mica and illite

The adsorption of thallium (Tl) onto phyllosilicate minerals plays a critical role in the retention of Tl in soils and sediments and the potential transfer of Tl into plants and groundwater. Especially micaceous minerals are thought to strongly bind monovalent Tl(I), in analogy to their strong binding of Cs. To advance the understanding of Tl(I) adsorption onto phyllosilicate minerals, we studied the adsorption of Tl(I) onto Na- and K-saturated illite and Na-saturated smectite, two muscovites, two vermiculites and a naturally Tl-enriched soil clay mineral fraction. Macroscopic adsorption isotherms were combined with the characterization of the adsorbed Tl by X-ray absorption spectroscopy (XAS). In combination, the results suggest that the adsorption of Tl(I) onto phyllosilicate minerals can be interpreted in terms of three major uptake paths: (i) highest-affinity inner-sphere adsorption of dehydrated Tl

Topics: Adsorption; Aluminum Silicates; Cesium; Clay; Minerals; Silicates; Siloxanes; Soil; Thallium

In response to addressing potassium (K) deficiency in soil and decreasing agricultural production costs, the potential of K-bearing phyllosilicate minerals that can be directly used as an alternative K source has been investigated using sodium tetraphenylboron (NaTPB) extraction and an intensive cropping experiment. The results showed that the critical value of K-release rate and leaf K concentration was 3.30 g kg(-1) h(-1) and 30.64 g (kg dry matter)(-1), respectively under the experimental conditions. According to this critical value, the maximum amount of released K that could be utilized by a plant with no K deficiency symptoms was from biotite (27.80 g kg(-1)) and vermiculite (5.58 g kg(-1)), followed by illite, smectite and muscovite with 2.76, 0.88 and 0.49 g kg(-1), respectively. Ryegrass grown on phlogopite showed K deficiency symptoms during the overall growth period. It is concluded that biotite and vermiculite can be directly applied as a promising and sustainable alternative to the use of classical K fertilizers, illite can be utilized in combination with soluble K fertilizers, whereas muscovite, phlogopite and smectite may not be suitable for plant growth. Further field experiments are needed to assess the use of these phyllosilicate minerals as sources of K fertilizer.

Topics: Agriculture; Aluminum Silicates; Ferrous Compounds; Fertilizers; Lolium; Minerals; Potassium; Silicates; Tetraphenylborate

Physicochemical simulation (pH, electrolytes and temperature) of three physiological media was carried out in order to follow the release of trace elements contained in seven edible clays (mainly kaolinite, illite, muscovite and quartz) collected from the West African countries of Côte d'Ivoire, Guinée and Sénégal. These clays are ingested by pregnant women for diverse reasons that are related to their condition. Simulated oral (6.5

Topics: Africa, Western; Aluminum Silicates; Clay; Diet; Electrolytes; Female; Gastrointestinal Tract; Humans; Hydrogen-Ion Concentration; Kaolin; Minerals; Pica; Pregnancy; Quartz; Soil; Temperature; Trace Elements

Adsorption of three surfactants of different nature, Triton X-100 (TX100) (non-ionic), sodium dodecylsulphate (SDS) (anionic) and octadecyltrimethylammonium bromide (ODTMA) (cationic) by four layered (montmorillonite, illite, muscovite and kaolinite) and two non-layered (sepiolite and palygorskite) clay minerals was studied. The objective was to improve the understanding of surfactant behaviour in soils for the possible use of these compounds in remediation technologies of contaminated soils by toxic organic compounds. Adsorption isotherms were obtained using surfactant concentrations higher and lower than the critical micelle concentration (cmc). These isotherms showed different adsorption stages of the surfactants by the clay minerals, and were classified in different subgroups of the L-, S- or H-types. An increase in the adsorption of SDS and ODTMA by all clay minerals is observed up to the cmc of the surfactant in the equilibrium solution is reached. However, there was further TX100 adsorption when the equilibrium concentration was well above the cmc. Adsorption constants from Langmuir and Freundlich equations (TX100 and ODTMA) or Freundlich equation (SDS) were used to compare adsorption of different surfactants by clay minerals studied. These constants indicated the surfactant adsorption by clay minerals followed this order ODTMA>TX100>>SDS. The adsorption of TX100 and ODTMA was higher by montmorillonite and illite, and the adsorption of SDS was found to be higher by kaolinite and sepiolite. Results obtained show the influence of clay mineral structure and surfactant nature on the adsorption capacity of surfactants by clays, and they indicate the interest to consider the soil mineralogical composition when one surfactant have to be selected in order to establish more efficient strategies for the remediation of soils and water contaminated by toxic organic pollutants.

Topics: Adsorption; Alkanes; Aluminum Silicates; Bentonite; Clay; Kaolin; Magnesium Compounds; Magnesium Silicates; Minerals; Octoxynol; Quaternary Ammonium Compounds; Silicon Compounds; Sodium Dodecyl Sulfate; Soil Pollutants; Spectrum Analysis; Surface-Active Agents