期刊
COLLOID AND INTERFACE SCIENCE COMMUNICATIONS
卷 23, 期 -, 页码 1-5出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.colcom.2018.01.001
关键词
Laponite; X ray diffraction; Swelling; Desorption; Thermogravimetric analysis
资金
- CNPq (National Council for Scientific and Technological Development) [200247/2015-8]
- Sao Paulo Research Foundation (FAPESP) Brazil [2012/24047-3]
- FAPESP (CEPID) [2013/07914-8]
This paper investigates water sorption and dehydration of model synthetic clay (Laponite) and highlights the large differences with natural Na-smectite clays. Measurements were done by combining for the first time thermogravimetric analysis and X-ray diffraction methods on Laponite powders stored in atmospheres with controlled relative humidity. Laponite exhibits a very good reproducibility of the sorption diagram and appears as the most hygroscopic among Na-smectites. The interlayer distance increases from 11 to 20 angstrom when the ratio r = n(H2O)/n(Na) increases from 2 to 22, in agreement with recent numerical simulations. The desorption process, in this range of r, in isothermal conditions follows a first order kinetics with two regimes around r* = 7 which is close to the coordination number of Na+ ions in concentrated NaCl solution. Activation energies and frequency factors are derived for the two regimes of desorption and discussed in relation with stability of the cationic complex.
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