The preparation of gold nanoparticles in triton N-42 reverse micelles after preliminary concentration from acid sulfate-chloride solutions

The distribution of Au(III) between an acid (3 mol/l HCl) aqueous phase and a micellar Triton N-42 solution in n-decane was studied as a function of the concentration of Na₂SO₄ (0–3.55 mol/l). The high distribution coefficients (200–500) allow 50-fold absolute concentration to be performed at a 90% extraction. Au⁰ nanoparticles were obtained by the injection solubilization of a reducing agent (hydrazine) into micellar extracts. At low solubilization capacities (≤1 vol %) and high reducing agent concentrations (≥0.2 mol/l) in Triton N-42 micelles, stable systems of Au⁰ nanoparticles suitable for the spectrophotometric determination of gold were obtained. At high solubilization capacities and low hydrazine concentrations, reduction was accompanied by coagulation and sedimentation processes. These processes were studied by spectrophotometry and the static and dynamic light scattering methods.     

NONCOOPERATIVE MANAGEMENT OF THE NORTHEAST ATLANTIC COD FISHERY: A FIRST MOVER ADVANTAGE

The point of departure for this analysis is Bjørndal and Lindroos [2012], who developed an empirical bioeconomic model to analyze cooperative and noncooperative management of Northeast Atlantic cod. In their analysis, only constant strategies were analyzed for noncooperative games. In this paper, nonconstant strategies are considered. Moreover, the fishery in question is characterized by cooperative management. What may happen in the real world is that one nation breaks the cooperative agreement by fishing in excess of its quota. Often, it takes time for the other agent to detect this and respond. In this paper, we allow this kind of delayed response into a two‐agent noncooperative game so that, if country 2 exceeds its quota, there will be a time lag before this is detected by country 1; moreover, there may also be a delay until country 1 is able to respond. Results show that the outcome critically depends on the length of these two lags as well as initial conditions.     

Extraction of triaquatrinitrorhodium form with calix[<Emphasis Type="Italic">n</Emphasis>]arenethiaethers from nitric acid nitrite–nitrate solutions

Comparison of extraction properties of macrocyclic calix[4,6]arenethiaethers (CATE) with their acyclic analogs R₂S (R = C₆H₁₃, C₈H₁₇) for the recovery of [Rh(NO₂)₃(H₂O)₃]⁰ rhodium form from nitric acid solutions was carried out. Rhodium recovery with CATE (0.05 M) in the absence of accelerating additives under optimal conditions exceeds 90% at 5–10-fold preconcentration and is only 1–3% for R₂S (1 M). Extraction kinetics was studied and hypothesis on the mechanism of multiple acceleration of rhodium recovery was proposed for CATE extraction, the mechanism includes the formation of intermediate product of colloidal- chemical nature on account of the surface activity of the macrocycle and its reaction with rhodium accompanied by rhodium chelation to the sulfur atoms of neighboring fragments of the macrocycle. The obtained results are of interest for the development of methods for the isolation of fission rhodium from nitrate–nitrite nitric acid solutions.     

Study of extraction systems based on the mixtures of phosphorylated calix[4,6]arenes with dioctyl sulfide for recovery of triaquatrinitrorhodium species from acid nitrate-nitrite solutions

A comparison was made for extraction systems based on the mixtures of calix[n]arenes phosphorylated at the upper and lower rims (PCA, n = 4 and 6) with dioctyl sulfide (DOS) for recovery of rhodium in the form of [Rh(H₂O)₃(NO₂)₃]⁰ from acid nitrate-nitrite media. Because of inertness of rhodium compounds, the main attention was devoted to extraction kinetics. The kinetic efficiency of DOS + PCA systems was found to be much higher than that for DOS alone, whereas the components of the mixtures do not extract rhodium. Alkyl(ethyl)calixphosphine oxides are the most promising, they behave as accelerating additives in extractant mixtures. Extraction kinetics of [Rh(H₂O)₃(NO₂)₃]⁰ species was studied and extraction systems were selected to develop method for the recovery of fission rhodium.     

Films and composites of gold nanoparticles stabilized by abietic acid

We studied the usefulness of dispersions of gold nanoparticles (Au-NPs) stabilized by abietic acid for manufacturing films on glass and silicon substrates and composites with nanosized and powder materials exemplified by SiO₂ and TiO₂ NPs, expanded graphite (EG), carbon nanotubes (CNTs), a porous carbon material (PCM), PCM containing 6% nitrogen, and CeO₂ powder.     

Surface characterization of Ag/Titania adsorbents

The Ag/Titania adsorbent for selective removal of the desulfurization-refractive polycyclic aromatic sulfur heterocycles (PASHs) from liquid hydrocarbon fuels was prepared, its total and the Ag specific surface area were determined and the surface reaction sites in the sorbent that may be active in the adsorptive selective desulfurization were characterized by several spectroscopic and surface science techniques. The sorbent contains Ag, Ti, O and spurious C on its surface, as by the XPS measurements. Silver is present as an oxide, as judged by the XPS Auger parameter (AP). The complementary electron spin resonance (ESR) spectroscopy confirms that the majority of Ag is present in the diamagnetic Ag¹⁺ form, with the minor concentration (∼0.1% of total Ag) present as Ag²⁺. The findings by XPS and ESR are confirmed by the XRD, UV-vis spectroscopy and thermodynamic considerations. The supported Ag is highly dispersed on the surface of the titania support, with the particle size of ∼30-60 Å depending on Ag content, with an Ag specific surface area of ∼7-14 m²/g, vs. the total surface area of ∼114-58 m²/g.     

Thiourea stripping of rhodium from organic phases resulting from extraction with a mixture of dialkyl sulfide and alkylanilinium nitrate from acid nitrate-nitrite aqueous solutions of triaquatrinitrorhodium(III)

In continuation of our studies on the extraction of rhodium from acid nitrate-nitrite aqueous solutions with a mixture of alkylanilinium nitrate and dialkyl sulfide, a back-extraction of rhodium was studied. Thiourea (TU) is an efficient agent for the back-extraction of rhodium and concomitant noble metals (Pd, Ru, Ag). The back-extraction of rhodium proceeds via coordination mechanism, [Rh(tu)₆](NO₃)₃ being the major product. Aqueous 1 mol/L solution of TU ensures stripping of at least 91% rhodium and provides its relative concentrating up to 4 times (time of phase contact is 5 min, temperature 20?C35°C). The presence of palladium and other noble metals in extract does not affect the Rh stripping.     

Crystal and Molecular Structure of trans-[Pd(Bu2S)2(NO2)2]

Single crystals of the [PdL₂(NO₂)₂] complex were obtained for the first time, where L is di-n-butylsulfide. Single crystal and powder diffraction studies provided new data on the molecular and crystal structure of this compound.