²⁹Si and ²⁷Al MAS NMR study of the zeolitization of kaolin by alkali leaching

Abstract

The alkali leaching of two aluminosilicates, kaolinite and metakaolinite, with aqueous NaOH has been studied. Both silicates gave hydroxysodalite (HS) with or without the evanescent zeolite NaA. X-ray diffraction and high-resolution 29Si and 27Al MAS-NMR spectroscopy provide information about the reaction sequence of the clay. The conversion starts with the formation of an amorphous gel precursor at a rate which depends on the alkali concentration but not on the choice of kaolinite or metakaolinite as starting material. The rate of zeolitization of this gel is much faster when it is obtained from kaolinite, probably because it is more homogeneous.

Synthesis of zeolites A and P from 1:1 and HS from 2:1 clays

“…We note the absence of characteristic line of the HS phase as observed by Sanz et al [29]. According to the NMR study of zeolite [13], the 29 Si signal of the sample obtained from natural kaolinite KTM (Fig. 3) presents a single line resonance at -91.5 ppm.…”

“…The chemical shifts located at -107.35, -106.92, -97.59,-91.87 and -87.25 ppm (Fig. 12) correspond to the HS zeolite [11,13].…”

“…Zeolites with higher Si:Al ratio can be synthesized using kaolinite or metakaolinite with NaOH and colloidal silica as reported in several works and patents [8][9][10][11][12][13][14][15][16][17]. 1 To whom any correspondence should be addressed.…”

Comparative Studies of Chemically Synthesized Polymers Aniline and o-Toluidine Nanocomposite Using Algerian Montmorillonite

“…3. The spectra of Maghnite exhibits mainly the typical resonance at 2.9 ppm of octahedral aluminium (6Al) in a phyllosilicate but also a small but significant contributions at 60 and 68 ppm assigned to aluminium tetrahedrally co-ordinated to oxygen (4Al) (Samajovà et al, 1992;Benharrats et al, 2003). www.intechopen.com…”

A new strategy for synthesis of microspheres amphiphilic block copolymer based on Epichlorohydrin and N-viny-2-pyrrolidone induced by an ecologic clay catalyst called Maghnite-H+ (Algerian MMT)

“…These clay minerals swell in water into a manner similar to smectites, and have interlayer charge densities higher than that of smectites [14]. Unlike natural clay minerals, they have high crystallinity, controllable composition and fewer impurities [15]. For this reasons, the use of such modified Maghnite as host materials is expected to be more advantageous than the use of raw natural clay minerals(Maghnite-Na + ) [16].Biodegradable polymers should non-toxic, capable of maintaining good mechanical integrity until degraded, and capable of controlled rates of degradation [17].…”