The incorporation of aluminum into silicate ions in alkaline aqueous solutions, studied by aluminum-27 n.m.r.

Synthesis of stoichiometrically controlled reactive aluminosilicate and calcium-aluminosilicate powders

“…This was done manually (using the diffractogram of an empty sample holder) in order to preserve any diffraction intensity from the amorphous content of the powders, however this introduces a small broad hump at lower angles due to differences in diffraction plane height between full and empty sample holders. [46,47], zeolites [48] and mullite [49]. Al(V) and Al(IV) are commonly observed in mullite-like structures in aluminosilicate glasses where charge balancing cations are not in excess [43], and as such any Al existing as Al(V) and Al(VI) in samples A and B is likely to provide some charge balancing to the negative charge associated with tetrahedral Al sites.…”

Theoretical study of formation mechanism of aluminosilicate in the synthesis of zeolites

“…Cundy et al [4] described a typical hydrothermal zeolite synthesis as follows: the start materials containing Si-O and Al-O bonds are converted by an aqueous mineralizing medium (OH -and/or F -) into the crystalline product containing Si-O-Al bonds whose micro-porosity is defined by the crystal structure. Therefore, the polycondensation occurring between silicate and aluminate ions in a solution mixture is one of the elementary reaction steps of zeolite synthesis [5,6]. Small aluminosilicate anion species are technologically significant, which are proposed as the nucleation precursors and growth units for zeolite crystal, and thus understanding the formation mechanism of Si-O-Al linkage is of scientific importance.…”

“…Small aluminosilicate anion species are technologically significant, which are proposed as the nucleation precursors and growth units for zeolite crystal, and thus understanding the formation mechanism of Si-O-Al linkage is of scientific importance. There have been some experimental [6][7][8][9][10][11][12][13][14][15] and theoretical [16][17][18][19][20][21][22] studies on the aluminosilicate oligomers in solution and colloid.…”

“…The 27 Al NMR spectra revealed evidences for Al bound to zero, one, two, three, and four Si atoms through oxygen atoms. The bands located at chemical shifts (from the signal for Al(H 2 O) 6 3-) of about 80, 75, 70, 65, and 60 ppm are assigned to the q 0 , q 1 , q 2 , q 3 , and q 4 , respectively [6,[13][14][15]. In addition, the observed NMR data showed that at the high pH value and relatively low Al concentration, the free Al monomers appear to be in the form of Al(OH) 4 -, with possible trace amounts of Al(OH) 6 3-[7, 15].…”

Aluminium‐27 NMR investigation of the influence of cation type on aluminosilicate solutions

“…Moreover, exchange rates between anionic species have been studied 4,5 by varying temperature or pH, and the evolution of spectra with time has been examined. 4 Aluminium-27 NMR is especially powerful because highquality NMR spectra can be acquired in a short time (¾10 min), in sharp contrast to 29 Si NMR spectra, though the latter have significantly better resolution.…”