M. A. Olazabal

SELECTIVE EXTRACTION OF VANADIUM (V) FROM SOLUTIONS CONTAINING MOLYBDENUM (VI) BY AMMONIUM SALTS DISSOLVED IN TOLUENE

ABSTRACT Several separation schemes, involving liquid-liquid extraction procedures, were found to be theoretically feasible in order to separate Vanadium and Molybdenum based on computer simulation of the acid-base properties of these metals, where cationic and anionic (both mono and polynuclear) species are formed as the pH increases. A liquid cationic extractant (LIX 26), a basic alkylamine (Alamine 336) and a quaternary ammonium salt (Aliquat 336) were experimentally tested. Among them, the sulphate of the quaternary ammonium salt extracts V(V) selectively and quantitatively from Mo(VI) solutions in the basic range 8 < pH < 9. A close relation between the extraction of the metals and the distribution of their species in the aqueous phase has been found. The sulphate forms of Alamine 336 and Aliquat 336 extract quantitatively both metals at the pH where anionic polynuclear species are predominant.

Raman spectra of the different phases in the CaSO4-H2O system.

Although it is known that the CaSO4/H2O system is formed by at least five different phases, this fact is not correctly documented in Raman spectroscopy studies. The main problem detected in the literature was the incorrect definition of the anhydrite, which produced the assignation of different spectra for a single compound. In this sense, two different spectra were clearly identified from the bibliography, which showed different main Raman bands at 1017 or 1025 cm(-1), although anhydrite could be present even as three different polymorphous species with different structures. A better understanding of the whole system obtained from a review of the literature allowed new conclusions to be established. Thanks to that revision and the development of different thermodynamical experiments by Raman spectroscopy, the Raman spectra of each phase were successfully identified for the first time. In this way, the main Raman bands of gypsum, bassanite, anhydrite III, anhydrite II and anhydrite I were identified at 1008, 1015, 1025, 1017 and 1017 cm(-1), respectively. To conclude this work, the contradictions found in literature were critically summarized.

Development of a Modified Bromley's Methodology (MBM) for the estimation of ionic media effects on solution equilibria. Part 2. Correlation of the molar and molal interaction parameters with the charge and crystal radii of the ions

Abstract The interaction parameters of strong electrolytes obtained for both the molar and molal scales using the Modified Bromleys Methodology (MBM) have been correlated with the ionic charge and individual crystal radius of each ion. The correlation function for each ion with opposite counterions is a straight line centered in the water radius value (1.39 × 10−10m). These correlations allow the prediction of values of unknown interaction parameters of a cation with several anions even if only one interaction parameter of the cation with a given anion is known.

Buildings as repositories of hazardous pollutants of anthropogenic origin.

In the present work the pollutant content of diverse building materials was evaluated by the combination of spectrometric and chromatographic techniques. A first non-destructive analysis carried out by μ-XRF and Raman spectroscopy revealed a high impact of pollutants, which reached depths higher than 6mm. The quantitative analyses pointed out that black crust as accumulation nucleus where concentration values up to 3408 mg/kg of lead, 752 mg/kg of chromium or 220 mg/kg of arsenic, high amounts of diverse sulphates and nitrates as well as substantial amounts of polycyclic aromatic hydrocarbons (PAHs) of a clear pyrolytic source were determined. On the other hand, samples without black crust showed also a surprising soluble salt content up to 5%. Polychlorinated biphenyls (PCB) were found to be absent in all material types. The chemometric analysis of the quantitative results revealed that the accumulation capacity and the subsequent pollutant content depends on the type of construction materials, being mortars the most susceptible.

Development of a Modified Bromley's Methodology for the estimation of ionic media effects on solution equilibria: Part 3. Application to the construction of thermodynamic models

Abstract The development of the Modified Bromleys Methodology (MBM) is extended for the estimation of the activity coefficients of individual species in aqueous solution at 25°C in single and mixed ionic media. The estimation is compared with literature data of activity coefficients of mixtures of electrolytes in water and applied to (a) the prediction of the ionic product of water in aqueous solutions containing different salts which are commonly used as background electrolytes (NaCl, KNO3 and NaClO4) and (b) the equilibrium constants of the Cr(VI)–H2O system.

Spectroscopic evaluation of the environmental impact on black crusted modern mortars in urban–industrial areas

AbstractA multianalytical characterisation of black crusted modern construction materials from buildings located in the Bilbao Metropolitan area (North Spain) was carried out. According to the mineral composition determined by Raman spectroscopy, calcite and hematite were the major compounds found while aragonite, limonite, rutile, quartz and some aluminosilicates such as obsidian or amazonite (KAlSi3O8) were also present in minor percentages. As deterioration products, gypsum and anhydrite were widely found not only in the surface but also in the inner part of strongly deteriorated samples. Coquimbite (Fe2(SO4)3·9H2O) was identified as well in the most protected facade where high amounts of Fe, having probably an anthropogenic origin, were measured by micro X-ray fluorescence (μ-XRF). Zn was found to be in high amounts while Cu, Pb, Ti, Mn, Sr and K were identified as minor elements. Considering the non-expected concentrations found for some anthropogenic elements, a sequential extraction was carried out in order to determine their chemical form by means of ion chromatography and inductively coupled plasma mass spectrometry. The orientation of the facades, which had a different influence from rain washing and industrial and traffic impact, was shown to affect the accumulation of different compounds in the black crust. Finally, the MEDUSA software was used to simulate the reactions among the original compounds, deposited pollutants and the atmospheric acid gases in order to explain the presence of the decaying species found. FigureMultianalytical Speciation protocol applied on the analysis of modern mortars

Development of a Modified Bromley's Methodology for the estimation of ionic media effects on solution equilibria: Part 4. The chemical model of Fe(III) with the halide ligands in aqueous solution at 25°C

Abstract The Modified Bromleys Methodology (MBM) has been used to construct the basic chemical model between Fe(III) and OH− and the halide ligands Cl−, Br− and F− in NaClO4 medium at 25°C, obtaining the thermodynamic constants and the corresponding interaction parameters for each equilibrium. This basic model has been extended to KNO3, HCl, and KCl media obtaining the corresponding interaction parameters. The applicability of the model is also discussed.

The thermodynamic model of inorganic arsenic species in aqueous solutions Potentiometric study of the hydrolitic equilibrium of arsenic acid.

Protonation constants of arsenic acid were determined at different ionic strengths in NaClO(4) (0.1, 0.5, 1.0, 3.0 mol dm(-3)), NaCl (0.5 and 1.0 mol dm(-3)) and KCl (0.5, 1.0 and 3.0 mol dm(-3)) ionic media by means of a potentiometric study. The distribution of arsenate species was defined depending on two important variables in natural environments: pH and composition. All the experimentation was performed at 25 degrees C. The differences found in the protonation constants for different medium compositions, were explained by the different behaviour of the interaction parameters of the species considered in the different media and ionic strengths. These parameters were reported for all hydrolitic As(V) species and were calculated using the Modified Bromleys Methodology (MBM). The corresponding thermodynamic stepwise formation constants were also determined (log degrees K(1)=11.58+/-0.01, log degrees K(2)=7.06+/-0.01, log degrees K(3)=2.25+/-0.01). All the results obtained showed not only the importance of the ionic strength but also of the composition of the ionic medium on the distribution of the acid-base species of As(V) as a function of pH in natural waters.

Optimization of two methods based on ultrasound energy as alternative to European standards for soluble salts extraction from building materials.

The Italian recommendation NORMAL 13/83, later replaced by the UNI 11087/2003 norm, were used as standard for soluble salts extraction from construction materials. These standards are based on long-time stirring (72 and 2h, respectively) of the sample in deionized water. In this work two ultrasound based methods were optimized in order to reduce the extraction time while efficiency is improved. The instrumental variables involved in the extraction assisted by ultrasound bath and focused ultrasounds were optimized by experimental design. As long as it was possible, the same non-instrumental parameters values as those of standard methods were used in order to compare the results obtained on a mortar sample showing a black crust by the standards and the optimized methods. The optimal extraction time for the ultrasounds bath was found to be of two hours. Although the extraction time was equal to the standard UNI 11087/2003, the obtained extraction recovery was improved up to 119%. The focused ultrasound system achieved also better recoveries (up to 106%) depending on the analyte in 1h treatment time. The repeatabilities of the proposed ultrasound based methods were comparables to those of the standards. Therefore, the selection of one or the other of the ultrasound based methods will depend on topics such as laboratory facilities or number of samples, and not in aspects related with their quality parameters.

THE RECOVERY OF COBALT AND NICKEL FROM ACIDIC SULPHATE SOLUTIONS IN THE PRESENCE OF ALUMINUM.

ABSTRACT The sulphuric acid leaching of spent alumina-based catalysts from dehydrodesulphuration processes, previously treated by alkaline solutions to remove vanadium and/or molybdenum, yields a solution rich in Ni(H), Co(II) and Al7lpar;Iil7rpar;. In order to recover the two heavy metals the aluminum impurity must be eliminated. Several separation routes, including precipitation and liquid-liquid extraction, were first tested by computer simulation. Three of them were then checked at a laboratory stage. The separation of the three metals can be accomplished by selective extraction, as a function of pH, using CYANEX 272 7lpar;Cyanamid Co.)dissolved in hexane. Aluminum is first quantitatively removed in one extraction step at pH = 4.7 with a phase ratio Vaq/Vorg=5 followed by one scrubbing step at pH = 3.1 with Vorg = 1Cobalt is then quantitatively removed in two extraction steps, at pH = 6.3 with Vaq/Vorg=5 followed by one scrubbing step at pH =5.0 with Vaq/Vorg=1 The purified nickel in the final aqueous...