Absorption of pyrimidines, purines, and nucleosides by Co, Ni, Cu and Fe /III-montmorillonite /clay-organic studies XIII/

Absorption of pyrimidines, purines, and nucleosides by copper, nickel, cobalt, and iron montmorillonit

Absorption of pyrimidines, purines and nucleosides by Li, Na, Mg, and Ca montmorillonite /clay organic studies 12/

Absorption of purines, pyrimidines, and nucleoside in aqueous solution by montmorillionite occurring as cation exchange reactio

Debye-Waller B values for some NaCl-type structures and interionic interaction

Debye-Waller B values of NaCl, KCl, MgO and AgCl are calculated from lattice dynamics based on a simple, rigid-ion type, interaction model. The parameters introduced in the model have intelligible significance. The present approach compares favourably with experimental evidence and previous physical calculations

Mineralogical, optical, geochemical, and particle size properties of four sediment samples for optical physics research

X-ray diffraction and spectroscopy were used to investigate the mineralogical and chemical properties of the Calvert, Ball Old Mine, Ball Martin, and Jordan Sediments. The particle size distribution and index of refraction of each sample were determined. The samples are composed primarily of quartz, kaolinite, and illite. The clay minerals are most abundant in the finer particle size fractions. The chemical properties of the four samples are similar. The Calvert sample is most notably different in that it contains a relatively high amount of iron. The dominant particle size fraction in each sample is silt, with lesser amounts of clay and sand. The indices of refraction of the sediments are the same with the exception of the Calvert sample which has a slightly higher value

Structural location and role of hydrogen ions in kaolinite and its products in aluminum removal

Issued as Quarterly reports no. [1-7], Annual report and Final report, Project no. G-41-625 (subproject is E-18-625/Moody/School of Ceramic Engineering

Adsorption of Cetylpyridinium Chloride & Cetyltrimethylammonium Bromide on Bentonite

680-68

Quinoline Sorption on Na-Montmorillonite: Contributions of the Protonated and Neutral Species

Dilute aqueous solutions of quinoline were contacted with Na-montmorillonite to elucidate the sorption process of the neutral and protonated species. Sorption occurs via a combination of ion exchange and molecular adsorption and yields S-type isotherms. Exchange between the quinolinium ion (QH+ and Na can be described by means of Vanselow selectivity coefficients and a thermodynamic exchange constant (Kex). Due to the apparent adsorption of the neutral species at high mole fractions (x) of the solid phase, the thermodynamic standard state was defined as 0.5 mole fraction. The selectivity at pH ~4.95 of the QH+ species over Na (at XQH+ 0.5) was determined to be Kv = 340. At pH ≥ 5.5 surface mole fractions of 0.5 could not he obtained without adsorption of the neutral species. This study suggests that at dilute solution concentrations quinoline is sorbed preferentially as the cation even at pHs \u3e\u3e pKa. A critical surface-solution concentration is apparently necessary for adsorption of the neutral species

Physico-chemical properties and industrial potential of some clay deposits in Calabar area, south eastern Nigeria

Clay samples collected from 10 locations in Calabar, Cross River State, Nigeria were evaluated to determine their suitability for industrial applications. The samples were pulverized, dried, sieved and quantitatively analyzed. Physical properties determined were viscosity (11-15 secs), density (1072-1769 kg m-3), plasticity index (33-50%), particle size and firing characteristics. The clays were classified as fat clays or elastic silt. Results showed that all the clay samples were uniformly graded with fine texture and have the ideal silica value averaging 47.73% but the alumina content of the samples are lower than theoretical values of pure montmorillonite (28.3%) and kaolinite (39.5%), with averaging 18.0%. X-ray analysis indicated that the dominant clay mineral found in all the samples is kaolin with occasional illite and the main non-clay mineral as quartz. Considerable amounts of Fe2O3 (2.79-6.95%) along withsome impurity oxides such as MgO (0.08-0.98%), CaO (0.12-0.95%), K2O (0.28-1.82%), Na2O (1.02- 1.87%) and TiO2 (0.96-1.20%) were found in all the clay minerals. These properties indicated that the clays are of low grade (non- refractory) due to the low alumina content. The low alumina content with the relatively high plasticity index and the pleasant color characteristics of the clays on firing, suggest that the clays have the potentials for use in the production of brick, ceramic and pottery products

Diagenesis of ferriferous phases in the Northampton ironstone in the Cowthick quarry near Corby (England)

Berthierine, siderite and pyrite are the major ferriferous phases in the Northampton ironstone (NIS). Mineralogical and chemical data suggest a formation of these phases in a diagenetic marine environment changing from post-oxic to sulphidic conditions. Berthierine was formed first when the Fe2+ activity in the diagenetic system increased. Later, this phase was partially replaced by siderite and/or pyrite. A second stage of the diagenetic development in the NIS with increasing CO2 partial pressure (PCO2 ) is documented by siderite. The isotopic composition (δ18O mean value: -1.7‰PDB; δ13C mean value: -8.6‰PDB) points to siderite precipitation from a marine porewater environment with a microbial CO2 source. The shift from post-oxic to sulphidic conditions is indicated by the occurrence of pyrite and can be considered as a final stage. The diagenetic processes in the marine environment and the formation of the ferriferous phases were stopped by the influx of brackish or fresh water when the Midland Shelf turned estuarin