ABSTRACT. High charged swelling micas, with layer charge comprised between 2 and 4, has been found to readily swell with water and that complete cation exchange (CEC) can be achieved. Due to their high CEC, applications like radioactive cation fixation or removal of heavy metal cations from waste water were proposed. Their applicability can be controlled by the location of the interlayer cation in a confined space with a high electric field. In synthetic brittle micas, the interlayer cation has a low water coordination number; therefore their coordination sphere would be completed by the basal oxygen of the tetrahedral layer as innersphere complexes (ISC). However, no direct evidence of these complexes formation in brittle micas has been reported yet. In this contribution, we mainly focus on the understanding the mechanisms that provoke the formation of ISC in high charge swelling micas, Mica-n. A whole series of cations (X) were used to explore the influence of the charge and size of the interlayer cation. Three brittle swelling micas, Mica-n (n=4, 3 and 2), were selected in order to analyze the influence of the layer charge in the formation of ISC. The contribution of the ISC has been analyzed thorough the evolution of the 060 reflection and the changes in the short-range order of the tetrahedral cations will be followed 29 Si and 27 Al MAS-NMR. The results showed that ISC was favored in X-Mica-4 and that provoked a high distortion angle between the Si-Al tetrahedra. When the content of aluminum decreases, the electrostatic forces between the layers are relaxed, and the hydrated cations did not interact so strongly with the tetrahedral sheet, having the opportunity to complete their hydration sphere.
The major components of the wastewater from the petroleum refineries are benzene, toluene and phenol and one of the techniques applied to the treatment of effluents is sorption using organo-functionalized clay. The materials exploited in the present study are a family of surface-functionalized synthetic micas and their sorption capacities for non-ionic organic pollutants are analyzed. The organo-functionalization of their surface provides them the capacity to sorb effectively non-ionic pollutants in the interface. Their adsorption performance is a function of the alkylamonium properties such as the chain * Corresponding author E-mail: alba@icmse.csic.es 2 length, the mass fraction and the organization of the organic cation in the interlayer space of the micas.
The structure of high-charged micas, Na-n-micas (n = 2 and 4), a family of synthetic silicates with a wide range of applications, was investigated through the use of (17)O solid-state NMR at natural abundance in order to preserve quantitative spectral information. The use of a very high-field and highly sensitive probehead, together with (17)O NMR literature data allowed for the detection of an isolated signal at 26 ppm, assigned partially to AlOAl, as evidence of the violation of Lowenstein's rule for Na-4-mica.
Stability of colloidal clay minerals dispersion of fundamental in many industrial processes. Therefore, surface charge of the synthetic swelling high-charged mica family, Na-Mica-n (n=2 or 4, n is the total layer charge) were investigated to study its colloidal dispersion stability as a function of the framework and interlayer space composition. Na-Mica-n (n=2 or 4) micas were synthesized and functionalized with ethylammonium, mercaptoethylammonium or octadecylammonium. Their zeta-potential evolutions as a function of solution pH were correlated with their structural, compositional and morphological characteristics. The results have shown that the total charge of swelling high charged micas, Mica-n, didn´t affect significantly their colloidal dispersion stability, the interlayer composition and interlayer cation arrangement were the main factors of colloidal behaviour. The synthesis and functionalization of those synthetic micas can be tuned for their optimal use.
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