Juan Manuel Madariaga

Brazilian coal mining residues and sulphide oxidation by Fenton's reaction: an accelerated weathering procedure to evaluate possible environmental impact.

Fentons reaction is proposed as an accelerated weathering test for sulphides associated with Brazilian Coal Mining Residues (CMR), that are exposed to oxygen and water during the mining of coal. TEM and SEM/EDX were used to evaluate the nature, occurrence and distribution of minerals in remaining coals and other lithological units, before and after applying the test. Oxidation of CMRs was examined by analyzing soluble sulphur (sulphate) and dissolved metals by ICP-MS or ICP OES. As dissolved sulphate increases, dissolved Zn, Cd, Cu and Co concentrations increase, leading to undetectable amounts in the remaining solid phases; dissolved Ni and Mn also increase with the mobilized sulphur, but the remainder in the solids is the most important fraction; Fe and Pb are not mobilized due to precipitation as jarosite or hematite in the case of Fe or as sulphate in the case of Pb. Agreement between the observed results and the predictions by geochemical modelling is discussed.

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.

Comparison of accelerated solvent extraction with microwave-assisted extraction and Soxhlet for the extraction of chlorinated biphenyls in soil samples

Abstract The extraction and determination of chlorinated biphenyls (CBs) in soils and solid wastes is an ongoing subject of study. This is an overview article that compares the microwave-assisted extraction (MAE) and accelerated solvent extraction (ASE) techniques. The extraction of CBs by ASE has been optimised taking into account the variation of pressure, temperature and extraction time by means of experimental design and the Simplex approach. The recoveries obtained under the optimum conditions are compared and discussed with those obtained from MAE and Soxhlet extractions.

Study of environmental pollution and mineralogical characterization of sediment rivers from Brazilian coal mining acid drainage

Acid drainage from coal mines and metal mining is a major source of underground and surface water contamination in the world. The coal mining acid drainage (CMAD) from mine contains large amount of solids in suspension and a high content of sulphate and dissolved metals (Al, Mn, Zn, Cu, Pb, Fe, etc.) that finally are deposited in the rivers. Since this problem can persist for centuries after mine abandonment, it is necessary to apply multidisciplinary methods to determine the potential risk in a determinate area. These multidisciplinary methods must include molecular and elemental analysis and finally all information must be studied statistically. This methodology was used in the case of coal mining acid drainage from the Tubarao River (Santa Catarina, Brazil). During molecular analysis, Raman Spectroscopy, electron bean, and X-ray diffraction (XRD) have been proven very useful for the study of minerals present in sediment rivers near this CMAD. The obtained spectra allow the precise identification of the minerals as jarosite, quartz, clays, etc. The elemental analysis (Al, As, Fe, K, Na, Ba, Mg, Mn, Ti, V, Zn, Ag, Co, Li, Mo, Ni, Se, Sn, W, B, Cr, Cu, Pb and Sr) was realised by inductively coupled plasma mass spectrometry (ICP-MS). Statistical analysis (Principal Component Analysis) of these dates of concentration reveals the existence of different groups of samples with specific pollution profiles in different areas of the Tubarao River.

Green copper pigments biodegradation in cultural heritage: from malachite to moolooite, thermodynamic modeling, X-ray fluorescence, and Raman evidence.

Moolooite (copper oxalate), a very rare compound, was found as a degradation product from the decay of malachite in several specimens of Cultural Heritage studied. Computer simulations, based on heterogeneous chemical equilibria, support the transformation of malachite to moolooite through the intermediate copper basic sulfates or copper basic chlorides, depending on the presence of available free sulfate or chloride anions in the chemical system. Raman and X-ray fluorescence spectral evidence found during the analysis of the three case studies investigated supported the model predictions. According to the study, the presence of lichens and other microorganisms might be responsible for the decay phenomena. This work tries to highlight the importance of biological attack on specimens belonging to Cultural Heritage and to demonstrate the consequences of oxalic acid, excreted by some of these microorganisms, on the conservation and preservation of artwork.

Use of Reflectance Infrared Spectroscopy for Monitoring the Metal Content of the Estuarine Sediments of the Nerbioi-Ibaizabal River (Metropolitan Bilbao, Bay of Biscay, Basque Country)

Multivariate partial least-squares (PLS) calibration models have been developed for the spatial and seasonal simultaneous monitoring of 14 trace elements (Al, As, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Sn, V, and Zn) in sediments from 117 samples taken in the estuary of the Nerbioi-Ibaizabal River. Models were based on the chemometric treatment of diffuse reflectance near-infrared (NIR) and attenuated total reflectance (ATR) mid infrared (MIR) spectra, obtained from samples previously lyophilized and sieved with a particle size lower than 63 microm. Vibrational spectra were scanned in both, NIR and MIR regions. Developed PLS models, based on the interaction between trace elements and organic mater provide good screening tools for the prediction of trace elements concentration in sediments.

Risk assessment of trace elements in sediments: The case of the estuary of the Nerbioi–Ibaizabal River (Basque Country)

Long term (January 2005-January 2008) monitoring of sediments was used to investigate metal pollution in the estuary of the Nerbioi-Ibaizabal River (Bilbao, Basque Country). Sediments were collected from eight representative locations of the estuary approximately every three months. The concentration of fourteen elements was measured in sediment extracts. Different graphical representations of the data set, simple statistical methods and sediment quality guidelines were combined to investigate trends in space and time, identify pollution sources, and assess sediment quality from a toxicological point of view. In general terms, the main trend reveals a significant fall in metal concentration over the period investigated. There are still certain points of the estuary with relatively high concentration of toxic metals, but the toxicological approach suggests that the risk for living organisms is not important.

Analytical diagnosis methodology to evaluate nitrate impact on historical building materials.

Nitrate salts have become of greater importance in the decay of materials from historical buildings due to changes in the environment. This work presents an analytical diagnosis methodology to evaluate the impact of nitrate salts in mortars and bricks, combining noninvasive and microdestructive analytical techniques together with chemometric and thermodynamic data analyses. The impact of nitrate salts cannot be well ascertained if other soluble salts are not taken into account. Therefore, the principal results from this work relate to nitrate salts but some results for other kinds of salts are included. Data from Raman microprobe spectroscopy and micro X-ray fluorescence (μ-XRF) are used to characterise the original composition and a first approximation of the nature of the decay compounds, mainly nitrates. The soluble salts are extracted and the anions and cations are quantified by means of ion chromatography with conductimetric detection for anions/cations and inductively coupled plasma mass spectrometry (ICP/MS) for cations. The values obtained allow two different data treatments to be applied. First, chemometric analysis is carried out to search for correlations among anions and cations. Second, thermodynamic modelling with the RUNSALT program is performed to search for environmental conditions of soluble salt formation. All the results are finally used to diagnose the impact of nitrates.

Comparison of microwave-assisted extraction and Soxhlet extraction for phenols in soil samples using experimental designs

A study and comparison of microwave-assisted extraction (MAE) and Soxhlet extraction for five phenols (phenol, 2-chlorophenol, 2-methylphenol, 2-nitrophenol and 2,4-dichlorophenol) in soils was carried out in order to establish a comparative analysis between the two techniques under their optimum conditions. The optimisation of both the MAE and Soxhlet extraction methods was achieved using experimental designs. The parameters studied were pressure inside the extraction vessel, extraction time, percentage of microwave power, solvent volume and percentage (v/v) of acetone in an acetone–hexane mixture for MAE and extraction time and percentage (v/v) of acetone in an acetone–hexane mixture for Soxhlet extraction. The simplex method was also used for obtaining the optimum conditions in some cases. The extracts were analysed by GC–MS or GC–FID.

Noninvasive and nondestructive NMR, Raman and XRF analysis of a Blaeu coloured map from the seventeenth century

A complete multianalytical study of a hand-coloured map from the seventeenth century is presented. The pigments atacamite, massicot, minium, gypsum, carbon black and vermilion were determined by means of XRF and Raman spectroscopy. The state of conservation of the cellulosic support was monitored by means of unilateral NMR. The analysis was nondestructive and noninvasive, and thus several spectra were collected from the same areas, yielding more reliable results without damaging the artwork. The role of copper pigments in the oxidation processes observed in the cellulosic support is discussed, as well as the possible provenance of atacamite as a raw material instead of as a degradation product of malachite.