Ultrasounds and microwave-assisted synthesis of mesoporous hectorites

Abstract

Stable mesoporous delaminated and silicate-bearing hectorites were synthesized at short times (1–2h) varying the pH of the hydrothermal treatment (7 and 10) and using microwaves and ultrasounds during the synthesis. The use of microwaves, ultrasounds and aging pH of 10 improved hectorite crystallinity. Additionally, longer times of ultrasounds involved a better incorporation of magnesium and lithium cations in the octahedral sheet for the delaminated hectorites prepared a pH 7. Delaminated hectorites showed higher BET areas (536–603m2/g) than silicate-bearing hectorites, due to delamination and probably to the presence of magnesium vacancies in the octahedral sheet. The formation of vacancies was favored with the use of microwaves and at short times of ultrasounds. This agrees with the C.E.C. values and the low amounts of lithium obtained for delaminated samples.