Ceramic nanomaterials from aqueous and 1,2-ethanediol supersaturated solutions at high temperature

The aim of this study was the synthesis and physicochemical characterization of some nanosized hydroxides/oxides interesting in the field of ceramic materials with the aim of developing new materials for technological applications in the field of high-performance coatings. In particular, attention was focused on ZrO2nH2O, ZrO2, Zn(OH)2, ZnO, Al2O3nH2O, and Al2O3. The synthesis was carried out in 1,2-ethanediol at 150-160 degrees C or in water at 90 degrees C at a high degree of supersaturation in order to achieved nucleation rate much greater than the growth rate. The obtained ZrO2nH2O, Zn(OH)2, and Al2O3nH2O particles were peptized to eliminate possible agglomeration and then calcinated at a suitable temperature to allow the formation of the corresponding anhydrous oxides. The synthesized particles were characterized by scanning and transmission electron microscopy, X-ray diffractometry, and differential thermal analysis coupled with thermogravimetry and Fourier transform infrared spectroscopy. The study showed that all the products can be obtained in the nanostructured crystalline form; ZrO2 presented the interesting feature of different tetragonal/monoclinic ratios depending on the solvent used for the synthesis. Preliminary results on the potentialities of these ZrO2 particles as agents for ultrahard coatings on ceramic surfaces were encouraging and very promising.     

Preparation of hybrid ion exchanger based on acrylamide for sorption of some toxic metal ions from aqueous waste solutions

Crystalline phases of polyacrylamide titanium tungstophosphate composite material has been synthesized via sol–gel method. The properties of its were determined using different technique. The ion-exchange capacities of the hybrid material for Cs⁺, Co²⁺ and Eu³⁺ ions it was found that 6.22, 2.76 and 1.38 mequiv. g^–1 respectively. The material was found that highly selective for Eu³⁺ and the selectivity sequence for sorption of Cs⁺, Co²⁺ and Eu³⁺ ions on polyacrylamide titanium tungstophosphate was found that; Eu³⁺ > Cs⁺ > Co²⁺. Thermodynamic parameters have been calculated for the studied ions showing that the overall adsorption process is spontaneous and endothermic. The experimental isotherm data were analyzed using the Langmuir and Freundlich models.     

Recovery of plutonium from aqueous waste solutions using porous zirconia spherical particles

Based on the Linssi database and UniSampo/Shaman software, an automated analysis platform has been setup for the analysis of large amounts of gamma-spectra from the primary coolant monitoring systems of a CANDU reactor. Thus, a database inventory of gaseous and volatile fission products in the primary coolant of a CANDU reactor has been established. This database is comprised of 15,000 spectra of radioisotope analysis records. Records from the database inventory were retrieved by a specifically designed data-mining module and subjected to further analysis. Results from the analysis were subsequently used to identify the reactor coolant half-life of ¹³⁵Xe and ¹³³Xe, as well as the correlations of ¹³⁵Xe and ⁸⁸Kr activities.     

Sorption of metal ions from multicomponent aqueous solutions by activated carbons produced from waste

Activated carbons produced by thermal treatment of a mixture of sunflower husks, low-grade coal, and refinery waste were studied as adsorbents of transition ion metals from aqueous solutions of various compositions. The optimal conditions and the mechanism of sorption, as well as the structure of the sorbents, were studied.     

Preparation of iron-aluminum powders from aqueous solutions and their physicochemical properties

Iron and iron-aluminum powders were obtained by the reduction of Fe(III) to α-Fe, occurring on a dispersed aluminum support. Their physical and mechanical properties were studied, and the possibility of obtaining compact samples with a lower bulk density as compared to known analogs, an elevated strength, and a high porosity was examined.     

Preparation of BaCrO4 particles in the presence of EDTA from aqueous solutions

BaCrO₄ particles with well-defined morphologies have been synthesized in the presence of EDTA as a crystal growth modifier from aqueous solutions. The influence of pH on the morphology of BaCrO₄ crystals with and without EDTA additive was investigated to better understand the formation mechanism. EDTA has a strong interaction with the crystal faces of BaCrO₄ and influences the final morphology of BaCrO₄ crystals. In the presence of EDTA, BaCrO₄ particles at pH?=?6 always exhibit a spindle-like morphology due to the large inhibition effect of EDTA on the BaCrO₄ crystallization. With decreasing pH, the particle morphology changes into a peanut-type at both pH?=?5 and pH?=?4 due to the relatively low inhibition and the following secondary heterogeneous nucleation and growth. The possible morphological evolution of BaCrO₄ particles is also proposed.     

Experimental studies of interfacial phenomena on innovative carbon nanomaterials in aqueous electrolyte solutions

Interfacial phenomena on the surface of carbon nanomaterials (CNM) in aqueous solutions in the presence of surfactants were studied experimentally and theoretically. The hydrodynamic radius and electrokinetic potential of particles of the dispersed phase and the concentration of functional groups on the CNM surface were found. The points of zero charge of solutions of the dispersed phase were measured, and so were their shifts with varying electrolyte concentrations, which make it possible to determine the pH values at which the CNM particles are electrically neutral.     

Biosorption of some ions on different bacterial species from aqueous and radioactive waste solutions

The uptake of metal ions, cerium, Ce(III); cobalt, Co(II); thorium, Th(IV); and uranium U(VI) by Bacillus pumilus-LRW1, Bacillus cereus-LRW2 and Micrococcus lylae-LRW3 from aqueous solution was examined as a function of metal ion concentration, pH, temperature, and the presence of some foreign ions. The bacterial species exhibited high affinity to accumulate metal ions from their solutions at pH 4–5.0±0.5. The amount of each ion (in mg) accumulated by one gram dry weight of each bacteria was calculated. The uptake by the Bacillus cereus-LRW2 from aqueous solutions and simulated radioactive wastes were also investigated. Electron microscopic investigations showed that the ions were accumulated around the cell wall.     

Recovery of plutonium from phosphate containing aqueous analytical waste solutions using macroporous anion exchange resin

Distribution ratios of Pu(IV) between 7.5M HNO₃+0.75M H₃PO₄+0.3M H₂SO₄ media and a macroporous anion-exchange resin Amberlyst A-26 (MP) increased from 40 to 250 when 1M aluminium nitrate was added to the aqueous medium. When 1M ferric nitrate was used in place of aluminium nitrate the distribution ratio further increased to 850. The 10% Pu(IV) breakthrough capacities with a 5 ml bed resin column, using synthetic feed solutions containing 1M aluminium nitrate, were 1.4 g l^–1, 3.2 g l^–1 at flow rates of 30 ml per hour and 10 ml per hour, respectively. The corresponding 10% Pu(IV) breakthrough capacities in the presence of 1M ferric nitrate were 8.5 g l^–1 and 12.8 g l^–1. More than 97% of plutonium could be recovered from actual analytical phosphate waste solutions.     

Preparation of nanosized sulfur particles from aqueous solutions of calcium and sodium polysulfides

Preparation of nanosized sulfur from solutions of calcium and sodium polysulfides was considered. Via measuring the optical density of dilute aqueous solutions of the polysulfides the sulfur hydrosol particle size was studied in relation to the storage time and viscosity of the solutions. It was found that the sulfur nanoparticle size can be controlled by varying the viscosity of solution and introducing polymer additions. The temporal stability of nanosized sulfur hydrosol particles was examined.     

Extraction of uranyl ions from aqueous solutions using silica-gel-bound macrocycles for alpha contaminated waste water treatment

The efficiency for the extraction of U(VI) of new modified silica gels, namely N-tripropionate (or N-triacetate)-substituted tetraazamacrocycles-bound silica gels, has been studied. The effect of the nature of the ligand, the pH and the temperature was studied both in batch experiments as well as in continuous extraction. These silica gels are good candidates for the extraction of U(VI) when compared to a commercially available acid-type chelating resin. The breakthrough and regeneration tests showed that the total removal of U(VI) from a contaminated solution can be achieved by using a column packed with such tetraazamacrocycles-bound silica gels. Finally, the use of a modified silica gel in a pilot device allowed the total decontamination of 50 m³ of real effluents containing traces of uranium, plutonium, and americium.     

Preparation of palladium nanoparticles with desired sizes in aqueous solutions

Methods have been developed for obtaining palladium nanoparticles with near-spherical shape and desired and controlled sizes from 2 to 50 nm via reduction of metal ions in aqueous solutions. The influence of sodium polyphosphate and sodium polyacrylate used as stabilizing agents on the sizes and aggregation and sedimentation stability of the particles has been revealed. The dependence of nanoparticle sizes on the initial concentration of palladium(II) ions has been established.     

Preparation of colloidal CdSe and CdS/CdSe nanoparticles from sodium selenosulfate in aqueous polymers solutions

Cadmium selenide nanoparticles formation at the interaction between CdCl2 and Na2SeSO3 in aqueous solutions of sodium polyphosphate and gelatin has been studied. Structural and optical properties of CdSe nanoparticles have been characterized. It has been shown that the temperature and the ratio of reagents concentrations are the basic parameters, controlling the size of CdSe nanoparticles. Photocatalytic activity of CdS nanoparticles in Na2SeSO3 reduction has been found and investigated; structural and optical properties of binary CdS/CdSe nanoparticles have been characterized. This photoreaction, when carried out in the presence of CdCl2, results in the formation of composite CdS/CdSe nanoparticles. It has been shown that slow interaction of adsorbed selenosulfate with surface-trapped CdS conduction band electrons is the limiting stage of the photocatalytic reaction.