Effective solid-phase extractants (SPE) have been developed based on multi-walled carbon nanotubes (CNTs) of various structures modified with an organic reagent – 2-mercaptobenzothiazole. Using scanning and transmission electron microscopy, the morphological and structural features of SPE samples and their elemental composition were determined. It has been shown that the specific surface area of modified CNTs is approximately two times lower compared to the original CNTs. It was revealed that the modified materials are coils of CNTs coated with a uniform organic shell 10-15 nm thick. The sorption capacity of the original nanotubes in 1 M HCl and their modified forms (0.1-3.0 M HCl) at room temperature and at 80°C was determined. It was found that in strongly acidic media, SPE based on G-183 CNTs and 2-mercaptobenzothiazole is effective, which sorbs Pt, Pd and Au at room temperature, and also Ru and Rh at a temperature of 80°C. The possibility of selective extraction of platinum group metals and gold with this sorbent in the presence of macroquantities of Al, Fe, Cu, Ca and Mg was assessed.

In this study, aerogels based on graphene oxide decorated with iron oxide nanoparticles are obtained by drying in supercritical isopropanol. For the synthesized samples with the calculated initial iron contents of 9, 18 and 36 wt %, the morphology and structure of the graphene matrix and iron-containing nanoparticles are studied using the scanning electron microscopy (SEM) and transmission electron microscopy (TEM) methods. Comparative investigations are conducted to analyze the carbon and hydrogen composition within the synthesized aerogels structure, followed by an assessment of their magnetic properties at ambient temperature. Sorption experiments are carried out for the extraction of heavy and rare earth elements from multicomponent aqueous solutions of a complex composition.

В настоящей работе методом сушки в сверхкритическом изопропаноле получены аэрогели на основе оксида графена, декорированного наночастицами оксидов железа. Методами сканирующей и просвечивающей электронной микроскопии изучены морфология и структура графеновой матрицы и железосодержащих наночастиц синтезированных образцов с расчетными исходными содержаниями железа 9, 18 и 36 мас.%. Проведены сравнительные исследования содержания углерода и водорода в структуре синтезированных аэрогелей, оценены их магнитные характеристики при комнатной температуре. Проведены сорбционные эксперименты при извлечении тяжелых и редкоземельных элементов из многокомпонентных водных растворов сложного состава.

Various methods for the oxidation of different types of carbon nanotubes (CNTs) in nitric acid and a mixture of nitric and sulfuric acids at various temperatures and durations of exposure are studied. Oxidation conditions that provide the high sorption activity of sorbents with respect to REE are found. Oxidized CNTs are characterized by acid-base titration and scanning electron microscopy, and the electrokinetic (ζ) potential of nanotube suspensions is determined as a function of pH. The elemental composition of CNTs is determined by ICP MS/AES methods. The sorption capacity of the oxidized CNTs with respect to a wide range of elements is determined. Their unique selectivity with respect to REE is revealed. A possibility of using oxidized CNTs for the efficient sorption preconcentration of REE with the aim to determine their ultralow concentrations in rocks is proved.

The removal of actinides and rare earth elements (REEs) in nitric acid solutions; produced in nuclear processes; is a challenging job. The present article describes the sorption behavior of oxidized multilayer graphene (o-MG) to actinides and rare earth elements (REEs) in nitric acid solutions (up to 3 mol L-1 HNO3), including nitrogen and phosphorus-containing reagents. The conditions for obtaining new sorption materials in a compact form; by adding directly a reagent (organic ligand) and a suspension of o-MG to nitric acid solutions; were optimized. o-MG was modified by using tetraoctyldiglycolamide, diphenyl-dibutylcarbamoyl-methyl-phosphine oxide, tri-octyl-phosphinoxide, di-(2-ethylhexyl) phosphoric acid, tributyl phosphate and di-2-ethyl-hexyl-methyl-phosphonate reagents were used. The formation time of the solid-phase extractants compact phase was 20-240 min. The new materials sorption capacity to U (VI), Th (IV), Pu (IV), La (III), Ce (III) and Eu (III) in nitric acid solutions (3 mol L-1 HNO3) was determined. The elements distribution coefficients were K-d similar to 10(3)-10(4) mL g(-1). The efficiency of the obtained materials was confirmed by the data on the solid-phase isolation and separation of actinides and REEs from nitric acid solutions (3 mol L-1 HNO3) in the presence of macro components (Cs, Sr, Fe, Mo, Pd, Zr, Co), which can be formed during recycling processes of spent nuclear materials and components used in nuclear medicine. (C) 2021 Elsevier B.V. All rights reserved.

Sorption procedures were developed for recovering U(VI), Pu(IV), and Am(III) with solid-phase extractants (SPEs) prepared by impregnation of Taunit carbon nanotubes and polystyrene supports with diphenyl(dibutylcarbamoylmethyl) phosphine oxide (CMPO) and tri-n-octylphosphine oxide (TOPO) The impregnation and actinide recovery were performed in the batch mode and using microcolumns. Procedures for support impregnation and SPE preparation are described. Conditions were found for sorption recovery of U(VI), Pu(IV), and Am(III) from 3 M HNO3 solutions. The possibility of actinide desorption was demonstrated. The effect of macrocomponents on the degree of actinide recovery was examined.

The sorption properties of solid-phase extractants (SPEs) prepared by impregnation of Taunit carbon nanotubes with adducts of diphenyl(dibutylcarbamoylmethyl)phosphine oxide (CMPO) and tri-n-octylphosphine oxide (TOPO) in HNO3 solutions were studied. The SPEs exhibit high ability to sorb U(VI), Pu(IV), Np(V), Am(III), and Eu(III) from nitric acid solutions, with good kinetic properties. The impregnation conditions and distribution coefficients of the radionuclides in their recovery from 3 M HNO3 were determined. The possibility of preparing SPEs by Taunit impregnation in HNO3 solutions with adducts of tributyl phosphate (TBP) and N,N′-dimethyl-N,N′-dioctylhexylethoxymalonamide (DMDOHEMA) and with Cyphos IL-101 phosphonium ionic liquid was demonstrated.

Two novel types of sorption materials for radionuclide recovery from nitric acid solutions have been developed: the solid-phase extractants prepared by impregnation of carbon nanotubes with organophosphorus and nitrogen containing ligands, as well as the polymer composites based on thermostabilized polyacrylonitrile and carbon nanotubes. Experimental data on study of the sorption properties of the novel materials towards actinides, rare earth elements and palladium are given.

The review of literature data related to the preparation, properties, and application of carbon nanotubes for sorption recovery of elements is given. Experimental data on the application of Taunit carbon nanofor radionuclide preconcentration from different solutions, as well as of Taunit-based solid-phase extractants for recovery of actinides and rare-earth elements from nitric acid solutions are presented.

A review of solid-phase extractants for radionuclide preconcentration and separation is presented. Examples of solid-phase extractants prepared by impregnation of various supports with compounds used in liquid extraction are considered. The possibilities of using carbon nanotubes and ionic liquids for preparing new solid-phase extractants are discussed. Experimental data on sorption recovery of actinides, europium, and palladium from nitric acid solutions with solid-phase extractants prepared by impregnation of carbon nanotubes and polymeric supports with ionic liquids and ligands are presented.

Solid extractants were prepared by noncovalent immobilization of phosphonium ionic liquids (ILs) on various polymeric materials, including fibrous materials. These sorption materials can be used for recovering Pu from 0.5–5 M HNO 3 . Immobilization of phosphorus-containing ligands on solid supports using phosphonium ILs yields a material recovering actinides from nitric acid solutions.

Sorption preconcentration of U(VI) on POLIORGS 34-n fibrous filled sorbent with amidoxime groups from model solutions like natural water was studied under static and dynamic conditions. The equilibrium (distribution coefficient) and kinetic (diffusion coefficient) parameters of the sorption were determined. Parameters of dynamic preconcentration of uranium by sorption on disks and in a column packed with POLIORGS 34-n under indicated conditions were calculated by mathematical modeling using the experimental data.

An approach was proposed to analyzing platinum-containing materials. It involves the high-temperature dissolution of samples in acids under the action of microwave radiation, the sorption preconcentration of noble metals on complexing adsorbents, and their instrumental determination after the microwave dissolution of the concentrate.

The behavior of carbonyl complexes of ruthenium and osmium in chloride solutions under exposure to UV light was studied by electronic absorption spectra and electron paramagnetic resonance. It was found that, under exposure to UV light, the M-CO bond (M = Ru, Os) breaks according to the reaction described previously for nitroso complexes. On the basis of electronic absorption spectra measured in solutions of complexes during exposure to UV light, it was revealed that the quantum yield of photoreaction products in hydrochloric acid solutions decreases in the following order: [RuCOCl5](2-) > [RuNOCl5](2-) > [OsCOCl5](2-). A procedure for the spectrophotometric determination of ruthenium and osmium complexes with multiply bonded ligands using exposure to UV light is developed. The adsorption of carbonyl and nitroso complexes of ruthenium and osmium by various adsorbents was studied as a function of the temperature and the concentration of HCl. It was found that the adsorption proceeds according to the anion-exchange mechanism. Conditions for preconcentration of nitroso and carbonyl complexes of ruthenium and osmium by the POLIORGS-IV-N adsorbent were chosen. Conditions for quantitative desorption of [RuCOCl5](2-) with thiourea used as an eluant were determined. A procedure for the adsorption-spectrophotometric determination of carbonyl complexes of ruthenium using exposure to UV light with the detection limit of ruthenium as low as 0.02 mu g/mL and an analytical range from 0.02 to 0.45 mu g/mL is developed.