Search results for "alkali"

Halloysite Nanotubes Loaded with Calcium Hydroxide: Alkaline Fillers for the Deacidification of Waterlogged Archeological Woods

2018

A novel green protocol for the deacidifying consolidation of waterlogged archaeological woods through aqueous dispersions of polyethylene glycol (PEG) 1500 and halloysite nanotubes containing calcium hydroxide has been designed. First, we prepared functionalized halloysite nanotubes filled with Ca(OH)2 in their lumen. The controlled and sustained release of Ca(OH)2 from the halloysite lumen extended its neutralization action over time, allowing the development of a long-term deacidification of the wood samples. A preliminary thermomechanical characterization of clay/polymer nanocomposites allows us to determine the experimental conditions to maximize the consolidation efficiency of the wood…

2012

Abstract. The oxidation of SO2 to sulfate on sea salt aerosols in the marine environment is highly important because of its effect on the size distribution of sulfate and the potential for new particle nucleation from H2SO4 (g). However, models of the sulfur cycle are not currently able to account for the complex relationship between particle size, alkalinity, oxidation pathway and rate – which is critical as SO2 oxidation by O3 and Cl catalysis are limited by aerosol alkalinity, whereas oxidation by hypohalous acids and transition metal ions can continue at low pH once alkalinity is titrated. We have measured 34S/32S fractionation factors for SO2 oxidation in sea salt, pure water and NaOCl…

Isotope-shift measurements of stable and short-lived lithium isotopes for nuclear-charge-radii determination

2010

Changes in the mean-square nuclear charge radii along the lithium isotopic chain were determined using a combination of precise isotope shift measurements and theoretical atomic structure calculations. Nuclear charge radii of light elements are of high interest due to the appearance of the nuclear halo phenomenon in this region of the nuclear chart. During the past years we have developed a new laser spectroscopic approach to determine the charge radii of lithium isotopes which combines high sensitivity, speed, and accuracy to measure the extremely small field shift of an 8 ms lifetime isotope with production rates on the order of only 10,000 atoms/s. The method was applied to all bound iso…

MZ-35, a new layered pentasil borosilicate synthesized in the presence of large alkali cations

2013

Abstract A new layered borosilicate has been synthesized in the presence of cesium and sodium cations and its structure has been solved by a combination of automated diffraction tomography (ADT) and X-ray powder diffraction (XRPD). MZ-35 has a composition NaCs 2 [BSi 7 O 16 (OH) 2 ](OH) 2 ·4H 2 O and features space group P-4m2. The unusually small unit cell ( a 7.3081 A, c 10.7520 A) is shared by two random-stacked configurations of the structure: a network of connected pentasil units related to the layer of RUB-18 and a bidimensional checkerboard of intersecting ladders of 4-membered rings. The two configurations are related by the simple face-sharing inversion of a hydroxyl-bearing tetrah…

The characterization of molecular alkaly metal azides

2006

Matrix isolation infrared (IR) studies have been carried out on the vaporisation of the alkali-metal azides MN(3) (M = Na, K, Rb and Cs). The results show that under high vacuum conditions, molecular KN(3), RbN(3) and CsN(3) are present as stable high-temperature vapour species, together with variable amounts of nitrogen gas and the corresponding metal atoms. The characterisation of these molecular azides is supported by ab initio molecular orbital calculations and density functional theory (DFT) calculations, and for CsN(3) in particular, by the detection of the isotopomers CS((14)N(15)N(14)N) and Cs((15)N(14)N(14)N). The IR spectra are assigned to a "side-on" (C(2v)) structure by comparis…

Geochemical constraints on basalt petrogenesis in the Strait of Sicily Rift Zone (Italy): Insights into the importance of short lengthscale mantle he…

2020

Igneous activity from the late Miocene to historic time (most recently 1891 CE) in the Strait of Sicily has created two volcanic islands (Pantelleria and Linosa) and several seamounts. These volcanoes are dominated by transitional (ol + hy-normative) to alkaline (ne-normative) basaltic lavas and scoriae; volcanic felsic rocks (peralkaline trachyte-rhyolite) crop out only on Pantelleria. Although most likely erupted through continental crust, basalts demonstrate no evidence of crustal contamination and are geochemically similar to oceanic island basalts (OIB). Despite their isotopic similarities, there are considerable compositional differences with respect to major and trace element geochem…

Trace element partitioning in lamproitic magmas—the Gaussberg olivine leucitite

2004

Abstract Partition coefficients for compatible and incompatible trace elements for use in modelling the origin and evolution of lamproitic and other potassic rocks are reported. These are based on values obtained by in situ determination using laser ablation microprobe-inductively coupled plasma-mass spectrometry (LAM-ICP-MS) on mineral/glass pairs in examples of the Gaussberg olivine leucitite, a classic leucite lamproite. Leucite/melt partition coefficients for 32 elements show values above 1 only for Cs and Rb, whereas values for Ni, Ga and Co are 0.4–0.1. DLc/Lq for most other elements are in the range 0.07–0.0005, and delineate a gently sloping pattern to lower values for elements gene…

Mobility and fluxes of major, minor and trace metals during basalt weathering and groundwater transport at Mt. Etna volcano (Sicily)

2000

Abstract The concentrations and fluxes of major, minor and trace metals were determined in 53 samples of groundwaters from around Mt Etna, in order to evaluate the conditions and extent of alkali basalt weathering by waters enriched in magma-derived CO 2 and the contribution of aqueous transport to the overall metal discharge of the volcano. We show that gaseous input of magmatic volatile metals into the Etnean aquifer is small or negligible, being limited by cooling of the rising fluids. Basalt leaching by weakly acidic, CO 2 -charged water is the overwhelming source of metals and appears to be more extensive in two sectors of the S-SW (Paterno) and E (Zafferana) volcano flanks, where out …

Geochemical mapping of magmatic gas–water–rock interactions in the aquifer of Mount Etna volcano

2001

Abstract Systematic analysis of major and minor elements in groundwaters from springs and wells on the slopes of Mt. Etna in 1995–1998 provides a detailed geochemical mapping of the aquifer of the volcano and of the interactions between magmatic gas, water bodies and their host rocks. Strong spatial correlations between the largest anomalies in pCO2 (pH and alkalinity) K, Rb, Mg, Ca and Sr suggest a dominating control by magmatic gas (CO2) and consequent basalt leaching by acidified waters of the shallow (meteoric) Etnean aquifer. Most groundwaters displaying this magmatic-type interaction discharge within active faulted zones on the S–SW and E lower flanks of the volcanic pile, but also in…

Amygdaloidal basalts: Isotopic and petrographic evidence for non-diagenetic crustal source of carbonate inclusions

1980

Even though carbonate amygdules in volcanics are generally assumed to be diagenetic in origin, the authors are of the opinion that almost all carbonate inclusions in the investigated amygdaloidal volcanic rocks from Sicily (Italy), Pindos (Greece) and Bohemia (Czechoslovakia), have a different origin. On the basis of a mineralogical, petrological and geochemical study these “amygdules” are interpreted as being remains ofmagmatic incorporation of carbonate. Therefore, the identification of carbonate globules in volcanics purely on field observations, is inadequate to distinguish true amygdules from carbonate assimilation remnants. A nomenclature of the various types of inclusions is proposed…