Alexander A. Pud

Extracting radionuclides from natural and anthropogenic sources addresses two challenges: remediating contaminated environments and enabling the separation of technologically important isotopes. Understanding how actinides interact and form complexes with polymer-based ligands allows the development of efficient extractants for selective remediation, supporting sustainable environmental protection and resource recovery strategies. Here, we report on the structure and actinide sorption properties of eco-friendly hybrid nanocomposite systems based on the natural mineral halloysite and multifunctional conjugated polymers. Three polyaniline (PANI)-based polymers and their nanocomposites with halloysite nanotubes (HNT) were synthesized and evaluated as sorbents for removing uranium and plutonium from aqueous solutions. The study included two PANI variants synthesized at high (60 °C) and low (1-2 °C) temperatures using different acid-dopants, H₂SO₄ and p-toluenesulfonic acid, and a PANI copolymer incorporating aminoterephthalic acid (PANIATA), which introduces carboxylic functional groups. X-ray photoelectron spectroscopy and electron microscopy revealed the formation of core-shell nanocomposites with HNT as the core and a polymer shell several nanometers thick. The HNT/PANI nanocomposites exhibited a synergistic enhancement in actinide retention capacity, exceeding the additive performance of the individual components. Sorption experiments with artificial groundwater and seawater confirmed the nanocomposites' selectivity for uranium. Analysis of the FTIR spectra of the polymer composites before and after uranium sorption provided detailed insight into uranyl cation-polymer complexation mechanisms responsible for high selectivity and sorption performance.

This work presents for the first time the modification and enhancement of sensory properties of a chemoresistive conductive core-shell nanocomposite of multi-walled carbon nanotubes (MWCNTs) and polypyrrole (PPy) doped by p-toluenesulfonate anions (TS) (MWCNT/PPy-TS) under long ultrasonic treatment in joint dispersions and, hence, under physico-chemical interactions with functionalized calixarenes (CA), namely calix[4]arene methylene-bis-phosphonic acid octasodium salt (CPA) and calix[4]arene sulfonic acid (CSA). The interactions are confirmed by a detailed analysis of FTIR spectra of a parent binary MWCNT/PPy-TS nanocomposite and its counterpart ternary MWCNT/PPy-TS/CA nanocomposites as well as by sensor measurements. The results of the latter show a strong enhancement of the sensitivity of the MWCNT/PPy-TS to isopropanol, acetone and ammonia vapors due to CSA and CPA additives, which, however, depends on the nature of functional groups of these CA.

In this paper, structural, electronic, and sensing properties of the poly(3‐methylthiophene) (P3MT) in two types of its core–shell nanocomposites with multiwall carbon nanotubes (MWCNTs) and poly(vinylidene fluoride) with different contents of the P3MT component (shell) are explored and are compared. The results indicate specific changes in the P3MT properties appear due to its interfacial interactions with the MWCNTs and PVDF components. In the case of the doped P3MT, charge transfer from MWCNT to P3MT leads to partial dedoping of the latter. The evidence of intermolecular charge transfer complex formation between undoped P3MT (donor) and MWCNTs (acceptor) is obtained. Changes in the properties of P3MT in nanocomposites are used to detect and to reliably recognize some chemical warfare agent's simulants of nerve agents and mustard gas. The sensitivity dependences of the nanocomposites on their work functions, Hansen solubility parameters and analytes electronegativity are studied. It is shown that the sensor response is controlled by a partial charge transfer if the difference between the work function of the sensing material and the electronegativity of the analyte molecules does not exceed a certain value (in the case herein ≈0.3 eV).

Sorption properties of polydopamine (PDA) for uranium and plutonium from an aqueous environment are reported at three different pH values (2, 4 and 6.5–7). In addition to deionized (DI) water, artificial groundwater (GW) and seawater (SW) were used with U uptake close to 100% in each case. PDA polymer has been identified as a material with extremely high sorption capacity Q_max ∼500 mg g⁻¹ of the polymer at pH 6.5 and high selectivity for uranium. Similar high sorption properties are revealed for plutonium uptake. PDA-uranyl and PDA-plutonium interactions responsible for the observed adsorption processes have been addressed with a set of experimental techniques including FTIR spectroscopy, electron microscopy and cyclic voltammetry.