Selective Separation of Pd(II) on Pyridine-Functionalized Graphene Oxide Prepared by Radiation-Induced Simultaneous Grafting Polymerization and Reduction

The recovery of precious metals like palladium (Pd) from secondary resources has enormous economic benefits and is in favor of resource reuse. In this work, we prepared a high efficiency pyridine-functionalized reduced graphene oxide (rGO) adsorbent for selective separation of Pd­(II) from simulated electronic waste leachate, by one-pot γ-ray radiation-induced simultaneous grafting polymerization (RIGP) of 4-vinylpyridine (4VP) from graphene oxide (GO) and reduction of GO. The poly­(4-vinylpyridine)-grafted reduced graphene oxide (rGO-g-P4VP) exhibits fast adsorption kinetics and high maximum adsorption capacity. The adsorption capacity is 105 mg g–1 in the first minute and reaches equilibrium within 120 min. The adsorption process follows the Langmuir model, from which the maximum adsorption capacity of Pd­(II) is estimated to be 177 mg g–1. We also proved that the adsorption mechanism of Pd­(II) on rGO-g-P4VP involves both ion exchange and coordination adsorption by XPS analysis. Most importantly, the loss of oxygen-containing groups due to reduction of GO not only facilitates the separation of adsorbent from aqueous solution but also reduces the electrostatic repulsion toward Pd­(II)­Cl42– in hydrochloric acid solution, leading to a higher adsorption selectivity of Pd­(II) over some common metal cations in electronic waste including Fe­(III), Cu­(II), and Al­(III) compared with poly­(4-vinylpyridine)-grafted graphene oxide (GO-g-P4VP) prepared by atom transfer radical polymerization. Other precious metals like Pt­(IV) and Au­(III) can also be recovered easily and selectively by rGO-g-P4VP. This work demonstrates that rGO-g-P4VP prepared by the facile RIGP is a promising adsorbent for recovery of precious metals from secondary resources like electronic waste leachate

Temperature Effect on the Absorption Spectrum of the Hydrated Electron Paired with a Lithium Cation in Deuterated Water

The absorption spectra of the hydrated electron in 1.0 to 4.0 M LiCl or LiClO4 deuterated water solutions were measured by pulse radiolysis techniques from room temperature to 300 °C at a constant pressure of 25 MPa. The results show that when the temperature is increased and the density is decreased, the absorption spectrum of the electron in the presence of a lithium cation is shifted to lower energies. Quantum classical molecular dynamics (QCMD) simulations of an excess electron in bulk water and in the presence of a lithium cation have been performed to compare with the experimental results. According to the QCMD simulations, the change in the shape of the spectrum is due to one of the three p-like excited states of the solvated electron destabilized by core repulsion. The study of s → p transition energies for the three p-excited states reveals that for temperatures higher than room temperature, there is a broadening of each individual s → p absorption band due to a less structured water solvation shell

Enhanced Versatility in Thorium Removal: Mesoporous Silica-Coated Magnetic Nanoparticles Functionalized by Phenanthroline Diamide as a Selective Adsorbent

In order to promote the sustainable development of nuclear energy through thorium (Th(IV)) recycling, we synthesized SiO2-coated magnetic functional nanocomposites (SiO2@Fe3O4) that were modified with 2,9-diamide-1,10-phenanthroline (DAPhen) to serve as an adsorbent for Th(IV) removal. SiO2@Fe3O4-DAPhen showed effective Th(IV) adsorption in both weakly and strongly acidic solutions. Owing to its porous structure that facilitated rapid adsorption kinetics, equilibrium was achieved within 5 and 0.5 min at pH 3 and 1 mol L–1 HNO3, respectively. In weakly acidic solutions, Th(IV) primarily formed chemical coordination bonds with DAPhen groups, while in strongly acidic solutions, the dominant interaction was electrostatic attraction. Density functional theory (DFT) calculations indicated that electrostatic attraction was weaker compared to chemical coordination, resulting in reduced diffusion resistance and consequently faster adsorption rates in strongly acidic solutions. Furthermore, SiO2@Fe3O4-DAPhen exhibited a high adsorption capacity for Th(IV); it removed Th(IV) through chelation and electrostatic attraction at pH 3 and 1 mol L–1 HNO3, with maximum adsorption capacities of 833.3 and 1465.7 mg g–1, respectively. SiO2@Fe3O4-DAPhen also demonstrated excellent tolerance to salinity, adsorption selectivity, and radiation resistance, thereby highlighting its practical potential for Th(IV) removal in diverse contaminated water sources. Hence, SiO2@Fe3O4-DAPhen represents a promising choice for the rapid and efficient removal of Th(IV)