Extraction of Se(iv) and Se(vi) from aqueous HCl solution by using a diamide-containing tertiary amine.

Here, we investigated the mechanism underlying the extraction of Se(iv) and Se(vi) from aqueous HCl solutions by -2-ethylhexyl-bis(-di-2-ethylhexyl-ethylamide)amine (EHBAA). In addition to examining extraction behavior, we also elucidated structural properties of the dominant Se species in solution. Two types of aqueous HCl solutions were prepared by dissolving a Se oxide or a Se salt.

Speciation and separation of platinum(iv) polynuclear complexes in concentrated nitric acid solutions.

Understanding the solution chemistry of Pt(iv) is crucial for the hydrometallurgy of precious metals. To gain such an understanding, the speciation and separation of Pt(iv) complexes in concentrated HNO solutions were investigated via Pt L edge X-ray absorption fine structure (XAFS) spectroscopy. The XAFS results for concentrated HNO solutions of NaPt(OH) revealed the dominant presence of Pt polynuclear complexes, wherein the formation of Pt(iv) polynuclear complexes depended on the metal concentration and the NaPt(OH) dissolution temperature.

Unique Anion-exchange Properties of 3,3'-Diaminobenzidine Resulting in High Selectivity for Rhodium(III) over Palladium(II) and Platinum(IV) in a Concentrated Hydrochloric Acid Solution.

The effective recovery of Rh(III) from mixtures also containing Pd(II) and Pt(IV) is one of the most difficult tasks in platinum group metal refining. Adding 3,3'-diaminobenzidine (DAB) to 7 and 10 M HCl aqueous solutions containing Rh(III), Pd(II), and Pt(IV) chlorido species affords the effective separation of Rh(III) from Pd(II) and Pt(IV) through a process where Rh(III) becomes sequestered into solid phases composed of DAB. The stoichiometry and inner coordination sphere of the metal in Rh-DAB complexes were determined by estimating the Rh(III), H, and Cl concentrations in the solid phase and X-ray absorption fine structure measurements to clarify the mechanism of DAB selectivity for Rh(III).

Proton Chelating Ligands Drive Improved Chemical Separations for Rhodium.

Current methods for the extraction of rhodium carry the highest carbon footprint and worst pollution metrics of all of the elements used in modern technological applications. Improving upon existing methods is made difficult by the limited understanding of the molecular-level chemistry occurring in extraction processes, particularly in the hydrometallurgical separation step. While many of the precious metals can be separated by solvent extraction, there currently exist no commercial extractants for Rh.

Mechanisms of Se(IV) Co-precipitation with Ferrihydrite at Acidic and Alkaline Conditions and Its Behavior during Aging.

Understanding the form of Se(IV) co-precipitated with ferrihydrite and its subsequent behavior during phase transformation is critical to predicting its long-term fate in a range of natural and engineered settings. In this work, Se(IV)-ferrihydrite co-precipitates formed at different pH were characterized with chemical extraction, transmission electron microscopy (TEM), and X-ray absorption spectroscopy (XAS) to determine how Se(IV) is associated with ferrihydrite. Results show that despite efficient removal, the mode and stability of Se(IV) retention in the co-precipitates varied with pH.

Comparison of the Extractabilities of Tetrachloro- and Tetrabromopalladate(II) Ions with a Thiodiglycolamide Compound.

Using N,N,N',N'-tetra-2-ethylhexyl-thiodiglycolamide (TEHTDGA) in n-dodecane as the extractant, we compared the percentages of Pd(II) extracted from HCl and HBr solutions, and analyzed the structures of the Pd(II)-extractant complexes. For comparison, similar experiments were performed with di-n-hexyl sulfide (DHS), a well-known sulfide-type extractant. TEHTDGA extracted Pd(II) from both HCl and HBr solutions much faster than DHS.

Mechanism of Cs Removal from Fukushima Weathered Biotite by Heat Treatment with a NaCl-CaCl Mixed Salt.

An in situ extended X-ray absorption fine structure (in situ EXAFS) spectroscopic analysis at high temperature was conducted to investigate the mechanism of Cs removal from weathered biotite (WB) from Fukushima, induced by heating with a mixed salt of NaCl and CaCl. This indicated that most Cs remained in WB during heating at 200-700 °C. In addition, the in situ EXAFS spectra gradually changed on heating with the mixed salt and a completely different spectrum was observed for the sample after cooling from 700 °C to room temperature (RT).

Extraction of Lanthanide and Actinide Ions from Aqueous Mixtures Using a Carboxylic Acid-Functionalized Porous Aromatic Framework.

Porous aromatic frameworks (PAFs) incorporating a high concentration of acid functional groups possess characteristics that are promising for use in separating lanthanide and actinide metal ions, as required in the treatment of radioactive waste. These materials have been shown to be indefinitely stable to concentrated acids and bases, potentially allowing for multiple adsorption/stripping cycles. Additionally, the PAFs combine exceptional features from MOFs and inorganic/activated carbons giving rise to tunable pore surfaces and maximum chemical stability.

A Reliable Hybrid Adsorbent for Efficient Radioactive Cesium Accumulation from Contaminated Wastewater.

Cesium (Cs) removal from nuclear liquid wastewater has become an emerging issue for safeguarding public health after the accident at the Fukushima Daiichi Nuclear Power Plant. A novel macrocyclic ligand of o-benzo-p-xylyl-22-crown-6-ether (OBPX22C6) was developed and successfully immobilized onto mesoporous silica for the preparation of hybrid adsorbent. The benzene ring π electron is the part of crown ether of OBPX22C6 for easy orientation of the macrocyclic compound for making the π electron donation with Cs complexation.

Ultimate selenium(IV) monitoring and removal from water using a new class of organic ligand based composite adsorbent.

This work reports the selenium (Se(IV)) detection and removal from water by ligand functionalized organic-inorganic based novel composite adsorbent. The composite adsorbent was prepared by direct immobilization of N,N'-di(3-carboxysalicylidene)-3,4-diamino-5-hydroxypyrazole onto the mesoporous silica monolith. The adsorbent exhibited distinct color change in the presence of various concentrations of Se(IV).

Selective cesium removal from radioactive liquid waste by crown ether immobilized new class conjugate adsorbent.

Conjugate materials can provide chemical functionality, enabling an assembly of the ligand complexation ability to metal ions that are important for applications, such as separation and removal devices. In this study, we developed ligand immobilized conjugate adsorbent for selective cesium (Cs) removal from wastewater. The adsorbent was synthesized by direct immobilization of dibenzo-24-crown-8 ether onto inorganic mesoporous silica.

Structural properties of the inner coordination sphere of indium chloride complexes in organic and aqueous solutions.

The nature of the inner coordination sphere of In(3+) present in both the organic and aqueous solutions during the solvent extraction of In(3+) from an aqueous HCl solution with tri-n-octyl amine (TOA) was investigated by In K-edge XAFS. This information was then used to clarify the details of the extraction properties of indium chloride anion complexes with TOA. In aqueous HCl solution (0.

Selective lanthanide sorption and mechanism using novel hybrid Lewis base (N-methyl-N-phenyl-1,10-phenanthroline-2-carboxamide) ligand modified adsorbent.

This study aims to develop a highly selective Lewis base adsorbent to investigate the selective sorption and recovery of Eu(III) and Sm(III) from wastewater. The oxygen and nitrogen donor atoms containing Lewis base N-methyl-N-phenyl-1,10-phenanthroline-2-carboxamide (MePhPTA) ligand was synthesized and subsequently an adsorbent was prepared by direct immobilization onto mesoporous silica. Determined maximum adsorption capacities were 125.

Efficient arsenic(V) removal from water by ligand exchange fibrous adsorbent.

This study is an efficient arsenic(V) removal from contaminated waters used as drinking water in adsorption process by zirconium(IV) loaded ligand exchange fibrous adsorbent. The bifunctional fibers contained both phosphonate and sulfonate groups. The bifunctional fiber was synthesised by graft polymerization of chloromethylstyrene onto polyethylene coated polypropylene fiber by means of electron irradiation graft polymerization technique and then desired phosphonate and sulfonate groups were introduced by Arbusov reaction followed by phosphorylation and sulfonation.

Local coordination about La(3+) in molten LaCl3 and its mixtures with alkali chlorides.

The local structure around the La(3+) ions in molten LaCl(3) and its mixtures with alkali and alkaline earth chlorides has been investigated by using extended X-ray absorption fine structure (XAFS) and molecular dynamics (MD) techniques. Such mixtures, which are of current technological interest, are known to be thermodynamically nonideal, and there has been a good deal of work to understand the structural effects factors that contribute to the nonideality. New experimental methods allow observations at the La K-absorption edge at the high temperatures of interest, and the ability of the technique to obtain reliable information even at very low La(3+) concentrations in multicomponent mixtures is demonstrated.

Extended X-ray absorption fine structure investigation of adsorption and separation phenomena of metal ions in organic resin.

Analytical technique using organic resins has already been well-developed, and its applications are employed in various fields; nevertheless, the chemical phenomena occurring inside the resin remain unclear for the most part. In the present study, we apply EXAFS spectroscopy to elucidate the adsorption and separation phenomena of metal ions by organic resin. That is, the chemical species of trivalent lanthanides (Ln(III)) adsorbed in a tertiary pyridine resin from hydrochloric acid and nitric acid solutions have been determined by EXAFS.

[Refraction-contrast bone imaging using synchrotron radiation].

The X-ray refraction-contrast imaging using synchrotron radiation with some X-ray energies is successfully performed at B120B2 of SPring-8. The refraction-contrast images of bone samples such as human dried proximal phalanx, wrist, upper cervical vertebrae and sella turcica, and as mouse proximal femur, using the synchrotron X-ray are always better in image contrast and resolution than those of the absorption-contrast images using the synchrotron X-ray and/or the conventional X-ray tube. There is much likeness in the image contrast and resolution of trabeculae bone in the human dried proximal phalanx between X-ray energy of 30 keV at sample-to-film distance of 1m and those of 40, 50 keV at those of 4,5m, respectively.