorption mechanism was discussed in view of the kinetics and thermodynamics data. Based on the results, the prepared hydrogel composite can be applied as a promising, cost-effective, eco-friendly, and efficient material for uranium (VI) decontamination.

A Fe ₃ O ₄ @Cyanex-923 nanoadsorbent was prepared and applied as an efficient candidate for uranium( vi ) removal from aqueous solutions.