ALBERT

Beschreibung: The interaction of montmorillonite with sotalol hydrochloride (4-(1-hydroxy-N-isopropylaminoethyl) methane sulfanilide) was studied by means of adsorption isotherms, XRD and IR spectroscopy. The amount of sotalol adsorbed depended on pH, the maximum amount adsorbed (0·56 mEq g−1) being considerably less than the exchange capacity of the mineral (0·80 mEq g−1). XRD and IR data revealed that the sotalol is adsorbed into the interlayer space, forming a monolayer complex with a d001 spacing of 17·7 Å, and that the mechanisms involved are cation exchange and ion-dipole interactions. Experiments on the in vitro desorption of the drug from the sotalol-montmorillonite complex indicated that desorption is affected by pH, by the salt concentration of the electrolyte, and by the elimination rate of the desorbed organic cations.

Beschreibung: Dry grinding of pyrophyllite (Hillsboro, USA) has been studied by X-ray diffraction (XRD), specific surface area measurements (BET) and scanning electron microscopy (SEM). At the beginning of the grinding process, some effects such as delamination, gliding and folding of the layers, and decrease in particle size were detected by SEM and XRD, resulting in a large increase in specific surface area, up to a maximum of ∼60 m2·g−1. Marked changes in the structure take place between 30 and 32 mins grinding. Longer grinding times increase the degree of disorder and SEM and specific surface area data suggest that aggregation occurs. XRD results indicate that some residual order persists in the degraded structure.

Beschreibung: Ferric precipitates in the water column at the San Telmo acidic mine pit lake in the Iberian Pyrite Belt, southwest Spain, have been studied by scanning electron microscopy, energy dispersive X-ray spectrometry, X-ray diffraction, X-ray fluorescence, inductively coupled plasma mass spectrometry and other complementary techniques. These Fe(III) precipitates were recovered from sediment traps which were left at different depths (25, 35, 40 and 100 m) in the lake for several months. Seasonal variations in the water chemistry were recorded to link the mineralogical findings to vertical and temporal changes in aqueous composition. The results indicate that schwertmannite is the first Fe(III) mineral to crystallize after the oxidation of Fe(II), in agreement with previous studies. Schwertmannite is kinetically favoured in comparison to other Fe(III) minerals, and it buffers the pH at 2.6–3.0. It is metastable, and alters to a (H3O+)- and (K+)-bearing jarosite (containing 58 mol.% H3O+ and 42 mol.% K+ on average) at lower pH (e.g. at pH 2.2–2.5 in the summer season), either in the water column (during settling) and/or in the benthic sediments, in a time period of weeks to months. The extent of hydronium substitution at the alkali site in the jarosite reflects the higher activity of free aqueous protons in solution (10−2.2 to 10−3.0) in comparison to the activities of K+ (10−4.5) and Na+ (10−3.2). Microscopic examination of mixed schwertmannite–jarosite precipitates found in the water column suggest that some textural and compositional features of metastable schwertmannite (e.g. the internal ‘pincushion’ arrangement and incorporation of trace amounts of Mg, Al, As and Pb) are conserved in the jarosite during the early stages of the mineralogical transformation, but many of these relics are lost in the later stages of crystal growth. Despite the hydronium-rich nature of the jarosite solid solution, this material is also an important sink for K+, which decreases in concentration with decreasing pH unlike most of the other major cations in the water column (notably Na+, Mg2+, Ca2+, Al3+, Fe3+, Cu2+, Zn2+). In addition to the release of Fe3+ to the aqueous solution, the conversion of schwertmannite to (H3O+, K+)-bearing jarosite consumes protons and thus may represent an additional pH control at San Telmo and other acidic mine pit lakes of the area.

Beschreibung: Ferric precipitates in the water column at the San Telmo acidic mine pit lake in the Iberian Pyrite Belt, southwest Spain, have been studied by scanning electron microscopy, energy dispersive X-ray spectrometry, X-ray diffraction, X-ray fluorescence, inductively coupled plasma mass spectrometry and other complementary techniques. These Fe(III) precipitates were recovered from sediment traps which were left at different depths (25, 35, 40 and 100 m) in the lake for several months. Seasonal variations in the water chemistry were recorded to link the mineralogical findings to vertical and temporal changes in aqueous composition. The results indicate that schwertmannite is the first Fe(III) mineral to crystallize after the oxidation of Fe(II), in agreement with previous studies. Schwertmannite is kinetically favoured in comparison to other Fe(III) minerals, and it buffers the pH at 2.6–3.0. It is metastable, and alters to a (H3O+)- and (K+)-bearing jarosite (containing 58 mol.% H3O+and 42 mol.% K+on average) at lower pH (e.g. at pH 2.2–2.5 in the summer season), either in the water column (during settling) and/or in the benthic sediments, in a time period of weeks to months. The extent of hydronium substitution at the alkali site in the jarosite reflects the higher activity of free aqueous protons in solution (10–2.2to 10–3.0) in comparison to the activities of K+(10–4.5) and Na+(10–3.2). Microscopic examination of mixed schwertmannite–jarosite precipitates found in the water column suggest that some textural and compositional features of metastable schwertmannite (e.g. the internal 'pincushion' arrangement and incorporation of trace amounts of Mg, Al, As and Pb) are conserved in the jarosite during the early stages of the mineralogical transformation, but many of these relics are lost in the later stages of crystal growth. Despite the hydronium-rich nature of the jarosite solid solution, this material is also an important sink for K+, which decreases in concentration with decreasing pH unlike most of the other major cations in the water column (notably Na+, Mg2+, Ca2+, Al3+, Fe3+, Cu2+, Zn2+). In addition to the release of Fe3+to the aqueous solution, the conversion of schwertmannite to (H3O+, K+)-bearing jarosite consumes protons and thus may represent an additional pH control at San Telmo and other acidic mine pit lakes of the area.

Beschreibung: This paper is based on microprobe analysis (Ta, Nb, Fe, Mn, Ti, W, Sn) and Fe3+ EPR spectra of cassiterite samples from 14 tin deposits from the Iberian Hercynian Massif. The interpretation of microprobe data, atomic ratios (Fe+Mn)/(Nb+Ta), and Fe3+ EPR spectra reveal that the coupled substitution: 3Sn4+ = (Fe,Mn)2+ + 2(Nb,Ta)5+ is dominant in cassiterites from pegmatites, and high-temperature quartz veins and in the dark zones of cassiterites.The mechanisms:2Sn4+ = Fe3+ + (Nb,Ta)5+ andSn4+ + O2− = Fe3+ + OH−are dominant in those from medium-low temperature quartz veins and in the light zones of cassiterites.

Beschreibung: This study is the first to investigate the mineral composition of the atmospheric particulate matter deposited at Rio Tinto, Spain, an historical mining district of world-class importance, with emphasis on metal-bearing particles and their environmental implications. The dustfall is composed of quartz, feldspars, phyllosilicates (mica, chlorite and/or kaolinite) and a variety of accessory heavy minerals, the most common being primary sulfides (pyrite, chalcopyrite with minor galena, sphalerite and bornite) and their oxidation products (notably goethite, hematite and jarosite). This mineral assemblage suggests a local source of wind-blown dust and it is consistent with the large deposition levels of sulfide-related elements (As, Bi, Cd, Cu, Pb, Sb and Zn) registered at the sampling site adjacent to the mine waste dumps. However, the generation of potentially harmful dust particles is not restricted to mine wastes. Anthropogenic metallic compounds arising from a nearby hazardous waste disposal centre can make a relevant additional contribution to the metal deposition, particularly for Fe, Ni, Cr and Mn. Atmospheric fallout is a major mechanism for metal input to soils and plants around or near the mining area.

Beschreibung: The Carrión lacustrine basin (≈10 km2), central Spain, is filled with Neogene-Quaternary sediments (20–25 m thick) rich in palygorskite. Two clay units of ∼15 m thick are of particular interest in the basin. The lower one contains over 75% phyllosilicates (palygorskite up to 90%, smectites and illite) in marginal areas (facies A), and it is laterally bound by a distal facies (B) also rich in clay minerals (smectites and illite, and some palygorskite) and gypsum, and includes dolomitic marl intercalations. The composition at the top is primarily marly, with some gypsum (C). The upper clay unit, mainly clay-size material, (D) is rich in smectites, palygorskite and sepiolite, and contains carbonate intercalations near the top. A statistical treatment of the mineralogical and chemical composition data from 120 samples, using principal factor analysis, suggests that: (a) illite and smectite are detrital in origin; (b) palygorskite was formed by transformation of illite and smectite involving reaction with Mg; and (c) sepiolite was a neoformation product favoured by evaporation of silica- and Mg-bearing waters.

Beschreibung: A mineralogical study and multivariant geochemical analysis have been carried out to determine the sedimentation processes and the influence of surrounding rocks on sediments. Analyses were made on the clay fraction of sediments and on bulk samples of rocks from nearby reliefs in the Sorbas Basin (SE Spain). Source rocks were identified by statistical analysis of trace elements and by comparison of the crystallographic parameters of phyllosilicates in sediments and supposed sources. Palaeoenvironmental conditions are recorded by specific elements in the clay minerals. The study of the B and Mg content and of the different types of smectites and palygorskite found in distinct areas has permitted a description of these conditions for this Basin. In this way, different types of deposition environment, showing varying degrees of confinement and influence from marine or continental water, have been distinguished.

Beschreibung: Structural formulae and other crystallochemical parameters were used to study different species of dioctahedral micas in clay and coarse gravel fractions of horizons from a red soil (Ultic Haploxeralf) in southern Spain. Mineralogical analyses using X-ray powder diffraction, and measurements of the b0 parameter revealed dioctahedral micas, illite and paragonite. Structural formulae established from electron microprobe analysis and energy dispersive X-ray analysis showed the illites to be K mica related in elemental composition and structure to muscovite and phengite. The paragonites were found to be closer to ideal mica. Structural formulae for Na-K dioctahedral micas were obtained with crystallochemical characteristics intermediate between those of Na micas and K micas. The possibilty of these micas representing individual mineral phases or intergrowths of Na and K micas is discussed. In the soil profile, micas from the Bt horizon showed the largest crystallochemical changes induced by pedogenesis.

Beschreibung: The adsorption by different silicate minerals of some heavy metals, present in industrial waste water, has been studied. These adsorbents (mainly clay minerals) are readily available, inexpensive materials and offer a cost-effective alternative to conventional treatment of wastes from the metal finishing industry. The results show that some mineral species are suitable for the purification of such residual waters down to the limits prescribed by current legislation concerning industrial wastes. The Langmuir model was found to describe such adsorption processes best. Sepiolite (Orera, Spain) has an adsorption capacity of 8.26 mg g-1 for Cd2+, the capacities depending on the metal adsorbed in the order: Cd2+ 〉 Cu2+ 〉 Zn2+ 〉 Ni2+. This mineral shows the highest sorption capacity relative to the other minerals studied. Factors in the reaction medium such as pH and ionic strength influenced the adsorption process.