Dilute Mineral Acid Research Articles

Development and application of new iondashexchange techniques for the separation of the platinum group and other siderophile elements from geological samples

Two new aniondashexchange techniques have been developed for the separation of the platinum group elements Ru, Pd, Ir, Pt and the siderophile metals Re, Ag, Zn and Cd from geological samples following a NiS fire assay digestion procedure. Both methods are simple and permit the isolation of these elements in sufficient purity for quantitative analysis by isotope dilutiondashinductively coupled plasma mass spectrometry (ID-ICPMS) at yields of 75–95%. The high affinity of the considered elements to anion exchange resins allows the use of small (1.25 ml) columns even for the processing of 5–10 g sized silicate rock samples. Following fire assay digestion and dissolution of the NiS buttons in aqua regia, the samples are loaded onto the resin bed as solutions in 1 M HCl. After elution of the bulk sample matrix with dilute HCl and HNO 3, Zn and Cd are stripped from the column using 0.8 M HNO 3. Small amounts of bromine water are added to the dilute mineral acids for the stabilization of strongly retained Ir(IV). Following this, the iondashexchange techniques permit the sequential elution of Ag, Re and the PGE using 11 M HCl, 8 M HNO 3 and 13.5 M HNO 3. The iondashexchange methods have been applied to separation of Ru, Pd, Re, Ir and Pt from the geological reference material SU-la prior to concentration measurements by ID-ICPMS. Our analytical results are in good agreement with previously published data for this sample and display an external reproducibility (based upon repeat dissolutions) of approximately 2–10% for the elements considered in this study.

Voltammetric and XPS investigations of polynuclear ruthenium-containing cyanometallate film electrodes

Glassy carbon electrodes coated with thin films of mixed valence ruthenium-oxo-species stabilized by cyanoruthenate or cyanoferrate crosslinks were investigated by cyclic voltammetry and X-ray photoelectron spectroscopy (XPS). Electrochemical deposition was accomplished in dilute mineral acid solutions (e.g. 10 mM H 2SO 4) containing millimolar concentrations of RuCl 3 + K 4Fe(CN) 6, or RuCl 3 + K 4Ru(CN) 6, or OsCl 3 + K 4Ru(CN) 6. Film deposition is attributed to growth of compact and conducting lattices with significant oxo- (MOM) and cyano-bridging (M′CNM), in which M represents Ru, or Os, while M′ refers to Ru or Fe. Particular attention was devoted to the polynuclear ruthenium oxide microstructure (RuORu) crosslinked with cyanoruthenate and cyanoferrate, designated as RuORuCN and RuoFeCN respectively. From an electrochemical point of view, the mixed metal RuOFeCN behaves in a manner analogous to the RuORuCN film electrode, and indeed these modified electrodes are capable of catalyzing the oxidation of several substrates in acidic solutions. Depending on the applied potential, two distinct and selective reactive sites are recognizable in the electro-oxidation processes of As(III) and 2-furaldehyde at both RuOFeCN and RuORuCN film electrodes. XPS characterization of these ruthenium-containing cyanometallate films shows clear evidence of the existence of two oxidation states of ruthenium (Ru 3d region), which are respectively attributed to oxo-ruthenium(IV) and dioxo-ruthenium(VI) or Ru(V) in the oxide framework of the inorganic lattice.

Metal-ion binding affinity of azole-modified oxirane and thiirane resins

The azole ligands pyrazole, imidazole, 1,2,4-triazole and tetrazole have been immobilized onto poly(glycidyl methacrylate) p(GMA-O) and onto its sulfur analogue p(GMA-S), which contains a thiirane ring instead of an oxirane ring. The ligands were introduced using ring-opening reactions of the pendant oxirane or thiirane groups with the azoles, resulting in formation of the chelating ion-exchange resins PYROH, IMOH, TRIOH, TETOH, PYRSH, IMSH, TRISH and TETSH. The resins have been characterized by solid-state 13C cross-polarization and magic-angle spinning NMR, FT-IR spectroscopy and elemental analysis. Batch extraction capacities were determined for the chloride salts of Cu 2+, Ni 2+, Co 2+, Zn 2+ and Cd 2+ in buffered solutions in the pH range 0.9–6.0. Both modified oxirane and thiirane resins are very selective for Cu 2+ in the presence of other divalent heavy metal ions. The maximum uptake capacities for Cu 2+ for the oxirane resins under non-competitive conditions are 0.28 mmol/g for TRIOH, 0.39 mmol/g for IMOH and 1.14 mmol/g for PYROH. The resin TETOH is an exception, and does not show any detectable uptake of M 2+ at all. The maximum uptake capacities for Cu 2+ for the thiirane resins under non-competitive conditions are 0.87 mmol/g for TETSH, 0.96 mmol/g for TRISH, 0.58 mmol/g for IMSH and 0.98 mmol/g for PYRSH. The 4 thiirane resins also sorb noticeable amounts of Cd 2+ and Zn 2+ especially the resin PYRSH. The maximum uptakes of Cd 2+ and Zn 2+ for PYRSH are 0.65 and 0.74 mmol/g respectively. The complexation of Cd 2+ and Zn 2+ by the thiirane is ascribed to the presence of thiol groups. The resins PYROH and PYRSH have the highest uptake capacity for Cu 2+ of all the resins tested. The M 2+-uptake sorption behavior of all the 8 resins show very steep pH-dependent curves, i.e. virtually no M 2+-uptake below pH 2.5 and, depending on the particular metal ion, maximum uptake at pH 5.5. The thiirane resins are stable in the presence of dilute mineral acid, as was shown by regeneration experiments performed with 1.0 M H 2SO 4.

Synthesis and Ion-Exchange Behavior of a New Three-Component Ion-Exchange Material: Zirconium(IV) Arsenate Vanadate

Abstract Zirconium(IV) arsenate vanadate was prepared by adding a mixture comprising 0.05 M sodium hydrogen arsenate and 0.05 M sodium metavanadate to an aqueous solution of zirconium(IV) dichloride oxide (0.05 M) in different volume ratios at pH 1. The material possessed a good ion-exchange capacity of 1.20 and 1.30 meq g−1 of exchanger for the Na+ and K+ ion, respectively, and was fairly stable in dilute mineral acids, but insoluble in water, acetic acid, formic acid, ethanol, and 1,4-dioxane. The distribution coefficients of a large number of metal ions were determined in different solvent systems.

Recycling of egyptian bagasse pith wastes in the synthesis of cationic resins

AbstractA series of sulfonated cationic resins have been prepared and characterized from Egyptian bagasse pith wastes (as a source of cheaper and renewable material) with m‐cresol and paraformaldehyde as a crosslinking agent. Reaction conditions for the preparation are presented and properties of the synthesized sulfonated bagasse pith‐m‐cresol‐formaldehyde resins are described and compared with resin not containing bagasse pith. The synthesized resins are stable in water, dilute mineral acids (1 M), organic solvents, and to thermal treatment. The resins having a cation exchange capacity up to 2.91 meq g‐1 of dry resin, are being introduced as new exchangers. The synthesized resins are used in the study of the possible separation of some bivalent cations.

Characterization of basic proteins from goldfish myelin.

Myelin basic protein (MBP) from common goldfish (Carassius auratus) myelin was extracted with dilute mineral acid. Immunological cross-reactivity of the goldfish MBP, with polyclonal antisera raised against bovine MBP, suggested that the goldfish protein has epitopes for these antibodies. It also reacted with a monoclonal antibody specific for a seven amino acid epitope (130-137) conserved in the MBP of most mammalian species. To characterize the charge heterogeneity of this protein, we iodinated the protein with 125I and chromatographed it on a carboxymethyl cellulose-52 column together with a nonlabeled acid soluble fraction prepared from human white matter as a carrier protein. All of the goldfish protein was recovered in the unbound fraction, demonstrating that it was less cationic than the carrier protein (human MBP). We have also examined the urea alkaline gel profile of the goldfish MBP together with the human C-1, C-2, C-3, C-4, and C-8 components. The results from these experiments indicated that this MBP extracted from goldfish brain myelin lacked the microheterogeneity that is associated with MBPs from higher vertebrates. The MBPs from goldfish myelin were separated into their isoforms by reversed-phase HPLC. Amino acid compositions were determined for both the 17- and 14-kDa goldfish proteins. Amino acid analysis revealed similarities with the compositions of other MBPs; however, the serine content in both the 17- and 14-kDa proteins was higher than that of the human C-1, the mouse C-1 protein, and the shark proteins. The HPLC-purified 14-kDa goldfish protein was chemically cleaved with CNBr for partial sequence analysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Flow of Air, Nitrogen, and Hydrogen through Porous Glass Tubes

Abstract A simple apparatus for obtaining diffusion data for porous tubes is described. It was used for determining the permeation rates of air, nitrogen, and hydrogen through porous 96% SiO2 glass tubes. To increase flow, these tubes were subjected to multiple etch/wash treatments using aqueous NH4F solutions at room temperature followed by successive hot washes in dilute mineral acid and distilled water. Further increases in permeation rates were achieved by subjecting the base glass used in the preparation of the porous glass to long heat treatments at its phase-separation liquidus prior to leaching and etching. Diffusion data show that the permeability of porous glass is not degraded on heating at temperatures up to 800°C, and that the separation ratios of the experimental glasses are in good agreement with values expected from Graham's law of diffusion. The role of heat treatment of the base glass, etch/wash treatments of the porous glass, and moisture in the gas stream are discussed.

Selective extraction of Hg(II) from aqueous mineral acid solution containing iodide ions using 2-benzylpyridine in benzene

A method for the selective extraction of mercury has been developed. The extraction of Hg(II) by 2-benzylpyridine (BPy) in benzene from dilute mineral acid solution containing iodide ions has been investigated, and variables such as concentration of acids, iodide and the extractant have been optimized. The optimum conditions for the extraction of Hg(II) by 0.1M BPy/benzene are: 0.01M (HCl, HNO3, H2SO4)+0.01M KI. The distribution coefficients and separation factors of 19 elements relative to Hg(II), have been reported. Effect of anions such as ascorbate, acetate, citrate, oxalate and thiosulfate has also been studied. The method developed could find useful applications in selective extraction of small amounts of mercury from environmental samples.

Electrochemistry of carbonaceous materials: 2. Anodic electroactivity of coal slurries in 85% phosphoric acid media

Current-potential curves of suspended coal (Sulcis basin, Sardinia, Italy) in 85% H 3PO 4 were taken on a platinum electrode at 100 °C. Anodic current in the potential range of 0–1.5 V versus saturated calomel electrode was due to some humic acid-type substances released by coal in the electrolyte. The leaching of organic matter increased with the lowering of the particle dimensions, and the related oxidation currents attained stable values even during slurry formation. Current-potential curves were still unchanged when coal was filtered off from the suspension. Previous washing of ground coal with diluted mineral acids, including H 3PO 4, did not dissolve any significant amount of the substances responsible for the electrochemical activity of the coal sample examined.

Acid-catalyzed hydrolysis of 5-enolpyruvylshikimate 3-phosphate (EPSP) and some simple models of its vinyl ether functional group

Rates of hydrolysis of the vinyl ether functional groups of 5-enolpyruvylshikimate 3-phosphate (EPSP), α-methoxyacrylic acid, and methyl α-methoxyacrylate were measured in concentrated and dilute mineral acid solutions and carboxylic and buffers, and rate profiles were constructed from the data so obtained

Hemicellulose bioconversion to polyanionic heteropolysaccharides.

Anionic polysaccharides, traditionally obtained from plant or algal sources, have a variety of commercial uses. Such gums from microorganisms have received increased recent interest. We have initiated a program to investigate the bioconversion of pentosans to rheologically useful anionic extracellular polysaccharides (AEPS). A number of earlier-described species, including Cryptococcus laurentii, Klebsiella pneumoniae, Arthrobacter viscosus, and Pseudomonas ATCC 31260, appear to have potential in this regard. These organisms can individually convert either xylose, enzymatic oligomeric hemicellulose digests, dilute mineral acid hemicellulose ("TVA") hydrolysates, or a five-monosaccharide mixture simulating sulfite process liquors to AEPS. The formation parameters, compositions, mol-wt distributions, and the intrinsic viscosities of these purified AEPS are exemplified. Substitution of pentose as the major substrate for glucose can result in changes in mol-wt distribution or in the percentage of noncarbohydrate substituents in some AEPS. Pursuit of these observations may lead to interesting structure-property relationships and toward rheological applications for pentosan-derived AEPS.

Synthesis and Characterisation of Scandium (III)‐, Yttrium (III)‐, and Lanthanum (III) Violurate Complexes

AbstractSc3+‐, Y3+ ‐and La3+ violurate complexes were prepared. The isolated complexes are freely soluble in water, dilute mineral acids, MeOH, Me2CO, DMF, DMS, partially soluble in AcOH and insoluble in EtOH, CHCl3 and CCl4. Molecular compositions of the complexes were formulated on the basis of elemental analysis, molar conductivity and infrared spectra. The IR spectra of violuric acid and its metal complexes reveal that bonding takes place through coordination bond between the central metal ion and the oxygen atom of the oxygen atom of the oximino (CN = O) group and convalenet bond between the central metal ion and oxygen atom of the phenolic (ketonic, COH) group in the case of 1:2 and 1:3 complexes, and through coordination bond between the central metal ion and COH and NH groups in the case of 2:3 complexes. All the isomorphous complexes detected by the X‐ray powder patterns [the (2:3) Sc3+‐VA and (2:3) Y3+‐VA complexes, (1:2) Sc3+‐VA, (1:2) Y3+‐VA and (1:2) La3+‐VA complexes, and the (1:3) Y3+‐VA and (1:3) La3+‐VA complexes] have similar X‐ray, eletronic and IR spetrograms and chemical formulae. The electronic spectra in DMF and in nujol mulls characterise the octahedral stereochemistry for the investigated complexes.

ChemInform Abstract: A Facile Synthesis of 3‐Aryl‐4‐pyrazoleacetic Acids and of Their 4,5‐Dihydro Derivatives.

N-1-Unsubstituted-3-aryl-4-pyrazoleacetic acids and their 4,5-dihydro derivatives can conveniently be prepared by cyclization of 3-benzoyl-3-butenoic acids with hydrazine hydrate in acetic acid and subsequent treatment with bromine in acetic acid or, respectively, with diluted mineral acids.

A facile synthesis of 3‐aryl‐4‐pyrazoleacetic acids and of their 4,5‐dihydro derivatives

AbstractN‐1‐Unsubstituted‐3‐aryl‐4‐pyrazoleacetic acids and their 4,5‐dihydro derivatives can conveniently be prepared by cyclization of 3‐benzoyl‐3‐butenoic acids with hydrazine hydrate in acetic acid and subsequent treatment with bromine in acetic acid or, respectively, with diluted mineral acids.

The bicyclo [2.1.0] Pentane way to the diquinane alcohol part of natural triquinanes. A high yield access starting from trimethylsilyloxycyclopentene.

Trimethylsilyloxycyclopentene reacts exclusively with ethyl propiolate in the presence of ZrCl 4 to give a [2+2] adduct (alcohol 6, 90 %). After protection, the stereoselective cyclopropanation via 1,3-dipolar addition of 2-diazopropane followed by sensitized photocleavage, leads with good yields to the bicyclo [2.1.0] pentane derivative 11. By deprotection and solvolytic cleavage with dilute mineral acid, the diquinane alcohol 5 is obtained quantitatively and stereospecifically.

Preparation of some lanthanide violurate complexes

AbstractViolurate complexes of Ce3+, Pr3+, Pr4+, Nd3+, Sm3+, Eu3+, Gd3+, Dy3+, Ho3+, Er3+, and Yb3+ were prepared. The prepared complexes are freely soluble in hot water and dilute mineral acids. Thermal analysis (DTA, DTG, and TGA) show that the solid complexes are characterized by endo‐ and exothermic bands, indicating that they are degradated at different temperature stages. The IR spectra of the ligand and its metal complexes reveal that bonding takes place through coordination bonds between the central metal ion and the oxygen atom of the oximino (C = NO) group and the oxygen of the phenolic (ketonic group . All the isomorphous complexes, detected by the X‐ray diffraction patterns, have similar IR spectra.

Cyclopropene als C3-Synthesebausteine: Cyclopentenole und große Ringe aus 2-Aminobicyclo[2.1.0]pentan-Derivaten über Ringerweiterungsreaktionen

The readily available methyl 3,3-dimethylcyclopropene-1-carboxylate undergoes [2+2] cycloaddition with enamines to give 2-aminobicyclo [2.1.0] pentane derivatives in moderate to good yields. These compounds are quantitatively transformed into 3-cyclopentenols by treatment with dilute mineral acids. From enamines derived from medium-ring ketones and morpholine, tricyclic adducts are formed, which eliminate morpholine under flash-thermolysis conditions at 600 o C to give macrocycles containing an E double bond and an allenic system

Ring opening of pyrrolidonecarboxylic acid via a metal chelate.

l-Pyrrolidonecarboxylic acid (PCA) is a cyclic compound derived on intramolecular dehydration of l-glutamic acid. The conventional method used for the conversion of PCA to glutamic acid has been hydrolysis with strong acids or alkalis at high temperatures. On the reaction of metallic ions such as zinc with PCA, a chelate compound of glutamic acid, and not a metallic salt of PCA, was found to precipitate. This chelate compound dissolved in a dilute mineral acid and glutamic acid crystallized out at the isoelectric point. The yield achieved with this novel direct ring opening of PCA at neutral pH reached 93.1 %.

Biosorption of copper by fungal melanin

Melanin obtained from Aureobasidium pullulans and Cladosporium resinae was an efficient biosorbent for copper. Copper uptake could be expressed using various adsorption isotherms; melanin from A. pullulans obeyed Freundlich and Langmuir isotherms whereas C. resinae melanin followed the BET isotherm indicating a more complex type of adsorption than in A. pullulans. In general, uptake capacities of melanin were greater than for intact biomass and the higher uptake by pigmented rather than albino biomass could be correlated with the presence of melanin. Cu2+ was less readily desorbed from melanin by dilute mineral acids than from intact biomass and again, the relative ease of Cu2+ desorption from pre-loaded pigmented or albino biomass was correlated with the presence or absence of melanin. Mg2+ and Zn2+ appeared to be the most effective cations for desorption with Na+ and K+ the least effective. The addition of melanin to a coppercontaining culture of the albino strain of A. pullulans resulted in some reduction of toxicity.

Ammonia—Hydrazine conversion processes: XVI. Conversion of benzophenone azine into hydrazine catalyzed by sulphonic acids in a two-phase system

Lipophilic sulphonic acids revealed excellent activity as catalysts for the hydrolysis of benzophenone azine (Ph 2C N N CPh 2) into hydrazine in a two-phase system of xylene and 2 N sulphuric acid. High yields of hydrazine (89.8-93.2%) were obtained with a catalytic amount of dodecyl- or didecylbenzenesulphonic acid (2 mol-%, relative to the amount of azine) at 90°C for 1 h. These values are in sharp contrast to the 0.64% yield of hydrazine obtained in the absence of sulphonic acid. For high catalytic activity, dilute mineral acid should be present in the aqueous phase for effective regeneration of the free sulphonic acid. Strongly hydrophilic p-toluenesulphonic acid was extracted almost entirely into the aqueous phase and was less active catalytically at high concentrations.