Vermiculite

About: Vermiculite is a research topic. Over the lifetime, 2320 publications have been published within this topic receiving 37142 citations.

Method for obtaining laminar phyllosilicate particles having controlled size and products obtained using said method

Abstract: The present invention relates to a method for producing laminar phyllosilicate particles (for example: kaolinite, montmorillonite, pyrophyllite, bentonite, smectite, hectorite, sepiolite, saponite, laponite, halloysite, vermiculite, mica, chlorite, illite and mixtures) with or without surface modification, the largest dimension of which (in the so-called D100) has a size of 0.05 to 15 microns; as well as to the phyllosilicate particles that can be produced according to said method and to the use of such particles as additives in plastic or ceramic matrices for producing materials that can be used in multiple sectors.

Synthesis of a Mineral−Organic Hybrid by Treatment of Phlogopite with Phenylphosphonic Acid

Abstract: The reaction between natural phlogopite, having the idealized formula KMg3(AlSi3O10)(OH)2, and phenylphosphonic acid under soft conditions (24 h, 80 °C, reflux) originated a new layered material of the following idealized composition: [Mg(H2O)2]0.5(AlSi3O6)(O3PC6H5)2·2H2O. The reaction mechanism involves the rupture of the trioctahedral layers of phlogopite and the formation of a new basal spacing of a hydrophobic type that is occupied by phenylphosphonic groups in a pseudomonomolecular arrangement. Simultaneously, the mobile K+ ions become partially substituted by [Mg(H2O)2]2+ groups, a hydrophilic space of the vermiculite type thus being obtained.

Chemical and mineralogical transformations in three tropical soils due to permeation with acid mine drainage

Abstract: The chemical and mineralogical compositions of three tropical soils, before and after permeation with 19–24 pore volumes of acid mine drainage (AMD), were assessed using X-ray diffraction and chemical analyses, in order to consider their potential value as clay liners. After permeation the CEC of one soil (Soil K) was reduced, partly due to structural modification of smectite by AMD. Conversely, the other soils (Soils A and H) showed increased CEC values due to structural changes in mixed layer vermiculite minerals, resulting in the formation of vermiculite as a separate phase in the soils. The specific surfaces of the soils were reduced. AMD caused changes in the variable charge properties of the soils due to the composite effects of soil pH and organic matter reduction and the changes in composition of exchangeable ions. Dolomite, gibbsite, diaspore, magnesioferrite and hydroxy apatite were dissolved from the soils. Chlorite was mildly altered but kaolinite was structurally resistant to AMD attack. Jarosites were, however, formed in all the soils. It was concluded that the tropical soils studied could be effective sinks for zinc and nickel from AMD, but that Soils A and H would be the most desirable clay liners for acid mine waste containment due to their low hydraulic conductivity, high sorptive capacity and compatibility with AMD.

Thermodynamic study of Na-K-Ca exchange reactions in vermiculite

Abstract: The exchange of Na, K, and Ca ions in vermiculite has been studied between 50 and 1500C at a total normality of 0.1. The free energy changes were negative in the Na ~ K, Ca ~ K, and Na ~ Ca exchange reactions, and the cation preference in the vermiculite was Na < Ca < K in the temperature range examined. The enthalpy changes, calculated by application of the van't Hoffequation to the relation between equilibrium constant and temperature, were positive. The cation preference in the vermiculite seems to have been largely controlled by the increase in entropy which was due to the positive values of the entropy change term in the solid for the Na-K and Ca-K exchanges and the positive values of the entropy change in the solution for the Na-Ca exchange. From a thermodynamic analysis of the cation- mixing properties in vermiculite, the observed free energy change in the Na-K exchange was determined solely by the differences of the intrinsic electrostatic binding energy of the cations on the clay surface. That in the Na-Ca exchange was interpreted by taking into account an extra interaction energy of Ca-Ca pairs in addition to the intrinsic energy change. Furthermore, an additional interaction energy between K ions and the clay surface appears to have been added to the free energy change in the Ca-K exchange. In the Na ~ K and Ca ~ K exchange reactions a structural modification occurred in the K-equivalent fraction (RI0 range 0.05--0.6, and a regularly interstratified phase of 15-A and 10-A members was formed at 0.05 < Y(K < 0.4.