Study of pillar precursors [Ga(III)–Al(III), Ln(III)–Al(III), Zr(IV)] for hydrothermally stable pillared clays

Abstract

The hydrolysis of mixed solutions of Al(III), Ga(III), Al(III), Ln(III) and Zr(IV) was studied by potentiometric, spectrophotometric and 27 Al - and 71 Ga -NMR techniques. For the Al–Ga system formation of GaAl 12(OH) 11+ 28 species seems more probable into the pH range 4≤pH≤5. Afterwards, the Al 13(OH) 7+ 32 species predominate in agreement with thermodynamic data obtained by SUPERQUAD program. Both tetrahedral Ga IV and Al IV may coexist in solution, the interval being defined by potentiometric methods. For the Ln(III)–Al(III) systems 27 Al -and 139 La -NMR does not confirm the chemical interaction between the two species in solution, but the physicochemical properties of the La–Al/PILCS were different than Al/PILCS, suggesting a strong interaction in the solid state. Ce(III) and Ce(IV) ions do interact with Al(III) in solution, into the pH range 2.78<pH<3.99, according with the spectrophotometric behavior. Finally, the Zr(IV) hydrolysis was followed by UV in the pH range greater than 2.0, showing the formation of Zr 4(OH) 8+ 8 species, which was verified by calculations using SQUAD program, but the precipitation occurs at pH>3.0.